Common Faults and Elimination Methods of Relief Valve

1.The system pressure cannot be adjusted up

(1) Fault phenomenon: the system pressure cannot be increased (the relief valve is faulty).

Cause analysis: ① The overflow valve spool is stuck at the open position;② The damping hole of the overflow valve is blocked;③ The spring of the overflow valve is broken.

Elimination method: ① Remove and overhaul the overflow valve to ensure that the pre-tightening force of the bonnet fastening screw remains consistent;② Drag the damping hole of the overflow valve spool;③ Replace the spring.

(2) Fault phenomenon: the system pressure cannot be increased (pilot valve fault).

Cause analysis: ① The poppet valve of the pilot valve is not installed or damaged;② The spring of the pilot valve is not installed or broken.

Elimination method: ① Install or replace the pilot valve poppet valve;② Install or replace the pilot valve spring.

2.Sudden increase in system pressure

(1) Fault phenomenon: the system pressure suddenly rises (relief valve fault).

Cause analysis: The relief valve spool is insensitive and suddenly stuck when it is closed.

Elimination method: overhaul or replace the relief valve spool.

(2) Fault phenomenon: the system pressure suddenly rises (pilot valve fault).

Cause analysis: ① The spring of the pilot valve is stuck;② The spool of the pilot valve is stuck.

Elimination method: ① replace the pilot valve spring;② overhaul or replace the pilot valve spool.

3.Sudden drop in system pressure

(1) Fault phenomenon: the system pressure suddenly drops (relief valve fault).

Cause analysis: ① The damping hole of the overflow valve core is suddenly blocked; ② The gasket of the overflow valve is suddenly damaged.

Elimination method:① Overhaul or replace the overflow valve spool; ② Replace the gasket.

(2) Fault phenomenon: the system pressure suddenly drops (pilot valve fault).

Cause analysis:①The spring of the pilot valve is broken; ②The spool of the pilot valve is damaged.

Elimination method: ① replace the pilot valve spring; ② overhaul or replace the pilot valve spool.

4.Sudden fluctuation of system pressure

(1) Fault phenomenon: sudden fluctuation of system pressure (relief valve fault).

Cause analysis: ①The damping hole is too large; ②The damping hole of the relief valve spool is blocked and open; ③The movement of the relief valve spool is not sensitive, and it moves when it is stuck. 

Elimination method:①Appropriately reduce the diameter of the damping hole; ②Replace the relief valve and check the quality of the hydraulic oil; ③Repair or replace the relief valve spool.

(2) Fault phenomenon: sudden fluctuation of system pressure (pilot valve fault).

Cause analysis:①The pressure regulating spring of the pilot valve is bent; ②The conical surface of the pilot valve spool and the seat cone are in poor contact, and the wear is uneven; ③The lock nut of the screw for adjusting the pressure is loose.

Elimination method:①Replace the pressure regulating spring; ②Replace the pilot valve; ③Tighten the lock nut after pressure regulation.