Testing Pressure Relief Valves on Quincy compressor

by Josh
(NE)

I was checking the PRV's on our Quincy 5HP Two-Phase 80 gallon compressor. There is one on top of the motor, one at the top of the tank, and one on the side of the tank where the pressure gauge is. I pulled on all three, but only the one on the side of the tank released air, then I pushed it back in. The other two pulled out, but automatically pulled back in, not releasing any air. The motor was not running at this time, but the pressure gauge did read 150psi. Does the motor have to be running and building pressure for the other two PRV's to release air when testing?

Comments for Testing Pressure Relief Valves on Quincy compressor

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Jan 15, 2015
Pressure issue on Quincy
by: Bill

If you think about how the compressor works, in order for it to start more easily on cut in, all the pressure in the pump has to be gone.

The compressed air that's filled the tank, however, isn't something you would want to bleed off before you got a chance to use it.

Therefore, it's the tank check valve keeping the 150 PSI in the tank (which allows you to bleed air when you test the PRV) and it's the unloader valve that ensures that the air pressure still over the piston(s) is gone when the air compressor stops, meaning that there should not be any air pressure in the pump to bleed off when you test the PRV.

Those PRV's are there in case the whole system over pressurizes due to a pressure switch failure.

Bill

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