Hydraulic Relief Valve Abnormal Noise: Common Causes and Complete Solutions

Abnormal noise from hydraulic relief valves is one of the most frequent hydraulic system faults encountered by equipment operators and maintenance technicians. Typical noise types include continuous buzzing, sharp squeaking, periodic chatter and impact knocking sound. Many users ignore slight relief valve noise at first, but long-term abnormal operation will lead to system pressure fluctuation, oil temperature surge, seal damage and even premature failure of the relief valve core.

To solve hydraulic relief valve abnormal noise fundamentally, we need to sort out all root causes and match targeted repair solutions one by one.

1. Oil Liquid Pollution & Impurity Blockage 

Tiny metal scraps, dust and colloidal dirt mixed in hydraulic oil will stick to the spool and valve seat of the relief valve. These impurities prevent the valve spool from fitting closely and moving smoothly. The spool will vibrate rapidly under unstable oil pressure, producing obvious high-frequency chatter noise. Meanwhile, blocked small damping holes will break the internal pressure balance of the relief valve and worsen abnormal noise.

Solutions

• 1-1 Replace contaminated hydraulic oil completely and clean the hydraulic oil tank thoroughly

• 1-2 Disassemble and flush the relief valve spool, damping holes and valve seat with clean hydraulic oil

• 1-3 Install or replace high-precision oil filter elements to avoid secondary oil pollution

2. Unstable System Pressure & Pressure Fluctuation

If the hydraulic pump supplies unstable flow, or the system has sudden load changes, the inlet pressure of the relief valve will rise and drop repeatedly. The relief valve opens and closes frequently in a short time, causing violent vibration and impact noise between spool and valve seat. This fault often occurs in variable pump hydraulic systems.

Solutions

• 2-1 Check the working condition of the hydraulic pump and repair or replace the faulty pump

• 2-2 Add pressure-stabilizing components to stabilize overall system pressure

• 2-3 Avoid frequent sudden load changes during equipment operation

3. Damaged or Fatigue Internal Spring

The internal pressure regulating spring is the core part of a relief valve. Long-term high-pressure compression, spring fatigue deformation, spring breakage or spring offset will cause uneven elastic force. The valve spool cannot keep stable opening, resulting in regular vibration and continuous buzzing noise.

Solutions

• 3-1 Disassemble the relief valve to inspect spring elasticity, straightness and integrity

• 3-2 Replace worn, deformed or broken pressure regulating springs directly

• 3-3 Choose matched original springs instead of non-standard accessories

4. Air Mixed Inside Hydraulic Oil

Air entering the closed hydraulic circuit will form air bubbles inside the relief valve. When high-pressure oil squeezes air bubbles, cavitation occurs, generating sharp cavitation knocking noise. Air mixing usually happens due to insufficient oil volume, damaged oil suction pipeline seal or loose pipe joints.

Solutions

• 4-1 Refill hydraulic oil to standard liquid level

• 4-2 Check all oil suction pipelines, tighten loose joints and replace aging sealing rings

• 4-3 Run the hydraulic system under no-load condition to exhaust residual air inside the circuit

5. Improper Pressure Setting and Resonance

If the relief valve pressure is set too close to the system working pressure, the relief valve will stay in a critical opening state all the time. Slight pressure changes will trigger spool vibration. Besides, the vibration frequency of the relief valve may resonate with the hydraulic pump, producing amplified harsh noise.

Solutions

• 5-1 Reset the relief valve pressure: set the safety pressure 10%~15% higher than normal working pressure

• 5-2 Avoid the relief valve working in long-term critical overflow state

• 5-3 Adjust installation position to avoid mechanical resonance with hydraulic pump

6. Worn Valve Core and Valve Seat

Long-term high-pressure overflow will cause wear on the valve spool sealing surface and valve seat. Poor sealing fit leads to internal pressure leakage, unstable spool movement and persistent abnormal noise. This fault mostly appears on hydraulic equipment with long service time.

Solutions

• 6-1 Detect sealing tightness of valve core and valve seat

• 6-2 Grind slight worn sealing surfaces; replace the whole relief valve for serious wear

Conclusion

Hydraulic relief valve abnormal noise is never trivial noise. The core inducements are oil contamination, mixed air, spring failure, pressure instability and component wear. Daily regular oil maintenance, reasonable pressure setting and timely exhaust can effectively prevent relief valve chatter and buzzing noise. Once abnormal noise appears, troubleshoot step by step according to the above causes to restore stable and quiet operation of the entire hydraulic system.