How to solve the problem of high vacuum degree in the suction pipe of the main pump of the WY20 excavator?

The WYZO type hydraulic excavator produced by our company has been basically recognized by users since it was launched on the market. However, there are still some problems. Mainly, due to structural limitations during the design process, in order to facilitate the maintenance and repair of the diesel engine, the length of the oil suction pipe of the main oil pump (A8V80SR4R121F1 plunger pump) was increased, resulting in a large vacuum degree when the pump port sucks oil. This leads to a decline in the reliability of the main oil pump's operation.

Due to the poor self-priming ability of the main pump itself, there are strict requirements for the vacuum degree of the pump's oil suction port. According to the main pump's user manual, the vacuum degree value of the oil suction port must not exceed 0.02MPa. For this reason, we conducted on-site measurements of the vacuum degree at the oil suction port of the WY20 excavator at the aluminum plant construction site in Xin 'an County. The maximum vacuum degree at the main pump's oil suction port was measured to be 0.02MPa, which was exactly at the edge of the specified value and had a certain impact on the service life of the main pump. After analysis, we decided to solve the problem of a large vacuum degree value at the suction port of the main oil pump from the design perspective.

1. The causes of the vacuum degree at the suction port of the main oil pump

The LR6105 diesel engine adopted on the WY20 hydraulic excavator is produced by the Second Engine Factory of the First Tractor Corporation by introducing the technology of the British Licardo Company. Its high-pressure pump, diesel filter and oil filter are all located on the left side. When designing, considering the maintenance and upkeep of the diesel engine, the high-pressure pump, diesel filter and oil filter were placed at the front of the excavator. The crankshaft output end was on the left side of the excavator, while the hydraulic oil tank was on the right side of the excavator platform. As a result, the suction pipe was 2.5 meters long and had three bends, which increased the suction resistance of the main oil pump. Although the oil tank was preloaded (0.05MPa), it was still difficult to counteract the pressure drop caused by its resistance, thus creating a vacuum at the pump port

For the reasons mentioned above, only by shortening the length of the suction pipe of the main oil pump and reducing the pipe resistance can the vacuum degree at the suction port of the main pump be eliminated.

2 Solution

The objective to be achieved is to reduce the vacuum degree of the main pump suction pipe, making the vacuum degree value lower than 0.005MPa.

The solution is as follows: The original positions of the hydraulic oil tank and diesel tank remain unchanged, and the upper platform structure does not make major alterations. Only the installation direction of the diesel engine on the excavator is reversed by 180°, and its bracket is slightly modified to shorten the length of the main pump suction pipe from the original 2.5m to 0.6m

3 Conclusion

The improved prototype was tested on the construction site and it was found that:

When the oil tank is pre-pressurized, the vacuum degree at the suction port of the main pump is zero under the four working conditions: the valve is in a neutral position, the boom lifting and rotation combined action, the walking and rotation combined action, and the four oil cylinders combined action.

(2) When the oil tank is not pre-pressurized, the maximum vacuum degree under the above four working conditions is 0.004MPa. It can be seen that the vacuum degree at the suction port of the main pump of the improved prototype has significantly decreased, reaching the predetermined goal.