A pressure relief valve on a rack receiver lifted during a hot spell and has been losing refrigerant slowly ever since, even though system pressure is now normal. What is the correct repair?
Correct Answer
C) Replace the relief valve, because a valve that has discharged may not reseat
A pressure relief valve is designed to open once and protect the vessel, and it is not guaranteed to seal again afterward. Debris carried past the seat, or distortion of the seat itself, leaves a path that weeps continuously. Adjusting a relief valve destroys its set pressure and its listing, and capping the outlet defeats the safety device entirely. The valve is a replacement item once it has discharged.
Why This Is the Correct Answer
Relief valves are not designed to reseal reliably after they have relieved. Anything that passed the seat can hold it open, and the seat can deform under the discharge. A weeping valve is therefore replaced rather than adjusted, which restores both a tight refrigerant circuit and a working overpressure protection for the receiver.
Why the Other Options Are Wrong
Option A: Tighten the valve down against its seat until the weeping stops
Adjusting a relief valve changes the pressure at which it protects the vessel and voids its listing. It is not a field-adjustable component.
Option B: Leave it in service, since it will reseat once cooler weather returns
The weep will continue in any weather, because it is caused by a damaged or fouled seat rather than by current system pressure.
Option D: Cap the valve outlet so the escaping refrigerant is contained in the system
Capping the outlet disables the vessel's overpressure protection. That converts a refrigerant loss into the possibility of a receiver rupture.
Memory Technique
A relief valve is a one-shot bodyguard. Once it takes the hit, it retires.
Reference Hint
A pressure relief valve that has discharged may not reseat tightly and should be replaced rather than adjusted or capped.
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