English 
Spanish 
Hydraulic cylinder air explosion failure
1. While “air explosion” failures in hydraulic cylinders are relatively uncommon, they pose a severe risk. If air is not fully purged from the cylinder and gas remains entrained in the hydraulic fluid, the rapid movement of the piston rod causes the air to undergo sudden, extreme compression. This generates instantaneous high temperatures and pressures that exceed the heat resistance limits of the sealing materials, leading to failures such as seal scorching or extrusion—phenomena also referred to as “scorching failures.” Following such an event, the internal piston seal is typically destroyed or carbonized, carbonization occurs at the contact points between the piston and the guide sleeve, the guide sleeve’s O-ring is scorched, and the guide sleeve retaining ring is extruded; in severe cases, localized deformation of the cylinder barrel—manifesting as “bulging”—may even occur.
Solution:
(1) During commissioning, ensure standardized operating procedures are followed and bleed as much air as possible from the hydraulic cylinder beforehand;
(2) Do not immediately switch to high-speed operation when starting the hydraulic cylinder;
(3) Apply grease to the groove of the Y-ring sealing lip to prevent air entrapment and accumulation.
The hydraulic cylinder fails to operate.
2. Excessive resistance in the moving parts of the actuator.
Solution: Eliminate issues such as jamming or binding within the actuator mechanism; improve the guidance and lubrication of the moving parts.
3. Hydraulic pressure at the inlet is too low and fails to meet the specified value.
Solution: Check the hydraulic circuit for leaks and rectify them; inspect the piston and piston rod seals for damage, aging, or looseness; check the hydraulic pump and pressure valves for malfunctions.
4. The fit of the hydraulic cylinder’s sliding components is too tight, resulting in excessive seal friction.
Solution: Use an H8/f8 fit between the piston rod and the guide sleeve; verify that seal dimensions strictly adhere to standards; if V-type seals are used, adjust the seal friction to an appropriate level.
5. Due to improper design or manufacturing, the effective working area of the piston exposed to pressurized oil during the return stroke (after reaching the end of the stroke) is too small.
Solution: Modify the design and remanufacture the component.
6. Hydraulic fluid is not entering the cylinder.
Solution: Inspect oil lines and circuits—particularly hose fittings—for blockages, checking the circuit sequentially from the cylinder back to the pump to clear any obstructions; check the seal between the relief valve’s poppet and seat; inspect the solenoid valve spring for damage or the solenoid coil for burnout; check for sluggish switching in the hydraulic circuit.
7. Excessive back pressure in the hydraulic cylinder.
Solution: Reduce the back pressure. A primary reason for a hydraulic cylinder failing to operate is insufficient inlet pressure (i.e., inadequate working pressure). Common causes of insufficient working pressure include: malfunctions in the hydraulic pump, drive motor, or pressure-regulating valve; clogged oil filters, undersized oil passages, or fluid viscosity that is too high or too low; excessive air in the fluid; severe contamination; incorrect piping connections; or a damaged pressure gauge.
8. The piston rod is subjected to excessive lateral loads, causing binding, cylinder scoring, or seizure.
Solution: When installing the hydraulic cylinder, ensure the cylinder’s axis aligns with the direction of movement; ensure the load acts as close to the cylinder axis as possible to avoid eccentricity. For long hydraulic cylinders operating horizontally, the piston rod may sag under its own weight, creating uneven loading on the guide sleeve and piston; this can damage the cylinder head seal, cause oil leakage, and lead to the piston seizing within the cylinder barrel. Measures to address this include: enlarging the piston and machining its outer surface into a barrel shape to allow for self-alignment and improved load distribution, thereby reducing or preventing cylinder scoring; and using a spherical joint for the connection between the piston and the piston rod.
Hydraulic cylinder stick-slip
9. Air trapped inside the hydraulic cylinder causes the working fluid to act like an elastic medium.
Solution: Thoroughly bleed the air; check the hydraulic pump’s suction line diameter and the integrity of the suction line connections to prevent air from being drawn into the pump.
10. The moving mechanism lacks sufficient rigidity, creating an elastic system.
Solution: Increase the rigidity of the relevant components to reduce elastic deformation.
11. Poor installation alignment/precision of the hydraulic cylinder.
Solution: Improve the assembly quality of the hydraulic cylinder.
12. Excessive seal friction.
Solution: Use an H8/f8 fit between the piston rod and the guide bushing; ensure seal dimensions are manufactured strictly according to standards; when using V-type seals, adjust the seal friction to an appropriate level.
The hydraulic cylinder is sluggish in operation.
13. Air is present inside the hydraulic cylinder.
Solution: Bleed the air using the air bleed valve; check the seals at the reciprocating section of the piston rod for air intake and replace the seals if necessary.
14. When a hydraulic cylinder equipped with a cushioning device starts in the reverse direction, the piston often pauses momentarily or retracts.
Cause: The orifice of the check valve is too small, restricting oil flow into the cushioning chamber—potentially causing a vacuum—which leads to the aforementioned issue the moment the cushioning plunger leaves the end cap. Solution: Enlarge the check valve orifice.
15. At high piston speeds, the check valve’s steel ball moves with the oil flow, blocking the valve port and causing irregular hydraulic cylinder operation.
Solution: Replace the steel ball with a poppet valve or spool featuring a guide shoulder.
16. The inner lining of the rubber hose is peeling, causing intermittent oil flow and irregular hydraulic cylinder operation.
Solution: Replace the rubber hose.
17. The hydraulic cylinder is subjected to a lateral load.
Solution: Follow the same troubleshooting steps used for the “hydraulic cylinder fails to operate” issue.
18. The hydraulic pump is operating irregularly, exhibiting sluggish rotation or signs of mild seizure.
Solution: Address the issue based on the specific type of hydraulic pump and the root cause of the malfunction.
★★★Review of selected articles in our hydraulic cylinder engineering newsletters:
- What are the common installation methods of hydraulic cylinders?
- How to select a hydraulic cylinder? Here are the precise selection steps!
- Hydraulic cylinder buffer device, common faults and solutions
- How to test internal leakage in hydraulic cylinder?
- Disassembly and assembly methods and precautions of hydraulic cylinder
- Why does the hydraulic cylinder get strained? How to solve it? Let me tell you everything!
- Why is the hydraulic cylinder still leaking oil after replacing the sealing ring
- Difference between single-acting cylinder and double-acting cylinder. How to choose?
- Disassembly methods and precautions of hydraulic cylinder
- Hydraulic cylinder: The relationship between the force, pressure and cylinder diameter, how to choose a type？
- What types of seals are used in a hydraulic cylinder?