Hydraulic Pump Trouble Shooting

Common Hydraulic Pump Problems

Cavitation

Cavitation occurs when the pump system can’t draw a full charge of oil, leading to noise and overheating around the shaft and front bearing. Other indicators include malfunctioning hydraulic cylinders or milky hydraulic oil. To address cavitation, inspect the pump suction strainer. Clean it thoroughly with a solvent and blow dry with an air hose. Even tiny deposits in the wire mesh can restrict oil flow. If you find varnish deposits on internal surfaces of pumps or valves, the system is operating too hot, and a heat exchanger should be installed.

Next, check for a clogged pump inlet. Ensure hoses are not collapsed and use hoses designed for pump inlets, which have an internal wire spiral to prevent collapse. Also, ensure the air breather on the reservoir isn’t clogged. In systems with a small air volume above the oil, the pump could experience cavitation during its extension stroke. Verify the oil viscosity as some pumps can’t prime heavy oil. In cold weather, using oil with a high viscosity index can prevent cavitation damage during startup.

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Hydraulic Pump Failure and Maintenance Tips

Suction Strainer and Oil Quality

Check the suction strainer size. Ensure it is correct and increase its size if possible.
Use high-quality oil. can reduce varnish and sludge formation.
Follow the recommended pump speed. pulley and gear ratios, and ensure the original electric motor hasn’t been replaced with a faster one.
Ensure the pump matches the system’s flow requirements. pump delivering higher flow than the system can handle can overload the suction strainer, necessitating a size increase.

Air in the System

Air in a new system typically purges within 30 minutes. Let the machine idle before operating to accelerate air removal. To identify air entry points, ensure proper oil levels; the pump intake should be well below the minimum oil level. Check the oil level with extended cylinders and avoid overfilling the reservoir.

Inspect the pump shaft seal. Worn seals on gear pumps, vane pumps and piston pumps can allow air to enter. Check all plumbing and joints in the pump inlet line for leaks. Pour oil over suspected leaks; noise cessation indicates a leak. Inspect the inlet port and rod seals of cylinders, as air may enter through damaged threads or improperly counterbalanced cylinders. Also, check the main tank return line to ensure it discharges well below the minimum oil level.

Water Contamination

Water in the system causes milky oil during operation and clear oil after shutdown. Water may enter through:

Leaks in a heat exchanger.
Condensation inside the reservoir. Tap off fluid from the bottom of the reservoir to prevent this.
Improper tubing or piping. these enter and leave below the oil level.
Shaft seal leaks. Overhead reservoirs can create pressure behind the seal, causing leakage.

Additional Issues

Excessive oil temperatures (200°F or higher) can shorten shaft seal life. Abrasives in the oil cause wear and scoring. To solve this problem, seal the reservoir air tight and maintain a maximum of 2 PSI above the oil. Leakage around pump ports may stem from over-tightening taper pipe threads into straight thread ports, which damages the threads.

Incorrect pump direction can result from reversed motor leads. Always ensure the pump runs in the direction marked on its nameplate or case. Regularly check suction strainer cleanliness, proper oil levels, and the condition of vanes, valves, or pistons. Verify the correct oil viscosity and maintain mechanical integrity, such as the shaft and coupling. Ensure motor and pump speeds are aligned.