Glossary · Pneumatics and hydraulics
Valve
Also known as: Fluid power valve
German: Ventil
In fluid power and process engineering, a valve is a component that controls the direction, pressure or flow of a fluid by opening, closing or partially obstructing flow paths.
- Fluid power
In one sentence
A valve controls the direction, pressure or flow of a fluid by opening, closing or partly obstructing flow paths.
Example
The hydraulic circuit contains directional control valves for the cylinders, a pressure-relief valve at the pump and check valves for load holding.
How it applies
- Engineering: Fluid power valves fall into directional, pressure, flow and shut-off valves; process valves (control valves, ball valves, butterfly valves) are a related family with their own standards.
- Commissioning: Each valve's function, setting and behavior on loss of energy are checked against the design.
- Maintenance: Valves are common failure points due to contamination, wear and sticking.
- Documentation: Use a consistent labeling scheme so valve labels in circuit diagrams, parts lists, HMI texts and on the machine match. State valve type precisely in texts ("pressure-relief valve", not just "valve") where the function matters for safety.
Fluid power valve vs. process control valve
Fluid power valves control energy flow to actuators. Process control valves regulate the process medium itself, for example flow in a pipeline, and are usually positioned by an actuator and positioner.