Pneumatic vs. Hydrostatic Leak Testing
Pneumatic vs. Hydrostatic Leak Testing
(OP)
Does anyone have a reference chart that compares equivalency of pressures to detect leaks. For example if I am using a testing medium of Helium @ 150psi to detect leaks, how much hydro pressure would be needed to detect the same leak?





RE: Pneumatic vs. Hydrostatic Leak Testing
We often see thread leaks on pneumatic tests that would not leak on a hydrostatic test at twice the pressure.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Pneumatic vs. Hydrostatic Leak Testing
RE: Pneumatic vs. Hydrostatic Leak Testing
RE: Pneumatic vs. Hydrostatic Leak Testing
If you assume leakage is by diffusion, that too is an easy enough calculation based on constant concentration difference.
However, real leaks are more complex than that.
Detecting a leak consists of two distinct things: 1) getting enough material to leak and 2) having a way to detect what has leaked, and where it's leaking. So equivalent leakage rates are only meaningful if your only means of detection is by watching the pressure drop in a filled system over a period of time.
The difference between water and any gas as a test medium is huge- water is a very dense and vastly more viscous fluid with a huge surface tension (absent entirely from consideration for gases)
RE: Pneumatic vs. Hydrostatic Leak Testing
If we assume that the leak is large enough that molecular diffusion isn't the limiting factor,just think of the ratio of viscosity between the two media. That ratio will be more than 100, and then think of how much water you can detect compared to He.
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P.E. Metallurgy, Plymouth Tube
RE: Pneumatic vs. Hydrostatic Leak Testing
RE: Pneumatic vs. Hydrostatic Leak Testing
RE: Pneumatic vs. Hydrostatic Leak Testing
STF
RE: Pneumatic vs. Hydrostatic Leak Testing
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Pneumatic vs. Hydrostatic Leak Testing
RE: Pneumatic vs. Hydrostatic Leak Testing
My question is : is it possible to calculate a max allowed air pressure drop whilst the water test will be satisfied ?
Any comment will be appreciated. Thanks
RE: Pneumatic vs. Hydrostatic Leak Testing
Much more sensitive than standard hydro.
This was a case where we didn't want to use air because of the stored energy involved.
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P.E. Metallurgy, Plymouth Tube
RE: Pneumatic vs. Hydrostatic Leak Testing
RE: Pneumatic vs. Hydrostatic Leak Testing
Read the OP, boo1.
STF
RE: Pneumatic vs. Hydrostatic Leak Testing
RE: Pneumatic vs. Hydrostatic Leak Testing
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Pneumatic vs. Hydrostatic Leak Testing
Not particularly relevant though. A properly conducted helium test (using a mass spec) will find leaks at very small fractions of the hydrotest pressure that would NEVER leak with water. Don't really think you can make an equivalency..
RE: Pneumatic vs. Hydrostatic Leak Testing
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Pneumatic vs. Hydrostatic Leak Testing
----------------------------------------
The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Pneumatic vs. Hydrostatic Leak Testing
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Pneumatic vs. Hydrostatic Leak Testing
We never told anyone one that we were testing with butane, the other engineer was a smoker.
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P.E. Metallurgy, Plymouth Tube
RE: Pneumatic vs. Hydrostatic Leak Testing
While I don't know of the specific correlations you seek, as others have already stated I suspect at least for many practical circumstances a quite low level of air pressure or vacuum, with careful view or other sensors, may well reveal some VERY small, even if quite high applied hydro-pressure, leak paths.
RE: Pneumatic vs. Hydrostatic Leak Testing
hydrostatic testing I have used for high pressure testing, so if it fails it will not explode. safety factor.
helium works great for testing for leaks with a sniffer. testing welds, bellows, that require sealed leak proof containment.
RE: Pneumatic vs. Hydrostatic Leak Testing