Hydraulic cylinders are hydraulic actuators that convert hydraulic energy into mechanical kinetic energy and perform linear reciprocating motion (or oscillating output motion). They have characteristics such as simple structure, reliable operation, no transmission gap, and stable movement. They are widely used in the hydraulic systems of various mechanical equipment.

As a general mechanical pneumatic component, abnormalities will inevitably occur during the application stage. In severe cases, it may directly cause the equipment to not work. Therefore, their daily inspection and maintenance are very important. Generally, the common faults of hydraulic cylinders can be classified as misoperation of hydraulic cylinders, inability to push loads, and downward movement or crawling of the piston after air cut-off.

Essentially, the key parts that cause hydraulic cylinders to be prone to common faults include hydraulic cylinders, pistons, the inner wall of hydraulic cylinders, guide sleeves, the sealing of pistons and piston seals, etc. The key parts can be classified into four categories:

First, the piston and piston cooperate to prevent wear through friction.

Second, the piston rod seal is damaged.

Third, the mating surface between the piston and the guide sleeve is worn and bruised.

Fourth, other seals are damaged, etc.

It is a consensus in the hydraulic industry that no actuation of hydraulic cylinders should be one of the common fault conditions. When this problem occurs, as operators, how should we diagnose and eliminate the root cause of the fault? We can start from the following points:

1. If there is hydraulic oil entering the tank, check whether the hydraulic oil entering the tank has sufficient pressure.

    ①. If the system has a fault, the root cause is that there is a fault problem with the pump or pressure relief valve. The fault condition of the pump or pressure relief valve should be checked in time and eliminated.

    ②. If there is serious internal leakage, the piston and the piston are loose, and the hydraulic seal is seriously damaged. At this time, the piston and the piston should be tightened and the hydraulic seal should be replaced in time.

    ③. If there is a fault with the pressure regulating valve and the system's set working pressure is too low, the pressure valve fault should be eliminated and the pressure should be adjusted again until the required value can be reached. If necessary, the pressure should be recalculated. According to the pressure magnitude, the equipment can be re-tested.

    ④. When there are problems such as missing installation or serious damage of the sealing ring on the piston, deep grooves on the inner wall hole of the hydraulic cylinder, and loosening of the nut that locks the piston on the piston, resulting in serious communication between the oil inlet and return chambers of the hydraulic cylinder, it cannot operate normally at this time. At this time, measures such as replacing the sealing ring on the piston and other maintenance measures should be taken.

2. Under working conditions, check whether there is pressure oil entering the hydraulic cylinder. If there is no pressure oil entering the hydraulic cylinder, the reasons and troubleshooting methods are as follows:

    ①. The hydraulic reversing valve before the installation of the hydraulic cylinder did not change direction in time. When there is no pressure oil entering the hydraulic cylinder, check the direct cause of the hydraulic reversing valve not changing direction and eliminate it.

    ②. The hydraulic station device does not supply oil. Check whether the hydraulic station system and other key hydraulic solenoid valves and other accessories have failures. 
 ③. Why doesn't the hydraulic cylinder actuate and how should it be solved? Hydraulic oil does not enter the hydraulic cylinder. Solution: Check whether the oil pipeline, hydraulic cylinder circuit, and hose joints are blocked. Check the relevant return oil pipelines from the hydraulic cylinder to the hydraulic station in turn and solve the blockage; check whether the sealing between the poppet valve and the valve seat of the pressure relief valve is good; check whether the solenoid valve spring is damaged or the solenoid coil is burned out, and whether the oil pipeline is malfunctioning.
 ④. The transverse load on the piston is too large, especially when it is stiff, or the cylinder is scratched, seized, or bitten.

Troubleshooting method: When installing the hydraulic cylinder, ensure that the centerline position of the cylinder is consistent with the actuating direction, so that the load borne by the hydraulic cylinder passes through the centerline of the cylinder as much as possible to avoid eccentricity. When the long hydraulic cylinder rotates horizontally, the piston becomes rigid due to gravity, causing the guide sleeve and piston to be eccentrically loaded, resulting in damage and oil leakage of the cylinder head seal.

The following measures can be taken: increase the piston rod plan and process the inner surface of the piston into a drum shape so that the piston can self-align, improve the stress condition, and reduce and prevent cylinder scratching; the connection between the piston and the piston adopts a spherical joint.  
 ⑤. The back pressure of the hydraulic cylinder is too large.

Troubleshooting method: Reduce the back pressure. The main reason why the hydraulic cylinder cannot act is that the hydraulic oil pressure at the oil inlet is too low, that is, the pressure is insufficient. The pressure of the hydraulic system is insufficient. The main reasons are that there are faults in the hydraulic pump, drive motor, and pressure reducing valve. Other reasons include: clogged oil filter, too small inner diameter of the oil pipeline, too high or too low viscosity of the hydraulic oil; excessive air entering the hydraulic oil; serious pollution; wrong pipeline connection; damaged pressure gauge, etc.