Detecting and Diagnosing Hydraulic Cylinder Bypass

Hydraulic cylinders are critical components in many industrial machines and systems, but sometimes issues like bypassing can affect their performance. This article will guide you through the steps to diagnose a hydraulic cylinder for bypassing issues, identify potential causes, and ensure proper operation.

Introduction to Bypassing

Bypassing in hydraulic cylinders refers to the unintended flow of hydraulic fluid through the cylinder when it should not be happening, often due to valve malfunctions or fluid contamination. Detecting bypassing is essential for maintaining optimal performance, safety, and efficiency of the hydraulic system.

Methods of Detecting Bypassing

There are several methods to detect bypassing in a hydraulic cylinder. One common method is to apply a static load to the cylinder while the valves are centered. If the piston moves, it indicates that the cylinder is bypassing. This is a clear sign that the valves may not be functioning correctly, and the possibility of valve leakage needs to be investigated.

Conducting a Static Load Test

To conduct a static load test, follow these steps:

Disconnect the hydraulic system from the cylinder to prevent damage during the test. Cap the cylinder ports to ensure that the only flow going through the cylinder is the bypass flow. Apply a static load to the cylinder and observe the piston movement. If the piston moves, it confirms that the cylinder is bypassing. Disconnect and reassemble the cylinder carefully.

Other Indications of Bypassing

Other signs that may indicate bypassing include:

Valve Squeal

Bypassing can cause the valves to squeal or produce a noise when the cylinder is in operation. If you hear excessive noise coming from the hydraulic system, it could be a sign that the cylinder is bypassing. Carefully listen for any unusual sounds and check for any issues with the valves.

Increased Load on the Hydraulic Pump

Another indicator of bypassing is an increased load on the hydraulic pump. When the cylinder is working properly, the pump should not have to work harder. If the pump feels like it's struggling or laboring, reduce the fluid load and check for bypassing.

Common Causes of Bypassing and their Solutions

There are several common causes of bypassing in hydraulic cylinders. These include:

Valve Leakage

Valve leakage is one of the most common reasons for bypassing. This can occur due to wear and tear, dirt, or contaminants in the hydraulic fluid. To diagnose and resolve valve leakage, follow these steps:

Inspect the valves for any visible signs of wear or damage. Clean the valves using proper cleaning methods, which may include chemical cleaning or disassembly for thorough cleaning. Replace the valves if they are beyond repair or are showing significant wear. Reinstall the valves and test the cylinder again to ensure that bypassing has been resolved.

Contaminated Fluid

If the hydraulic fluid is contaminated with air or debris, it can cause the cylinder to bypass. To address this issue:

Replace the contaminated fluid with clean, fresh hydraulic fluid. Filter the fluid to remove any remaining debris or air bubbles. Ensure that the fluid reservoir is properly sealed to prevent further contamination.

Conclusion

Detecting and diagnosing bypassing in hydraulic cylinders is crucial for maintaining the performance and reliability of hydraulic systems. By recognizing the signs and conducting proper tests, you can identify the root cause of bypassing and take the necessary steps to resolve the issue. This ensures that your hydraulic equipment operates efficiently and safely.