What is hydraulic cylinder?
Hydraulic cylinder is a hydraulic actuator that converts hydraulic energy into mechanical energy and performs linear reciprocating motion (or swing motion).
It has the characteristics of simple structure, reliable work, no transmission gap and smooth movement, etc.
It is widely used in hydraulic systems of various machines.
As a general-purpose industrial equipment, failure problems will inevitably occur during use.
In severe cases, it may directly lead to equipment shutdown, so the daily diagnosis and maintenance of its faults are very important.
Generally speaking, the failure of a hydraulic cylinder can be summarized as incorrect action of the hydraulic cylinder, inability to push the loads and pistons to slide or crawl.
Hydraulic cylinder troubleshooting
From the essence, the main parts that lead to the failure of hydraulic cylinders include oil cylinder, piston rod, cylinder block, guide sleeve, piston and cylinder rod sealing, etc. The main parts can be grouped into four categories:
Ⅰ. Wear and tear on the mating surfaces of the piston and piston rod
Ⅱ. Wear and tear on the mating surfaces of the piston rod and the guide sleeve;
Ⅲ. Broken piston seal
Ⅳ. Damage to other seals and etc.
The consensus of the hydraulic industry is that no action of the hydraulic cylinder should be one of the most common fault conditions. When this problem arises, how do we, as operators, diagnose and eliminate the root cause of its failure?
In working condition, check if any pressure oil enters the hydraulic cylinder
If no pressure oil enters the hydraulic cylinder, the reasons and troubleshooting methods are as follows:
- The reversing valve before the hydraulic cylinder installation is not reversing in time. When no pressure oil enters the hydraulic cylinder, check the root cause of the non-reversing of the reversing valve and eliminate it;
- The system is not supplied with oil. Check the cause of the failure of the hydraulic pump and main hydraulic valve, then eliminate it.
If oil enters the cylinder, check whether the oil entering the cylinder has sufficient pressure.
- If the system fails, it is mainly because there is a problem with the pump or the relief valve. The failure of the pump or the relief valve should be checked in time and eliminated;
- The internal leakage is serious, the piston and the piston rod are loosened, and the seal is seriously damaged.At this time, the piston and the piston rod should be tightened and the seals should be replaced in time;
- The pressure regulating valve is faulty. When the system setting pressure is too low, troubleshoot the pressure valve and readjust the pressure until the required value can be reached. If necessary, recalculate the working pressure and replace the high-quality pressure regulating component whose value can be adjusted again;
- When the sealing ring on the piston is missing or seriously damaged,or when there is a deep groove in the cylinder bore and the nut that locks the piston on the piston rod becomes loose, this will cause severe string cavity of the hydraulic cylinder inlet cavity and the components will not be able to move normally. At this time, the seal ring on the piston should be replaced and other repair measures should be taken.
Oil enters and the pressure meets the requirements, but the load is relatively large, causing the hydraulic cylinder to be unable to move and still unable to work. In response to this situation, we should investigate one by one from several aspects:
- Check whether the load is too large (larger than the predetermined value),in particular, it is necessary to check whether the additional load caused by the poor installation of the hydraulic cylinder is too large. Only then can the hydraulic cylinder be calibrated and installed correctly;
- Check whether the connection between the hydraulic cylinder and the load is correct.When the load is connected incorrectly, it may cause the movement of cylinder and jammed phenomena. At this time, the rigid fixed connection can be changed to a movable articulated connection or a ball head connection, and the surface is preferably a spherical surface;
- When there is a problem in the structure of the hydraulic cylinder, such as the end face of the piston and the end face of the cylinder barrel are closely fitted, the area of the piston bearing force is insufficient when cylinder starting, so the load cannot be pushed.Or the check valve circuit on the cylinder of the buffer device is blocked by the piston. You have to handle each case individually;
- Poor assembly of the hydraulic cylinder (such as the poor concentricity between the piston rod, the piston and the cylinder head, the poor parallelism between the hydraulic cylinder and the table, the small clearance between the guide sleeve and the piston rod, etc.) causes the piston rod jammed and cannot be moved;
- Caused by hydraulic circuits. The main reason is that the oil level in the back pressure chamber of the hydraulic cylinder communicates with the fuel tank, the reversing valve that communicates with the oil return does not operate, the shut-off valve does not open, and the throttle valve is closed. As a result, oil return is blocked, and this can be handled according to specific problems;
- If dirt enters the sliding part and the sliding part of the cylinder is stuck and cannot move, the part should be cleaned as soon as possible;
- The hard chromium plated on the piston rod stuck the piston rod due to falling off. In this case, you need to stop processing immediately to avoid accumulation of tumors, which may be more difficult at that time.