Applicable to excavator hydraulic relief valve 723-40-50100

The working principle is:

The pressure of the spring is adjusted and the pressure of the hydraulic oil is controlled. As can be seen from the figure: when the pressure of hydraulic oil is less than the pressure required for work, the spool is pressed by the spring at the inlet of hydraulic oil. When the pressure of hydraulic oil exceeds the allowable pressure of its work, that is, when the pressure is greater than the spring pressure, the spool is jacked up by hydraulic oil, and the hydraulic oil flows in, flows out from the right mouth in the direction shown, and returns to the tank. The greater the pressure of hydraulic oil, the higher the spool is pushed up by hydraulic oil, and the greater the flow of hydraulic oil back to the tank through the relief valve. If the pressure of the hydraulic oil is less than or equal to the spring pressure, the spool falls and seals the hydraulic oil inlet. Because the hydraulic oil output pressure of the oil pump is fixed, and the hydraulic oil pressure of the working cylinder is always smaller than the hydraulic oil output pressure of the oil pump, there will always be some hydraulic oil flowing back to the tank from the relief valve during normal work to maintain the working pressure balance of the hydraulic cylinder and normal work. It can be seen that the role of the relief valve is to prevent the hydraulic oil pressure in the hydraulic system from exceeding the rated load and play a safety protection role.