Hydraulic cylinders are the workhorses of many industrial applications, converting hydraulic energy into mechanical force with ease. With their simple design, smooth movement, and reliable operation, these powerhouses are an essential component of hydraulic systems in various machinery.
However, like any other industrial equipment, hydraulic cylinder failures can occur, leading to equipment shutdown and downtime. That’s why it’s crucial to diagnose and maintain faults regularly.
In this comprehensive guide, we’ll explore the main components that contribute to hydraulic cylinder failures and how to diagnose and resolve common issues.
From wear and tear on the mating surfaces to broken piston seals and damage to other seals, we’ll cover it all.
We’ll also delve into the most common fault conditions, including incorrect operation, inability to push loads, and difficulty with piston movement or slippage.
Whether you’re a seasoned hydraulic systems operator or new to the game, this guide is packed with valuable information to help you keep your hydraulic cylinders running smoothly and efficiently.
So, let’s dive in!
What is hydraulic cylinder?
Hydraulic cylinders are hydraulic actuators that convert hydraulic energy into mechanical energy and produce linear, reciprocating motion or swinging motion.
The hydraulic cylinder has several notable characteristics, including its simple structure, reliable operation, absence of transmission gaps, and smooth movement. Due to its versatility, it is widely utilized in hydraulic systems of various machinery.
However, as a general-purpose industrial equipment, failures are bound to occur during its use. In extreme cases, these failures can result in equipment shutdown, making daily diagnosis and maintenance of faults essential.
In general, hydraulic cylinder failures can be categorized as incorrect operation, inability to push loads, and difficulty with piston movement or slippage.
Hydraulic cylinder troubleshooting
From a fundamental perspective, the main components that contribute to hydraulic cylinder failures include the oil cylinder, piston rod, cylinder block, guide sleeve, piston, and cylinder rod sealing. These components 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 guide sleeve III. Broken piston seals IV. Damage to other seals, etc.
The hydraulic industry widely recognizes that incorrect operation of the hydraulic cylinder is one of the most common fault conditions. To diagnose and resolve this issue, operators must identify the root cause of the failure.
While the hydraulic cylinder is in operation, check if any pressure oil is entering it. If there is no pressure oil entering the cylinder, the causes and solutions are as follows:
- The reversing valve before the hydraulic cylinder installation is not switching in a timely manner. If no pressure oil is entering the hydraulic cylinder, check the root cause of the reversing valve’s failure to switch and resolve it.
- The system is not receiving oil. Check the cause of the failure of the hydraulic pump and main hydraulic valve and resolve it.
If oil is entering the cylinder, verify that the oil pressure is sufficient. If the system is not functioning properly, it is likely due to an issue with the pump or the relief valve. Check and resolve any problems with the pump or relief valve in a timely manner.
In the case of serious internal leakage, looseness of the piston and piston rod, and serious damage to the seals, tighten the piston and piston rod and replace the seals promptly.
If the pressure regulating valve is faulty, adjust the pressure setting until the required value is reached. If necessary, recalculate the working pressure and replace the pressure regulating component with one that can be adjusted to the desired value.
When the sealing ring on the piston is missing or seriously damaged, or 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 cavitation in the hydraulic cylinder inlet cavity, resulting in abnormal movement of the components. In this case, replace the sealing ring on the piston and take other necessary repair measures.
If oil is entering the cylinder and the pressure meets the requirements, but the load is too large causing the hydraulic cylinder to be unable to move, several factors should be investigated:
- Check if the load is larger than the predetermined value, particularly if any additional load caused by poor hydraulic cylinder installation is too large. If so, calibrate and reinstall the hydraulic cylinder correctly.
- Verify that the connection between the hydraulic cylinder and the load is correct. Incorrect connections can cause movement and jamming issues. In this case, consider changing the rigid fixed connection to a movable articulated connection or ball head connection, with a spherical surface being preferred.
- Inspect the hydraulic cylinder structure, such as ensuring that the end face of the piston and the end face of the cylinder barrel are properly fitted, and that the piston bearing area is sufficient when the cylinder starts. Also, check if the check valve circuit on the cylinder buffer device is blocked by the piston. Address each issue individually.
- Poor hydraulic cylinder assembly, such as poor concentricity between the piston rod, piston, and cylinder head, poor parallelism between the hydraulic cylinder and the table, and small clearances between the guide sleeve and the piston rod, can cause piston rod jamming.
- Issues in the hydraulic circuit, such as communication of the oil level in the back pressure chamber of the hydraulic cylinder with the fuel tank, non-operation of the reversing valve that communicates with the oil return, failure to open the shut-off valve, and closing of the throttle valve, can result in blocked oil return. Address specific problems as they arise.
- If dirt enters the sliding parts and causes them to become stuck, clean the parts immediately.
- If the hard chromium plating on the piston rod falls off and causes it to become stuck, stop processing immediately to prevent the buildup of tumors, which could make the issue more difficult to resolve later.