OM NDT TRAINING amp CONSULTANCYwwwomndtorg

PENETRANT TESTING L-II

Prepared by MAHESH PANDITASNT NDT L-III

>

Basic principle of a Liquid Penetrant

bull DPI is based upon capillary action where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities Penetrant may be applied to the test component by dipping spraying or brushing After adequate penetration time has been allowed the excess penetrant is removed and a developer is applied The developer helps to draw penetrant out of the flaw so that an invisible indication becomes visible to the inspector Inspection is performed under ultraviolet or white light depending on the type of dye used - fluorescent or non fluorescent (visible)

Basic principle of a Liquid Penetrant

bull DPI is based upon capillary action where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities Penetrant may be applied to the test component by dipping spraying or brushing After adequate penetration time has been allowed the excess penetrant is removed and a developer is applied The developer helps to draw penetrant out of the flaw so that an invisible indication becomes visible to the inspector Inspection is performed under ultraviolet or white light depending on the type of dye used - fluorescent or non fluorescent (visible)

Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of and in opposition to external forces like gravity The effect can be seen in the drawing up of liquids between the hairs of a paint-brush in a thin tube in porous materials such as paper It occurs because of intermolecular forces between the liquid and surrounding solid surfaces

Intermolecular forces are forces of attraction or repulsion which act between neighboring particlesSurface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension Surface tension is typically measured in dynescm the force in dynes required to break a film of length 1 cm Water at 20degC has a surface tension of 728 dynescm The surface tension of water decreases significantly with temperature Soaps and detergents further lower the surface tension

Basic principle of a Liquid Penetrant

bull When a liquid comes into contact with a surface both cohesive and adhesive forces will act on it These forces govern the shape which the liquid takes on Due to the effects of adhesive forces liquid on a surface can spread out to form a thin relatively uniform film over the surface a process known as wetting Alternatively in the presence of strong cohesive forces the liquid can divide into a number of small roughly spherical beads which stand on the surface maintaining minimal contact with the surface

Basic principle of a Liquid Penetrant

bull Cohesive forces are the intermolecular forces which cause a tendency in liquids to resist separation These attractive forces exist between molecules of the same substance For instance rain falls in droplets rather than a fine mist because water has strong cohesion which pulls its molecules tightly together forming droplets

Basic principle of a Liquid Penetrant

bull Adhesive forces are the attractive forces between unlike molecules In the case of a liquid wetting agent adhesion causes the liquid to cling to the surface on which it rests When water is poured on clean glass it tends to spread forming a thin uniform film over the glasses surface This is because the adhesive forces between water and glass are strong enough to pull the water molecules out of their spherical formation and hold them against the surface of the glass thus avoiding the repulsion between like molecules

>

Basic principle of a Liquid Penetrant

bull When the cohesive force of the liquid is stronger than the adhesive force of the liquid to the wall the liquid concaves down in order to reduce contact with the surface of the wall When the adhesive force of the liquid to the wall is stronger than the cohesive force of the liquid the liquid is more attracted to the wall than its neighbors causing the upward concavity

>

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Basic principle of a Liquid Penetrant

bull The meniscus is the curve in the upper surface of a liquid close to the surface of the container or another object caused by surface tension It can be either convex or concave depending on the liquid and the surface

bull A convex meniscus occurs when the molecules have a stronger attraction to each other (cohesion) than to the material of the container (adhesion) causing the surface of the liquid to cave downward

bull This may be seen between mercury and glass in barometers and thermometers Conversely a concave meniscus occurs when the molecules of the liquid are attracted to those of the container causing the surface of the liquid to cave upwards This can be seen in a glass of water

Basic principle of a Liquid Penetrant

bull When the cohesive force of the liquid is stronger than the adhesive force of the liquid to the wall the liquid concaves down in order to reduce contact with the surface of the wall When the adhesive force of the liquid to the wall is stronger than the cohesive force of the liquid the liquid is more attracted to the wall than its neighbors causing the upward concavity

>

>

Basic principle of a Liquid Penetrant

bull The meniscus is the curve in the upper surface of a liquid close to the surface of the container or another object caused by surface tension It can be either convex or concave depending on the liquid and the surface

bull A convex meniscus occurs when the molecules have a stronger attraction to each other (cohesion) than to the material of the container (adhesion) causing the surface of the liquid to cave downward

bull This may be seen between mercury and glass in barometers and thermometers Conversely a concave meniscus occurs when the molecules of the liquid are attracted to those of the container causing the surface of the liquid to cave upwards This can be seen in a glass of water

>

Basic principle of a Liquid Penetrant

bull The meniscus is the curve in the upper surface of a liquid close to the surface of the container or another object caused by surface tension It can be either convex or concave depending on the liquid and the surface

bull A convex meniscus occurs when the molecules have a stronger attraction to each other (cohesion) than to the material of the container (adhesion) causing the surface of the liquid to cave downward

bull This may be seen between mercury and glass in barometers and thermometers Conversely a concave meniscus occurs when the molecules of the liquid are attracted to those of the container causing the surface of the liquid to cave upwards This can be seen in a glass of water

Basic principle of a Liquid Penetrant

bull The meniscus is the curve in the upper surface of a liquid close to the surface of the container or another object caused by surface tension It can be either convex or concave depending on the liquid and the surface

bull A convex meniscus occurs when the molecules have a stronger attraction to each other (cohesion) than to the material of the container (adhesion) causing the surface of the liquid to cave downward

bull This may be seen between mercury and glass in barometers and thermometers Conversely a concave meniscus occurs when the molecules of the liquid are attracted to those of the container causing the surface of the liquid to cave upwards This can be seen in a glass of water

Basic principle of a Liquid Penetrant

bull The height to which the liquid rises is directly proportional to the surface tension of a liquid and to the cosine of the angle of contact

bull The viscosity of the liquid is not a factor in the basic equation of capillary rise Viscosity is related to the rate at which a liquid will flow under some applied unbalanced stress in itself viscosity has a negligible effect on penetrating ability

bull In general however very viscous liquids are unsuitable as penetrants because they do not flow rapidly enough over the surface of the work piece consequently they require excessively long periods of time to migrate into fine flaws

>

>

Basic principle of a Liquid Penetrant

The ability of a given liquid to flow over a surface and enter surface cavities depends principally on the followingbull Cleanliness of the surfacebull Configuration of the cavitybull Cleanliness of the cavitybull Size of surface opening of the cavitybull Surface tension of the liquidbull Ability of the liquid to wet the surfacebull Contact angle of the liquid

>

Penetrant Dwell

The factors that influence the length of time for the penetrant to enter and fill a surface void include bull Void sizebull Penetrant materialbull The type of discontinuitybull Penetrant viscosity and bull The cleanliness of the discontinuity

>

Basic principle of a Liquid Penetrant

bull If θ is less than 90deg (Fig 1a) the liquid is said to wet the surface or to have good wetting ability

bull if the angle is equal to or greater than 90deg (Fig 1b and c) the wetting ability is considered poor

bull If θ is greater than 90deg the liquid is depressed in the tube and does not wet the tube wall and the meniscus is convex (Fig 2c)

>

Figure 2

>

History of PT

bull A very early surface inspection technique involved the rubbing of carbon black on glazed pottery whereby the carbon black would settle in surface cracks rendering them visible Later it became the practice in railway workshops to examine iron and steel components by the oil and whiting method by Magna flux in (Chicago)

>

History of PT

bull In this method a heavy oil was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged After removal and careful cleaning the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed once the alcohol had evaporated The object was then vibrated by being struck with a hammer causing the residual oil in any surface cracks to seep out and stain the white coating

>

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

>

Basic principle of a Liquid Penetrant

The ability of a given liquid to flow over a surface and enter surface cavities depends principally on the followingbull Cleanliness of the surfacebull Configuration of the cavitybull Cleanliness of the cavitybull Size of surface opening of the cavitybull Surface tension of the liquidbull Ability of the liquid to wet the surfacebull Contact angle of the liquid

>

Penetrant Dwell

The factors that influence the length of time for the penetrant to enter and fill a surface void include bull Void sizebull Penetrant materialbull The type of discontinuitybull Penetrant viscosity and bull The cleanliness of the discontinuity

>

Basic principle of a Liquid Penetrant

bull If θ is less than 90deg (Fig 1a) the liquid is said to wet the surface or to have good wetting ability

bull if the angle is equal to or greater than 90deg (Fig 1b and c) the wetting ability is considered poor

bull If θ is greater than 90deg the liquid is depressed in the tube and does not wet the tube wall and the meniscus is convex (Fig 2c)

>

Figure 2

>

History of PT

bull A very early surface inspection technique involved the rubbing of carbon black on glazed pottery whereby the carbon black would settle in surface cracks rendering them visible Later it became the practice in railway workshops to examine iron and steel components by the oil and whiting method by Magna flux in (Chicago)

>

History of PT

bull In this method a heavy oil was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged After removal and careful cleaning the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed once the alcohol had evaporated The object was then vibrated by being struck with a hammer causing the residual oil in any surface cracks to seep out and stain the white coating

>

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Basic principle of a Liquid Penetrant

The ability of a given liquid to flow over a surface and enter surface cavities depends principally on the followingbull Cleanliness of the surfacebull Configuration of the cavitybull Cleanliness of the cavitybull Size of surface opening of the cavitybull Surface tension of the liquidbull Ability of the liquid to wet the surfacebull Contact angle of the liquid

