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Introduction to Non Destructive Testing

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NDTAbility

to detect the condition of the object without destroying the functionality of the object BASIC METHODS Visual Inspection - VT Penetrant Testing - PT Magnetic Particle Testing- MT Ultrasonic Testing - UT Radiographic Testing - RT

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Visual Inspection

Inspection object surface visually is called Visual Inspection May or may not use accessories Gauges for identifying the dimensions of surface Magnifying glasses Borescope for internal inspection Thermal chalks, Thermocouple, for the temperature measurement Etching for checking surface condition

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Etchingfor

identification of gross metallurgical discontinuity such as in welds. For detecting the surface opening Fore runner to Penetrant Testing Different Etchants available for different metals

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Advantages & DisadvantagesAdvantages Simple Less training required Relatively less costly equipment Disadvantages Slow Inspector Fatigue is more Surrounding environmental factors are important

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Penetrant InspectionIs

a method that reveals discontinuities open to surface by the seepage of a liquidpenetrant medium into a surface open discontinuity which seeps out after removing the excess penetrant revealing the discontinuity

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Stages of Penetrant TestingPre

cleaning Application of penetrant Dwell Time Cleaning of Excess penetrant Application of Developer Inspection Post Cleaning

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DYE SYSTEMS

SOLVENT REMOVABLE DYE

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DYE SYSTEMS

WATER WASHABLE DYE

POST EMULSIFICATION DYE

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PT Indications

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Penetrant TestingAdvantages Simple method Easy to train personnel Cheap Quick Disadvantages Onlyopen defects can be detected

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Magnetic Particle TestingWhen

a ferromagnetic material is magnetised the flux lines flow inside the component When there is a discontinuity in the material there is flux leakage The leakingflux attracts a magnetic medium resulting in an indication.

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Types of magnetisationLongitudinal

Magnetisation Circular MagnetisationAC

Magnetisation DC Magnetisation HWDC magnetisation

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Magnetic Particle TestingCOIL METHOD YOKE METHOD.

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Types of Magnetisation Circular Magnetisation

HEAD SHOT METHOD

PROD METHOD

CENTRAL CONDUCTOR

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Magnetic Particle Testing

PROD METHOD

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MAGNETIC MEDIUMDry Wet Fluorescent Requires Ultra violet lamp in darkened area More sensitive than

Non

Fluorescent

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Magnetic Medium - DryMedium

Dry Medium

microns Mixture of spherical and elongated powders Spherical shape helps in mobility Elongated shape helps in alignment to magnetic field

about 30 50

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DemagnetisationResidual

magnetism affects further operation such as welding. Demagnetisation is preferably done with AC Object is moved slowly away from coil After demagnetisation residual magnetism is checked with gauss meters

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Magnetic Particle TestingPre

- Cleaning Magnetisation Applying magnetic medium Inspection Post cleaning Demagnetization

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MagnetisationMagnetisation

to be applied in two mutually perpendicular direction Magnetic medium to appliedwhen the magnetisation is `ON' Adequacy of field to be checked by field indicator (Pie Gage ) Magnetic medium could be wet or dry / Fluorescent or non-fluorescent

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Advantages & DisadvantagesAdvantages For detecting surface & sub-surface discontinuity Can be tested rapidly Not very costly Relatively less skill required for testing Disadvantages Onlyuseful in ferro-magnetic materials Demagnetisation may be required for many ofthe parts

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Ultrasonic TestingA

beam of high frequency wave is introduced into the test object which gets reflected from the surface of any discontinuity Used to detect and locate the surfaceand internal discontinuities Amplitude of a reflected sound pulse is nearly proportional to the size of the reflector

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Ultrasonic Testing

For Detecting internal flaws For almost all the materials metals, ceramic, rubber, composites etc.. Requires only one side access Portable equipment Non hazardo

us Can test up to about 10 m of steel

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Ultrasonic Testing

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ULTRASONIC TESTING PULSE ECHO TECHNIQUETransducer acts as a pulser and receiver Can detect the location and depth of defect Only one side access is required

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ULTRASONIC TESTING THROUGH TRANSMISSION TECHNIQUE Separate transmitter and receiver Accurate Alignement of transmitter and receiver required Cannot locate the depth of defect

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PROBES

NORMAL BEAM PROBE

DUAL CRYSTAL PROBE

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Location of defectsBP : Beam Path Depth of defect :BP

D = BP Cos a Position of defect P = BP Sin a

IE

DEFECT ECHO

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R diogr phy TestingEmploys

x r ys or g mm r ys to penetr te n object, detect discontinuities by recordingthe difference on recording device For intern l fl ws Perm nent record R di tion S fety is m jor concern

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B sic PrincipleX

r y m chines or Ir 192 or Co 60 m in sources of r di tion Hole type or Wire typepenetr meters used for checking sensitivity of r diogr phSource R di tion

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R diogr phyUses

Penetr meters for ensuring the qu lity of the r diogr phy procedure Penetr meters re hole type nd wire type Sufficient r diogr phic density is required for the r diogr ph for proper ev lu tion

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Techniques

Single W ll Single Im geJob Film Weld

Double w ll Single im geSource R di tion

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Techniques

Double W ll Double Im geJob Film Weld

P nor mic ExposureSource R di tion

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DOUBLE WALL DOUBLE IMAGEASTM Hole Type Penetr meter

SINGLE WALL SINGLE IMAGE

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DIN Wire Type Penetr meterTungsten Tungsten Inclusion Inclusion

PorosityPorosity

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Sl g Inclusion

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POROSITY

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