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Troubleshooting Piston and Hydrostatic Pumps and Their Impact on the System and Diesel Engine

Piston and hydrostatic pumps are widely used in industrial hydraulic systems and heavy machinery due to their high efficiency and ability to operate under high pressure. However, if they are faulty, worn out, or improperly adjusted, they can cause issues such as performance loss, excessive load on the engine, unusual leaks, pressure drop, and even engine smoke. Below, we examine 10 of the most common problems in these pumps and recommended solutions to fix them.

Causes:
• Incorrectly adjusted relief valve, leading to abnormally high pressure.
• Blockage in the pump’s outlet path (filters, control valves, or hoses), increasing pressure and overloading the engine.
• Failure in the pressure control mechanism of a variable piston pump, causing excessive pressure buildup.

Solution:
• Check and adjust the relief valve pressure according to the system’s design.
• Clean the oil outlet paths and filters to prevent blockages.
• Inspect and adjust the swash plate angle in variable piston pumps.

Causes:
• Oil temperature increases, reducing its viscosity, leading to pressure and flow loss.
• Gradual wear of pistons, cylinder block, and valve plate, reducing volumetric efficiency.
• Filter clogging, restricting adequate oil flow to the pump.

Solution:
• Replace hydraulic oil if its viscosity drops or it becomes contaminated.
• Inspect and replace worn pump components (pistons, cylinder block, valve plate).
• Clean or replace the oil filter to ensure proper oil supply to the pump.

Causes:
• Internal leakage in the control valve, allowing unintended oil flow.
• Failure in the swash plate angle control mechanism, causing unintended oil flow.
• Contaminants or failure in the return oil path, reducing pressure and leading to unintended movement.
• Worn saddle bearing, bearing seat, or the back of the swash plate that rests on the saddle bearing, causing unwanted movement.

Solution:
• Check and replace the control valve to prevent oil leakage.
• Inspect and adjust the swash plate mechanism in hydrostatic pumps.
• Clear any blockages or contaminants in the return oil path.
• Inspect and, if necessary, replace the saddle bearing, bearing seat, and the back of the swash plate.

Causes:
• Issue in the oil drain system from the pump or hydraulic motor, increasing pressure behind the shaft seal.
• Blocked or undersized oil drain lines to the hydraulic tank, causing excessive pressure on the shaft seal.
• Malfunctioning or clogged check valves in the drain system, preventing oil from exiting.

Solution:
• Inspect and clear the drain paths to ensure proper oil flow.
• Increase the diameter or optimise the oil drain path to the hydraulic tank.
• Check and clean or replace check valves in the drain system.

Causes:
• Excessive engine load due to high hydraulic system pressure.
• Internal pump seizure or excessive friction, increasing resistance and load on the engine.
• Improper pump installation or worn couplings, causing vibration and extra load on the engine.

Solution:
• Check and adjust the hydraulic system pressure and ensure the relief valve functions properly.
• Inspect bearings and internal pump components to prevent seizure.
• Check and align the pump and engine properly, ensuring the coupling is in good condition.

Causes:
• Cavitation (air bubbles in the oil), causing a knocking sound.
• Excessive wear in the valve plate or internal pump bearings.

Solution:
• Inspect for air leaks in the suction line and bleed the system to remove trapped air.
• Inspect and replace the valve plate and internal bearings if they are worn.

Causes:
• Poor-quality or contaminated oil, reducing lubrication efficiency.
• Excessive operating pressure, causing excessive heat generation.

Solution:
• Replace hydraulic oil with the correct type as recommended by the manufacturer.
• Inspect and adjust the system pressure to prevent excessive load on the pump.

Causes:
• Worn pistons, cylinder block, or valve plate, reducing pressure.
• Internal oil leakage, causing a drop in pressure.

Solution:
• Replace worn components and inspect the valve plate function.
• Fix internal leaks within the hydraulic system.

Causes:
• Worn or damaged coupling between the engine and pump.
• Misalignment between the engine and pump.

Solution:
• Check and replace the coupling if damaged.
• Precisely align the engine and pump to reduce vibrations.

Causes:
• Dirty return oil filter or blocked return lines.
• Presence of contaminants in the oil.

Solution:
• Clean the return path and replace the oil filter.
• Check and replace the oil if contaminated.
Conclusion

To prevent these issues:

✔ Regularly check and adjust system pressure and ensure the relief valve operates correctly.

✔ Keep oil pathways clean and replace filters as needed.

✔ Inspect and adjust the swash plate mechanism in hydrostatic pumps.

✔ Ensure the oil drain system is functioning properly and free from blockages.

✔ Align the pump and engine properly and replace worn couplings.
By following these maintenance and troubleshooting steps, you can extend the lifespan of hydraulic pumps, improve system performance, and reduce engine strain.

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Why does the return oil path get clogged?

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