>

Penetrant Dwell

The factors that influence the length of time for the penetrant to enter and fill a surface void include bull Void sizebull Penetrant materialbull The type of discontinuitybull Penetrant viscosity and bull The cleanliness of the discontinuity

>

Basic principle of a Liquid Penetrant

bull If θ is less than 90deg (Fig 1a) the liquid is said to wet the surface or to have good wetting ability

bull if the angle is equal to or greater than 90deg (Fig 1b and c) the wetting ability is considered poor

bull If θ is greater than 90deg the liquid is depressed in the tube and does not wet the tube wall and the meniscus is convex (Fig 2c)

>

Figure 2

>

History of PT

bull A very early surface inspection technique involved the rubbing of carbon black on glazed pottery whereby the carbon black would settle in surface cracks rendering them visible Later it became the practice in railway workshops to examine iron and steel components by the oil and whiting method by Magna flux in (Chicago)

>

History of PT

bull In this method a heavy oil was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged After removal and careful cleaning the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed once the alcohol had evaporated The object was then vibrated by being struck with a hammer causing the residual oil in any surface cracks to seep out and stain the white coating

>

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Penetrant Dwell

The factors that influence the length of time for the penetrant to enter and fill a surface void include bull Void sizebull Penetrant materialbull The type of discontinuitybull Penetrant viscosity and bull The cleanliness of the discontinuity

>

Basic principle of a Liquid Penetrant

bull If θ is less than 90deg (Fig 1a) the liquid is said to wet the surface or to have good wetting ability

bull if the angle is equal to or greater than 90deg (Fig 1b and c) the wetting ability is considered poor

bull If θ is greater than 90deg the liquid is depressed in the tube and does not wet the tube wall and the meniscus is convex (Fig 2c)

>

Figure 2

>

History of PT

bull A very early surface inspection technique involved the rubbing of carbon black on glazed pottery whereby the carbon black would settle in surface cracks rendering them visible Later it became the practice in railway workshops to examine iron and steel components by the oil and whiting method by Magna flux in (Chicago)

>

History of PT

bull In this method a heavy oil was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged After removal and careful cleaning the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed once the alcohol had evaporated The object was then vibrated by being struck with a hammer causing the residual oil in any surface cracks to seep out and stain the white coating

>

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Basic principle of a Liquid Penetrant

bull If θ is less than 90deg (Fig 1a) the liquid is said to wet the surface or to have good wetting ability

bull if the angle is equal to or greater than 90deg (Fig 1b and c) the wetting ability is considered poor

bull If θ is greater than 90deg the liquid is depressed in the tube and does not wet the tube wall and the meniscus is convex (Fig 2c)

>

Figure 2

>

History of PT

bull A very early surface inspection technique involved the rubbing of carbon black on glazed pottery whereby the carbon black would settle in surface cracks rendering them visible Later it became the practice in railway workshops to examine iron and steel components by the oil and whiting method by Magna flux in (Chicago)

>

History of PT

bull In this method a heavy oil was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged After removal and careful cleaning the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed once the alcohol had evaporated The object was then vibrated by being struck with a hammer causing the residual oil in any surface cracks to seep out and stain the white coating

>

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Figure 2

>

History of PT

bull A very early surface inspection technique involved the rubbing of carbon black on glazed pottery whereby the carbon black would settle in surface cracks rendering them visible Later it became the practice in railway workshops to examine iron and steel components by the oil and whiting method by Magna flux in (Chicago)

>

History of PT

bull In this method a heavy oil was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged After removal and careful cleaning the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed once the alcohol had evaporated The object was then vibrated by being struck with a hammer causing the residual oil in any surface cracks to seep out and stain the white coating

>

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

History of PT

bull A very early surface inspection technique involved the rubbing of carbon black on glazed pottery whereby the carbon black would settle in surface cracks rendering them visible Later it became the practice in railway workshops to examine iron and steel components by the oil and whiting method by Magna flux in (Chicago)

>

History of PT

bull In this method a heavy oil was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged After removal and careful cleaning the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed once the alcohol had evaporated The object was then vibrated by being struck with a hammer causing the residual oil in any surface cracks to seep out and stain the white coating

>

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

History of PT

bull In this method a heavy oil was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged After removal and careful cleaning the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed once the alcohol had evaporated The object was then vibrated by being struck with a hammer causing the residual oil in any surface cracks to seep out and stain the white coating

>

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Why a Penetrant Inspection Improves the Detectability of Flaws

bull 1) It produces a flaw indication that is much larger and easier for the eye to detect than the flaw itself

bull 2) it produces a flaw indication with a high level of contrast between the indication and the background

bull 3) The developer serves as a high contrast background as well as a blotter to pull the trapped penetrant from the flaw

>

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Visual Acuity of the Human Eye bull Due to the physical features of the eye there is a threshold

below which objects cannot be resolved This threshold of visual acuity is around 0003 (0076mm) inch for a person with 2020 vision

bull 2020 vision it means that when you stand 20 feet away from the chart you can see what the normal human being can see

bull The human eye is more sensitive to a light indication on a dark background and the eye is naturally drawn to a fluorescent indication

bull With a light indication on a dark background indications down to 0003 mm (00001 inch) may be seen when the contrast between the flaw and the background was high

bull But dark indication on a lighter background canrsquot

>

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Visual Acuity of the Human Eye

The eye has a visual acuity threshold below which an object will go undetected This threshold varies from person to person but as an example the case of a person with normal 2020 vision can be considered As light enters the eye through the pupil it passes through the lens and is projected on the retina at the back of the eye Muscles called extra ocular muscles move the eyeball in the orbits and allow the image to be focused on the central retinal or fovea

>

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

>

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

>

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

>

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

The retina is a mosaic of two basic types of photoreceptors rods and cones Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm and are used for vision under dark or dim conditions There are three types of cones that give us our basic color vision L-cones (red) with a peak sensitivity of 564 nm M-cones (green) with a peak sensitivity of 533 nm and S-cones (blue) with a peak sensitivity of 437 nm

>

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Visual Acuity of the Human Eye bull The standard definition of normal visual acuity (2020 vision) is

the ability to resolve a spatial pattern separated by a visual angle of one minute of arc Since one degree contains sixty minutes a visual angle of one minute of arc is 160 of a degree

bull For the case of normal visual acuity the angle Theta is 160 of a degree By bisecting this angle we have a right triangle with angle Theta2 that is 1120 of a degree Using this right triangle it is easy to calculate the distance X2 for a given distance d

bull X2 = d (tan Theta2) bull under normal lighting conditions the eye is most sensitive to a

yellowish-green color

>

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Visual Acuity of the Human Eye bull When the light levels drop to near total darkness the response of

the eye changes significantly by the scotopic response curve bull At this level of light the rods are most active and the human eye

is more sensitive to the light present and less sensitive to the range of color

bull At this very low light level sensitivity to blue violet and ultraviolet is increased but sensitivity to yellow and red is reduced

bull Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions

>

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

System performance checksbull System performance checks involve processing a test specimen

with known defects to determine if the process will reveal discontinuities of the size required

bull The most commonly used test specimen is the TAM or PSM panel These panel are usually made of stainless steel that has been chrome plated on one half and surfaced finished on the other half to produced the desired roughness The chrome plated section is impacted from the back side to produce a starburst set of cracks in the chrome There are five impacted areas to produce range of crack sizes Each panel has a characteristic ldquosignaturerdquo and variances in that signature are indications of process variance

>

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Sherwin PSM-5 Penetrant System Monitor Panel

bull A stainless steel panel 0090ldquo(2286mm) thick and measuring 4 x 6 inches A chrome plated strip runs the length of one side of the panel Five crack centers are evenly spaced in the chrome plating in order of magnitude the largest is readily visible with low sensitivity penetrants while the smallest is difficult to observe even with high sensitivity materials Adjacent to the chrome plated section is a grit blasted area of medium roughness to judge penetrant wash characteristics

>

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

System performance on PSM

The minimum number of crack indications on PSM panel shall be visible as followsLevel frac12 and 1 ndash three indicationsLevel 2 - four indicationsLevel 3 and 4 - five indications Removability test on PSMAt least 75 of the grit blasted panel shall show no evidence of background fluorescence

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Basic Processing Steps of a Liquid Penetrant Inspection

bull 1) Surface preparation The surface must be free of oil grease water or other contaminants that may prevent penetrant from entering flaws

bull 2) Penetrant Application Once the surface has been thoroughly cleaned and dried the penetrant material is applied by spraying brushing or immersing the part in a penetrant bath

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

3) Penetrant Dwell The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect Minimum dwell times typically range from five to 60 minutes Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry 4) Excess Penetrant Removal 5) Developer Application A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible

>

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

6) Indication Development The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws This development time is usually a minimum of 10 minutes 7) Inspection Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present8) Clean Surface The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable

>

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Contaminants bull Coatings such as paint are much more elastic than metal and

will not fracture even though a large defect may be present just below the coating

bull The part must be thoroughly cleaned as surface contaminates can prevent the penetrant from entering a defect

bull Surface contaminants can also lead to a higher level of background noise since the excess penetrant may be more difficult to remove

bull contaminates that must be removed include paint dirt flux scale varnish oil etchant smut plating grease oxide wax decals machining fluid rust and residue from previous penetrant inspections

