Electro-hydraulic Push Rod Failure Causes and Internal Leak Detection Methods

1. Internal oil leakage

Internal oil leakage refers to a small amount of fluid escaping from the high-pressure chamber to the low-pressure chamber within hydraulic components, such as the leakage of hydraulic fluid from the high-pressure to the low-pressure chamber in hydraulic transmission; oil leakage from the pressure passage of the directional valve back to the return oil passage, etc.

2. Leaked oil

Leakage oil refers to the small amount of liquid that leaks from the inside of components to the outside. This includes, for instance, oil leakage from the end face of gear pumps; leakage from hydraulic oil hoses, etc. The leakage of hydraulic systems mainly takes several forms, such as gap leakage, multi-porous leakage, adhesive leakage, and power leakage.

Reason

Design and Manufacturing Issue: After testing and calculation, the actual pre-compression rate of the hydraulic push rod for the scraper unloader is 5%, which is below the minimum pre-compression rate value.

The groove dimensions and precision of seals are significant factors affecting pre-compression rate. While there are standards to follow when designing seal grooves, they should be determined based on actual usage in different situations. The design intention of the circuit is clear; it is to maintain pressure during the rapid advance of the feed hydraulic cylinder to ensure the self-locking capability of the cylinder. At this point, the hydraulic cylinder is stationary, approaching a static seal condition. Therefore, the groove dimensions and tolerances of the seal should be selected based on the static seal condition, and the pre-compression rate of the seal should be chosen to be slightly larger. The groove of the hydraulic cylinder seal in the circuit is designed for dynamic sealing conditions, with an overly small pre-compression rate selected. Combined with insufficient attention during the manufacturing process, the grooves were too deep, leading to oil leakage when stationary.

2. Maintenance and Maintenance Issues: In reality, leakage situations are often complex, involving a combination of various causes and circumstances. However, most oil leakage in electro-hydraulic actuators is caused by seal failure.