With the development of hydraulic system of injection molding machine towards medium and high pressure, pilot operated relief valve is widely used in the control oil circuit of hydraulic system of injection molding machine.
In practice, in order to maximize its effectiveness, maintain the control system, accurately and timely diagnose and eliminate the failure of the pilot relief valve is a key link. The failure of the pilot relief valve will cause the injection molding machine to fail to operate. According to the phenomenon, the causes are analyzed as follows: the pilot valve core spring is broken, and the anion hole is blocked; The pilot valve port is poorly sealed, and the main valve core is stuck. The corresponding elimination measures are to replace or add a flat pad at the broken point for emergency use, and clean and dredge; Grind or open the oil circuit for emergency use, grind and clean.
Unstable pressure limiting: Unstable pressure limiting of pilot relief valve indicates that the pressure of hydraulic system is too low or too high, the action of hydraulic actuator is weak or the oil pipe, pump body and valve body burst. The causes of this failure are: improper pressure adjustment; The spring of the pilot valve core is bent or becomes soft; The oil is too dirty or the oil flow is not smooth. The corresponding elimination measures are readjustment, correction, padding or replacement, replacement and cleaning. Unstable pressure limiting of the pilot type relief valve is a gradual failure, and the failure of the pilot type relief valve is a sudden failure. After the failure is eliminated, the pressure controlled by the pilot type relief valve should be readjusted according to the pressure limited by the injection molding machine system.