Pressure reducing valves are used to provide a stable pressure to part of a circuit that requires a lower pressure than the pumps supply. This may be required because the actuator or loads are not designed to take the full system pressure. Pilot valves may require a lower pressure to that of the main stage.
Often, particularly in mobile equipment, the pilot pressure control feeds are supplied by pressure reducing valves rather than being limited by relief valves.
Pressure reducing valves don't create pressure, they simply close the flow path to stop the flow when the load pressure reaches the reducing valve's setting. Reducing valves sense the pressure downstream of the valve, unlike relief valves which sense the pressure upstream of the valve.
While reducing valves may be more energy efficient than relief valves they do still convert all of the energy lost from the supply pressure to the set pressure, into heat.
See pressure control valve in our symbols sections for more details.
Pressure reducing valves come in direct and pilot operated versions. Cartridge, platen or line mounted valves are also available.
Some reducing valves have a relief function as well as the reducing function. This means that if the load pressure increases above the reducing valve's setting, it will relieve the pressure from the load.
As with most hydraulic valves the direct operated versions a faster and more dynamic with less internal leakage. The pilot operated versions tend to me more stable and give better characteristics over a higher flow range.
The quality of control and operating environment will probably dictate which design you choose.
Look at the supplier's datasheet to find the most appropriate working range.
Make sure you have good clearance between reduced pressure and any relief valve reset pressures. Don't forget you may have significant pressure drops in pipework and fittings between different valves.
Reducing valves may be set to zero pressure for delivery of equipment.
Make sure all of the air is vented from the circuit before setting.