How to Solve The Failure of Hydraulic Cylinder?

Hydraulic cylinders are not well known to the public because they are widely used in the machinery industry, and their role is very important in heavy industry. Hydraulic cylinders are widely used in various hydraulic systems. an indispensable part of. However, the machine is always a machine and cannot achieve perfect utility. Once the hydraulic cylinder fails, it will affect the safe operation of the entire mechanical equipment. The following is an analysis of some common faults of hydraulic cylinders and preventive measures.

1. Hydraulic Cylinder Does Not Work

Due to the inaccurate stop position of the piston rod in the hydraulic cylinder, insufficient thrust of the piston rod, too low movement speed of the piston rod, unstable work and other faults, the hydraulic cylinder cannot drive the load movement. The specific cause analysis and treatment measures are as follows:

Oil Leakage Inside The Hydraulic Cylinder

There are two main types of oil leakage inside the hydraulic cylinder: the piston rod of the hydraulic cylinder and the inner hole of the piston, and the oil leakage caused by excessive wear of the piston seal. The reason for the oil leakage between the piston rod and the inner hole of the piston is the aging, wear and deformation of the seals. Timely replacement of the seals can solve this problem.

The main reasons for excessive piston seal wear are:

● The back pressure is too high due to the imbalance of the speed control valve;

● Errors in installing seals cause hydraulic oil pollution;

● In the process of installing the hydraulic cylinder, there are sundries and low-quality sealing materials. Excessive wear of the piston seal will cause the hydraulic cylinder to work weakly, and will also lead to the wear of the cylinder barrel and the phenomenon of pulling the cylinder.

The solution is to adjust the speed control valve in time, replace and clean the filter element of the oil filter, and replace the hydraulic oil.

Oil Leakage In Hydraulic Circuit

Oil leakage of hydraulic circuit mainly refers to oil leakage of valve parts and hydraulic pipeline. The treatment method is to judge the oil leakage status of each pipeline and valve parts through the reversing valve, and repair and replace the oil leaking valve parts and pipelines in time.

The Hydraulic Oil Returns Directly to The Oil Tank Through The Relief Valve

If debris jams the spool of the relief valve, the relief valve becomes normally open, the hydraulic oil returns directly to the oil tank, the hydraulic cylinder cannot get enough pressure of hydraulic oil, and it cannot perform continuous action with load. Insufficient power to drive the load to work. In this case, you should check and adjust the relief valve.

2. The Hydraulic Cylinder Is Insensitive And Blocked

The insensitivity of the hydraulic cylinder means that the hydraulic cylinder can execute the action after receiving the action command, but it must wait for a short time before it can execute the action, or sometimes it executes the action and sometimes does not execute the action.

The fault analysis and treatment measures for the insensitive hydraulic cylinder are as follows:

Air enters the hydraulic cylinder. The main reason for the air entering the hydraulic cylinder is that the seal of the reciprocating part of the piston rod is damaged and air is sucked in.

Hydraulic cylinder repair measures: replace the damaged sealing ring, open the exhaust valve of the hydraulic cylinder, and discharge the air.

The hydraulic pump is blocked or slightly seized, resulting in irregular operation of the hydraulic pump. In this case, repair the hydraulic pump in time.

When the hydraulic cylinder with buffer device is started in reverse, due to the small check valve hole, the hydraulic oil flowing into the buffer chamber is insufficient, and the piston temporarily stops working or reverses.

The solution is to enlarge the hole of the one-way valve.

One-way valve blocked. When the piston moves at a high speed, the steel ball in the one-way valve moves with the hydraulic oil, which is easy to block the valve hole of the one-way valve, resulting in the hydraulic cylinder unable to move regularly. The solution is to replace the steel ball with a cone valve with a guide shoulder to prevent clogging.

The oil circuit is not smooth. The inner wall of the rubber hose falls off, causing the oil circuit to be blocked, and the hydraulic cylinder lags behind. The solution is to replace the rubber hose.

