Hello,

PRESSURE RELIEF VALVE :

• Normally closed type Valve
• Fitted in bypass line to reservoir tank
• Outlet is connected to reservoir tank
• It opens when the inlet pressure  (System Pressure or Pilot Pressure) becomes more than preset value

PRESSURE REDUCING VALVE :

• Normally Open type Valve
• Fitted in Main line to system
• Outlet is connected to the system
• It closes when outlet pressure( System Pressure or Pilot Pressure) becomes more than Preset value

Hope it helps

Hello,

The function of a pressure relief valve is to limit the maximum pressure in a hydraulic system. It closes normally and opens only when the system pressure exceeds the setting of the pressure relief valve, by releasing pressurized oil to the lower pressure side or tank. Whereas on the other hand, the pressure reducing valve limits the pressure for the system to less than the maximum pressure. It opens normally and closes only when the system pressure at the output of the reducing valve exceeds its set pressure. But if we replace a pressure relief valve with a pressure reducing valve, the required pressure cannot be generated. Because there is no longer the necessary restriction to generate pressure and the flow will be directed to the tank due to their constructional difference.

Hope this helps.

Good luck!