Seven Key Points for Hydraulic System Troubleshooting and Daily Maintenance

1. Main Root Causes of Hydraulic Failures

Industry statistics show that about 70%–80% of hydraulic system failures are related to hydraulic oil contamination, including solid particles, water and entrained air. Contamination accelerates wear of pumps and valves, causing spool sticking, seal failure and sluggish actuator movement. Oil management is therefore the core of hydraulic maintenance.

2. Seven Daily Maintenance Points

• Oil cleanliness control: take regular samples and check the NAS grade; keep servo systems within NAS 7 and proportional systems at NAS 8–9; the return line must have a filter rated no coarser than 10µm.
• Oil temperature management: normal operating temperature is 30–55℃; above 60℃ oxidation accelerates and oil life halves for every 10℃ rise. Any abnormal temperature rise should immediately trigger checks of the cooler and relief valve.
• Prevent air ingress: keep tank level above the midpoint of the sight glass, ensure reliable suction-line sealing and vent the system before operation; air bubbles cause creeping, noise and actuator judder.
• Water control: water content above 0.1% significantly reduces oil-film strength; regularly check the tank breather dryer and protect outdoor equipment from water ingress.
• Periodic seal replacement: rubber seals generally age after 2–3 years; replace on schedule even without visible leakage to avoid sudden failures.
• Fastener inspection: high-pressure line fittings and flange bolts easily loosen under vibration and should be part of daily checks.
• Sensible spare-parts stock: seal repair kits and spools for Rexroth, Parker and similar valve brands are wear parts — keep safety stock.

3. Quick Diagnosis of Common Faults

No or insufficient pressure: first check whether the relief valve is stuck, the oil level is too low, or pump rotation direction is correct. Actuator creeping: usually caused by air in the system or poor guide lubrication. Valve failure to reverse: check solenoid coil resistance and whether the spool is jammed by particles. Keeping a fault log and analyzing trends enables the shift from "fix after failure" to "preventive maintenance".