Re: MT Through Paint

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Re: MT Through Paint
Posted by: Martin Lugg , E-mail: martin@tscinspectionsystems.com, on December 12, 2001 at 12:21 :
In Reply to: Re: MT Through Paint posted by : David Hermanutz , E-mail: hermanutzd@ahtpanametrics.com.au, on December 12, 2001 at 06:56 :
: : I am interested in any qualification activities or information regarding magnetic particle testing through paint. We have a particular application where coating removal is costly and difficult. We are considering manufacturing a standard with EDM notches. Any experience?
: .
: : Mike Leger
: : Diablo Canyon Power Plant
: .
: Dear Mike,
.
: The idea of testing through paint is a bit of an issue depending on which regulation authority that is governing your equipment.
.
: Most codes state that MT cannot be done through paint "."
.
: A special prcedure may be developed by a Level 3 MT technician that may be acceptable outside of these realms.
.
: Some key areas to look into:
.
: Maximum thickness of coating (typically most bridge, crane and refinery coatings far exceed what is possible with MT )
.
: Coating material must also be 100% non-ferromagnetic
.
: Coating thickness must be tested in all areas wher MT is to occur. Coating is often much thicker in corners where undercut / cracking is most likely to occur.
.
: Minimum Defect size required.
.
: EDM samples will often be much easier to detect with MT than a real crack. ( EDM are straight narrow and you know where they are vs Cracks which are small crooked and in all sort,s of locations )
.
:
: There are several advanced testing systems that use electrical test methods that could be used instead of MT testing, although they would also have the same qualification difficulties with teh EDM vs real crack specimens.
.
: Eddy Current testing has been adopted into code in the North Sea due to the harsh testing environment. This method is quite effective if the Technician is experienced and trained on eddy current weld testing.
.
: Please feel free to contact PCN or The Welding Institute on their website for this document.
.
: Best Regards,
.
: David Hermanutz
: Panametrics Melbourne
.
Uniform Field electromagnetic techniques, such as ACFM, are even better for this application. The use of a uniform field allows them to work through thicker coatings than conventional eddy current techniques, and also allows the magnetic field to be modelled so that depth sizing does not rely on comparison with slots in calibration blocks.
ACFM is now widely used on painted or coated structures, particularly on welded steel, and for underwater inspection.

Information on ACFM

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Re: MT Through Paint John Hansen 13:21 12/14/2001 (0)

Re: MT Through Paint Dent McIntyre 17:02 12/12/2001 (0)

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: : : I am interested in any qualification activities or information regarding magnetic particle testing through paint. We have a particular application where coating removal is costly and difficult. We are considering manufacturing a standard with EDM notches. Any experience? : : . : : : Mike Leger : : : Diablo Canyon Power Plant : : . : : Dear Mike, : . : : The idea of testing through paint is a bit of an issue depending on which regulation authority that is governing your equipment. : . : : Most codes state that MT cannot be done through paint "." : . : : A special prcedure may be developed by a Level 3 MT technician that may be acceptable outside of these realms. : . : : Some key areas to look into: : . : : Maximum thickness of coating (typically most bridge, crane and refinery coatings far exceed what is possible with MT ) : . : : Coating material must also be 100% non-ferromagnetic : . : : Coating thickness must be tested in all areas wher MT is to occur. Coating is often much thicker in corners where undercut / cracking is most likely to occur. : . : : Minimum Defect size required. : . : : EDM samples will often be much easier to detect with MT than a real crack. ( EDM are straight narrow and you know where they are vs Cracks which are small crooked and in all sort,s of locations ) : . : : : : There are several advanced testing systems that use electrical test methods that could be used instead of MT testing, although they would also have the same qualification difficulties with teh EDM vs real crack specimens. : . : : Eddy Current testing has been adopted into code in the North Sea due to the harsh testing environment. This method is quite effective if the Technician is experienced and trained on eddy current weld testing. : . : : Please feel free to contact PCN or The Welding Institute on their website for this document. : . : : Best Regards, : . : : David Hermanutz : : Panametrics Melbourne : . : Uniform Field electromagnetic techniques, such as ACFM, are even better for this application. The use of a uniform field allows them to work through thicker coatings than conventional eddy current techniques, and also allows the magnetic field to be modelled so that depth sizing does not rely on comparison with slots in calibration blocks. . : ACFM is now widely used on painted or coated structures, particularly on welded steel, and for underwater inspection. .

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