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February 2011 - Blue light in PT and MT

Written by Administrator
Tuesday, 01 February 2011 20:40

Actinic blue light (A-blue: 400-480 nm) at 440 nm instead of ultraviolet (UV-A) light is currently tested and its use for PT and MT applications is the topic of different meetings.

Some primes are yet careful to limit its use to inspections carried out before the final one, while keeping mandatory ultraviolet (UV-A) light for final inspections. We cannot yet know whether blue light will be accepted for final inspections. Maybe a crystal ball would be helpful!

One of our papers(1) on this Website gives some clues:

‘‘For some cases inspection under a blue light is very useful as it allows for the making of some repair without being in dimmed light areas.

We think that it should be possible to make a quick "first-inspection" under a reasonable level of visible light. On the other hand, inspection "as per the rules" should be performed when looking for indications of very small discontinuities, as reliability of inspection would be affected. The lower the number of useless photons, the better the inspection: quicker, less arduous, hence more reliable.’’

In a paper to come, we will explain how human eyes work, and you may understand it would be a useful step especially to carry out fluorescent penetrant examination without the boring darkness of an inspection booth.

By the way, some changes are made in the 2010 edition of the ASME Boiler and Pressure Vessel Code (BPVC).

Paragraph T-777.3 "Fluorescent Magnetic Particles with Other Fluorescent Excitation Wavelengths" comes now as: "Alternatively to the requirements in T-777.2, the examinations may be performed using alternate wavelength light sources which cause fluorescence in specific particle coatings." and "Any alternate light wavelength light sources and specific particle designations used shall be qualified ..."

Then the question is: who qualifies, and what is the applicable procedure? Auditors won’t be short of work!

Obviously, this point should be considered for any further development, such as when writing new standards/specifications or when revising these documents, but also by the fluorescent materials manufacturers.


ASME ASME's Boiler and Pressure Vessel Code (BPVC), West Caldwell, New Jersey, 2010 Edition.

(1) Patrick DUBOSC and Pierre CHEMIN, Tomorrow's penetrants (follow-up), DPCNEWSLETTER N°021, February 2010 on our Website:

Last Updated ( Thursday, 19 May 2011 15:28 )