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Certificates of halogens and sulphur analysis

Written by Administrator
Wednesday, 01 April 2009 08:27

In France many years ago the first PT materials user to ask for low in sulphur and low in halogens materials was a major aircraft equipment manufacturer.

During an International Conference on Aircraft Industry in the '70s, one of us asked an other European major manufacturer:
- "What about analysis of PT materials for halogens and sulphur contents?"
Our host very honestly replied:
- "In fact we don't worry, it's far too expensive!"

Could you believe it?

This requirement seemed useless to some people, though it became soon evident that, due to the specific alloys used in turbine engines and nuclear plants, it should be a major concern.

Indeed testing for these chemicals does not come for cheap.

The induced cost may be quite heavy when batches are small and material price quite low: dry developers match exactly this situation.

On the other hand when batches are very large the analysis cost is spread on a very large quantity and the cost per liter/gallon is marginal. This applies to fluorescent penetrants in bulk or to colour contrast penetrants or non-aqueous wet developers (NAWD), either in bulk or in spray cans.

In the '70s these analyses may be performed in-house by the manufacturer/supplier or subcontracted to independent laboratories.

Materials used in the French CNPE (nuclear utilities) shall be analysed only by laboratories agreed by ÉLECTRICITÉ DE FRANCE (EDF). Cost as well as delivery time may be somewhat different depending on the labs.

PT materials suppliers first opted for issuing a separate invoice for this service; but many customers did not want to endorse the additional cost, stating that this should be paid for by the primes.

Some customers had primes in aerospace industry and/or in nuclear industry as well as primes not at all involved in these areas, and were reluctant to pay for two stocks of PT materials (one coming with analyses and an other without) or for analysed PT materials used for primes not interested in these analyses.

So more and more the PT suppliers chose to "spread" the analyses costs on every liter/gallon or kilogram/pound of all the materials they manufactured. This made the products manufactured in small quantities to bear an acceptable additional cost while price of the products manufactured in huge quantities was almost not increased.

One interesting question is: did the manufacturers/suppliers play fair?

In fact the following examples are here as food for thought. There are supposed to no longer exist. But future papers will help you to be alerted to some ... unfair practices.

One manufacturer manufactured one satisfactorily batch, and then gave the same batch number to several additional batches.

One manufacturer whose certificates stated only "typical figures: less than ..." without any mention of the real figure for the specific batch.

One manufacturer which nevertheless stated its halogenated products (solvents and NAWD) met the EDF less than 200 ppm requirement, after evaporation when the EDF specification is very clear: no evaporation allowed before analyses. Analyses shall be performed on the product as supplied.


By the way what is a batch?

The EDF definition is: the quantity manufactured in one tank (which may as small as a 10-liter/2 gal can, or as large as a 10,000 litres/2,645 US gal/2,200 Imp gal tank, or even large) at the same time. That means a new batch number shall be given, and new analyses performed, if some raw materials are poured in the tank even if not empty. This to prevent the following process:

As long as the same raw materials with the same batch numbers are used to manufacture, say, a penetrant, the same batch number is given to the product ... and no additional analyses are performed!

More and more primes go to their materials suppliers plants to take samples for future analysis, and samples are taken from DELIVERED products and analysed. These cross-checks are discouraging enough to have these examples as old stories only.

But are we so sure that analyses always give the right figures?
A future paper will again make you think twice!

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 ( Friday, 20 May 2011 08:34 )