how to test gas pipe tightness
how to test gas pipe tightness
(OP)
As I know, Gas pipe must be tested with air pressure to prove that the pipes are gas tight. Usually a test pressure will be taken for 15mins for in-house pipe, and 24 hours for city distributed pipes. I wonder what kind instrument should be taken for this kind of testing. U-tubes or other manometers are used?





RE: how to test gas pipe tightness
The actual instruments vary, I've seen anything from simple bourdon-tube style pressure gauges (have to be calibrated first, or at least recently) up to 24 hr temperature & pressure chart recorders.
RE: how to test gas pipe tightness
On lines that only require a short duration (1/2 - 1 hour) test, a calibrated gauge is used.
Distribution lines are tested in place so your test bench should be safe.
We typically weld pipe up to the meter and others pipe into the building, but the in building leak tests I have seen were 2 hour at 100psi, again using a calibrated guage.
JTMcC.
RE: how to test gas pipe tightness
I continue to recommend to all young plant engineers not to utilize pneumatic pressure testing on equipment and piping. This is just too hazardous a method as compared with hydrostatic pressure testing. If you have had a reasonable amount of years under your belt and seen the failed attempts at pneumatic testing, you'll know what I'm talking about.
Unless you have a very serious and tough reason for doing a pneumatic test, then I would advise you to seek the lead advice and assistance of an experienced engineer in carrying out this procedure.
Art Montemayor
Spring, TX
RE: how to test gas pipe tightness
He specifically mentioned distribution lines, where the sections tested are almost always small, short and low pressure.
Of course you wouldn't test 500' of 14" to 1500psi using air, that would be almost criminal. But 25' of 3/4", at 100psi is no threat to safety. Even 4000' of 4", under 4' of dirt, at 100psi is harmless, a weld failure will not send pipe flying.
This is done thousands of times every day, a crew fabricates a 25' service from the main at the street to a newly constructed home or business, they put 100psi of air in the service, soap test the joints, wait 30 minutes, and if it holds pressure they go do a couple more.
regards,
JTMcC.