Throttle / Flow Control Valve
A throttle valve restricts the flow area to limit the flow rate passing through and therefore the actuator speed. In the simple type the flow rate depends on pressure differential as well as area; in the pressure compensated type the flow rate stays constant even when the load changes. All of the throttled energy turns into heat.
There are three common forms, and the choice directly changes behavior:
- Fixed restriction (orifice): non-adjustable, a single hole. Cheap and failure-free, but the flow rate varies with load.
- Adjustable restriction: the area is set with a needle valve; it usually comes with a check valve for free reverse flow.
- Pressure compensated type: contains a stage that holds the pressure differential across the orifice constant; the flow rate becomes independent of load.
The heat calculation must not be overlooked: throttling 20 l/min across a 100 bar drop produces about 3.3 kW of heat. Limiting speed by throttling continuously can upset the system's thermal balance.
This is exactly where proportional lever control offers an alternative. Instead of restricting speed with a permanent orifice, you can reach the target speed by shaping the joystick characteristic and limiting maximum lever travel. Speed is then tuned to the need, and full flow rate remains available when required.
Where this term is used: How Are Manual Hydraulic Levers Controlled Remotely? A Comparison of 6 Methods