Safety Valve

[MrPotatoHead]

I am building my second launcher. It is another pneumatic. The chamber consists of a end cap and a sleeve that actually but up to one another, so the entire chamber is double walled.

What kind of pressure would be safe to go up to? Normally I would install a 125psi safety valve. But was thinking maybe I should not limit myself on this one because it is fully double walled, except for the barrel. I would imagine that it is not as important on the barrel as the pressure is only exhausting through it.

[benstern]

What size pvc pipe did you use? I would say a max of 200 psi if you use pressure rated pvc.

[MrPotatoHead]

Sorry good point. 3" chamber and yes pressure rated PVC, but can't remember the psi off the top of my head.

The only way i could see the barrel becoming the weak link is if some how the projectile gets logged in the barrel, but then again pressure would drop due to the expanded volume size.

[Shrimphead]

Let's see a pic of the gun.

[MrCrowley]

yeah i wouldnt go over 175psi myself but thats up to you.

[M3NT4L]

Like crowly said please do not exeeed 175 because you are risking too much and besides if you dont have a compressor is a btch to pump it. The safety popoff is unnessesary because with a psi gauge why would you need one its not like you will just go over 125 accidentaly, all it will do is restrict you from pumping over 125.

[Shrimphead]

Are the fittings on the chamber double-walled in any way? That's why I wanted to see a pic of the gun.

[MrCrowley]

even if they are double walled the first layer of pipe can still crack under pressure, can't it?

[Velocity]

Yeah it can. Unless the two layers are completely, 100% together (essentially forming 1 very thick piece of pipe), double-walls will not do anything. As soon as the first one blows, it will simply blow through the outer wall

[frankrede]

the second wall may help reinforce it liek when you blow up a balloon with it in your fist,maybe I dont know

[Hotwired]

Yes if the inner pipe expands a little under pressure so it presses against the outer pipe the outer pipe can help deal with the force.

The tighter they fit together the better though.