Pro's and Con's on use of an overpressure relief valve. What do you think? An arborist wants your opinion.

[treehousedan]

I used my air cannon to set pilot lines in the top of trees to pull up my climbing rope but wish to chat about safety.

So for an abundance of caution after reading the pipe manufactures waring about pressuring sch 40/80 pvc pipe makes me wonder just what is a realistic burse pressure. I choose to use 2" sch 80 gray pvc pipe for my air chamber connected to a 1 1/2" ball valve with a tee handle. For a barrel I use an 18" long aluminum tube 48 mm od, 2 mm wall yields 44 mm id which fits a 43 mm golf ball nicely. The valve tee handle is tuff to twist while aiming so I add a short length of 1/2" pipe bolted to each wing that extends to create an easy pull release. My Ryobi battery powered air compressor tool maxes out at 150 psi so I filled with water and just a few cc's of air it held 150 psi all night filled with water. All said I can not see me ever filling to max as 60 psi launches my throwbags plenty high into the tree. All said and done to I add the relief valve or not plus has anyone know about an air cannon bursting?

[mrfoo]

Relief valve might work, might not. PVC doesn't age well. It doesn't like UV. It doesn't like shocks. It doesn't like scratches. It particularly doesn't like cyclic shock loading. Pressure testing it is basically useless - one day it might work fine, and the next day it's a grenade. If you're using it as a tool, my advice would be to use a different air chamber, something that can be realistically pressure tested, and have that testing actually mean something.

[JimmyT]

I used my air cannon to set pilot lines in the top of trees to pull up my climbing rope but wish to chat about safety.

So for an abundance of caution after reading the pipe manufactures waring about pressuring sch 40/80 pvc pipe makes me wonder just what is a realistic burse pressure. I choose to use 2" sch 80 gray pvc pipe for my air chamber connected to a 1 1/2" ball valve with a tee handle. For a barrel I use an 18" long aluminum tube 48 mm od, 2 mm wall yields 44 mm id which fits a 43 mm golf ball nicely. The valve tee handle is tuff to twist while aiming so I add a short length of 1/2" pipe bolted to each wing that extends to create an easy pull release. My Ryobi battery powered air compressor tool maxes out at 150 psi so I filled with water and just a few cc's of air it held 150 psi all night filled with water. All said I can not see me ever filling to max as 60 psi launches my throwbags plenty high into the tree. All said and done to I add the relief valve or not plus has anyone know about an air cannon bursting?

I know a couple guys who had air cannons explode on them. The reason their PVC air tanks exploded wasn't because they pumped it up beyond the rated pressure, but it was due to the tank being compromised in some way. I think one of them hit it against something sharp and it exploded and the other used it in freezing conditions. Both of those explosions would not have been prevented by a pressure relief valve since it would have been set to a much higher pressure than the actual burst pressure of their specific tanks in those situations.