Al's Annual Inspection Thread 2015

[JamesCH95]

Originally Posted by Thad House

Something Ive always wondered, and I've always gotten different answers to. Is the 125 for the pressure relief valve the pressure it releases to, or the pressure it starts releasing. I've always seen that if its set to never let the pressure go above 125, it usually reliefs down to about 110 psi. If we set it so it wont let the pressure go above 135, if reliefs down to 125. Which method is correct? Some inspectors ive seen want it one way, and some want it another.

Originally Posted by FrankJ

I always set the cracking pressure, the pressure that the relief first opens to 125 PSI. The full flow pressure is somewhat higher. The re-seat pressure is usually somewhat lower. If the pressure is different at inspection, we adjust to accommodate the inspector. It is not a precision device. You do not want the cracking pressure anywhere near the working pressure.

^What this guy said.

The specific wording "... to release air at 125psi..." is the key phrase. Does the valve release air at 125psi (or lower)? If yes, you're good to go. If no, then you're illegal. Thus I would wager your first setup to be correct, where it opens at 125psi and closes at 110psi. Allowing the pressure to reach 135 psi is CLEARLY a violation of the rules [R76] blue box.