A hydraulic pump is the power source of a hydraulic system, also known as a "power element." It converts the mechanical energy input from a prime mover (electric motor, internal combustion engine, etc.) into hydraulic energy to drive the actuators in the hydraulic system. In every hydraulic system, the hydraulic pump is an indispensable power device. Hydraulic pumps have a wide range of applications, from large engineering machinery to small hydraulic tools. Therefore, understanding common hydraulic pump malfunctions is essential knowledge for every engineer. Autos has compiled troubleshooting methods and maintenance precautions for common malfunctions to provide engineers with basic knowledge for better understanding hydraulic systems.
1. Main causes and troubleshooting methods for a hydraulic pump failing to draw in or discharge oil during operation
(1) Damage to the pump, pump motor, or coupling between the motor and pump. The pump, motor, or coupling should be replaced promptly.
(2) Low oil level in the tank or pump installation position too high, causing the pump to fail to draw in oil. The oil level in the tank should be increased to the indicated level, or the pump height should be adjusted to ensure the pump's suction head is within the specified range.
(3) The oil pump seal is aged or damaged, allowing air to enter the pump and reducing oil suction. Check the pump shaft seal and replace it with a new seal or replace the pump altogether.
(4) The oil contains impurities, increasing its viscosity. The oil suction filter or oil pipe may be clogged, preventing normal oil suction. Clean the oil pipe and filter promptly and replace the grease regularly according to relevant regulations.
Common Troubleshooting Methods and Daily Maintenance of Hydraulic Pumps
2. Main Causes and Solutions for Hydraulic Pumps Discharging Oil but Insufficient Pressure and Reduced Efficiency
(1) Severe wear of sliding parts inside the pump, resulting in low volumetric efficiency and excessive axial or radial clearance. The solution is to replace the pump or overhaul it.
(2) Damaged oil pipes or poor sealing at the suction end allow air to enter. Check all connections and seal them or replace the oil pipes.
(3) The oil pump pipe is clogged, and the filter contains a lot of debris. Clean it promptly to ensure the cleanliness of the pipes and filter.
(4) The variable pump is improperly adjusted, and the overflow valve core is severely worn. Readjust the flow rate, replace the overflow valve, and ensure stable pump operation.
(5) The oil pump speed is not at the rated speed, or there is debris inside the pump. Select a suitable motor according to the instruction manual. If there is debris inside the pump, clean it promptly.
3. Main causes and troubleshooting methods for severe noise during hydraulic pump operation
(1) In most cases, it is caused by insufficient oil suction, such as a clogged oil filter; low oil level, air intake; air intake at the pump's oil seal, etc. Check the oil level in the tank promptly, replace damaged pipes, check the pump body seal, clean the oil pipes and filter, and change the grease regularly.
(2) The oil viscosity is too high, the oil temperature is too low, or there are air bubbles in the oil. Change the oil according to the season. (3) Mechanical installation problems: Damaged coupling between the pump and motor, or misalignment between the pump and motor causing excessive vibration and noise during operation. Check the wear of the coupling, replace it promptly, and align it according to installation requirements.
(4) Pump speed is too high, or an unsuitable motor is selected. Reduce the pump speed and select a suitable motor.
(5) Air enters due to worn pump oil seal, or loose pump end cover bolts. Replace the pump shaft seal and tighten the gland bolts.
(6) Gear pump gears have low precision or poor contact, or internal parts are damaged. Replace the gears or grind and repair them, and replace damaged parts.
(7) Gear pump axial clearance is too small, or the perpendicularity of the gear inner hole and end face, or the parallelism of the two holes on the pump cover, exceeds the tolerance. Replace the gear pump promptly.
(8) Oil pump overflow valve is blocked. Clean or replace the overflow valve.
(9) Vibration is caused by unstable pipeline fixing. Secure the pipeline properly.
4. Main Causes and Troubleshooting Methods for Hydraulic Pump Body Oil Leakage
(1) Damaged center spring in the plunger pump causes loss of sealing between the cylinder and the distributor plate. Replace the spring and reseal.
(2) Damaged oil seal or sealing components, worn or poorly sealed seals at pipeline connection points. Replace the seals.
(3) Worn internal pump components with excessive clearance. Replace or reconfigure the components.
Common Troubleshooting Methods and Daily Maintenance of Hydraulic Pumps
5. Main Causes and Troubleshooting Methods for Hydraulic Pump Overheating
(1) Oil viscosity is too high or too low. Prolonged use results in excessive impurities in the oil. Change the oil promptly and use oil of suitable viscosity.
(2) Severe wear of the pump side plate and bushing against the gear end face causes overheating. Replace the side plate and bushing or replace the pump immediately.
(3) Insufficient oil tank capacity leads to poor heat dissipation and high oil temperature. Increase the oil tank capacity and expand the heat dissipation area. 6.1 Pre-operation checks for hydraulic pumps
(1) Check if the hydraulic pump is installed accurately and reliably, if the screws are tightened, and if the coupling installation meets the requirements;
(2) Check if the pump body is filled with oil;
(3) Check if the pump's rotation direction matches the inlet and outlet ports;
(4) Check if the safety valve of the hydraulic system is adjusted to the specified pressure value.
Common troubleshooting methods and daily maintenance of hydraulic pumps
6.2 Precautions during hydraulic pump operation
Do not start the pump at full speed abruptly. The prime mover switch should be jogged several times under unloaded conditions before continuous no-load operation. This is to remove as much air as possible from the pipeline. After running under no-load for 1-2 minutes without any abnormalities, gradually load the pump. During loading, there should be no abnormal vibration, noise, or leakage. Otherwise, immediately stop the pump, inspect, analyze, and troubleshoot the problem. 6.3 Maintenance After Hydraulic Pump Operation
If the pump is not used for a long period, drain the oil and refill it with oil of low acid value. Apply anti-rust oil to exposed machined surfaces and seal all oil ports with screw plugs to prevent contaminants from entering.
7. Summary
Hydraulic pumps have a wide range of applications and play an important role in industrial and agricultural production. Many factors affect the pump's lifespan during use, including its design and manufacturing, the selection of components related to pump use (such as couplings and oil filters), and the operation during commissioning. This article mainly explains common faults and their solutions, as well as precautions during operation. Regular inspection and maintenance, and timely detection of equipment defects, can extend the pump's service life.
