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PCP's and Operating Pressures

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scion19801:
Try being next to an airbag blowing out on a fully loaded double axle dump truck and being next to it in a car with driver window down as it makes a low angle declining sharp turn into a work area.. Big BOOM and pressure wave. Scared the kids in the car, and had them crying.

sharpend:
To weigh in with some personal experience. Pressure vessels are regulated by DOT because these vessels are (can be/ may be) transported on the roads, and require routine re-cert, every 5-10 yrs. Re-cert of a cylinder involves filling the vessel with water completely so little airspace remains, placed inside of a steel water jacketed test apparatus, and the pressure brought up to the 5/3 testing pressure with regard to 3000psi (edit: sorry, mixing units here...nee 200 bar) aluminum cylinders, that being 5000 psi. The water jacket of the test apparatus has a sight glass by which is measured the expansion of the tank, and expansion beyond a certain point will fail a tank, typical cause being metal fatigue. I had a 80cf Luxfer fail and it was a loud pop, rather than an explosion that would have destroyed our building, because there there is little gaseous air in the apparatus, water being incompressible. That being said, I had an instructor at Pearl Harbor who was doing some home mixing of decompression gas, and suffered catastrophic failure of cylinder that totally destroyed the back side of his officer's billet. One more story. I replaced our LPG tanks (edit: 2 LPG tanks) at our house last year. Typically LPGs are certified for twelve years, after which need re-cert, or destroy the tank (by stamping out the cert date and serial #). I have two 9 gal LPGs and when one is empty I drive it into town and get filled. Down the road, just before twelve year service life expires, I will fill both and dope one of them permanently in place at the house. I will buy one new LPG tank, which is transported over the road to get filled, while old fixed tank supplies needs for a day or two. Switch back to newer tank after getting filled. By my estimates, current average gas usage, the old fixed tank will last about another 8 years before empty, that cylinder never transported over the road and presented to the LPG station for refill, which will refuse service because out of cert hydro. Hydro from the Greek, because tested water-filled in water jacket to DOT specs. I have come across oxy tanks collared with "Curtis-Wright" and mfg dates from WWII, with a long list of hydro dates stamped around the shoulder. Anyway, I shoot a Gauntlet 25 and stock 13ci cylinder, and routinely overfill to 3300psi and allow cooling from the adiabatic heating, while loading mags, resetting targets, &c. Just saying, if you are nice to your cylinders and never intend to have someone else fill your cylinders, nor transport on public roads, then a hydro down the road, well....

Mark

scion19801:
iirc tanks 2" in diameter and under never need hydro or recertification. All tanks above this diameter need it every 5 years.

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