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Quotation: 50 € - Expense: 1.5 million €!

Written by Administrator
Wednesday, 01 July 2009 09:56

When a 50 € (35 £, 75 $) quotation becomes a 1.5 million € (1.05 m£, 2.25 m$) expense.*

*Note: prices have been adjusted to current prices

In the '80s a manufacturer of large aeroengine parts asked its penetrant materials supplier how to improve working conditions in the penetrant booth. They wanted us to install a far more powerful exhaust system.

1- The current situation

On arrival, we asked some questions. The fluorescent water-washable penetrant was electrostatically sprayed in a large booth, something like as 6 meters long, 6 meters wide and 4 meters high. Operators complained about a "penetrant cloud" making it quite uncomfortable to work in the booth, even with respiratory masks.

We decided to go to the booth and to see the real working conditions.

A rolling cart with a 2 meter-dia. part on was put in place. Doors closed. The operator began spraying the fluorescent penetrant, and quickly, that's true, the booth was full of fluorescent aerosols, though the exhaust fan was extracting vapour. And an impressive quantity of penetrant was dropping from the bottom of the part to the ground--lost for nothing.

This exhaust fan was quite powerful, as when it was put in the "ON" position, the booth's walls moved a bit inward. Fresh air taken from the workshop, out of the booth, was without doubt going in: our legs felt it!

2- The culprit

A look to the manometer measuring the pressure of the compressed air used to push the penetrant in the reservoir immediately gave us the answer: pressure was a bit more than 100 kPa (1 bar, 14.5 psi). The major part of the sprayed penetrant did not go to the part but in the air!

We asked why such a high figure, when 20 to 30 kPa (0.2 to 0.3 bar) would probably be enough. We were told that low figures would not be efficient; further a prime's procedure asked for at least 100 kPa (1 bar) for the "pushing air".

We suggested to do as we thought it right. Using a 30 kPa (0.3 bar) pressure every bit of the part's surface was covered, there was almost no penetrant dropping from the part. And no penetrant cloud at all! Everyone in the booth was enthusiastic. Problem solved!

3- Three weeks later

Three weeks later we were again close to the plant. A phone call made it possible for us to come back to the booth, very confident that everyone was still happy. Surprise! We were told that the situation was as bad as previously!

A quick survey in the booth led us to the culprit: again the air pressure! The manometer was again set at a bit more than 100 kPa (1 bar)! We explained that three weeks before, tests carried out at 30 kPa (0.3 bar) had been very successful indeed.

-"Why this coming back to 100 kPa (1 bar)?"

-"We work here in 2 shifts. You met the morning shift, but when the afternoon shift came and saw the meter at 30 kPa (0.3 bar), they adjusted it to 100 kPa (1 bar), and finally, as it is written in the prime's procedure."

We explained that the prime's procedure may be valid for one specific electrostatic spray gun, but may be wrong for others. We explained also that the result, i.e. the complete covering of the part, was as good with 30 kPa (0.3 bar) as with 100 kPa (1 bar), that the working conditions were far better, penetrant consumption far lower, that the waste water installation would have less penetrant to retain.

4- An incredible discussion

The person in charge of the installation nevertheless asked for a more powerful installation. We explained that a more powerful exhaust installation would need a reinforcement of the booth, as the structure would crash due to the depression of the equipment. Another point to consider was that in winter, having a far larger volume of air extracted would mean a similar larger volume of outside cold air entering the workshop to compensate for the air drawn by the booth: more calories, a higher air speed in the workshop. Add to this the stronger noise, vibrations.

-"So, Sir, what do you suggest?"

-"I suggest that a washer be put in the compressed air line to make it impossible to have more than 30 kPa (0.3 bar) (dynamic, i.e. when pushing the penetrant) in the reservoir. If you need some invoicing, say we put that at 50 €."

-"Well, Sir, technically, it is very interesting. But we have asked last year our boss to fund about 1.5 M€ for this booth refurbishment/exhaust system improvement. We got the authorisation some weeks ago. It is now impossible for us to tell that a 50 € device would make it!! Sorry!"

Incredible? No, real life!

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 10:18 )