entrapped air during pressure test
entrapped air during pressure test
(OP)
I'm seeking good technical info regarding how entrapped air effects pressure water or pressure sewer pipelines. In particular, assuming not all air is evacuated, what could happen during a static leakage test? How will gaskets behave versus the pipe wall? Since air is compressible, will the actual pressure in the pipeline be what is showing on a pressure gauge? Any experience to share or good texts to recommend?





RE: entrapped air during pressure test
J. D. Jackson B.S. M.E. & B.S. E.E.
TransContinental Engineering
RE: entrapped air during pressure test
I will always invalidate a short test (less than 4 hours) that behaves like it has air in the system. I will use judgement on invalidating a 24 hour test because of air, but the decision will usually be a re-test.
The best technique I've found is for my test procedures to include a 24-48 hour soak time (where it is reasonable to add test liquid) before the test begins. This lets evolving air get vented out high-point vents during the soak period (like JDJackson says, if you don't have them, install them) and most systems can pass a test the first time.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
RE: entrapped air during pressure test
Best regards
Morten
RE: entrapped air during pressure test
RE: entrapped air during pressure test
Best regards
Morten
RE: entrapped air during pressure test
I've seen this tried with pretty poor success. There are 2 problems here: (1)any pig will have some bypassed flow and you really can't predict the mix of fluids ahead of the pig and (2) most of the problem with tests is disolved air in the liquid that evolves out during the soak period. Just filling the line is usually pretty effective at shifting the air that was in the pipe prior to the test.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
RE: entrapped air during pressure test
Also foam pigs will negotiate quite tight bends.
Stephen A