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Well that was kind of my point.... You can bet that somebody, somewhere, has left a QB inside a car at 150*F.... and I would equally bet that had even ONE failed, we would have heard all about it.... To put this in perspective, a properly filled CO2 tank, filled to 100% of its rated capacity by weight, would be close to 3000 psi at 150*F, and by then the 3K burst disc would likely have failed.... If the tank was only 75% full, however, the pressure would be under 2000 psi at the same temperature.... Now don't get me wrong, I'm not suggesting that you store any CO2 gun at 120*F, let alone expose it to 150*F.... However, it is to look after those circumstances that a gun is designed with a large safety margin.... ASME rules for pressure vessels require a 3.5:1 safety margin to burst (ie based on the UTS of the material) above the Maximum Safe Working Pressure (MSWP).... Any vessel over 2" diameter must be Hydrotested on a regular schedule to 5/3 of the MSWP.... For CO2 tanks, they are rated at 1800 psi MSWP, and Hydrotested to 3000 psi, and fitted with a 3K burst disc.... However, the burst pressure for that 1800 psi rating must be at least 6300 psi, giving over a 2:1 safety margin at the point the burst disc lets go.... or inside that 150*F car interior....
I'm not telling everyone to use 1800 psi as their fill pressure on a QB, because some of them don't have the valve sitting against the steel backing block.... The valve only has one mounting screw, but the backing block has two more, and they should ALL be taking the load.... One of those three screws holds down the receiver, so you should never pull the barrel off a QB with gas in it for that reason.... Computer FEA analysis has shown that the flange on the front retaining nut on the tube is the weakest point on a QB78, and depending on the quality of the steel we assume it has a MSWP of about 1700-2000 psi.... The two screws that retain the tank block on a QB79 have an even lower MSWP, but again, we have never seen a failure on CO2.... I do know of one tank block that pulled out by shearing the screws at 2600 psi when the regulator failed, but the action was out of the gun, and the two additional stock screws weren't in place.... Whether they would have prevented the failure is doubtful, but again, we don't see failures in QB79s on CO2....
When I am converting a QB to HPA, I always check the valve to make sure it is against the backing block, and insert a shim if necessary, so all 3 screws share the load.... If I am using more than 1100-1200 psi on a QB79, I install an extra shear pin in the tank block for added safety.... Once I address these obvious, and well known, potential weakest points, on a regulated QB I still use a 1.8K burst disc, which limits my setpoint to less than 1500-1600 psi so that I won't blow the disc.... On a properly inspected and prepared QB78, I would not personally have a problem filling to 1800 psi, but I would not go past that without special modifications to valve and end plug mounting.... The tube itself, assuming mild steel tubing, could fail at as low as 8000 psi, which means that since we don't know what it is made of, 2300 psi would be a safe MSWP.... Having said that, the virtually identical tube on an XS-60c has survived testing to 10,000 psi without failing, although other components failed well before that....
Bob
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!
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