What are the common faults of pressure control valves, and how can they be troubleshooted?
2024-09-13
Unstable pressure fluctuations
Cause of the failure
When air enters the fluid, its volume changes with pressure fluctuations, leading to pressure variations.
The spool of the relief valve or pressure-reducing valve becomes stuck, preventing it from moving freely. This results in unstable valve opening and, consequently, pressure fluctuations.
The system contains a vibration source, which causes the pressure control valve to vibrate, resulting in pressure fluctuations.
Exclusion method
Perform an air bleed on the system by loosening the bleed valve in the system or installing a vent at the highest point of the pipeline to allow air trapped in the fluid to escape.
Remove the valve core and inspect it for wear, scratches, or debris that may be causing obstruction. If any of these issues are found, clean, grind, or replace the valve core, ensuring that the clearance between the valve core and the valve seat meets the specified requirements.
Identify and eliminate vibration sources within the system, such as tightening equipment like pumps and motors, and installing vibration-damping pads.
Pressure can't be increased.
Cause of the failure
The pilot valve seat of the relief valve has cracks or poor sealing, causing the pressure oil to flow directly back to the reservoir through the pilot valve via the solenoid control valve—preventing sufficient pressure from building up.
The spool of the pressure relief valve is stuck in the normally open position due to spring fatigue, breakage, or jamming, preventing the outlet pressure from rising.
The system suffers from numerous leaks—such as damaged seals on hydraulic cylinder pistons and loose pipe connections—which result in significant fluid loss and prevent the system from building up high pressure.
Exclusion method
Replace the cracked pilot valve seat, and grind the sealing surfaces of both the valve seat and valve spool to ensure a tight seal.
Replace worn or broken springs, and clean or replace any stuck valve spools to ensure the pressure relief valve functions properly.
Locate the leak, replace the damaged seals, tighten any loose pipe connections, and repair the leaking area.
The pressure won't come down.
Cause of the failure
The spool of the relief valve is stuck by contaminants and remains in the normally open position, preventing the pilot-operated relief valve from closing properly, which results in the system pressure being unable to drop.
The damping orifice of the pressure relief valve becomes clogged, preventing the spool from moving freely and causing it to remain permanently in a wide-open position, which results in the outlet pressure failing to drop.
The pressure relay malfunctions, sending an incorrect signal that prevents the associated control valve from operating properly, ultimately resulting in the pressure failing to drop.
Exclusion method
Clean the spool and valve port of the relief valve to remove any impurities, ensuring the spool moves freely and seats securely.
To clear the damping hole of the relief valve, you can use a fine steel wire or compressed air, ensuring that hydraulic fluid flows smoothly through the hole and allowing the spool to adjust properly.
Check the setting and operational status of the pressure relay, adjust it to the correct setting, or repair any faults to ensure it functions properly.
Excessive noise
Cause of the failure
The oil has too high a viscosity, resulting in significant flow resistance, which causes the load-holding valve to generate noise when the pressure control valve is operating.
Poor sealing between the valve core and valve seat leads to oil leakage and noise generation.
The pressure control valve is not securely installed, causing vibrations and noise during operation.
Exclusion method
Select an oil with the appropriate viscosity according to system requirements, such as switching to a lower-viscosity oil.
Grind the sealing surfaces of the valve core and valve seat, or replace the seals to ensure a tight seal and minimize fluid leakage.
Reinstall the pressure control valve, using the appropriate fastening bolts to ensure a secure fit—and if necessary, add vibration-damping pads for extra stability.
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