Pressure Reducing Valve
A pressure reducing valve is the element that keeps a sub-circuit fed from the main system at a lower and constant pressure. Unlike a relief valve, it regulates not the inlet pressure but the outlet pressure. Typically 20-40 bar is used in pilot circuits, and lower values in brake and clutch circuits.
The valve continuously measures the pressure in the outlet line. When the set value is reached it throttles the passage and holds the outlet constant; when demand rises it opens again. This way a 30 bar pilot circuit can be fed from a system operating at 200 bar.
- Difference from a relief valve: a relief valve limits inlet pressure by dumping the excess to tank; a reducing valve targets the outlet pressure.
- Drain: most types have a separate drain line and it must return to tank without pressure.
- Application area: pilot supply, clamping and holding circuits, attachment protection lines.
On machines with pilot operated valves this element indirectly determines how far the motion opens: when pilot pressure drops the main spool cannot complete its full stroke and motion slows down. In electronic lever control this is one of the hydraulic side causes behind the complaint "I opened the lever fully but the speed is not enough."
Where this term is used: How Are Manual Hydraulic Levers Controlled Remotely? A Comparison of 6 Methods