>

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Pre-cleaningbull Regardless of the penetrant chosen adequate pre-cleaning

of work pieces prior to penetrant inspection is absolutely necessary for accurate results Without adequate removal of surface contamination relevant indications may be missed because

bull The penetrant does not enter the flawbull The penetrant loses its ability to identify the flaw

because it reacts with something already in itbull The surface immediately surrounding the flaw retains

enough penetrant to mask the true appearance of the flaw

>

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Cleaningbull Alkaline cleaners can be detrimental to the penetrant

inspection process if they have silicates in concentrations above 05 percent

bull Sodium meta-silicate sodium silicate and related compounds can adhere to the surface of parts and form a coating that prevents penetrant entry into cracks

bull some domestic soaps and commercial detergents can clog flaw cavities and reduce the wettability of the metal surface thus reducing the sensitivity of the penetrant

>

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Cleaning methodsSelection of a cleaning method depends upon the type of contaminant to be removed and the type of alloy being cleanedThis cleaning methods are generally classified asbull Chemical bull Mechanical bull Solvent (methylene chloride isopropyl

alcoholnaptha)bull or any combination of these

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Cleaning methodsbull Chemical cleaning methods include alkaline or acid cleaning pickling or

chemical etchingbull Mechanical cleaning methods include tumbling wet blasting dry abrasive

blasting wire brushing and high pressure water or steam cleaning Tumbling or rumbling is a technique for smoothing and polishing a rough surface on relatively small parts Metal tumbling is used to burnish(plastic deformation of a surface due to sliding contact with another object) deburr(neaten and smooth the rough edges) clean radius de-flash descale remove rust polish brighten surface harden prepare parts for further finishingMechanical cleaning methods should be used with care because they often mask flaws by smearing adjacent metal over them bull Solvent cleaning methods include vapor degreasing solvent spraying

solvent wiping and ultrasonic immersion using solvents bull Probably the most common method is vapor degreasing However ultrasonic

immersion is by far the most effective means of ensuring clean parts but it can be a very expensive capital equipment investment

Mechanical methodsbull Abrasive tumbling Removing light scale burrs welding flux

braze stop-off rust casting mold and core material bull Wire brushing removing light deposits of scale flux and stop-off

Stop-off which are blends of metallic-oxides used to stops molten brazing filler metal (BFM) from flowing into areas where it is not required

bull Stop-Off is a brazing aid commonly used in silver and aluminum brazing It is used to prevent the flow of flux and metal to unwanted areas during brazing

bull High-pressure water and steam used with an alkaline cleaner or detergent removing typical machine shop soils such as cutting oils polishing compounds grease chips etc

bull Ultrasonic cleaning used with detergent and water or with a solvent removing adherent shop soil from large quantities of small parts

Chemical methodsbull Alkaline cleaning Removing braze stop-off rust scale oils

greases polishing material and carbon deposits ordinarily used on large articles where hand methods are too laborious

bull Acid cleaning Strong solutions for removing heavy scale mild solutions for light scale weak (etching) solutions for removing lightly smeared metal

Solvent methodsbull Vapor degreasing removing typical shop soil oil

and grease usually employs chlorinated solvents not suitable for titanium Nickel alloys and certain stainless steel

bull Solvent wiping Same as for vapor degreasing except a hand operation may employ non-chlorinated solvents used for localized low-volume cleaning

bull Minimal washing or under-emulsification can result in excessive background which could mask the flaws and render them undetectable

Common Uses of Liquid Penetrant Inspection

bull LPI can be used to inspect almost any material provided that its surface is not extremely rough or porous It include the following

bull Metals (aluminum copper steel titanium etc) bull Glass bull Many ceramic materials bull Rubber bull Plastics

It can only be used to inspect for flaws that break the surface of the sample Some of these flaws are listed below 1 Fatigue cracks 2 Quench cracks 3 Grinding cracks 4 Overload and impact fractures 5 Porosity 6 Laps 7 Seams 8 Pin holes in welds 9 Lack of fusion along the edge of the bond line

Advantages of Penetrant Testing

bull High sensitivity to small surface discontinuities

bull Large areas and large volumes of partsmaterials can be inspected rapidly and at low cost

bull Parts with complex geometric shapes are routinely inspected

bull Aerosol spray cans make penetrant materials very portable

Disadvantages of Penetrant Testingbull Only surface breaking defects can be detected bull Only materials with a relatively nonporous

surface can be inspected bull Pre-cleaning is critical since contaminants can

mask defects bull Metal smearing from machining grinding and

grit or vapor blasting must be removed prior to LPI

Disadvantages of Penetrant Testing

bull The inspector must have direct access to the surface being inspected

bull Surface finish and roughness can affect inspection sensitivity

bull Post cleaning of acceptable parts or materials is required

bull Chemical handling and proper disposal is required

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Chemical methodsbull Alkaline cleaning Removing braze stop-off rust scale oils

greases polishing material and carbon deposits ordinarily used on large articles where hand methods are too laborious

bull Acid cleaning Strong solutions for removing heavy scale mild solutions for light scale weak (etching) solutions for removing lightly smeared metal

Solvent methodsbull Vapor degreasing removing typical shop soil oil

and grease usually employs chlorinated solvents not suitable for titanium Nickel alloys and certain stainless steel

bull Solvent wiping Same as for vapor degreasing except a hand operation may employ non-chlorinated solvents used for localized low-volume cleaning

bull Minimal washing or under-emulsification can result in excessive background which could mask the flaws and render them undetectable

Common Uses of Liquid Penetrant Inspection

bull LPI can be used to inspect almost any material provided that its surface is not extremely rough or porous It include the following

bull Metals (aluminum copper steel titanium etc) bull Glass bull Many ceramic materials bull Rubber bull Plastics

It can only be used to inspect for flaws that break the surface of the sample Some of these flaws are listed below 1 Fatigue cracks 2 Quench cracks 3 Grinding cracks 4 Overload and impact fractures 5 Porosity 6 Laps 7 Seams 8 Pin holes in welds 9 Lack of fusion along the edge of the bond line

Advantages of Penetrant Testing

bull High sensitivity to small surface discontinuities

bull Large areas and large volumes of partsmaterials can be inspected rapidly and at low cost

bull Parts with complex geometric shapes are routinely inspected

bull Aerosol spray cans make penetrant materials very portable

Disadvantages of Penetrant Testingbull Only surface breaking defects can be detected bull Only materials with a relatively nonporous

surface can be inspected bull Pre-cleaning is critical since contaminants can

mask defects bull Metal smearing from machining grinding and

grit or vapor blasting must be removed prior to LPI

Disadvantages of Penetrant Testing

bull The inspector must have direct access to the surface being inspected

bull Surface finish and roughness can affect inspection sensitivity

bull Post cleaning of acceptable parts or materials is required

bull Chemical handling and proper disposal is required

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Solvent methodsbull Vapor degreasing removing typical shop soil oil

and grease usually employs chlorinated solvents not suitable for titanium Nickel alloys and certain stainless steel

bull Solvent wiping Same as for vapor degreasing except a hand operation may employ non-chlorinated solvents used for localized low-volume cleaning

bull Minimal washing or under-emulsification can result in excessive background which could mask the flaws and render them undetectable

Common Uses of Liquid Penetrant Inspection

bull LPI can be used to inspect almost any material provided that its surface is not extremely rough or porous It include the following

bull Metals (aluminum copper steel titanium etc) bull Glass bull Many ceramic materials bull Rubber bull Plastics

It can only be used to inspect for flaws that break the surface of the sample Some of these flaws are listed below 1 Fatigue cracks 2 Quench cracks 3 Grinding cracks 4 Overload and impact fractures 5 Porosity 6 Laps 7 Seams 8 Pin holes in welds 9 Lack of fusion along the edge of the bond line

Advantages of Penetrant Testing

bull High sensitivity to small surface discontinuities

bull Large areas and large volumes of partsmaterials can be inspected rapidly and at low cost

bull Parts with complex geometric shapes are routinely inspected

bull Aerosol spray cans make penetrant materials very portable

Disadvantages of Penetrant Testingbull Only surface breaking defects can be detected bull Only materials with a relatively nonporous

surface can be inspected bull Pre-cleaning is critical since contaminants can

mask defects bull Metal smearing from machining grinding and

grit or vapor blasting must be removed prior to LPI

Disadvantages of Penetrant Testing

bull The inspector must have direct access to the surface being inspected

bull Surface finish and roughness can affect inspection sensitivity

bull Post cleaning of acceptable parts or materials is required

bull Chemical handling and proper disposal is required

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Common Uses of Liquid Penetrant Inspection

bull LPI can be used to inspect almost any material provided that its surface is not extremely rough or porous It include the following

bull Metals (aluminum copper steel titanium etc) bull Glass bull Many ceramic materials bull Rubber bull Plastics

It can only be used to inspect for flaws that break the surface of the sample Some of these flaws are listed below 1 Fatigue cracks 2 Quench cracks 3 Grinding cracks 4 Overload and impact fractures 5 Porosity 6 Laps 7 Seams 8 Pin holes in welds 9 Lack of fusion along the edge of the bond line

Advantages of Penetrant Testing

bull High sensitivity to small surface discontinuities

bull Large areas and large volumes of partsmaterials can be inspected rapidly and at low cost

bull Parts with complex geometric shapes are routinely inspected

bull Aerosol spray cans make penetrant materials very portable

Disadvantages of Penetrant Testingbull Only surface breaking defects can be detected bull Only materials with a relatively nonporous

surface can be inspected bull Pre-cleaning is critical since contaminants can

mask defects bull Metal smearing from machining grinding and

grit or vapor blasting must be removed prior to LPI

Disadvantages of Penetrant Testing

bull The inspector must have direct access to the surface being inspected

bull Surface finish and roughness can affect inspection sensitivity

bull Post cleaning of acceptable parts or materials is required

bull Chemical handling and proper disposal is required

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

It can only be used to inspect for flaws that break the surface of the sample Some of these flaws are listed below 1 Fatigue cracks 2 Quench cracks 3 Grinding cracks 4 Overload and impact fractures 5 Porosity 6 Laps 7 Seams 8 Pin holes in welds 9 Lack of fusion along the edge of the bond line

