A flow-control mechanism that opens and closes by moving a stem linearly perpendicular to the sealing surface. When closed, a spring or fluid pressure forces the valve head tightly against a matched circular seat to seal the port. They are used extensively in internal combustion engines to control intake and exhaust gases, and in hydraulic systems where a leak-tight seal is required.
Heard on the job
The engine is losing compression because a piece of carbon is holding the exhaust poppet valve open.
Insider tip
Unlike spool valves, they do not suffer from sliding wear on the sealing surface, making them excellent for high-pressure sealing.
Also heard as
- mushroom valve