Quantifying Leaks

[pvcguy]

Does anyone have a quick and easy method of quantifying the amount of leaking during a hydrotest using the pressure applied and the pressure drop over a defined period of time. We have hydrotested exchangers and found a pressure drop. The question always is "how big is the leak"?

Thanks

 

[edellison]

the drop of pressure over a period of time would be a good way to describe a leak ,say 50psi/60 minutes. thing to keep in mind is everything leaks, it's just a matter of how much time does it take to see the leakage. to most people it's a pass/fail test or leak/no leak but that isn't really true

 

[PSE]

Along the lines of what edellison indicates:

At a initial test pressure of X, pressure drop may not exceed Y over a time frame of T minutes.

Since you will not necessarily know if the drop is a single leak or multiples, calling out an overall performance specification might be your way to go. You could possibly add a tolerance on the number of visible leaks etc. Of course, make sure your test equipment does not have leaks itself (or qualify them) before performing time based checks.

Regards,

 

[mloew]

pvcguy,

Found this in the FAQ section of Cincinnati Test Systems, Inc.


Question:
How do you decide what is an acceptable leak rate specification?
Answer:
First one must accept that everything leaks something over time. The leakage may be several molecules of gas per year to some higher amount. Once you accept that everything leaks, you must quantify a tolerance amount that meets the part’s functional requirements.
Download application bulletin, AB120, How to Establish an Acceptable Leak Rate Criteria for Automated Testing.

Is this helpful?

I have worked with this supplier in the past.


Best regards,

Matthew Ian Loew
"I don't grow up. In me is the small child of my early days" -- M.C. Escher

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[mloew]

The link is not quite right. Here is one that works:

http://www.cincinnati-test.com/downloads/pdf/app_bulletin/ab120a.pdf

Best regards,

Matthew Ian Loew
"I don't grow up. In me is the small child of my early days" -- M.C. Escher

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[NGiLuzzu]

I would suggest to take also a look at ASME BOILER & PRESSURE VESSEL CODE, Section V "Nondestructive Examination", Article 10 "Leak Testing", Appendix IV "Pressure Change Method".

Hope this helps, 'NGL