As an executing component, once the hydraulic cylinder does not work, it not only affects the mechanical action, but may also cause equipment shutdown and affect production efficiency. Based on years of experience in hydraulic systems, we will systematically analyze common causes to help you quickly locate and troubleshoot faults.
I. Insufficient oil supply power of the hydraulic pump
The hydraulic pump is the power source of the entire system, responsible for converting mechanical energy into hydraulic energy to drive the cylinder movement. If the pressure and flow output by the hydraulic pump are insufficient, the cylinder will be unable to generate sufficient thrust, move slowly, or even remain stationary.
�� The causes of this situation include: pump body wear, severe internal leakage, poor oil suction of the pump, or poor oil quality issues.
2. Sticking or damage of the directional control valve leading to incorrect switching of the oil circuit
The function of the directional control valve is to control the flow of oil to the cylinder. If the spool sticks, the groove is blocked by contaminants, the seal ages, or even the electromagnetic coil fails, the cylinder will not receive the correct oil circuit signal and thus be unable to perform actions.
⚠️ This type of problem is most common on-site. For example, spool sticking or internal leakage will cause the system to appear to have pressure but the cylinder remains stationary.
III. System Contamination with Air or Hydraulic Fluid
When air enters the hydraulic system, since air is a compressible medium, it causes the 'soft pedal' phenomenon in the system: slow pressure buildup, unstable cylinder operation, and even insufficient thrust generation.
At the same time, hydraulic fluid contamination (such as moisture, particulates) can damage seals, scratch the inner wall of the cylinder, and impede the smooth flow of oil circuits.
�� Maintenance要点: Air must be purged, and the hydraulic fluid must be clean and meet specification requirements.
IV. Electrical Control System Faults
Modern hydraulic systems are often closely integrated with electrical control, such as PLC output controlling direction valves, solenoid valve power, etc. If the control signal transmission fails, the wiring contact is poor, or the control module is faulty, the cylinder will be 'unable to receive instructions'.
✔ It is recommended to check whether the PLC parameters, harness connections, and sensor status are normal.
V. Wear of Seals or Internal Damage to the Cylinder
The internal seals of the cylinder (piston seal, rod seal) will naturally wear over time with use. Once they age or break, internal leakage occurs, leading to insufficient cylinder force or even failure to operate.
In addition, mechanical issues such as bent rods, scratches on the inner wall of the cylinder barrel, and piston jamming can also cause the cylinder to 'fail'.
�� In particular, seal problems are one of the most common causes of hydraulic cylinder failures.
6. Blockage of the return oil line or excessive resistance in the return circuit
Even if the system has pressure, if the return circuit of the oil cylinder is blocked or the resistance is too large, it will restrict the normal operation of the oil cylinder. The inability of the hydraulic oil to flow will cause the hydraulic cylinder to be unable to move.
It is recommended to check whether the return oil filter is clogged, whether there is any bending or compression in the pipeline, etc.
VII. Design or Installation Factors
After ruling out the above causes, consider issues related to cylinder design or installation:
✔ Inappropriate cylinder bore selection leading to insufficient force generation
✔ Unreasonable piston area design resulting in excessively small effective area
✔ Incorrect installation angle or positioning causing excessive lateral load
These factors can all affect the normal operation of the cylinder.
�� Summary
A hydraulic cylinder failing to work is often not caused by a single factor but rather a combination of multiple possible issues.
The following is the priority order for checking common faults:
Check if the system pressure is sufficient
Inspect whether the directional control valve switches normally
Check the oil
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