Glossary · Pneumatics and hydraulics
Check valve
Also known as: Non-return valve, One-way valve
German: Rückschlagventil
In fluid power, a check valve is a valve that allows flow in one direction and blocks it in the opposite direction, typically by a ball, poppet or disk pressed onto a seat by a spring or by the reverse pressure.
- Fluid power
In one sentence
A check valve lets fluid flow in one direction and blocks reverse flow, usually with a spring-loaded ball, poppet or disk.
Example
A pilot-operated check valve on a hydraulic cylinder holds the load when the directional valve is in its center position.
How it applies
- Engineering: Check valves prevent backflow, protect pumps and hold loads. Pilot-operated check valves can be opened by a control pressure to allow controlled lowering.
- Commissioning: Installation direction must match the circuit diagram; a reversed check valve blocks the function.
- Maintenance: A check valve that holds a load keeps pressure trapped in the circuit. Before opening lines, that pressure must be released by the documented procedure.
- Documentation: Mark load-holding valves in the circuit diagram and describe how to lower loads and release trapped pressure safely during maintenance. A load-holding check valve is not a substitute for mechanical load securing when people work under a load.
Check valve vs. shut-off valve
A check valve works automatically depending on flow direction. A shut-off valve is actuated deliberately to block flow in both directions.