3. The Movement of The Hydraulic Cylinder Has Crawling Phenomenon

Crawling phenomenon is one of the common faults of hydraulic cylinders. It means that the hydraulic cylinder jumps and stops when it performs actions, which generally occurs in low-speed motion. The influencing factors of hydraulic cylinder crawling are divided into internal and external factors of hydraulic cylinder.

Causes and solutions outside the hydraulic cylinder:

● Increase the stiffness of the motion mechanism to avoid the formation of an elastic motion mechanism.

● The installation accuracy of the hydraulic cylinder is not up to standard, causing the hydraulic cylinder to crawl. Improve the assembly accuracy of the hydraulic cylinder and ensure the assembly quality of the hydraulic cylinder.

● The crawling phenomenon caused by the large change of friction force. The large change in friction force means that the difference in the friction coefficient between the relative moving parts is too large. The solution is to apply molybdenum disulfide lubricating oil on the surface of the relative moving parts to make the lubrication condition good and prevent crawling.

● Factors in the manufacture and assembly of guide rails. The friction coefficient of the guide rail is large and the force condition is not good, which may easily lead to the creeping phenomenon of the hydraulic cylinder. The solution is to improve the manufacturing and assembly quality of the guide rails.

Internal reasons and solutions of hydraulic cylinders:

● Air enters the hydraulic system to form an elastic working medium. The diameter of the suction pipe of the hydraulic pump should meet the requirements of use, and the joints are well sealed to prevent air from entering the hydraulic system.

● The friction in the sealing part of the hydraulic cylinder is large, which causes the hydraulic cylinder to crawl. The solution is to adjust the cooperation between the piston rod and the guide sleeve to H8/f8, and control the dimensional accuracy of the sealing ring.

● The hydraulic cylinder has excessive wear, strain and bite.

● The piston rod is bent as a whole or in part. The treatment method is to replace or correct the piston rod. If the piston rod extends out of the hydraulic cylinder too long, the piston rod should be supported to prevent bending.

● The inner hole of the cylinder barrel and the guide sleeve are not concentric, and the movement of the piston is blocked, resulting in a creeping phenomenon. The solution is to adjust the concentricity between the inner hole of the cylinder and the guide sleeve.

● The inner diameter of the cylinder of the hydraulic cylinder is deformed, and the straightness is not good. Use a boring machine to repair the straightness of the cylinder bore, and then select the appropriate diameter piston.

● The coaxiality of the nuts at both ends of the piston rod of the hydraulic cylinder is not good. The cause is that the nut is too tight, and the solution is to loosen the nut properly.

4. Hydraulic cylinder precautions

Problems Needing Attention In The Repair of Hydraulic Cylinder

In the installation and maintenance of the hydraulic cylinder, the stroke of the piston rod should be considered to ensure that the parallelism between the piston rod and the cylinder barrel is within the design range. During maintenance, in order not to pollute the hydraulic oil and valve parts, it is required to keep the environment clean. Before cleaning each part with cleaning oil, use compressed air to blow off the debris on it. After cleaning, wipe the parts clean before assembling. In order to prevent deterioration of seals, the type of hydraulic oil should be considered when selecting seals.

Hydraulic Oil

A series of preventive measures should be taken for the storage of hydraulic oil. First, pollution should be prevented, and the entry of relative dust, water and other oils should be avoided; secondly, the storage temperature of hydraulic oil should be controlled between -20 and +30 degrees; Direct sunlight, especially in summer, should block the hydraulic oil to avoid oxidative deterioration. Regularly replace the hydraulic oil to ensure the cleanliness of the hydraulic oil.

Working Process

When using the hydraulic cylinder, it is not allowed to use overload; it is not allowed to operate rudely. Do not allow foreign objects to hit the hydraulic cylinder. Do not allow the hydraulic cylinder to work in a high temperature environment. When the coordination of several hydraulic cylinders is required, set the stroke to avoid asynchronous work.