Advantages of Penetrant Testing

bull High sensitivity to small surface discontinuities

bull Large areas and large volumes of partsmaterials can be inspected rapidly and at low cost

bull Parts with complex geometric shapes are routinely inspected

bull Aerosol spray cans make penetrant materials very portable

Disadvantages of Penetrant Testingbull Only surface breaking defects can be detected bull Only materials with a relatively nonporous

surface can be inspected bull Pre-cleaning is critical since contaminants can

mask defects bull Metal smearing from machining grinding and

grit or vapor blasting must be removed prior to LPI

Disadvantages of Penetrant Testing

bull The inspector must have direct access to the surface being inspected

bull Surface finish and roughness can affect inspection sensitivity

bull Post cleaning of acceptable parts or materials is required

bull Chemical handling and proper disposal is required

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Advantages of Penetrant Testing

bull High sensitivity to small surface discontinuities

bull Large areas and large volumes of partsmaterials can be inspected rapidly and at low cost

bull Parts with complex geometric shapes are routinely inspected

bull Aerosol spray cans make penetrant materials very portable

Disadvantages of Penetrant Testingbull Only surface breaking defects can be detected bull Only materials with a relatively nonporous

surface can be inspected bull Pre-cleaning is critical since contaminants can

mask defects bull Metal smearing from machining grinding and

grit or vapor blasting must be removed prior to LPI

Disadvantages of Penetrant Testing

bull The inspector must have direct access to the surface being inspected

bull Surface finish and roughness can affect inspection sensitivity

bull Post cleaning of acceptable parts or materials is required

bull Chemical handling and proper disposal is required

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Disadvantages of Penetrant Testingbull Only surface breaking defects can be detected bull Only materials with a relatively nonporous

surface can be inspected bull Pre-cleaning is critical since contaminants can

mask defects bull Metal smearing from machining grinding and

grit or vapor blasting must be removed prior to LPI

Disadvantages of Penetrant Testing

bull The inspector must have direct access to the surface being inspected

bull Surface finish and roughness can affect inspection sensitivity

bull Post cleaning of acceptable parts or materials is required

bull Chemical handling and proper disposal is required

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Disadvantages of Penetrant Testing

bull The inspector must have direct access to the surface being inspected

bull Surface finish and roughness can affect inspection sensitivity

bull Post cleaning of acceptable parts or materials is required

bull Chemical handling and proper disposal is required

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

TYPES OF PENETRANT MATERIALS

Type 1 - Fluorescent Penetrants High sensitive comes usually green in color and fluoresce brilliantly under ultraviolet light

Type 2 - Visible Penetrants Less sensitive usually red in color viewed under adequate white light less vulnerable to contaminants

Type 3 ndash Dual mode penetrants Viewed under black light or white light

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

The Type- I Penetrant have five sensitivity levels-

Level frac12 - Ultra Low Sensitivity Level 1 - Low Sensitivity Level 2 - Medium Sensitivity Level 3 - High Sensitivity Level 4 - Ultra-High Sensitivity

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Before selection of a type of penetrant method we must have a knowledge of

bull Surface condition of the work piece being inspected

bull Characteristics of the flaws to be detectedbull Time and place of inspectionbull Size of the work piecebull Sensitivity requiredbull Materials cost number of parts size of area

requiring inspection and portability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Penetrants are classified on the basis of penetrant type

bull Type I Fluorescent

bull Type II Visible

Method A Water washable

Method B Post emulsifiable-lipophilicMethod C Solvent removable

Method D Post emulsifiable-hydrophilic

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Application of Penetrant

Bybull Flowingbull Brushingbull Swabbingbull Dippingbull SprayingWork pieces should not be submerged during the entire penetrant dwell time Heating is also not recommended because volatization difficulty in washing and decrease in fluorescence can occur

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Water-washable penetrant (method A)bull Designed so that the penetrant is directly

water washable from the surface of the work piece

bull It is a self emulsifying penetrantbull It is susceptible to over washing

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

quality controlbull The wash temperature pressure and time are three parameters that are

typically controlled in penetrant inspection process specification bull A coarse spray or an immersion wash tank with air agitation is often used bull When the spray method is used the water pressure is usually limited to

276 kNm2 (40 psi) bull The temperature range of the water is usually specified as a wide range

(eg 10 to 38oC (50 to 100oF) in AMS 2647A)bull some penetrants can fade at high temperatures due to dye vaporization or

sublimationbull To prevent harming the penetrant material drying temperature should be

kept to under 71oCbull In a fluorescent penetrant inspection the amount of penetrant brought to

the surface by developer must exceed the dyes thin film threshold of fluorescence or the indication will not fluoresce

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Post-emulsifiable penetrantsbull Emulsifiers are liquids used to render excess penetrant on the

surface of a work piece water washablebull Method B lipophilic emulsifiers oil based are used as

supplied in ready-to-use form and function by diffusionbull work with both a chemical and mechanical actionbull mechanical action remove excess penetrant as the mixture

drains from the partbull In Chemical action the emulsifier diffuses into the remaining

penetrant and the resulting mixture is easily removed with a water spray

bull Water content (method B lipophilic) Monthly Not to exceed 5

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Emulsifiersbull Method D hydrophilic emulsifiers are water based

and are usually supplied as concentrates that are diluted in water to concentrations of 5 to 30 for dip applications and 005 to 5 for spray applications

bull Hydrophilic emulsifiers function by displacing excess penetrant from the surface of the part by detergent action

bull Hydrophilic emulsifier is slower acting than the lipophilic emulsifier Concentration (method D hydrophilic) Weekly Not greater than 3 above initial concentration

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Hydrophilic emulsifiersbull The major advantage of hydrophilic emulsifiers is

that they are less sensitive to variation in the contact and removal time

bull It is more sensitive than the lipophilic post emulsifiable

bull No diffusion takes placebull Work with both a chemical and mechanical actionbull Emulsification Time ranges from approximately

30 s to 3 min

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Prerinsebull When using method D (hydrophilic) a coarse water spray pre-rinse is needed

to assist in penetrant removal and to reduce contamination of the emulsifierbull Hydrophilic emulsifiers are water based water contamination is not a

problembull Water contamination of the lipophilic emulsifier is always a potential problem

due to the nature of the process Generally 5 water contamination can be tolerated

bull Contamination is not as a critical problem with post emulsifiable penetrant because water is usually not miscible and will separate from the penetrant

bull A coarse water spray is recommended using a pressure of 275 to 345 kPa (40 to 50 psi)

bull The pre-rinse water temperature should be 10 to 40 degC (50 to 100 degF) bull The pre-rinse time should be kept to a minimum (that is 30 to 90 s) because

the purpose is to remove excess penetrant so that the emulsifier does not become contaminated quickly

bull Rinse time should be determined experimentally for specific work pieces it usually varies from 10 s to 2 min

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Dryingbull Drying is best done in a recirculating hot-air drier that is

thermostatically controlled bull The temperature in the drier is normally between 65

and 95 degC (150 and 200 degF) bull The temperature of the work pieces should not be

permitted to exceed 70 degC (160 degF)bull Excessive drying at high temperatures can impair the

sensitivity of the inspection bull Because drying time will vary the exact time should be

determined experimentally for each type of work piece

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Penetrant Removal Process

bull Washing is used to define for water washablebull Rinsing is used for method B and D penetrantbull There are no of factors that influence spray rinse - bull The size of water droplet A course droplet size provides

optimum removal because it increase the mechanical forcebull Water pressure-10-40 psibull Water temperature- 10-38 degree celciousbull Spray angle - 45-75 degree is most effectivebull Nozzle to part distance - 6-24rdquo are acc and provide a

uniform rate of removalWashingRinsing is best with a fan shaped course spray It should stop once an acc background level is reached

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Post-emulsifiable penetrants (methods B and D)

bull Designed to ensure the detection of minute flaws in some materialsbull Separate emulsification is required to remove the penetrantbull The danger of over washing the penetrant out of the flaws is reducedbull These methods are the most reliable for detecting minute flawsbull Application of lipophilic emulsifier is done by dipping Brush on or spray on

application is not permitted because it would mechanically mix the emulsifier into the penetrant

bull Pre-rinsing prior to application of Hydrophilic emulsifier is recommended because it is incompatible with water

bull Concentration of hydrophilic emulsifier in spray application is usually 05-1 by volume however up to 5 may be used

bull Concentration of hydrophilic emulsifier by immersion application is usually 5-35 by volume depending on the manufacturer direction for mixing A slight agitation is necessary

bull Solvent removers never be sprayed or flowed on because excessive solvent will dilute entrapped penetrant which degrade the process

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Methods B and D1 pre-clean part 2 apply penetrant and allow to dwell 3 pre-rinse to remove first layer of penetrant 4 apply emulsifier and allow contact for specified time 5 rinse to remove excess penetrant 6 dry part 7 apply developer and allow part to develop and 8 inspect

Processing steps

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Solvent-removable penetrant (method C)

bull Used to inspect only a localized area of a work piece bull Inspect a work piece at the site rather than on a

production inspection basis bull Normally the same type of solvent is used for pre

cleaning and for removing excess penetrant bull This method is labor intensivebull When properly conducted and when used in the

appropriate applications the solvent-removable method can be one of the most sensitive penetrant methods available

