6 pound air test vs. 10 foot head water test?

I am not am not a Mechanical but have some limited experience. All of my work is in Civil. I have been proposed a question and am seeking some professional advice.
Is a 10-foot head water test comparable to a 6 pound air test for mechanical piping? The piping is located in an underfloor area. Additionally, are there cost benefits associated with the tests?

 

[TD2K]

Are you asking if that puts the same pressure on the piping?

If so, the answer is that the two pressures are close but not exact. 10 feet of water head is just over 4 psi (4.3 to be more precise).

The cost benefit as I see it is to find any leaks before everything is closed up and started up. Then, it's much more expensive to fix them.

Caution, I'm sort of a lurking process engineer so there 'may' be some code issues that I'm not familar with.

 

[KernOily]

There are Code issues involved here. To which code is your system designed and built?

Thanks!
Pete
P. J. (Pete) Chandler, PE
Mechanical, Piping, Thermal, Hydraulics
Processes Unlimited International, Inc.
Bakersfield, California USA
pjchandl@prou.com

 

[pmover]

Comanche1,
Suggest using water instead of air for static testing. Should there be a defect in system or a leak, the system pressure will rapidly decrease (not cause a lot of damage to surroundings) or leaks will easily be spotted. I know of a situation whereby a large pressure vessel was tested using nitrogen and a catastrophic failure occurred, resulting in signficant injuries to personnel and equipment. I know this does not answer your question, but something for you to consider.
pmover

 

[kstaylor]

A 10-15 psig air test is pretty standard for leak testing welds. Some sort of soap solution is used and visual inspection of each "soap tested" weld will quickly determine if there are any through-wall cracks or pin holes as soap bubbles will form in the vicinity of these defects. If leaks are found, repairs can be accomplished after depressuring the system once initial inspection has been completed. The advantage of air-soap testing welds over filling the system with water and applying a small head to the system is that draining the water may be problematic, especially if there are no low point drains.

Note neither of these procedures constitute a "pressure test" as required by most piping Codes. The stress applied by either procedure is much too low compared to a 150% hydrotest or a 110% pneumatic test as required by ASME B31.3 for example.