With the development of injection molding machine hydraulic system towards medium and high pressure, pilot relief valve is widely used in the control oil circuit of injection molding machine hydraulic system.

In practice, in order to maximize its efficiency and maintain the control system, accurate and timely diagnosis and removal of pilot relief valve fault is a key link. The failure of pilot relief valve will result in the failure of injection molding machine. According to the phenomenon, the reasons are as follows: the spring of pilot valve core is broken, the hole of Yinni is blocked; the sealing of pilot valve port is not good, and the main valve core is stuck. The corresponding elimination measures are to replace or add a flat pad at the broken place for emergency use, clean and dredge; grind or open the oil circuit for emergency use, grinding and cleaning.

Unstable pressure limit: the pressure limit of pilot relief valve is unstable, which means that the pressure of hydraulic system is low or high, the action of hydraulic actuator is weak or the oil pipe, pump body and valve body burst. The causes of this fault are: improper pressure adjustment; the spring of pilot valve spool is bent or softened; the oil is too dirty or the oil flow is not smooth. The corresponding elimination measures are readjustment, correction, pad or replacement, replacement and cleaning. The unstable pressure limit of pilot relief valve is a gradual fault, and the failure of pilot relief valve is a sudden failure. After troubleshooting, the pressure controlled by the pilot relief valve should be readjusted according to the pressure limited by the injection molding machine system.