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Colour contrast penetrant systems sensitivity comparison

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Written by Administrator
Tuesday, 01 June 2010 14:02

End of January, beginning '80s. A phone call from a user well aware of PT, MT, ET (Eddy current Testing) and UT (Ultrasonic Testing). This man is in charge of NDT in a company manufacturing huge gas turbines, vapour turbines and alternators.

- ‘‘I would like to let you know what we have been showed today.

Though we do not use your colour contrast PT materials we know them very well. Today a manufacturer new on the market came to show us his materials. He chose to compare his products with yours.’’

Comment: the products chosen as "reference" were the ones used in something as 90% of the French nuclear industry. Then EDF, the French Electricity Board, was commissioning a new nuclear power-plant every 4 months. Further the plants already in-service were maintained every 6 months, and these colour contrast PT materials (degreaser, penetrant and non-aqueous wet developer) were THE system to use.

The demonstration went very well for the new materials. Nichrome panels were used, and the new materials gave very clear indications while the reference system gave only poor results: indications were visible, but faint and as dotted lines in some areas.

The salesman was laughing:

- ‘‘You know that the reference system has a huge share of the market; but we have a tremendously far more sensitive system and my company should replace these renowned products quite soon.’’

I was impressed and began wondering how this could be. The salesman was very confident and began to pack up products, panels, etc., when an idea surged:

- ‘‘Please, let me have a look to your test panels’’.

The salesman's face suddenly stopped smiling. He was reluctant but finally I could have a look at the panels. The panel he used for his system was a 50 µm panel (*) while the one used for the reference system was a 30 µm one.

Though this man did not use our system at that time, he took time to phone us. The story is that we have not been the alone he phoned to, and the optimistic salesman was "blown" and his unfortunate company also in the NDT world!

When you get a fantastic demonstration, try to have some reasonable view of everything, take time to think just to be sure that you are not a plain sucker, good enough to pay for a miserable equipment.

(*) Nichrome panels come in four cracks dimensions: the so-called 50 µm panel has cracks 50 µm deep. Cracks width is 1/20 maximum of the depth: that means 2.5 µm maximum for this panel.
• The so-called 30 µm panel displays cracks 30 µm deep and 1.5 µm maximum wide.
• The so-called 20 µm panel: 20 and 1 µm maximum respectively.
• The so-called 10 µm panel: 10 and 0.5 µm maximum respectively.

Reference

(*) ISO 3452-3:1998 Non-destructive testing -- Penetrant testing -- Part 3: Reference test blocks, International Organization for Standardization, Geneva, Switzerland, 1998.


In the '60s a UK Company had a motto: "For every surface treatment problem, there is a product xxxxxx" (trademark we do not display).

Engineers and Commercial people in this Company had made a "translation": "With every surface treatment product xxxxxx (trademark we do not display), there is a problem".


This anecdote is there only to remind everyone that problems met in workshops may be due to the suppliers/manufacturers as well as to the users.

Our idea in these documents is NOT to target anyone, but on the contrary to bring to your knowledge some interesting cases which may prevent you to duplicate the same mistakes while performing Penetrant Testing (PT) or Magnetic Testing (MT).

All the ministories you will read are TRUE. We think they will be helpful:
• First as examples of specific technical --or non-technical-- requirements or peculiar problems.
• Second to let you see that the problems do not always come where you think they should come from.
• Third so that users feel free to ask for help from people (the experts) who may know more than they do.

Last Updated ( Thursday, 19 May 2011 20:37 )