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Solvent-removable penetrant (method C)

bull The use of excessive amounts of solvent must be avoided

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Solvent CleanerRemovers

bull Remove excess surface penetrant through direct solvent action bull There are two basic types of solvent removers bull flammable and nonflammable bull Flammable cleaners are essentially free of halogens but are

potential fire hazardsbull Nonflammable cleaners are widely used However they do

contain halogenated solvents which may render them unsuitable for some applications

bull Wipe the surface of the part with a clean dry cloth or paper towel Make only a single pass then fold the cloth and moisten with solvent to provide a clean surface for each succeeding wipe Repeat this procedure until there is little or no trace of penetrant

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Solvent CleanerRemovers

bull Excess surface penetrant is removed by wiping using lint-free cloths slightly moistened with solvent cleanerremover

bull It is not recommended that excess surface penetrant be removed by flooding the surface with solvent cleanerremover

bull Because the solvent will dissolve the penetrant within the defect and indications will not be produced

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Penetrant Application

bull Penetrants can be applied by -bull Immersingbull Sprayingbull Brushing bull The emulsifier on to the part is not

recommended by brushing either because the bristles of the brush may force emulsifier into discontinuities causing the entrapped penetrant to be removed

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Penetrant Application and Dwell Time

There are basically two dwell mode options-bull immersion-dwell (keeping the part immersed in the penetrant

during the dwell period) and bull drain-dwell (letting the part drain during the dwell period)bull Prior to a study by Sherwin the immersion-dwell mode was

generally considered to be more sensitive but recognized to be less economical because more penetrant was washed away and emulsifiers were contaminated more rapidly The reasoning for thinking this method was more sensitive was that the penetrant was more migratory and more likely to fill flaws when kept completely fluid and not allowed to lose volatile constituents by evaporation

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Penetrant Application and Dwell Time

bull However Sherwin showed that if the specimens are allowed to drain-dwell the sensitivity is higher because the evaporation increases the dyestuff concentration of the penetrant on the specimen

bull Sherwin also cautions that the samples being inspected should be placed outside the penetrant tank wall so that vapors from the tank do not accumulate and dilute the dyestuff concentration of the penetrant on the specimen

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Dwell TimeThe time required to fill a flaw depends on a number of variables which include the followingbull The surface tension of the penetrant bull The contact angle of the penetrant bull The dynamic shear viscosity of the penetrantbull The atmospheric pressure at the flaw openingbull The capillary pressure at the flaw opening bull The pressure of the gas trapped in the flaw by the penetrant bull The radius of the flaw or the distance between the flaw walls bull The density or specific gravity of the penetrant

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Dwell Timebull Microstructural properties of the penetrant AMS 2647A

requires that the dwell time for all aircraft and engine parts be at least 20 minutes while ASTM E1209 only requires a five minute dwell time for parts made of titanium and other heat resistant alloys

bull Generally there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry

bull Deutsch makes about dwell time is that if the elliptical flaw has a length to width ratio of 100 it will take the penetrant nearly ten times longer to fill than it will a cylindrical flaw with the same volume

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Quality Control of Penetrant

bull Deterioration of new penetrants primarily results from aging and contamination

bull the water content of water washable penetrants must be checked regularly Water-based water washable penetrants are checked with a refractometer

bull Non-water-based water washable penetrants are checked using the procedure specified in ASTM D95 or ASTM E 1417

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Quality check of penetrant materials

Penetrant bull Fluorescent brightness Quarterly Not less than 90of reference standardbull Sensitivity Monthly Equal to reference standardbull Removability (method A water wash only) Monthly Equal to reference

standardbull Water content (method A water wash penetrant only)-Monthly Not to exceed

5bull Contamination Weekly No noticeable tracers Emulsifiersbull Removability Weekly Equal to reference standardbull Water content (method B lipophilic) Monthly Not to exceed 5bull Concentration (method D hydrophilic) Weekly Not greater than 3 above

initial concentrationbull Contamination Weekly No noticeable tracers Developersbull Dry-developer form Daily Must be fluffy not caked

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Quality check of penetrant materialsDry Developer

bull Contamination Daily Not more than ten fluorescent specks observed in a 102 mm (4 in) circle of sample

Aqueous (soluble and suspended) developerbull Wettingcoverage Daily Must be uniformwet and must coat partbull Contamination Daily Must not show evidence of fluorescence

contaminatesbull Concentration Weekly Concentration shall be maintained as

specifiedOther

bull Black lights Daily Minimum 1000 microwattcm2 at 381 mm (15 in)bull White light Weekly Minimum 200 lx (20 ftc)bull System performance Daily Must equal reference standards

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Physical and Chemical Characteristics

bull Chemical stability and uniform physical consistencybull A flash point not lower than 95 degC (200 degF)bull Penetrants that have lower flash points constitute a

potential fire hazardbull A high degree of wettabilitybull Low viscosity to permit better coverage and minimum

drag outbull Ability to penetrate discontinuities quickly and

completelybull Sufficient brightness and permanence of color

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Physical and Chemical Characteristics

bull Chemical inertness with materials being inspected and with containers

bull Low toxicity to protect personnelbull Slow drying characteristicsbull Ease of removalbull Inoffensive odorbull Low costbull Resistance to ultraviolet light and heat fade

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

Chemical stabilitybull Tendency of a material to resist change or

decomposition due to internal reaction or due to the action of air heat light pressure etc

bull The properties of penetrant materials that are controlled by AMS 2644 and MIL-I-25135E include flash point surface wetting capability viscosity color brightness ultraviolet stability thermal stability water tolerance and removability

ultraviolet amp Thermal stability

Excessive heat1 evaporates the more volatile constituents which

increases viscosity and adversely affects the rate of penetration2 alters wash characteristics3 boils off chemicals that prevent separation and gelling of water soluble penetrants4 kills the fluorescence of tracer dyes

2 Generally thermal damage occurs when fluorescent penetrant materials are heated above 71oC

Temperaturebull The temperature of the penetrant materials and the part being

inspected should be from 10 to 49oC (80 to 120oF) bull Surface tension of most materials decrease as the temperature

increases raising the temperature of the penetrant will increase the wetting of the surface and the capillary forces

bull Raising the temperature will also raise the speed of evaporation of penetrants which can have a positive or negative effect on sensitivity

bull The impact will be positive if the evaporation serves to increase the dye concentration of the penetrant trapped in a flaw up to the concentration quenching point and not beyond

bull Freezing can cause separation to occur and exposure to high temperature for a long period of time can affect the brightness of the penetrant dyes

Flash pointbull The evaporation of the volatile constituents of penetrants

can alter their chemical and performance characteristicsbull Resulting in changes in inherent brightness removability

and sensitivity bull Liquid penetrant materials qualified to MIL-I- 25135D

(and subsequent revisions) have a flash point requirement of a minimum of 95 degC

bull Dilution of the penetrant liquid will affect the concentration of the dye and reduce the dimensional threshold of fluorescence

A penetrant must

bull spread easily over the surface of the material being inspected to provide complete and even coverage

bull be drawn into surface breaking defects by capillary action bull remain in the defect but remove easily from the surface of

the part bull remain fluid so it can be drawn back to the surface of the

part through the drying and developing steps bull be highly visible or fluoresce brightly to produce easy to see

indications bull not be harmful to the material being tested or the inspector

Penetrant Color and Fluorescencebull LPI materials fluoresce because they contain one or more dyes that absorb

electromagnetic radiation over a particular wavelength and the absorption of photons leads to changes in the electronic configuration of the molecules Since the molecules are not stable at this higher energy state they almost immediately re-emit the energy

bull Two different fluorescent colors can be mixed to interact by a mechanism called cascading

bull The emission of visible light by this process involves one dye absorbing ultraviolet radiation to emit a band of radiation that makes a second dye glow

bull The measurement of fluorescent brightness is detailed in ASTM E-1135 Standard Test Method for Comparing the Brightness of Fluorescent Penetrantsldquo

bull When using fluorescent penetrants a brightness comparison per the requirements of ASTM E 1417 is also often required This check involves placing a drop of the standard and the in-use penetrants on a piece of Whatman 4 filter paper and making a side by side comparison of the brightness of the two spots under UV light

Penetrant Color and Fluorescencebull The degree of fluorescence response under a given intensity of

ultraviolet radiation is dependent on the absorption of ultraviolet radiation which in turn depends on dye concentration and film thickness

bull Beers Law states that the intensity of the transmitted energy is directly proportional to the intensity of the incident light and varies exponentially with the thickness of the penetrant layer and its dye concentration Therefore when the dye concentration is increased the brightness of the thin layer of penetrant generally increases

bull A Meniscus-Method Apparatus can be used to measure the dimensional threshold of fluorescence

Function of developersbull Increase the brightness intensity of fluorescent

indications and the visible contrast of visible-penetrant indications

bull The developer also provides a blotting action which serves to draw penetrant from within the flaw to the surface spreading the penetrant and enlarging the appearance of the flaw

bull Decreases inspection time by hastening the appearance of indications

Developer propertiesbull The developer must be adsorptive to maximize blottingbull It must have fine grain size and a particle shape that

will disperse and expose the penetrant at a flaw to produce strong and sharply defined indications of flaws

bull It must be capable of providing a contrast background for indications when color-contrast penetrants are used

bull It must be easy to applybull It must form a thin uniform coating over a surface

