Firstly, let's understand the structural diagram of the balance relief valve. The overflow valve mainly consists of a main valve Main poppet and a pilot valve Pilot poppet for pressure regulation, both of which are cone valve structures. The spring of the main valve is very soft and can be easily compressed by hand, but the spring of the pilot valve is very hard and requires the use of adjustment tools to change its compression amount. There is a schematic diagram of a damping hole symbol between the main oil circuit P and the control oil circuit X. By connecting a direct acting relief valve to the control oil port of the main valve, the system pressure can be remotely controlled. If the pressure setting of the remote control valve is lower than that of the pilot valve, the system pressure is determined by the direct acting relief valve; If its setting value is high, it is still determined by the pilot valve. In the following design example, the remote control valve consists of three groups and the relief valve pressure setting value is lower than that of the main valve pilot valve. Any solenoid valve that is powered on will determine the pressure in the system. In the figure, the safe pressure that the system can obtain is 3000 PSI. In the following example, when the solenoid valve is powered on, the pilot valve spring loads the side bypass, allowing the relief valve to operate like an unloading valve, and the system pressure drops to about zero. Some relief valves allow the system pressure to be controlled by controlling the pressure on the spring side. In the example shown in the figure, the internal oil discharge port of the main relief valve is blocked. When the solenoid valve is not powered, the system pressure is still determined by the main valve; When the solenoid valve is powered on, the system pressure will be the sum of the set pressure of the main valve spring and the set pressure of the remote control relief valve.