Common Faults and Troubleshooting Methods of Axial Piston Pump
The piston pump serves as the power component of the hydraulic system, functioning as the heart of the entire hydraulic setup. Its failure can significantly impact the normal operation of the system. The following section outlines common causes of axial piston pump failures and provides corresponding solutions:
- Excessive Noise
(1) Presence of air inside the piston pump, often occurring during initial installation. Ensure the new pump is filled with hydraulic oil to lubricate the bearing, plunger, and cylinder.
Treatment Method: Open the oil filling port while the pump is running to discharge air from the pump.
(2) Low oil level in the tank, blocked oil suction pipe, or air leakage in the oil inlet pipe. Treatment Method: Add sufficient oil; clean the filter, clear the intake pipe; check and tighten the connecting screws of the oil inlet pipe.
(3) Improper installation of the oil pump and motor, causing inconsistent concentricity between the pump shaft and motor shaft, resulting in noise.
Treatment Method: Check and adjust the concentricity of the oil pump and motor installation.
(4) High viscosity of hydraulic oil, reducing the pump’s self-priming ability and volumetric efficiency.
Treatment Method: Choose hydraulic oil with appropriate viscosity; if the oil temperature is too low, heat it.
- Unstable Pressure Gauge Pointer
(1) Severe wear between the oil distribution plate and the cylinder block or between the plunger and the cylinder block, leading to excessive internal and external leakage.
Treatment Method: Check and repair the mating surface of the oil distribution plate and the cylinder block; replace the plunger if necessary; tighten the screws at each connection to eliminate leakage.
(2) In the case of an axial piston variable pump, a too-small variable angle can result in insufficient flow and increased internal leakage, causing pressure instability.
Treatment Method: Increase the variable angle of the variable mechanism appropriately to eliminate internal leakage.
(3) Blocked oil inlet pipe or increased oil suction resistance due to air leakage, leading to an unstable pressure gauge pointer.
Treatment Method: Clear the blocked oil inlet pipe, clean the inlet filter, check and tighten the connecting screws of the oil inlet pipe section, and eliminate leakage.
- Insufficient Flow Rate
(1) Low oil level in the fuel tank, blocked oil pipe or oil filter, or excessive air leakage causing increased resistance.
Treatment Method: Check the fuel tank oil level; add hydraulic oil if insufficient; unblock and clean blocked oil pipes and filters; tighten screws at each connection to eliminate air leakage.
(2) Failure to fill the oil pump with oil before running, leaving air inside.
Treatment Method: Fill oil from the oil return port of the oil pump to remove air.
(3) Broken central spring of the oil pump preventing plunger return, leading to poor sealing between the cylinder block and the oil distribution plate.
Treatment Method: Ensure the central spring of the oil pump has sufficient elastic force or replace if broken.
(4) Improper oil pump connection causing axial force on the pump bearing, resulting in a gap between the cylinder block and oil distribution plate.
Treatment Method: Change the connection method to eliminate axial force.
(5) For a variable axial piston pump, the variable angle may be too small.
Treatment Method: Adjust the variable angle appropriately if it’s too small.
(6) Contaminated hydraulic oil or wear between the cylinder block, oil distribution plate, or plunger causing excessive oil leakage.
Treatment Method: Check wear on the cylinder block, oil distribution plate, and plunger; repair or replace the plunger as needed.
(7) Low oil temperature causing decreased oil viscosity, increased internal leakage, and pump overheating.
Treatment Method: Select hydraulic oil with suitable viscosity based on oil pump temperature; identify and address reasons for abnormal oil temperature promptly.
- Serious Oil Leakage
(1) Poorly sealed joints of the oil pump, such as damaged sealing rings.
Treatment Method: Inspect and replace the sealing ring for each joint.
(2) Excessive wear between the oil distribution plate and cylinder block or plunger and contract body, leading to increased oil return pipe leakage and internal leakage.
Treatment Method: Grind the contact surface between the oil distribution plate and the cylinder block; match the cylinder block and plunger pair.
- Non-Zero Oil Displacement at Neutral Position
When the swash plate inclination angle of the variable axial piston pump is zero (neutral position), the output flow should be zero. However, deviations from the midpoint of the adjustment mechanism may occur due to controller misalignment, looseness, or damage.
Treatment Method: Re-zero, tighten, or replace the controller; address insufficient angular maintenance or wear of the tilt trunnion causing this phenomenon.
- Fluctuation of Output Flow
Output flow fluctuations can result from poor control of the variable mechanism, such as foreign matter entering the mechanism, scratches, wear marks, or scars on the control piston.
Treatment Method: Disassemble the hydraulic pump, replace damaged parts, increase damping, enhance spring stiffness, and adjust control pressure to stabilize control piston movement.
- Abnormal Output Pressure
(1) Low output pressure may be due to oil inlet pipeline leaks or large hydraulic system leakage.
Treatment Method: Identify and fix air leaks, tighten or replace seals, and adjust the overflow valve if necessary.
(2) High output pressure may result from rising circuit load or faults in directional valve, pressure valve, transmission device, or oil return pipeline.
Treatment Method: Check components other than the pump, adjust the relief valve if needed, and investigate and address issues causing excessively high pressure.
In addition to the troubleshooting guide, it is essential to follow proper maintenance procedures for plunger pumps:
Maintenance Procedures for Plunger Pump
After a period of operation, plunger pumps require regular maintenance, divided into first-level and second-level maintenance:
1. First-level Maintenance (1000-1200 hours)
- Clean the crankcase air filter.
- Tighten fastening nuts of each part.
- Adjust packing of the packing box.
- Check for leaks in the inlet and outlet valves.
- Inspect and ensure proper functioning of automatic control instruments and valves.
- Check and adjust the connecting belt.
2. Secondary Maintenance (4000-4800 hours)
In addition to first-level maintenance tasks, perform the following:
- Add grease to motor bearings.
- Check for loose pulleys and ensure end faces are in a plane.
- Calibrate instruments in the automatic control box and verify the vibration switch for reliable and sensitive automatic protection devices.
- Check and replace lubricating oil every six months, cleaning any dirt in the oil pool.