RT Inspection

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ROSI = Radiographic Onstream Inspection

A radiographic technique often used in refineries, offshore

platforms and various piping systems

Radiographic Onstream Inspection


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Detection of:ErosionCorrosionDepositsForeign Objects

Calculation of corrosion rates withperiodic ROSI inspections

Applications for ROSI


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Typical ROSI inspection areas

Applications for ROSI


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Radiography uses the properties of electromagnetic radiation

Radiography uses penetrating radiation that is directed towardsthe component to be inspected.

The component stops some of the radiation. The amount thatis stopped or absorbed is affected by material density andthickness differences.

These differences in absorption can be recorded on film, orelectronically.

ROSI basic principles


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SFD

D incl. isoleringD

Radiation source

Detector/film

D D incl insulation

ROSI inspection setup

SFD: Source to Film Distance

Minimum 3 times pipe diameter



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Measuredthickness

Penetrated thickness



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Commonly used radiation sources

Ir 192 < 75 mm Co 60 < 175 mm

Above values are penetrated thickness in the pipe chord, insulation excluded



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Films

High speed films E.g. Kodak Cx, Agfa D7 eller D8 are used.

Filmsize depends on the specific job.

Often one or more 30 x 40 cm films per exposure



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Screens

Increases sharpness

Reduces scattered radiation

Screen thickness 0,1 0,2mm lead when using Ir192.

Screen thickness 0,5 2,0mm lead when using Co60

For special applications 0,25 0,7mm steel screens canfurther improve sharpness.



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Diameter Thickness Source Media Insulation Time (CR) Time (film)

4" 8-11 mm Co60/20Ci Grey Water 100 mm 1,25 min 13 min

6" 11 mm Co60/20Ci Grey Water 100 mm 2,5 min 26 min

8" 11 mm Co60/20Ci Grey Water 100 mm 4 min 37 min

10" 18 mm Co60/20Ci Grey Water 100 mm 14 min 104 min12" 22 mm Co60/20Ci Grey Water 100 mm 30 min 230 min

16" 9,5 mm Co60/20Ci Grey Water 100 mm 4 min 48 min

4" 9 mm Ir192/24Ci Water none 2,5 min 15 min

4" 12 mm Ir192/24Ci Water none 3,5 min 22 min

6" 12 mm Ir192/24Ci Water none 4,2 min 25 min8" 9 mm Ir192/13.8Ci Water none 4,3 min 24 min

8" 8 mm Ir192/16.8Ci Diesel 80 mm 3 min 20 min

10" 8,5 mm Ir192/13.8Ci Water none 6,6 min not possible

12" 7 mm Ir192/13.8Ci Water none 9,1 min not possible

20" 20 mm 7.5 MeV Water none 2,5 min not possible

On-stream Exposuretimes



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Inspection of 2 valve

Film

Source



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Inspection of 8 pipe bend

Film

Source



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True thickness

Depicted thickness

R = Reduction factor



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Technique is not limited by material type or density.

Can inspect assembled components in operation

No surface preparation required.

Sensitive to changes in thickness, corrosion, voids and materialdensity changes.

Detects both surface and subsurface defects. Provides a permanent record of the inspection.

Parts with relatively high temperature can be inspected

ROSI Advantages


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Many safety precautions for the use of high intensity radiation.

Many hours of technician training prior to use.

Access to both sides of sample required.

Orientation of equipment and flaw can be critical.

Sensitive to vibrations in the part being examined.

Expensive initial equipment cost.

ROSI Disadvantages


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Danish authorities allow thesemaximum doserates:

At barrier: 0.06 mSv/h

At operator: 0.02 mSv/h

At controlled area: 0.0075mSv/h

Radiation warning barrier

Radiation Safety


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Film badge small piece of photographic filmin holder worn by worker. When processedwill indicate received dose by film density.

Geiger Counter - Indicates dose rate by measuringionisation of gas in sealed tube. Typically usedwhen making barrier.

Pocket dosimeters - are used to provide the wearerwith an immediate reading of his or her exposure tox-rays and gamma rays. As the name implies, theyare commonly worn in the pocket.

Radiation Safety


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There are three means of protection to helpreduce exposure to radiation:

Radiation Safety


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Measurement of remainingwallthickness

ROSI testing examples


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Detection of pipe defects



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Detection of deposits in pipe bend



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Detection of foreign objectsin pipe



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External corrosion



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External corrosion behind bracket



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FilmRadiografi

CRRadiografi

ROSI Digital Radiography


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Raw data Processed data Contrast andBrightness



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Advantages

Reduced exposure times

less radiation/higher productivity

High dynamic range

Reusable/no film costs

No need for darkrooms andchemicals/no special vehicles

Possibility for image processing

semi- or full automatic pro-cedures/reproducibility and higheraccuracy

Easy storage, retrieval and distribution

Easy sharing of information

Disadvantages

Expensive equipment

Image plates sensitive to dust andscratches

Storage and backup

hardware

Sensitive to scattered radiation

filtering



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4 Valve

6 Valve



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6 months old pipe bend 6 with a nominalthickness of 10.9 mm

Exposed with a 20 Ci Co60

Filled with grey water 200 degrees, noinsulation

Typical exposure time 2.5 min with CR and 17min with Agfa D7 film



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Radiographic Onstream Inspection

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