When a rising-stem gate or globe valve is opened all the way, a collar on the stem lands on the backseat and cuts the stuffing box off from line pressure. That can stop a packing leak and gives a degree of isolation for packing work, although many sites forbid repacking under pressure on the backseat alone. Used as a verb, to backseat a valve means to run it hard open onto that seat.
Backseat it and the packing leak should quit until we can get a clearance to repack it.
Many operators open fully and then back off a quarter turn, so the stem doesn't stick on the backseat and nobody mistakes a jammed valve for a shut one.
Also heard as
- back seat
- backseating
Related terms
Packing
Compressible rings packed around a valve stem to stop process fluid leaking out to atmosphere.
Stem
The rod that carries motion from the handwheel, lever or actuator through the bonnet to the closure member.
Bonnet
The cover that closes the top of a valve body and carries the stem, packing and often the yoke.
Repack
To pull the old packing out of a valve stuffing box and install a new set of rings.