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Temperaturebull The temperature of the penetrant materials and the part being

inspected should be from 10 to 49oC (80 to 120oF) bull Surface tension of most materials decrease as the temperature

increases raising the temperature of the penetrant will increase the wetting of the surface and the capillary forces

bull Raising the temperature will also raise the speed of evaporation of penetrants which can have a positive or negative effect on sensitivity

bull The impact will be positive if the evaporation serves to increase the dye concentration of the penetrant trapped in a flaw up to the concentration quenching point and not beyond

bull Freezing can cause separation to occur and exposure to high temperature for a long period of time can affect the brightness of the penetrant dyes

Flash pointbull The evaporation of the volatile constituents of penetrants

can alter their chemical and performance characteristicsbull Resulting in changes in inherent brightness removability

and sensitivity bull Liquid penetrant materials qualified to MIL-I- 25135D

(and subsequent revisions) have a flash point requirement of a minimum of 95 degC

bull Dilution of the penetrant liquid will affect the concentration of the dye and reduce the dimensional threshold of fluorescence

A penetrant must

bull spread easily over the surface of the material being inspected to provide complete and even coverage

bull be drawn into surface breaking defects by capillary action bull remain in the defect but remove easily from the surface of

the part bull remain fluid so it can be drawn back to the surface of the

part through the drying and developing steps bull be highly visible or fluoresce brightly to produce easy to see

indications bull not be harmful to the material being tested or the inspector

Penetrant Color and Fluorescencebull LPI materials fluoresce because they contain one or more dyes that absorb

electromagnetic radiation over a particular wavelength and the absorption of photons leads to changes in the electronic configuration of the molecules Since the molecules are not stable at this higher energy state they almost immediately re-emit the energy

bull Two different fluorescent colors can be mixed to interact by a mechanism called cascading

bull The emission of visible light by this process involves one dye absorbing ultraviolet radiation to emit a band of radiation that makes a second dye glow

bull The measurement of fluorescent brightness is detailed in ASTM E-1135 Standard Test Method for Comparing the Brightness of Fluorescent Penetrantsldquo

bull When using fluorescent penetrants a brightness comparison per the requirements of ASTM E 1417 is also often required This check involves placing a drop of the standard and the in-use penetrants on a piece of Whatman 4 filter paper and making a side by side comparison of the brightness of the two spots under UV light

Penetrant Color and Fluorescencebull The degree of fluorescence response under a given intensity of

ultraviolet radiation is dependent on the absorption of ultraviolet radiation which in turn depends on dye concentration and film thickness

bull Beers Law states that the intensity of the transmitted energy is directly proportional to the intensity of the incident light and varies exponentially with the thickness of the penetrant layer and its dye concentration Therefore when the dye concentration is increased the brightness of the thin layer of penetrant generally increases

bull A Meniscus-Method Apparatus can be used to measure the dimensional threshold of fluorescence

Function of developersbull Increase the brightness intensity of fluorescent

indications and the visible contrast of visible-penetrant indications

bull The developer also provides a blotting action which serves to draw penetrant from within the flaw to the surface spreading the penetrant and enlarging the appearance of the flaw

bull Decreases inspection time by hastening the appearance of indications

Developer propertiesbull The developer must be adsorptive to maximize blottingbull It must have fine grain size and a particle shape that

will disperse and expose the penetrant at a flaw to produce strong and sharply defined indications of flaws

bull It must be capable of providing a contrast background for indications when color-contrast penetrants are used

bull It must be easy to applybull It must form a thin uniform coating over a surface

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Flash pointbull The evaporation of the volatile constituents of penetrants

can alter their chemical and performance characteristicsbull Resulting in changes in inherent brightness removability

and sensitivity bull Liquid penetrant materials qualified to MIL-I- 25135D

(and subsequent revisions) have a flash point requirement of a minimum of 95 degC

bull Dilution of the penetrant liquid will affect the concentration of the dye and reduce the dimensional threshold of fluorescence

A penetrant must

bull spread easily over the surface of the material being inspected to provide complete and even coverage

bull be drawn into surface breaking defects by capillary action bull remain in the defect but remove easily from the surface of

the part bull remain fluid so it can be drawn back to the surface of the

part through the drying and developing steps bull be highly visible or fluoresce brightly to produce easy to see

indications bull not be harmful to the material being tested or the inspector

Penetrant Color and Fluorescencebull LPI materials fluoresce because they contain one or more dyes that absorb

electromagnetic radiation over a particular wavelength and the absorption of photons leads to changes in the electronic configuration of the molecules Since the molecules are not stable at this higher energy state they almost immediately re-emit the energy

bull Two different fluorescent colors can be mixed to interact by a mechanism called cascading

bull The emission of visible light by this process involves one dye absorbing ultraviolet radiation to emit a band of radiation that makes a second dye glow

bull The measurement of fluorescent brightness is detailed in ASTM E-1135 Standard Test Method for Comparing the Brightness of Fluorescent Penetrantsldquo

bull When using fluorescent penetrants a brightness comparison per the requirements of ASTM E 1417 is also often required This check involves placing a drop of the standard and the in-use penetrants on a piece of Whatman 4 filter paper and making a side by side comparison of the brightness of the two spots under UV light

Penetrant Color and Fluorescencebull The degree of fluorescence response under a given intensity of

ultraviolet radiation is dependent on the absorption of ultraviolet radiation which in turn depends on dye concentration and film thickness

bull Beers Law states that the intensity of the transmitted energy is directly proportional to the intensity of the incident light and varies exponentially with the thickness of the penetrant layer and its dye concentration Therefore when the dye concentration is increased the brightness of the thin layer of penetrant generally increases

bull A Meniscus-Method Apparatus can be used to measure the dimensional threshold of fluorescence

Function of developersbull Increase the brightness intensity of fluorescent

indications and the visible contrast of visible-penetrant indications

bull The developer also provides a blotting action which serves to draw penetrant from within the flaw to the surface spreading the penetrant and enlarging the appearance of the flaw

bull Decreases inspection time by hastening the appearance of indications

Developer propertiesbull The developer must be adsorptive to maximize blottingbull It must have fine grain size and a particle shape that

will disperse and expose the penetrant at a flaw to produce strong and sharply defined indications of flaws

bull It must be capable of providing a contrast background for indications when color-contrast penetrants are used

bull It must be easy to applybull It must form a thin uniform coating over a surface

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

A penetrant must

bull spread easily over the surface of the material being inspected to provide complete and even coverage

bull be drawn into surface breaking defects by capillary action bull remain in the defect but remove easily from the surface of

the part bull remain fluid so it can be drawn back to the surface of the

part through the drying and developing steps bull be highly visible or fluoresce brightly to produce easy to see

indications bull not be harmful to the material being tested or the inspector

Penetrant Color and Fluorescencebull LPI materials fluoresce because they contain one or more dyes that absorb

electromagnetic radiation over a particular wavelength and the absorption of photons leads to changes in the electronic configuration of the molecules Since the molecules are not stable at this higher energy state they almost immediately re-emit the energy

bull Two different fluorescent colors can be mixed to interact by a mechanism called cascading

bull The emission of visible light by this process involves one dye absorbing ultraviolet radiation to emit a band of radiation that makes a second dye glow

bull The measurement of fluorescent brightness is detailed in ASTM E-1135 Standard Test Method for Comparing the Brightness of Fluorescent Penetrantsldquo

bull When using fluorescent penetrants a brightness comparison per the requirements of ASTM E 1417 is also often required This check involves placing a drop of the standard and the in-use penetrants on a piece of Whatman 4 filter paper and making a side by side comparison of the brightness of the two spots under UV light

Penetrant Color and Fluorescencebull The degree of fluorescence response under a given intensity of

ultraviolet radiation is dependent on the absorption of ultraviolet radiation which in turn depends on dye concentration and film thickness

bull Beers Law states that the intensity of the transmitted energy is directly proportional to the intensity of the incident light and varies exponentially with the thickness of the penetrant layer and its dye concentration Therefore when the dye concentration is increased the brightness of the thin layer of penetrant generally increases

bull A Meniscus-Method Apparatus can be used to measure the dimensional threshold of fluorescence

Function of developersbull Increase the brightness intensity of fluorescent

indications and the visible contrast of visible-penetrant indications

bull The developer also provides a blotting action which serves to draw penetrant from within the flaw to the surface spreading the penetrant and enlarging the appearance of the flaw

bull Decreases inspection time by hastening the appearance of indications

Developer propertiesbull The developer must be adsorptive to maximize blottingbull It must have fine grain size and a particle shape that

will disperse and expose the penetrant at a flaw to produce strong and sharply defined indications of flaws

bull It must be capable of providing a contrast background for indications when color-contrast penetrants are used

bull It must be easy to applybull It must form a thin uniform coating over a surface

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Penetrant Color and Fluorescencebull LPI materials fluoresce because they contain one or more dyes that absorb

electromagnetic radiation over a particular wavelength and the absorption of photons leads to changes in the electronic configuration of the molecules Since the molecules are not stable at this higher energy state they almost immediately re-emit the energy

bull Two different fluorescent colors can be mixed to interact by a mechanism called cascading

bull The emission of visible light by this process involves one dye absorbing ultraviolet radiation to emit a band of radiation that makes a second dye glow

bull The measurement of fluorescent brightness is detailed in ASTM E-1135 Standard Test Method for Comparing the Brightness of Fluorescent Penetrantsldquo

bull When using fluorescent penetrants a brightness comparison per the requirements of ASTM E 1417 is also often required This check involves placing a drop of the standard and the in-use penetrants on a piece of Whatman 4 filter paper and making a side by side comparison of the brightness of the two spots under UV light

