A hydraulic pump is a hydraulic component with a complex structure composed of multiple moving parts. After operating for a period of time, its components are prone to wear and damage, leading to increased oil leakage, reduced system flow, decreased system pressure, and decreased volumetric efficiency. Practice has proven that timely fault diagnosis of the hydraulic pump, identifying the cause of the fault, troubleshooting, and timely maintenance and inspection of the hydraulic pump as required can effectively ensure the normal operation of the hydraulic pump and extend its service life.

1. Common faults of hydraulic pump

There are many types of hydraulic pump failures. Summarizing common hydraulic pump failures is a basic approach to correctly understanding hydraulic pump failure issues.

Common faults of hydraulic pumps include:

The improper selection of oil for the hydraulic pump results in low work efficiency of the hydraulic pump;

② The moving components of the hydraulic pump fail, and the hydraulic oil oxidizes and deteriorates;

③ Leakage;

④ Noise.

2. Fault cause analysis

2.1 The working efficiency of the hydraulic pump is not high

In hydraulic equipment, the hydraulic pump is regarded as the heart of the system, while hydraulic oil serves as the "blood" within the system. As hydraulic pumps evolve towards higher pressure, greater flow rate, lower noise, and longer lifespan, the rational selection of hydraulic pump oil directly impacts the performance and efficiency of the equipment, as well as the service life and maintenance costs of the hydraulic pump. Simultaneously, it can also extend the oil change interval of the fluid itself, saving on purchasing costs.

2.2 The moving components of the hydraulic pump fail, and the hydraulic oil oxidizes and deteriorates

The primary cause of hydraulic pump malfunctions and component failures is the presence of excessive contaminants in the hydraulic oil. Due to the diverse sources and forms of contaminants in the oil, the cleanliness of the oil directly impacts the operational status of the hydraulic pump and the lifespan of its components. Therefore, it is crucial to control the contamination of the oil used in the hydraulic pump. Common contaminants in the oil are solid particles.

2.3 Leakage issue

During the normal operation of a hydraulic pump, the oil should flow or stay in the component's cavity or pipeline, and different cavities have different pressures. If the oil flows to the cavity it should not be in or outside the system, leakage issues will occur. Leakage issues directly affect the normal operation of the entire hydraulic system. Leakage causes are divided into internal leakage and external leakage.

(1) Causes of internal leakage:

① Deviation in machining accuracy due to operational wear and tear;

② There were issues with the installation of the sealing parts and sealing rings during assembly, resulting in damage;

③ The selection of sealing type and sealing ring material is unreasonable.

(2) Causes of external leakage:

When the hydraulic system experiences vibration or impact, the hydraulic oil pipe connections may loosen;

② The sealing components of the hydraulic system aged during operation, resulting in poor sealing;

③ Wear occurs in hydraulic components during the mating process;

④ The long-term exposure of hydraulic components to high temperature and high pressure environments causes the sealing rubber to deteriorate.

2.4 Noise issue

Noise is both a form of pollution and a public hazard. The primary source of noise in hydraulic systems is the hydraulic pump. The mechanical vibrations and oil pulsations generated by the hydraulic pump are primarily induced by its noise. These vibrations and pulsations not only affect the hydraulic pump itself, but also impact other components of the hydraulic system, such as the oil tank and oil circuit, which may in turn induce even louder noise.

3. Fault resolution measures

During the operation of a hydraulic pump, the causes of malfunctions can vary, and it's possible for a single fault to arise due to multiple factors. Therefore, when addressing malfunctions, it is necessary to analyze each specific issue individually, in order to ensure efficient resolution of hydraulic pump malfunctions. Specifically, corresponding measures need to be taken for the various malfunctions mentioned above.

3.1 Proper selection of oil for hydraulic pumps

To ensure the normal operation and operational efficiency of the entire hydraulic system and machinery, it is essential to select the hydraulic pump oil correctly and reasonably. To choose the appropriate hydraulic oil, the first step is to ensure that the viscosity of the hydraulic oil is suitable, neither too high nor too low. If the viscosity is too low, it will increase internal and external leakage in the entire hydraulic pump and system, reduce the working efficiency of the hydraulic pump, increase power loss, exacerbate wear of the moving parts, and raise the oil temperature. If the viscosity is too high, it will increase the resistance for the hydraulic pump to suck in hydraulic oil, increase pressure loss in the hydraulic pump and hydraulic system, raise the oil temperature excessively, and generate excessive noise.

Therefore, the selection of hydraulic oil should be based on comprehensive factors such as the type of hydraulic pump, operating temperature, operating pressure, and economy. At the same time, the varieties and grades recommended by the hydraulic pump manufacturer's samples and instructions should also be considered. When selecting, it is generally necessary to first determine the applicable viscosity range and then determine the variety and grade of hydraulic oil. The commonly used hydraulic oils in the market mainly include environmentally acceptable hydraulic oil, high-pressure anti-wear hydraulic oil, and clean hydraulic oil. With the continuous enhancement of people's awareness of environmental protection, varieties of environmentally friendly hydraulic oils will continue to emerge and be used.

3.2 Pollution sources of hydraulic pump

(1) Residual pollutants. These are pollutants generated during the manufacturing, transportation, and assembly processes, such as burrs remaining from processing and metal shavings resulting from bumps during transportation or assembly.

(2) Invasive pollutants can be generated due to various factors such as poor sealing of the oil tank cap storing the oil, failure to filter the oil added to the tank according to regulations, and failure to strictly follow cleaning procedures during maintenance.

