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"Fridgy" internal pressure relief valve

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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"Fridgy" internal pressure relief valve

Unread postAuthor: c11man » Wed Nov 26, 2014 12:40 am

So after a good amount of time away from spudding, I decided to dig out the old brass/aluminum bearing cannon. And boy was it a good choice!

Anywhoo, I had my small compressor still working so I was set on up to 800psi, but since the duplex I am leasing at school has a nice 240v receptacle in the basement with a walkout door, I wanted to bring out my biggest compressor and get it up and running. At a mere 3.5hp and 90lbs its a tad on the large side (made in 1963 BTW). A bit of sketchy wiring and she roared to life!
Image

A few seconds later and the pressure gauge slowed down and stopped about here
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even though the motor did not slow down nor sound worked at all, it appears that deadspace in the pump head is limiting me to that pressure. So I dug out the air tank and put some pressure on the input to work it a bit more! Easily climbed past the previous pressure quickly but at 475 or so, I hear popping from the compressor and the output keeps dropping to 300 or so psi. I figured I knew the problem and after a bit of research it seems common to have a valve that opens with that kind of pressure differential inside :(

So has anyone else run into this kind of situation with any of your compressors? I know my small rotary compressor does not have one and I assume most standard small fridgys also lack this


Oh and here is my launcher next to it for scale, which is not the smallest
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Re: "Fridgy" internal pressure relief valve

Unread postAuthor: bravootome » Wed Nov 26, 2014 1:45 am

I am not sure i understand the problem, but in that electric box there is a termic resistance meant to stop the motor to overheat . I did canceled the resistance from my comprssor after running for 1 min or so and stopping at a certin pressure......now it's working fine....
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Re: "Fridgy" internal pressure relief valve

Unread postAuthor: c11man » Wed Nov 26, 2014 2:09 am

bravootome wrote:I am not sure i understand the problem, but in that electric box there is a termic resistance meant to stop the motor to overheat . I did canceled the resistance from my comprssor after running for 1 min or so and stopping at a certin pressure......now it's working fine....


The "problem" is that inside of the case, there is a pressure relief valve inside that limits the output to the 450-475psi. motor continues to run, just hear a pop and output pressure drops as it is vented back into the intake.
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