In a globe valve the disc moves straight down onto the seat; in a swing check it hangs from a hinge; in a butterfly valve it is the rotating plate in the bore; in a safety valve it is held on the nozzle by the spring. Discs may be plug-shaped, flat, ball-shaped or composition-faced. Gate valves call the same part a gate or wedge, and control valves call it a plug.
Disc nut backed off the stem on that globe, so the handwheel turns but nothing's moving.
Also heard as
- disk
- plug
- clapper
Related terms
Seat
The surface inside a valve that the closure member presses against to stop flow.
Globe valve
A linear-motion valve that throttles well because its disc moves straight onto a seat across an S-shaped flow path.
Check valve
A self-acting valve that lets fluid pass in one direction and closes on its own when flow tries to reverse.
Wedge
The tapered closure member of a gate valve that is driven down between two inclined seats to seal.