2026-07-24
Types of Relief valve & Solutions of common failures
1. Relief valves come in two types: direct-acting and pilot-operated.
Direct-acting: High sensitivity, fast response, smaller flow rate; suitable for safety valves and remote control valves.
Pilot-operated: Good stability, better opening and closing characteristics; suitable for pressure regulating valves.
The main uses of a relief valve are as follows:
· As a relief valve, to maintain constant pressure in the hydraulic system;
· As a safety valve, to prevent overload of the hydraulic system;
· Remote pressure regulation;
· Multi-stage pressure regulation of high and low pressure in the system;
· Combined with a solenoid valve, to unload the hydraulic system;
· As a brake valve, to buffer and brake the actuator;
· As a loading valve and back pressure valve.
2. Installation requirements and common faults of relief valves
(1) Installation requirements
· The medium used in the hydraulic system must be filtered, with a filtration accuracy of at least 20µm;
· The surface roughness of the surface connected to the valve must meet the following requirements; the flatness requirement is 0.01/100mm;
· The connecting plate of a plate valve and the insertion hole of an insert valve must be machined strictly according to the installation dimensions in the product description, and their accuracy must be guaranteed; each connecting port of a pipe valve must be fitted with a sealing ring;
· The screws used to install the valve must be high-strength screws (grade 10.9).
(2) Common Faults
A. Direct-acting type
• Poor fit between the valve core and seat results in excessive leakage or inability to adjust the pressure;
• Insufficient spring length and poor rigidity also prevent pressure adjustment.
B. Pilot-operated
• Blockage of the damping orifice, causing the main valve core to jam in the open position; bending or breaking of the main valve core return spring; breakage of the pilot valve pressure regulating spring; resulting in no pressure adjustment;
• Poor fit between the main valve core and the valve sleeve; poor sealing between the pilot valve cone and the valve; insufficient length, bending, or poor rigidity of the pressure regulating spring; all these can cause the pressure to not be adjusted to a high level;
• Sudden jamming of the main valve core in the closed position during operation; inability to open the pilot valve core, or bending and jamming of the pressure regulating spring; all these can cause a sudden increase in pressure;
• Sudden jamming of the main valve core in the open position during operation; sudden blockage of the damping orifice; sudden breakage of the pressure regulating spring; all these can cause a sudden decrease in pressure;
• Damage to the O-ring or combination gasket, causing external leakage;
• Improper valve core fit, bending of the pressure regulating spring, or misalignment with the adjusting rod can easily cause noise and vibration.
For more details , please check with hydraulic piston pump , hydraulic motor , gear box Manufacturer – Shanghai Belle Hydraulic
