The unloading valve is a valve that can unload the hydraulic pump under certain conditions. The unloading valve is usually a relief valve with a two-position two-way valve (usually a solenoid valve). Its function is to set the main pressure of the system (oil pump) when not unloading. When in the unloading state (by a two-position two-way valve) Valve action conversion) Pressure oil is directly returned to the tank, and the oil pump pressure drops to approximately zero to achieve some loop control, increase the life of the oil pump, and reduce power consumption. In the loop, it is incorporated into the loop. The pressure reducing valve is used to adjust the pressure required by the actuator. It is connected in series in the circuit and generally cannot be used interchangeably.