A fluid control valve featuring a rotating plug with internal passages that connect four distinct ports. By turning the central plug, an operator or mechanism can cross-connect adjacent lines, reverse flow direction, or isolate specific circuits. While historically common in steam engine cylinder controls, similar four-port rotary designs are used in hydraulic and pneumatic systems to control double-acting cylinders.
Heard on the job
Turn the four-way cock ninety degrees to reverse the pressure to the main cylinder.
Insider tip
In industrial settings, the term cock usually implies a simple manual quarter-turn plug valve, distinguishing it from automated spool valves that perform the same four-way function.
Also heard as
- four-way valve