Glossary · Pneumatics and hydraulics
Directional control valve
Also known as: Directional valve, Way valve
German: Wegeventil
In fluid power, a directional control valve is a valve that opens, closes or changes the connections between its ports to start, stop or change the direction of flow, described by the number of ports and switching positions, for example 5/2 or 4/3.
- Fluid power
In one sentence
A directional control valve starts, stops or redirects fluid flow by switching connections between ports, e.g. as a 5/2 or 4/3 valve.
Example
A 5/2 solenoid directional control valve extends and retracts a double-acting pneumatic cylinder.
How it applies
- Engineering: Valve designations (ports/positions), center position (closed, exhausted, pressurized) and actuation (solenoid, pilot, manual, spring return) determine machine behavior on power loss. Symbols follow ISO 1219-1.
- Commissioning: The behavior on de-energizing must match what the risk assessment assumed; this is checked in tests.
- Operation: Manual overrides allow valve operation without electrical signals and can cause unexpected motion.
- Documentation: Describe for each valve what the actuator does on loss of power and air, as this defines the Defined safe state of pneumatic and hydraulic axes. Warn about manual overrides and describe when they may be used.
Directional control valve vs. flow-control valve
A directional control valve decides where the fluid goes. A Flow-control valve decides how much flows, and thus the actuator speed.