What are the causes of hydraulic pump failure?

　When repairing, find the cause of the failure from the following three points and improve the system:
　　(1) Check the internal leakage of the boom cylinder. The simplest method is to raise the boom and see if there is any obvious free fall. If it falls significantly, disassemble the cylinder for inspection. If the seal is worn, it should be replaced.
　　(2) Check the control valve. First, clean the safety valve and check whether the valve core is worn. If it is worn, it should be replaced. If there is still no change after the safety valve is installed, check the wear of the control valve valve core. The general limit of the gap is 0.06 mm. If the wear is serious, it should be replaced.
　　(3) Measure the pressure of the hydraulic pump. If the pressure is too low, adjust it. If the pressure still cannot be adjusted after increasing the pressure, it indicates that the hydraulic pump is severely worn.
　　Generally speaking, the main reasons for the inability of the boom to lift under load are:
　　a. Severe wear of the hydraulic pump. Severe internal leakage occurs at low speeds; at high speeds, the pump pressure increases slightly, but due to pump wear and internal leakage, the volumetric efficiency decreases significantly, making it difficult to reach the rated pressure. Long-term operation of the hydraulic pump further exacerbates wear, increasing oil temperature, which causes wear of hydraulic components and aging/damage of seals, loss of sealing capacity, deterioration of hydraulic oil, and ultimately leads to failure.
　　b. Unreasonable selection of hydraulic components. The boom cylinder specifications are 70/40 non-standard series, and the seals are also non-standard parts, resulting in high manufacturing costs and inconvenient seal replacement. The small diameter of the boom cylinder inevitably leads to high system set pressure.
　　c. Unreasonable hydraulic system design. The control valve and full hydraulic steering gear are single-pump series, and the safety valve set pressure is 16 MPa, while the rated working pressure of the hydraulic pump is also 16 MPa. The hydraulic pump often works under full load or long-term overload (high pressure), and the system has hydraulic impact. The oil is not changed for a long time, the hydraulic oil is contaminated, and the hydraulic pump wear is aggravated, resulting in the hydraulic pump casing bursting (this type of failure was later discovered).
　　2. Improvements and Effects
　　(1) Improve the hydraulic system design. After repeated demonstrations, an advanced priority valve and load-sensing full hydraulic steering gear were finally adopted, as shown in Figure 2. The new system can prioritize the allocation of flow according to steering requirements, ensuring sufficient oil supply regardless of load size or steering wheel speed. The remaining part can be fully supplied to the working device circuit, eliminating power loss caused by excessive oil supply to the steering circuit, improving system efficiency, and reducing the working pressure of the hydraulic pump.
　　(2) Optimize the design of the boom cylinder and hydraulic pump to reduce system working pressure. Through optimization calculations, the boom cylinder adopts the standard series 80/4. The hydraulic pump displacement is increased from 10 ml/r to 14 ml/r, and the system set pressure is 14 MPa, which meets the lifting force and speed requirements of the boom cylinder.
　　(3) During use, attention should also be paid to the correct use and maintenance of the loader, regularly adding or replacing hydraulic oil, maintaining the cleanliness of the hydraulic oil, and strengthening daily inspection and maintenance.