Glossary · Pneumatics and hydraulics
Throttle valve
Also known as: Needle valve, Restrictor valve
German: Drosselventil
In fluid power, a throttle valve is a valve with an adjustable or fixed restriction that reduces flow; the resulting flow depends on the pressure difference across the valve and, in hydraulics, on the fluid's viscosity.
- Fluid power
In one sentence
A throttle valve restricts flow through a fixed or adjustable opening; the flow varies with pressure difference and viscosity.
Example
Throttle-check valves in the exhaust lines of a pneumatic cylinder set its extending and retracting speeds separately.
How it applies
- Engineering: Throttles are simple and cheap; combined with a check valve, they control speed in one direction only (throttle-check valve). Load-dependent speed changes are accepted where precision isn't needed.
- Commissioning: Throttles are adjusted with the real load and locked; exhaust throttling (meter-out) gives smoother pneumatic motion.
- Operation: Hydraulic throttle flow changes as oil warms up.
- Documentation: Mark throttles in the circuit diagram with their function ("speed Y1 extend") and describe adjustment and locking. Note that changing speeds can affect impact forces and the risk assessment.
Throttle valve vs. flow-control valve
A throttle valve's flow depends on pressure. A pressure-compensated Flow-control valve keeps flow largely constant despite pressure changes.
In pneumatic diagrams, identify throttle-check valves by their flow direction so technicians adjust the right one.