Pressure-Compensated Variable Displacement Swash Plate Pump
Four possible causes of reduction in performance (with reasoning):
1. Wear of swash plate or slipper pads
- Continuous piston contact with the swash plate surface causes wear or scoring.
- This results in loss of full piston stroke and inefficient transfer of force, reducing volumetric output.
- Symptoms: gradual loss of delivery pressure/flow even at high swash angles.
2. Internal leakage past pistons and cylinder block (barrel wear)
- Excessive clearance between piston shoes, bores, or valve plate face allows high-pressure oil to leak back to the low-pressure side.
- Reduces volumetric efficiency, particularly noticeable under load.
- Often no external signs, since leakage is internal.
3. Malfunction or wear of the compensator control valve
- If the pressure compensator spool sticks, is worn, or has weak springs, it may begin to destroke the swash plate prematurely.
- Pump will cut back delivery before reaching the design system pressure.
- Appears as “under-performance” even though the pump is still running smoothly.
4. Air ingress or cavitation at the suction side
- Even if the filter is clean, tiny leaks in suction pipe joints or shaft seals may allow air to enter.
- This causes cavitation or aerated oil, reducing the effective displacement and damaging pistons/valve plate over time.
- May not show obvious external leaks but performance loss is significant.