Penetrant Color and Fluorescencebull The degree of fluorescence response under a given intensity of

ultraviolet radiation is dependent on the absorption of ultraviolet radiation which in turn depends on dye concentration and film thickness

bull Beers Law states that the intensity of the transmitted energy is directly proportional to the intensity of the incident light and varies exponentially with the thickness of the penetrant layer and its dye concentration Therefore when the dye concentration is increased the brightness of the thin layer of penetrant generally increases

bull A Meniscus-Method Apparatus can be used to measure the dimensional threshold of fluorescence

Function of developersbull Increase the brightness intensity of fluorescent

indications and the visible contrast of visible-penetrant indications

bull The developer also provides a blotting action which serves to draw penetrant from within the flaw to the surface spreading the penetrant and enlarging the appearance of the flaw

bull Decreases inspection time by hastening the appearance of indications

Developer propertiesbull The developer must be adsorptive to maximize blottingbull It must have fine grain size and a particle shape that

will disperse and expose the penetrant at a flaw to produce strong and sharply defined indications of flaws

bull It must be capable of providing a contrast background for indications when color-contrast penetrants are used

bull It must be easy to applybull It must form a thin uniform coating over a surface

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Penetrant Color and Fluorescencebull The degree of fluorescence response under a given intensity of

ultraviolet radiation is dependent on the absorption of ultraviolet radiation which in turn depends on dye concentration and film thickness

bull Beers Law states that the intensity of the transmitted energy is directly proportional to the intensity of the incident light and varies exponentially with the thickness of the penetrant layer and its dye concentration Therefore when the dye concentration is increased the brightness of the thin layer of penetrant generally increases

bull A Meniscus-Method Apparatus can be used to measure the dimensional threshold of fluorescence

Function of developersbull Increase the brightness intensity of fluorescent

indications and the visible contrast of visible-penetrant indications

bull The developer also provides a blotting action which serves to draw penetrant from within the flaw to the surface spreading the penetrant and enlarging the appearance of the flaw

bull Decreases inspection time by hastening the appearance of indications

Developer propertiesbull The developer must be adsorptive to maximize blottingbull It must have fine grain size and a particle shape that

will disperse and expose the penetrant at a flaw to produce strong and sharply defined indications of flaws

bull It must be capable of providing a contrast background for indications when color-contrast penetrants are used

bull It must be easy to applybull It must form a thin uniform coating over a surface

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Function of developersbull Increase the brightness intensity of fluorescent

indications and the visible contrast of visible-penetrant indications

bull The developer also provides a blotting action which serves to draw penetrant from within the flaw to the surface spreading the penetrant and enlarging the appearance of the flaw

bull Decreases inspection time by hastening the appearance of indications

Developer propertiesbull The developer must be adsorptive to maximize blottingbull It must have fine grain size and a particle shape that

will disperse and expose the penetrant at a flaw to produce strong and sharply defined indications of flaws

bull It must be capable of providing a contrast background for indications when color-contrast penetrants are used

bull It must be easy to applybull It must form a thin uniform coating over a surface

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Developer propertiesbull The developer must be adsorptive to maximize blottingbull It must have fine grain size and a particle shape that

will disperse and expose the penetrant at a flaw to produce strong and sharply defined indications of flaws

bull It must be capable of providing a contrast background for indications when color-contrast penetrants are used

bull It must be easy to applybull It must form a thin uniform coating over a surface

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Developer propertiesbull It must be non fluorescent if used with fluorescent penetrantsbull It must be easy to remove after inspectionbull It must not contain ingredients harmful to parts being

inspected or to equipment used in the inspectionbull It must not contain ingredients harmful or toxic to the

operatorbull The fine developer particles both reflect and refract the

incident ultraviolet light allowing more of it to interact with the penetrant causing more efficient fluorescence The developer also allows more light to be emitted through the same mechanism This is why indications are brighter than the penetrant itself under UV light

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Developer Forms

bull Form A dry powderbull Form B water solublebull Form C water sus-pendiblebull Form d Non-aqueous Type 1 Fluorescent

(Solvent Based) bull Form e Non-aqueous Type 2 Visible Dye

(Solvent Based)

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Form A dry powder

bull Most common application by dusting or sprayingbull Only a portion of the surface of a large part applying

with a soft brush is adequatebull Dry developer does not provide a uniform white

background as the other forms of developers dobull Least sensitive but it is inexpensive to use and easy to

apply bull Excessive powder can be removed by gently blowing on

the surface with air not exceeding 35 kPa or 5 psi(max 20psi) or by shakinggentle tapping

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Form A dry powderbull Widely used with fluorescent penetrants but should not be used

with visible dye penetrants because they do not produce a satisfactory contrast coating on the surface of the work piece

bull It should be light and fluffy to allow for ease of application and should cling to dry surfaces in a fine film

bull powders should not be hygroscopic and they should remain dry bull If they pick up moisture when stored in areas of high humidity

they will lose their ability to flow and dust easily and they may agglomerate pack or lump up in containers or in developer chambers

bull Dry-developer form inspected daily Must be fluffy not caked

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Safety requirement

bull Handled with care because it can dry the skin and irritate the lining of the air passages causing irritation

bull Rubber gloves and respirators may be desirable if an operator works continuously with this

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Water-soluble developers (form B)bull It can be used for both type I or type II penetrantsbull It is not recommended for use with water-washable

penetrants because of the potential to wash the penetrant from within the flaw if the developer is not very carefully controlled

bull Supplied as a dry powder concentratebull Dispersed in water from 012 to 024 kgL bull The bath concentration is monitored for specific

gravity with hydrometerbull They should never be applied with a brush

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Water-suspendible developers (form C)

bull It can be used with either fluorescent (type I) or visible (type II) penetrants

bull With fluorescent penetrant the dried coating of developer must not fluoresce nor may it absorb or filter out the black light used for inspection

bull supplied as a dry powder concentrate which is then dispersed in water in recommended proportions usually from 004 to 012kgL

bull Specific gravity checks should be conducted routinely using a hydrometer to check the bath concentration

bull aqueous wet developers can cause leaching and blurring of indications when used with water-washable penetrants

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Water-suspendible developers (form C)

bull It contains dispersing agents to help retard settling and caking as well as inhibitors to prevent or retard corrosion of work pieces

bull It contains biocides to extend the working life of the aqueous solutions

bull It contains wetting agents to ensure even coverage of surfaces and ease of removal after inspection

bull They should never be applied with a brush

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Dryingbull Drying is achieved by placing the wet but well drained part in a

recirculating warm air dryer that is thermostatically controlled with the temperature held in between 65-95 degree celcious

bull The temperature of the work piece should not be permitted to exceed 70 degree celcious(160 F)

bull Excessive drying at high temp can impair the sensitivitybull If the parts are not dried quickly the indications will be blurred and

indistinct bull Properly developed parts in water soluble developer will have an

even pale white coating over the entire surface bull The surface of a part coated with a water suspendable developer

will have a slightly translucent white coating

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Advantages

bull Not require any agitation in water soluble but water suspendable developers require frequent stirring or agitation to keep the particles from settling out of suspension

bull Applied prior to drying thus decreasing the development time

bull The dried developer film on the work piece is completely water soluble and is thus easily and completely removed by simple water rinsing

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Non-aqueous solvent-suspendible developers (form D)

bull used for both the fluorescent and the visible penetrant process

bull This coating yields the maximum white color contrast with the red visible penetrant indication and extremely brilliant fluorescent indication

bull Supplied in the ready-to-use condition and contain particles of developer suspended in a mixture of volatile solvents

bull It also contain surfactants in a dispersant whose functions are to coat the particles and reduce their tendency to clump or agglomerate

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Non-aqueous solvent-suspendible developers

bull Most sensitive form of developer used with type I because the solvent action contributes to the absorption and adsorption mechanisms

bull It enters the flaw and dissolves into the penetrant This action increases the volume and reduces the viscosity of the penetrant

bull There are two types of solvent-base developersbull nonflammable (chlorinated solvents) and flammable

(non-chlorinated solvents) Both types are widely used

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Non-aqueous solvent-suspendible developers

bull Since the solvent is highly volatile forced drying is not required bull A non-aqueous developer should be applied to a thoroughly dried part

to form a slightly translucent white coating bull If the spray produces spatters or an uneven coating the can should be

discarded bull Plastic or lacquer developers are special developers that are primarily

used when a permanent record of the inspection is required bull Application by spraying either with aerosol container or by electrostatic

method Dipping pouring brushing are not suitable for applying solvent suspendible developer

bull Min recommended developing time is 10 min regardless of the developer used The developing time begins immediately after application of the developer

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

FUSIBLE WAX DEVELOPERbull A high-sensitivity high-resolving power inspection penetrant developer in

which the active developing ingredient is a waxy substance which is a solid or near-solid at room temperature but which becomes fluid at slightly elevated temperatures

bull The waxy developer material may be dissolved in a suitable carrier liquid such as water or other inert volatile solvent and is deposited on test parts by dipping brushing or spraying and allowing the carrier liquid to evaporate

bull When heat is applied to the test parts during oven drying or by heating subsequent to air-drying the waxy developer layer becomes a fluid and a liquid-film dilution expansion type development of penetrant entrapments in surface defects then takes place

bull When the test parts cool to room temperature the fluid waxy layer which now contains developed defect indications solidifies and prevents excessive bleeding and migration of the indications

