Post treatment of the Excavator worn hydraulic pump

After the hydraulic pump of excavator was seriously worn, we found the fault cause according to the following three points and improved the system:

a. Check the internal leakage of the boom cylinder. The simplest way is to raise the boom to see if it has obvious free fall. If the drop is obvious, disassemble the cylinder for inspection, and replace the sealing ring if it is worn

b. Check the control valve. First clean the safety valve and check whether the valve core is worn. If it is worn, replace it. If there is no change after the installation of the safety valve, check the wear of the control valve core. The service limit of the clearance is generally 0.06mm, and replace it if it is seriously worn
c. Measure the pressure of the excavator hydraulic pump. If the pressure is low, adjust it. If the pressure still cannot be adjusted, it indicates that the hydraulic pump is seriously worn

Generally speaking, the main reasons why the boom cannot be lifted with load are:

a. The hydraulic pump of excavator is seriously worn, and the leakage in the pump is serious when running at low speed; During high-speed operation, the pump pressure increases slightly, but due to the wear and internal leakage of the pump, the volumetric efficiency decreases significantly, so it is difficult to reach the rated pressure. The long-time operation of the hydraulic pump intensifies the wear and the increase of oil temperature, resulting in the wear of hydraulic components, the aging and damage of seals, the loss of sealing capacity, the deterioration of hydraulic oil, and finally the failure

b. The selection of hydraulic components is unreasonable. The specification of boom cylinder is 70 / 40 non-standard series, and the seals are also non-standard parts. The manufacturing cost is high and the replacement of seals is inconvenient. The small cylinder diameter of boom cylinder is bound to make the set pressure of the system high

c. The design of the hydraulic system is unreasonable. The control valve and the full hydraulic steering gear are single pump in series, the set pressure of the safety valve is 16MPa, and the rated working pressure of the hydraulic pump of the excavator is 16MPa. The hydraulic pump often works under full load or overload (high pressure) for a long time, and the system has hydraulic impact and does not change oil for a long time. The hydraulic oil is polluted, which intensifies the wear of the hydraulic pump, resulting in the bursting of the pump shell of the hydraulic pump (such faults have been found since)

Improvement and effect

a. Improve the design of the hydraulic system. After many demonstrations, the advanced priority valve and load sensing full hydraulic steering gear are finally adopted. The new system can give priority to the distribution of flow according to the Steering requirements. No matter the size of the load and the speed of the steering wheel, it can ensure sufficient oil supply, and the rest can be supplied to the working device circuit, so as to eliminate the problem caused by excessive oil supply in the steering circuit The power loss improves the system efficiency and reduces the working pressure of the excavator hydraulic pump

b. Optimize the design of boom cylinder and hydraulic pump to reduce the working pressure of the system. Through optimization calculation, the boom cylinder adopts standard series 80 / 4. The displacement of hydraulic pump is increased from 10ml / R to 14ml / R, and the set pressure of the system is 14MPa, which meets the requirements of boom cylinder lifting force and speed

c. Pay attention to the correct use and maintenance of the loader during use, add or replace the hydraulic oil regularly, maintain the cleanliness of the hydraulic oil, and strengthen daily inspection and maintenance