Don’t paint gas pipe

ChrisJ

Bob Harper said:

ChrisJ said:

Bob Harper said:

First of all, the IFGC/ NFPA 54 both call for 3 psi x 10 min. or 10x the maximum working pressure. Since most gas controls allow for 14 wci/ 0.5 psi that takes you to 5 psi. The test gauge cannot be greater than 5x the test pressure. At low pressure, that means a 25 psi gauge. At 90 psi, that's a 450 psi gauge. How big must a leak be for a 450 psi gauge's needle to move in 10 min. vs. the low pressure? The low pressure test is MUCH more accurate at finding small leaks. A large leak will be evident right away.
What if an unpainted pipe passes a 10,000 psi test then gets acid spilled on it? Does the high pressure test prevent changes to the piping? The test should be based upon the test conditions at the time. Painting protects the pipe. Sch. 40 pipe is not going to be adversely affected by surface corrosion. The paint inhibits further corrosion. Most shutoff valves are rated for 5 psi. The high pressure test can blow valve seats and bonnet seals thus causing a leak. You have to isolate appliance controls valves when testing > 14 wci. by disconnecting the piping and capping it.

I don't know about the 5X thing for gauges, but the way you worded that was the gauge cannot be larger than 5X. For me, testing 100 psi I'd want a 150 to 200 psi gauge.

How much gas has to leak for you to be able to detect a leak on a 200 psi gauge? In the lab, they use a Bubble-O-Meter on gas valves to detect ultra low level leaks. A gas combination valve is tested to ANSI stds. allowing 235 cc/hr through the valve's main operator and 215 cc/hr through the seals of the valve. Humans can detect the odorant in the gas that equates to a level of about 1-2 ppm. This means a leak at a level of about an ounce per year. Not gonna see that kind of leak manifesting as needle deflection on a high psi gauge. Low level leaks are detected at ultra-low pressures. Medium level leaks are detected by low psi gauges. Very high pressure leaks can be detected by sound, smell, high psi gauges and the inability to even get up to test pressure on a low psi gauge. A leak that requires 89 psi will be so bad that you will easily detect it using lower pressure gear. It's simply stupid. All this does not require an electronic gas sniffer or anything else. High pressure testing endangers the public rather than protecting.

Hi Bob,

I'm a bit confused, so I'd like to respectfully ask for some clarification.
If you have a leak that causes a 25 psi gauge to noticeably drop with a 5 psi test in 10 minutes, are you saying that the leak will still leak at the same rate at 100 PSI?, and therefore will not move the higher pressure gauge?