When the NACHI vane pump is running at low speed, the pump leaks seriously. When the pump is running at high speed, the pump pressure is slightly increased, but the volumetric efficiency is significantly reduced due to the wear and leakage of the pump. It is difficult to reach the rated pressure.
What should I do if the NACHI vane pump is seriously damaged when it is operated on the excavator? This problem is a headache for many users. When the NACHI vane pump is running at low speed, the pump leaks seriously. When the pump is running at high speed, the pump pressure is slightly increased, but the volumetric efficiency is significantly reduced due to the wear and leakage of the pump. It is difficult to reach the rated pressure. The long-term operation of the hydraulic pump intensifies the wear and the oil temperature rises, which causes the wear of the hydraulic components and the aging and damage of the seals, the loss of the sealing ability, the deterioration of the hydraulic oil, and finally the failure, in order to avoid such a thing, the following A&S Hydraulic Parts Co.,Ltd w，Noah, the technical engineer of the after-sales service department, came to give a detailed explanation about the handling of the NACHI vane pump after the excavator was damaged:
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First, the main reasons for the failure to increase the load on the boom are:
1. The selection of hydraulic components is unreasonable. The boom cylinder is 70/40 non-standard series, and the seals are also non-standard parts. The manufacturing cost is high and the seal replacement is inconvenient. The cylinder diameter of the boom cylinder is small, which will inevitably make the system set high pressure.
2. The hydraulic system design is unreasonable. The control valve and the full hydraulic steering gear are connected in series with a single pump, the safety valve is set to a pressure of 16 MPa, and the rated working pressure of the excavator hydraulic pump is also 16 MPa. Hydraulic pumps often work under full load or long-time overload (high pressure), and the system has hydraulic shock, long-term oil change, hydraulic oil contamination, and the hydraulic pump wear is aggravated, causing the hydraulic pump casing to burst. Such a fault).
Second, after the serious wear of the excavator NACHI vane pump, we will find the cause of the fault according to the following three points and improve the system:
1. Check the internal leakage of the boom cylinder. The easiest way is to raise the boom to see if it has a clear free fall. If the drop is obvious, remove the cylinder and check that the seal should be replaced if it is worn.
2. Check the control valve. First clean the safety valve and check if the spool is worn. If it is worn, it should be replaced. If there is no change after the safety valve is installed, check the wear of the valve stem of the control valve. The clearance limit is generally 0.06mm. If the wear is serious, it should be replaced.
3. Measure the pressure of the excavator hydraulic pump. If the pressure is low, the adjustment is made, and the pressure is still not adjusted, indicating that the hydraulic pump is seriously worn.
Third, improvement and effect
1. Improve hydraulic system design. After many arguments, the advanced priority valve and load sensing full hydraulic steering gear were used. The new system can preferentially distribute the flow according to the steering requirements. No matter the load size or the steering wheel speed, the oil supply is sufficient, and the remaining part can be fully supplied to the working device circuit, thereby eliminating the power caused by excessive oil supply to the steering circuit. Loss increases system efficiency and reduces the working pressure of the excavator hydraulic pump.
2. Optimize the design of the boom cylinder and hydraulic pump to reduce the system working pressure. Through optimization calculations, the boom cylinders are based on the standard series 80/4. The displacement of the hydraulic pump is increased from 10ml/r to 14ml/r, and the system setting pressure is 14MPa, which meets the lifting force and speed requirements of the boom cylinder.
3, In the course of use should also pay attention to the correct use and maintenance of the loader, regularly add or replace hydraulic oil, maintain the cleanliness of hydraulic oil, and strengthen daily inspection and maintenance.