What are the common failure modes of rexroth cylinders?

As a supplier of Rexroth cylinders, I've had the privilege of working closely with these high - performance hydraulic components in various industrial settings. Over the years, I've witnessed firsthand the different ways in which these cylinders can experience failures. Understanding these common failure modes is crucial for both users and maintenance teams to ensure the reliable operation of machinery and equipment that rely on Rexroth cylinders.

1. Seal Failure

One of the most prevalent failure modes in Rexroth cylinders is seal failure. Seals play a vital role in preventing hydraulic fluid leakage and maintaining the pressure within the cylinder. There are two main types of seals in a hydraulic cylinder: rod seals and piston seals.

Rod seals are located at the point where the piston rod exits the cylinder barrel. They prevent the hydraulic fluid from leaking out and also keep contaminants from entering the cylinder. Piston seals, on the other hand, separate the two chambers of the cylinder and ensure that the pressure difference between them is maintained.

Several factors can contribute to seal failure. Firstly, wear and tear over time are inevitable. As the cylinder operates, the seals are constantly in contact with moving parts, such as the piston rod and the cylinder wall. This friction can gradually wear down the seals, leading to leakage. For example, in high - cycle applications where the cylinder is constantly extending and retracting, the seals are subjected to more stress, increasing the likelihood of wear.

Secondly, improper installation can also cause seal failure. If the seals are not installed correctly, they may be damaged during the installation process. This could include cutting or nicking the seals, or not installing them in the correct orientation. Additionally, over - tightening or under - tightening the gland nuts that hold the seals in place can lead to premature failure.

Another factor is the compatibility of the seals with the hydraulic fluid. Different hydraulic fluids have different chemical properties, and if the seals are not compatible with the fluid, they can swell, harden, or deteriorate. For instance, using a mineral - based hydraulic fluid with seals that are designed for synthetic fluids can cause the seals to lose their integrity.

2. Rod Bending or Scoring

The piston rod is a critical component of the Rexroth cylinder. It transfers the force generated by the hydraulic pressure to the load. However, it is also susceptible to bending and scoring.

Rod bending can occur due to overloading. When the load applied to the cylinder exceeds its rated capacity, the piston rod may bend. This is especially common in applications where the load is not evenly distributed or where there are sudden shock loads. For example, in a construction equipment application, if the cylinder is used to lift a heavy object that is not properly balanced, the rod may experience excessive stress and bend.

Scoring of the piston rod can be caused by contaminants in the hydraulic fluid. If there are particles such as dirt, sand, or metal shavings in the fluid, they can act like abrasives and score the surface of the rod as it moves back and forth. This scoring can not only damage the rod itself but also cause accelerated wear of the rod seals. In addition, if the cylinder is operating in a dirty environment and the rod wiper seals are not effective in keeping out contaminants, the rod is more likely to be scored.

3. Cylinder Barrel Wear

The cylinder barrel is the housing for the piston and the hydraulic fluid. Wear in the cylinder barrel can have a significant impact on the performance of the cylinder.

One of the main causes of cylinder barrel wear is the lack of proper lubrication. Hydraulic fluid not only provides the power for the cylinder but also lubricates the moving parts. If the fluid level is low or if the fluid has degraded, there may not be sufficient lubrication between the piston and the cylinder wall. This can lead to increased friction and wear.

Another cause is the presence of contaminants in the fluid. As mentioned earlier, particles in the hydraulic fluid can act as abrasives and wear down the cylinder barrel. In some cases, corrosion can also occur, especially if the cylinder is operating in a humid or corrosive environment. Corrosion can weaken the cylinder barrel and lead to leakage.

4. Valve and Port Blockage

Rexroth cylinders are often equipped with valves and ports that control the flow of hydraulic fluid. Blockage of these valves and ports can prevent the cylinder from operating correctly.

Contaminants in the hydraulic fluid are the primary cause of valve and port blockage. Particles can accumulate in the small passages of the valves and ports, restricting the flow of fluid. This can lead to slow or uneven operation of the cylinder. For example, if a check valve is blocked, the cylinder may not be able to hold its position properly, or it may retract or extend unexpectedly.

In addition, deposits from the hydraulic fluid can also cause blockage. Over time, the additives in the hydraulic fluid can break down and form deposits. These deposits can build up in the valves and ports, reducing the flow area and affecting the performance of the cylinder.

5. Internal Leakage

Internal leakage occurs when hydraulic fluid bypasses the piston seals and flows from one chamber of the cylinder to the other. This can result in a loss of power and reduced efficiency of the cylinder.

Internal leakage can be caused by worn piston seals, as mentioned earlier. If the piston seals are damaged or worn, they can no longer effectively separate the two chambers of the cylinder, allowing fluid to leak between them. Another cause is damage to the cylinder walls or the piston itself. For example, if the cylinder wall has a scratch or if the piston has a crack, fluid can leak past these imperfections.

Impact on Equipment and Solutions

The failure of Rexroth cylinders can have a significant impact on the equipment they are installed in. It can lead to reduced productivity, increased downtime, and higher maintenance costs. For example, in a manufacturing plant, if a cylinder fails in a production line, the entire line may have to be shut down until the cylinder is repaired or replaced.

To address these failure modes, regular maintenance is essential. This includes checking the hydraulic fluid level and quality, inspecting the seals for wear, and cleaning or replacing the filters to remove contaminants. Additionally, proper installation and operation of the cylinders are crucial. Operators should ensure that the cylinders are not overloaded and that the equipment is used within its rated capacity.

If you are interested in our Rexroth cylinders, such as the CDH1 Cylinder, CST3 Cylinder, or CDH2 Cylinder, please feel free to contact us for more information and to discuss your specific requirements. We are committed to providing high - quality products and excellent customer service.

References

• "Hydraulic Cylinder Technology" by John F. Carlisle
• "Fluid Power Technology" by David Crolla
• Rexroth Hydraulic Cylinder Technical Manuals