A Self-creeping occurs when the piston moves without oil supply, caused by worn piston seals allowing internal leakage, a sticking directional valve spool that fails to close completely, or a failed check valve. Solutions include replacing the damaged piston seals, repairing or replacing the faulty directional valve, and verifying the check valve's sealing performance to ensure the cylinder holds position reliably when commanded.

A Seizure means the piston is stuck and cannot move. Causes include scoring of the cylinder bore, deformed piston, swollen seals that jam, or excessive contamination. Emergency treatment requires depressurizing the system first, disassembling the cylinder, cleaning out debris, repairing or replacing the scored barrel, deformed piston, and failed seals, then reassembling with proper lubrication and verifying correct clearances.

A Stick-slip is discontinuous piston movement caused by air trapped in the cylinder, uneven seal friction, insufficient guide lubrication, or incorrect oil viscosity. Solutions include bleeding air from the system, replacing aged seals, improving guide lubrication, and using clean hydraulic oil with the proper viscosity to eliminate uneven motion resistance.

A Abnormal noise results from air in the oil causing cavitation sounds, failed cushion devices producing impact noise, or a bent piston rod generating vibration. Solutions include bleeding air, repairing or replacing cushion devices, and straightening or replacing the bent piston rod to eliminate the vibration source.

A Pressure losses come from frictional resistance as oil flows through pipes and valves, internal and external leakage past seals, friction between seals and the piston rod and barrel, and pressure fluctuations caused by load changes. These losses collectively reduce the cylinder's effective output force.

A Insufficient thrust stems from low system pressure, leaking seals, worn barrel or piston, or blocked inlet piping. Diagnosis involves checking whether system pressure meets specifications, inspecting seals for leakage, disassembling to examine bore and piston wear, and cleaning inlet piping to ensure unrestricted oil flow. Targeted repair or replacement of affected components follows.

A Investigate whether the flow control valve is blocked or damaged—clean or replace it. Check if oil viscosity changes excessively with temperature and apply temperature control if needed. Examine the inlet piping for leaks and tighten fittings. Inspect the piston and seals for wear, repairing or replacing as necessary to maintain stable flow.

A Overheating accelerates seal aging, reduces oil lubricity, increases barrel and rod wear, affects motion accuracy, and can even deform the barrel. Cooling measures include using oil with suitable viscosity, repairing leaks, avoiding overloading, cleaning radiators or adding coolers, and improving equipment ventilation.

A Common faults include oil leakage from aged or damaged seals requiring replacement, slow operation from insufficient flow or internal leakage requiring pump and circuit checks, jerky motion from air in the oil requiring bleeding, abnormal noise from worn or loose internal parts requiring inspection and replacement, and complete failure to move from pump failure or severe damage requiring pump repair or cylinder replacement.

A A cylinder needs repair when there is visible oil leakage, unstable or irregular motion, insufficient starting force, abnormal noise during operation, or temperature rise above the normal range. These symptoms indicate internal wear, seal degradation, or component damage that requires inspection and corrective action to restore reliable performance and prevent further damage.