When NACHI vane pump runs at low speed, the leakage in the pump is serious. When it runs at high speed, the pressure of the pump increases slightly. However, due to the wear and internal leakage of the pump, the volume efficiency decreases significantly and it is difficult to reach the rated pressure.
When NACHI vane pump operates on excavator, what should we do if there is serious damage? This problem is a headache for many users. When NACHI vane pump runs at low speed, the leakage in the pump is serious. When it runs at high speed, the pressure of the pump increases slightly. However, due to the wear and internal leakage of the pump, the volume efficiency decreases significantly and it is difficult to reach the rated pressure. Long working hours of hydraulic pumps aggravate wear and tear, increase oil temperature, which results in wear of hydraulic components and aging and damage of seals, loss of sealing capacity, deterioration of hydraulic oil, and eventually lead to failure. To avoid such a thing, the following A&S Hydraulic Co., Ltd after-sales service technical engineer Odom will give a detailed account of NACHI vane pump in excavator damage. The treatment methods after the damage are as follows:
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First. The main reasons why the boom can not be lifted with load are as follows:
1. The selection of hydraulic components is unreasonable. The specifications of the boom cylinder are 70/40 non-standard series, and the seals are also non-standard parts. The manufacturing cost is high and the replacement of the seals is inconvenient. The small cylinder diameter of the boom cylinder will inevitably make the setting pressure of the system high.
2. The design of hydraulic system is unreasonable. The control valve and the full hydraulic steering gear are connected in series with a single pump. The setting pressure of the safety valve is 16 MPa, and the rated working pressure of the excavator hydraulic pump is 16 MPa. Hydraulic pumps often work under full load or long-term overload (high pressure), and the system has hydraulic impact, long-term no oil change, hydraulic oil is polluted, which aggravates the wear of hydraulic pumps, so that the shell of hydraulic pumps bursts (such failure has been found later).
Secondly, after serious wear and tear of excavator NACHI vane pump, we can find out the causes of failure according to the following three points, and improve the system:
1. Check the internal leakage of the boom cylinder. The simplest way is to raise the arm to see if it has a clear free fall. If the drop is obvious, remove the cylinder and inspect it. If the seal ring has worn out, it should be replaced.
2. Check the control valve. First, clean the safety valve, check whether the spool is worn, if worn, it should be replaced. If there is no change after the safety valve is installed, then check the wear condition of the control valve spool. The gap usage limit is generally 0.06mm, and the wear should be replaced seriously.
3. Measure the pressure of hydraulic pump of excavator. If the pressure is on the low side, adjustments will be made, and the pressure can not be adjusted, which indicates that the hydraulic pump is seriously worn.
Third. Improvement and Effect
1. Improving the design of hydraulic system. After many demonstrations, the advanced priority valve and load sensing full hydraulic steering gear are finally adopted. The new system can distribute the flow to the excavator first according to the steering requirement. No matter the load and the speed of the steering wheel, the oil supply can be sufficient. The remaining part can be supplied to the working device circuit, which eliminates the power loss caused by the excessive oil supply to the steering circuit, improves the efficiency of the system and reduces the working pressure of the excavator hydraulic pump.
2. Optimize the shape of the boom cylinder and hydraulic pump to reduce the working pressure of the system. Through optimization calculation, the standard series 80/4 of the boom cylinder is adopted. The displacement of 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. Attention should also be paid to the correct use and maintenance of loaders in the course of use, adding or replacing hydraulic oil regularly, maintaining the cleanliness of hydraulic oil, and strengthening routine inspection and maintenance.