The plug sits in a matching body bore and turns 90 degrees to open. Lubricated plug valves are sealed by grease-like sealant pumped through a fitting on top, which also frees a stuck plug; non-lubricated versions run the plug in a PTFE sleeve or liner. Eccentric plug valves, which swing the plug face away from the seat as it turns, are common in wastewater and slurry lines.
Gas meter set has a lubricated plug valve, shoot some sealant in it before you try to turn it or you'll twist the stem.
Also heard as
- plug cock
Do not mix it up with
- Ball valve: A ball valve uses a sphere between two seats; a plug valve uses a tapered or cylindrical plug that seals over a large area against the body bore.
Related terms
Ball valve
A quarter-turn valve that opens and closes by rotating a ball with a bore through it.
Seat
The surface inside a valve that the closure member presses against to stop flow.
Stem
The rod that carries motion from the handwheel, lever or actuator through the bonnet to the closure member.
Body
The main pressure-containing shell of a valve, carrying the flow passage and the end connections.