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Sensitivity ranking of developers

Ranking123456789

10

Developer FormNonaqueous Wet Solvent

Plastic FilmWater-Soluble

Water-SuspendableWater-Soluble

Water-SuspendableDryDryDryDry

Method of ApplicationSpraySpraySpraySpray

ImmersionImmersion

Dust Cloud (Electrostatic)Fluidized Bed

Dust Cloud (Air Agitation)Immersion (Dip)

Sensitivity ranking of developers per the Nondestructive Testing Handbook Sensitivity Ranking (highest to lowest) Developer Form Application Technique

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Developer Advantages Disadvantages

Dry Indications tend to remain brighter and more distinct over timeEasily to apply

Does not form contrast background so cannot be used with visible systemsDifficult to assure entire part surface has been coated

SolubleEase of coating entire part

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Coating is translucent and provides poor contrast (not recommended for visual systems)

Indications for water washable systems are dim and blurred

SuspendableEase of coating entire part

Indications are bright and sharpWhite coating for good contrast can be produced which work well for both visible

and fluorescent systems Indications weaken and become diffused after time

Nonaqueous

Very portableEasy to apply to readily accessible surfaces

White coating for good contrast can be produced which work well for both visible and fluorescent systems

Indications show-up rapidly and are well defined Provides highest sensitivity

Difficult to apply evenly to all surfacesMore difficult to clean part after inspection

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Stationary Inspection Equipment

The type of equipment most frequently used in fixed installations consists of a series of modular subunits bull Drain andor dwell stationsbull Penetrant and emulsifier stationsbull Pre- and post-wash stationsbull Drying stationbull Developer stationbull Inspection stationbull Cleaning stations

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Developer

bull Developer Station The type and location of the developer station depend on whether dry or wet developer is to be used

bull For dry developer the developer station is downstream from the drier but for wet developer it immediately precedes the drier following the rinse station

bull For wet there should also be a rack or conveyor on which parts can rest after dipping This will permit excess developer to run back into the tank

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Developerbull Suspendible developer baths settle out when not in use

therefore a paddle for stirring should be provided Continuous agitation is essential because the settling rate is rapid

bull Pumps are sometimes incorporated into the developer station for flowing the developer over large work pieces through a hose and nozzle and for keeping the developer agitated

bull In automatic units special methods of applying developer are required Flow-on methods are frequently used

bull This technique requires a nozzle arrangement that permits the work pieces to be covered thoroughly and quickly

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Inspection Stationbull Inspection station is simply a worktable on which work

pieces can be handled under proper lightingbull For fluorescent methods the table is usually surrounded by

a curtain or hood to exclude most of the white light from the area

bull For visible-dry penetrants a hood is not necessarybull Generally black (ultraviolet) lights (100 W or greater) are

mounted on brackets from which they can be lifted and moved about by hand

bull Because of the heat given off by black lights good air circulation is essential in black light booths

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Black light Intensity

bull UV ranging from 180 to 400 nanometers bull Recommended black light intensity is 1000 to 1600

microwattcm2bull The intensity of the black light should be verified at regular

intervals by the use of a suitable black light meter such as a digital radiometer

bull Warm up prior to use--generally for about 10 min bull UV light must be warmed up prior to use and should be on for at

least 15 minutes before beginning an inspection bull The inspector should allow time for adapting to darkness a 1-min

period is usually adequate bull White light intensity should not exceed 20 lx (2 ftc) to ensure the

best inspection environmentbull Switching the lamp on and off shorten the bulb life

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Black light Intensity

bull Penetrant dyes are excited by UV light of 365nm wavelength and emit visible light somewhere in the green-yellow range between 520 and 580nm

bull The source of ultraviolet light is often a mercury arc lamp with a filter

bull UV emissions below 310nm include some hazardous wavelengths

bull Bulbs lose intensity over time In fact a bulb that is near the end of its operating life will often have an intensity of only 25 of its original output

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Effect of UV lightbull Excessive UV light exposure can cause painful sunburn

accelerate wrinkling and increase the risk of skin cancer

bull UV light can cause eye inflammation cataracts and retinal damage

bull Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength where penetrants are designed to fluoresce

bull UV lamps sold for use in LPI application are almost always filtered to remove the harmful UV wavelengths

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

visible light intensity

bull visible light intensity should be adequate to ensure proper inspection 320 to 540 lx (30 to 50 ftc) is recommended

bull Lighting intensity should be verified at regular intervals by the use of a suitable white light meter such as a digital radiometer amp it should be calibrated at least every six months

bull Ultraviolet light measurements should be taken using a fixture to maintain a minimum distance of 15 inches from the filter face to the sensor

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Dimensional Threshold of Fluorescencebull The performance of penetrants based on the

physical constraints of the dyes can be predicted using Beers Law equation This law states that the absorption of light by a solution changes exponentially with the concentration of the solution

bull This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables

bull It = Io x e-lCt

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Dimensional Threshold of Fluorescence

Where It = Transmitted light intensityIo = Incident light intensitye = Base of natural log (271828)l = Absorption coefficient per unit of concentrationC = Dye concentrationt = Thickness of the absorbing layer controlled to a certain degree by the concentration of the fluorescent tracer dye in the penetrant

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Removabilitybull Dilution of the penetrant liquid will affect the concentration of

the dye and reduce the dimensional threshold of fluorescence bull The adhesive forces of the penetrant must be weak enough

that they can be broken by the removal methods used However in order for the penetrant to have good surface wetting characteristics the adhesive forces (forces of attraction between the penetrant and the solid surface being inspected) must be stronger than the cohesive forces (forces holding the liquid together) Proper formulation of the penetrant materials provides the correct balancing of these forces

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Post cleaning

bull Some residue will remain on work pieces after penetrant inspection is completed

bull Residues can result in the formation of voids during subsequent welding or unwanted stop-off in brazing

bull In the contamination of surfaces (which can cause trouble in heat treating) or in unfavorable reactions in chemical processing operations

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Post cleaning

bull ultrasonic cleaning may be the only satisfactory way of cleaning deep crevices or small holes However solvents or detergent-aided steam or water is almost always sufficient

bull The use of steam with detergent is probably the most effective of all methods

bull It has a scrubbing action that removes developers the heat and detergent remove penetrants it leaves a work piece hot enough to promote rapid even drying and it is harmless to nearly all materials

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Post cleaning

bull Vapor degreasing is very effective for removing penetrants but it is practically worthless for removing developers

bull It is frequently used in combination with steam cleaning

bull If this combination is used the steam cleaning should always be done first because vapor degreasing bakes on developer films

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Probability of detectionIn general penetrant inspections are more effective at finding bull small round defects than small linear defectsbull deeper flaws than shallow flawsbull flaws with a narrow opening at the surface

than wide open flawsbull flaws on smooth surfaces than on rough

surfaces

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

IndicationsTypical source of contaminations are -

Penetrant on hands of operators Contamination of wet and dry developer Penetrant rubbing off an indication on the specimen to a clean portion of

the surface of another specimen Penetrant spots on the inspection tableNon-relevant indications include those that appear on articles that are Press fitted keyed splined riveted or spot welded together and those appearing on casting as a result of loosely adherent scale or a rough surface due to burned in sand The most common source of false indication is poor washing of water

washable and post emulsified penetrants Penetrant inspection provides only indirect indications or flaws it cannot

always be determined at first glance whether an indication is real false or non-relevant A real indication is caused by undesirable flaw such as crack

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

True Indication

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Flaws revealed by PTbull Hot tears shrinkage crack open to the surfacebull Cold shutsfoldsinclusionlaps open to surfacebull Crater cracks ndash characteristics star shapedbull Pipe- irregular shapebull Grinding cracks- tight shallow randombull Fatigue crack-tightbull Stress corrosion cracks- tight to open

Non-relevant Indicationbull weld spatter scuff marks press-fit interference

braze runoff burrs etc

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Inspection

bull If developer films are too thick if penetrant bleed-out appears excessive if the penetrant background is excessive the work piece should be cleaned and reprocessed

bull One of the most accurate ways of measuring indications is to lay a flat gage of the maximum acceptable dimension of discontinuity over the indication If the indication is not completely covered by the gage it is not acceptable

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

Evaluationbull Each indication that is not acceptable should be evaluated It may be worse

than it appears it may be false or real Common method of evaluation includes-

bull Wipe the area of indication with a small brush or clean by cloth that is dampened with a solvent

bull Dust the area with a dry powder or spray it with a light coat of non-aqueous developer

bull Re-measure under appropriate lighting for the type of penetrant usedGenerally quality standards for the type of discontinuity detected by penetrant are established by following methods Adoption of standards that have been successfully used for similar work pieces Evaluation of the results of penetrant inspection by Destructive Examination Experimental and theoretical stress analysis

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

ASTM STANDARDSbull ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Methodbull ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination Using the

Lipophilic Post-Emulsificationbull Processbull ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the Water-

Washable Processbull ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the

Hydrophilic Post-Emulsificationbull Processbull ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the Solvent-

Removable Processbull ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent

Penetrantsbull AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component Maintenancebull ASME SEC V ASME Boiler and Pressure Vessel Code Section V Article 6bull MIL-STD-6866 Military Standard Inspection Liquid Penetrantbull MIL-STD-410 Nondestructive Testing Personnel Qualifications amp Certificationsbull MIL-I-25135 Inspection Materials Penetrant

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III

If you have any queries can contact wwwomndtorg or drop mail to

omndtcenterrediffmailcom

ThanksMAHESH PANDITASNT NDT L-III