What Are the Most Common Relief Valve Failures and How Can You Fix Them?

Author：SAIVS Time：2025-05-19 Click：

Common Relief Valve Failures and Solutions

Relief Valve Pressure Regulation Failures

1. Pressure Does Not Reach the Set Value

When adjusting the pressure handle, if the system pressure fails to reach the rated value, the main causes could include:

Deformed or broken pressure regulating spring
Severe leakage due to poor pilot valve sealing
Leakage from the remote control port
Improper sealing between the main spool and sleeve

Replace the faulty components and ensure all seals are intact to restore proper pressure control.

2. System Immediately Loses Pressure After Build-up

This issue is typically caused by blockage in the damping hole at the end of the main or pilot valve.

If blocked, pressure oil cannot enter the upper chamber of the main valve spool, causing it to stay open and continuously overflow system pressure.

Even when the pressure drops, the spool remains open, preventing pressure recovery regardless of handle adjustments.

Cleaning or replacing the blocked components is necessary.

3. System Overpressure — Valve Does Not Function

There are two main causes:

Blockage in the damping hole ahead of the pilot valve spool prevents pilot operation
The upper chamber of the main spool is sealed due to clogging

In both cases, the relief valve loses its limiting function, resulting in dangerously high system pressure. This can lead to serious damage like broken bolts or pump failure.

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Unstable Pressure and Pulsation

Causes of Pressure Instability

Oil contamination causing debris to block pilot valve ports
Sticky spool movement due to contamination
Air mixed in hydraulic oil
Excessive oil temperature
Poor contact between spool and valve seat
Oversized damping orifice reducing damping effect
System resonance

Recommended Actions

Use clean hydraulic oil, maintain regular filtration, ensure proper system ventilation, and optimize valve orifice size to stabilize pressure output.

Noise and Vibration Issues

Main Causes of Abnormal Noise

Resonance with nearby valve components
Worn pilot valve port or air in remote control port
Incorrect pipe diameter between remote port and main valve (recommended: 6mm)
Foreign matter inside the valve causing spool misalignment

When the spool sticks to one side under hydraulic force, it generates high-frequency vibration and noise, especially at pressures above 10 MPa.

This leads to spring vibration and abnormal system sound — often resembling a whistle — along with sharp pressure gauge oscillation.

Solution Tips

Replace springs with more appropriate specifications, switch to external drain, clear internal valve contamination, and consider upsizing the valve for larger flow rates.