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DPCNews 041 - Methods and techniques in NDT / Reference test blocks check / PT: a badly-designed oven
December 2011
Our redesigned monthly DPCNewsletter draws your attention on the papers published on this Website at the same time, or reminds you of some papers already published (all of them are still available!) on the same topics as those dealt with in the new papers.
The URL address of our Website is:
http://www.ressuage-magnetoscopie-penetranttesting-magnetictesting-dpc.info
We recommend you put it in your “Favorites” list.
Underneath, find the list of the new papers that you can read this month on our Website:
In the "Edito" section
Methods and techniques in NDT: a quite usual confusion, again
Once again, we have to draw our readers’ attention to some terms used on Websites and in documents, meetings, conferences, training documents, etc.
This month, the topic is "methods" versus "techniques", terms that, although they mean different things, are often used one for the other in Non Destructive Testing (NDT).
Reading this editorial, you will know the real difference between "methods" and "techniques".
In the "NEWS" section
PT reference test blocks check
We have received a very interesting question from a good ol’ friend:
"My question is quite simple: how do we check the modifications (wear) of the test panels used for fluorescent PT?
Do you know of standards or papers (and if so, where can I get them from?), which provide (or allow for the establishing of) a procedure to perform this check? Indeed, according to the PRI (NADCAP) questionnaire, any change in the dimensions of artificial discontinuities shall be less than 30% (further, measured on their longest dimension.) This is for the Tam panel/PSM® 5. However, how should we do for the Type 1 reference test blocks of the ISO 3452-3 standard?
How can one guarantee such an accuracy for the PSM-5 ® smallest defects? By using a binocular magnifier or a microscope? Shall one proceed under UV-A radiation?
Do you think small PT users can process it? Would it be better to require the PT panels’ suppliers to check panels? Alternatively, is it even better to replace the panels regularly, even if their price is a major obstacle? Once a year?
Thank you in advance for your help."
You will find our answer in this paper.
In the "Oldies but goodies" section
Penetrant Testing: a badly-designed drying oven
A short "Oldies but Goodies" story, again about a faulty design. It dates back to the early seventies … yes, an old story! A story for veterans, right.
A well-known French manufacturer of valves for car, truck, and even ship engines had bought a complete penetrant testing line. The valves were inspected using a water-washable fluorescent penetrant and a dry developer, listed in the QPL (Qualified Products List) of the American Military Specification MIL-I-25135 C (ASG), which was in force at that time.
Many parameters on this line, for instance the washing parameters, were … surprising, with a dramatic influence on the quality of detection.
The topic of this month is the drying oven.
In the "Mail inbox" section
Excessive background vs Insufficient background (Overwashing)
Further to our Mail Inbox of November 2011, titled "A too high fluorescent background brightness?" - Which criteria make it possible to claim that the fluorescent background is too high?, in which one of our readers told us that a NADCAP auditor has issued a Non-Compliance Report (NCR) due to a too high background.
We have received a comment from Bob Steffen, Process Engineering Metallurgist, Principal Fellow, an NDT Level 3 who has worked for 30+ years in the aerospace/defense industry.
We, Pierre CHEMIN and Patrick DUBOSC, welcome any comment, any idea. If you have some examples you would like to see discussed here, please give us all the useful indications. If you require confidentially, we would modify locations, names and some parameters to prevent any traceability.
Nevertheless, we are convinced that our site may be a kind of surge-valve: the topic is NOT to target this company, or that auditor; but it is always to make users think, to make them ask themselves, or others, the right questions.
We may also give advice, once again on a confidential basis if needed: please, feel free to ask questions, to document our data basis: about Material Safety Data Sheets (MSDS), about environment, a chemical name you don't understand, a Penetrant process you have heard about, etc.
We have plenty of examples, some being out of all the specifications/standards, which led to the discontinuities detection, when the "current, normal, processes" prevented discontinuity finding.