(3) Generation of pollutants. System pollution exceeds the prescribed level and is not promptly addressed, and residual pollutants in the fuel tank are not regularly removed.

3.3 Measures to control pollution of hydraulic pumps

Due to the complexity of pollutant sources, different measures should be taken for pollutants from various origins. For externally ingested pollutants, the primary measure is to strengthen protection; for pollutants generated during the operation of hydraulic pumps, the main approach is filtration and separation; and for residual pollutants, the main measure is cleaning. Meanwhile, in terms of design, it is also necessary to enhance the removal of factors that are not conducive to cleaning and flushing.

3.4 Leakage control measures

3.4.1 Internal leakage

(1) During assembly, pay special attention to the cleanliness of the sealing parts and sealing rings. To prevent damage to the sealing rings during assembly, it is necessary to strictly follow the relevant requirements for correct installation.

(2) The processing technology of parts must ensure that the precision and craftsmanship of grooves, slots, and surfaces in sealing areas strictly comply with the specifications. This is the basic condition for ensuring no internal leakage occurs.

(3) The use of integrated hydraulic valves in hydraulic systems can simplify the oil circuit layout and reduce the factors that lead to internal leakage.

(4) During the design process, the selection of seals and connectors should be based on their usage conditions to determine their materials and dimensions.

3.4.2 External leakage

(1) Utilize a reasonable pressure control device to maintain the system pressure at a relatively low value.

(2) For external leakage caused by vibration and shock, an accumulator can be used inside the system to reduce the shock; outside the system, a vibration-reducing bracket can be used to secure the oil pipe, thereby reducing shock and vibration.

(3) During the pipeline connection process, welding should be preferred and the use of pipe fittings minimized.

(4) When the taper pipe thread fails to meet the required sealing requirements during use, it can be replaced with an elbow, tee joint, or straight threaded joint.

3.5 Noise control measures

Under normal circumstances, the noise of a pump is directly proportional to its rotational speed. Therefore, to reduce noise, the rotational speed of the pump can be kept below 1500 r/min. To prevent the vibration of the pump from being transmitted to other parts and causing noise, a section of hose can be installed in all pipelines connecting the pump to the outside. This not only isolates the vibration but also absorbs pulsations. The noise generated when the pump pumps oil is mainly caused by cavitation vacuum formed by high viscosity and low temperature oil in the long suction pipe. The suppression method can be to use a suction pipe with a short length and a large diameter, or to set the height of the oil tank to be close to or higher than the pump.

4. Daily maintenance of hydraulic pump

4.1 Establish a maintenance system

Whether routine maintenance is conducted in a timely manner and the quality of hydraulic oil are factors that directly impact the service life of the hydraulic pump. To reduce the occurrence of hydraulic pump failures and effectively eliminate potential safety hazards, a comprehensive maintenance system should be established.

(1) Keep records. Staff members must strictly adhere to the inspection system in their operations. They should inspect and replace the oil every two to three months, regularly flush the oil filter, check whether the hydraulic oil has deteriorated, maintain the hydraulic system to prevent leaks, and ensure that no foreign objects enter the oil tank.

(2) Emphasize that inspection personnel should constantly monitor the readings of various measuring instruments, such as pressure gauges, pressure switches, oil temperature gauges, etc., check for leaks at valves and connections, ensure screws are tight, and strengthen the maintenance of mechanical components.

(3) Self-inspection. During patrol inspection, one should be able to distinguish whether the noise is caused by machinery or hydraulic noise by listening to it to judge the working status of the hydraulic system. In addition, it is necessary to regularly check the condition of the hydraulic oil to ensure the normal functioning of the hydraulic transmission medium.

4.2 Enhance the technical proficiency of maintenance personnel

(1) Regularly provide training on maintenance and assembly processes and other related knowledge to maintenance personnel, so that their theoretical knowledge can be gradually systematized.

(2) Establish a comprehensive learning and assessment mechanism, regularly organize training sessions for maintenance personnel, and ensure that their abilities and qualities in hydraulic pump maintenance are continuously improved.

(3) During the maintenance work of hydraulic pumps, establish a comprehensive apprenticeship education mechanism, allowing experienced mentors to guide newly hired maintenance personnel, ensuring the continuous transmission of practical experience and skills.

In summary, the fault diagnosis and maintenance of hydraulic pumps is a complex undertaking, especially as the types and mechanisms of hydraulic pumps become increasingly intricate. When a hydraulic pump malfunctions, it is necessary to efficiently and accurately diagnose the fault, systematically investigate, and identify the true cause. Regular maintenance should be carried out during the normal operation of the equipment to ensure its utilization rate and service life. Maintenance personnel need to continuously learn, foster a sense of change, and reflect and summarize in practice.

2026 July 3rd Week VAFEM Product Recommendation

Agricultural Wheel Hub Unit:

This type of product provides a complete maintenance-free sealed bearing unit with important advantages for farm applications. These quick-mount bearing units use long-life grease and seals.

Features and advantages of agricultural machinery hub unit:

Extended length, field-tested performance, stronger sealing performance, life-long grease lubrication, basic maintenance-free, simple installation and replacement procedures, special application design, low grease consumption, reduced maintenance and ownership costs, and ease of environmental Influence, improve production efficiency.

https://www.vafem.com/products/Agricultural-Wheel-Hub-Unit/898.html