As operating pressure creeps toward set pressure, the net seating force on the disc falls and the seat starts to pass. A simmering valve wastes product, wears the seat, and often fails to reseat cleanly after lifting. The standard fix is to keep operating pressure at about 90 percent of set or lower, or to choose a pilot-operated relief valve that stays tight closer to set.
Steam PSV on the drum is simmering, we're running too close to set, drop header pressure five pounds.
Also heard as
- simmering
Related terms
Safety valve
A spring-loaded pressure relief valve for steam, gas or vapor that opens with a rapid full lift at set pressure.
Pop
For a safety valve to lift suddenly and fully open, discharging with a loud blast at set pressure.
Chatter
Rapid, violent opening and closing of a relief or check valve that hammers the disc against the seat.
Weeping
Leaking a drop or wisp at a time from packing, a gasket, a threaded joint or a casting.