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?
- ATighten 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.
- BLeave 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.
- Replace the relief valve, because a valve that has discharged may not reseat
- DCap 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.
Why C is correct
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.
What this question is testing
This tests the correct disposition of a safety device after it has operated, which sits at the intersection of leak repair and safe service practice. The distractors are all things technicians are tempted to do when a valve weeps on a busy day.
On the job
Relief valve weeps are easy to miss because the discharge is often piped away from the machine and the loss is slow. On a hot roof after a condenser fan failure, a lifted valve can be the whole explanation for a system that has been low ever since. Recording the discharge when it happens and scheduling the valve for replacement is the practice that keeps a one-time event from becoming a season of losses.
Memory technique
A relief valve is a one-shot bodyguard. Once it takes the hit, it retires.
Exam tip
Anything that opened to protect the system is replaced, not readjusted. Never cap a relief path.
Where to look it up
A pressure relief valve that has discharged may not reseat tightly and should be replaced rather than adjusted or capped.