The working principle of this equipment is that a relief valve and a throttle valve are connected in parallel.
Part of the high-pressure oil p1 at the inlet goes to the actuator through the throttle valve, and the other part goes to the tank through the overflow port of the relief valve. The upper and lower ends of the relief valve are connected to the pressure oil p1 and p2 before and after the throttle valve respectively. When the outlet pressure p2 increases, the valve core moves downward, the overflow port is closed, the overflow resistance increases, and the inlet pressure p1 increases accordingly, so the pressure difference (p1-p2) before and after the throttle valve remains basically unchanged; vice versa. That is, the flow rate through the valve is basically not affected by the load.