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When I was just out of High school I worked for a utility company and we ran miles of 3/4" black pipe. I was always told the top pressure was 175 PSI, but the working pressure was much lower. This seemed more like a "working rule" rather than anything scientific. For high pressure we always used heavy wall pipe and fittings. In my own shop I use 3/4" pipe for all my perimeter air lines and run it at 135 psi with no problems. Good luck and be careful.
I was surprised to hear, from a local gas utility man once, that gas pressure within the pipe was only 4 psi. this isn't really on point, but it bears that out by referring to pipe capacities with pressures over 5 psi. So I wouldn't assume that existing gas piping could handle high pressure air for example.
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I saw ones made out of pvc before online, and that setup used hairspray and an ignitor or something similiar. They one they made and I made has a chamber to store the air between two valves. Open the first on to fill with air, close that when the gauge shows whatever pressure I want, the the second valve to release the air.
Mine is 4" & 2" sched 80 tubing, sched 40 fittings, grill ignitor to long reach fine tip NGK spark plug.
I built it about 12 years ago, & couldn't count the number of shots!
I would recomend a healthy tight wrap of duct tape around the tube bottom, as added insurance. It can't hurt, & may prevent a blow out!
The pressure of the black pipe you are looking at is normaly rated at 700 psi
What limits the rating is the pressure rating of the fittings used with it
150# WOG, Water, Oil, Gas Black or galv.- 125# steam sch40 A53cw pipe