Here, the main reasons why the excavator boom can not be lifted with load and the improvement methods are explained from the perspective of hydraulic pump, which is for reference only.
1. Main reasons
(1) The hydraulic pump of excavator is severely worn
Serious leakage in the pump during low-speed operation; During high-speed operation, the pump pressure increases slightly, but the volumetric efficiency decreases significantly due to pump wear and internal leakage, 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.
(2) Unreasonable selection of hydraulic components
The specification of boom cylinder is 70 / 40 non-standard series, and the seal is also non-standard, which has high manufacturing cost and inconvenient replacement of seal. The small cylinder diameter of boom cylinder is bound to make the set pressure of the system high.
(3) Unreasonable design of hydraulic system
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 is 16MPa. The hydraulic pump often works under full load or overload 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 explosion of the pump shell of the hydraulic pump.
2. Improvement and effect
(1) Improve hydraulic system design
After many demonstrations, the excavator hydraulic pump maintenance finally adopts the form of advanced priority valve and load sensing full hydraulic steering gear. The new system can give priority to the distribution of flow according to the Steering requirements, ensure sufficient oil supply regardless of the size of load and the speed of steering wheel, and the rest can be supplied to the working device circuit, Thus, the loss of success rate caused by excessive oil supply in the steering circuit is eliminated, the system efficiency is improved and the working pressure of the hydraulic pump is reduced. Reduce severe wear of excavator hydraulic pump.
(2) Optimization design of boom cylinder and hydraulic pump modeling
Reduce the working pressure of the system. Through optimization calculation, the boom cylinder adopts standard series 80 / 4. The displacement of the 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.
(3) Strengthen daily inspection and maintenance
Pay attention to the correct use and maintenance of the excavator during use, add or replace the hydraulic oil regularly, maintain the cleanliness of the hydraulic oil, and strengthen daily inspection and maintenance. Avoid serious wear of excavator hydraulic pump, so as to reduce the maintenance times of excavator hydraulic pump.
