Pneumatic vs. Hydrostatic Leak Testing 6

[Puddycat]

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?

 

[zdas04]

When bee smokers started being a problem I proposed running a hose from a small ice chest with a chunk of dry ice in it and using a hose off the drain to direct the "smoke" of sublimation/condensation to indicate any leaks (same way propane works), and some idiot said "we can't purposely release CO2 into the atmosphere". I mumbled "then stop exhaling" and left the meeting never to return.

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

 

[EdStainless]

When I ran vacuum furnaces, and we had one with issues we first pulled a vacuum and tested the joints using butane (a cigarette lighter), after we fixed those we moved on to He.
We never told anyone one that we were testing with butane, the other engineer was a smoker.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[rconner]

While I perhaps sense a little cynicism in this thread, as a matter of fact one can effectively "see" leaks with some applied vacuum, and even e.g. with vacuum applied on the outside e.g. of piping etc. It has reportedly been done, and perhaps even to some extent is codified at least for some purposes in weld inspection (e.g. in AWWA C206 Field Welding of Steel Water Pipe standard), with the use of a contraption referred to and described therein as a "look-box".
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.

 

[mfgenggear]

JUST MY OBSERVATION HERE PUDDyCAT.

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.

 

[tbuelna]

The OP mentioned "helium leak testing at 150psi". I would assume this means a 150psi delta. If the leak being detected is in a welded component, using an inert gas is nice because it won't contaminate the surfaces. On the other hand, using hydrostatic is much safer than using pneumatics for leak testing at high pressures. There are also some leak test fluids that can be easily detected using UV light.