The wheel excavator analyzed here adopts advanced technologies such as high-pressure variable displacement pump, variable displacement motor drive, two speed hydraulic shift transmission, elastic suspension device and unique folding arm. It has the characteristics of low center of gravity, good ride comfort, fast driving speed, safe and reliable whole machine and high operation rate. Generally, it is not easy to malfunction, but if it is not used in strict accordance with the operating procedures or maintenance is not strengthened, there will also be problems such as slow and weak lifting of boom.
Under the normal operation of the engine, when the right pilot control handle is pulled, the boom will rise and fall slowly and powerlessly, sometimes it will suddenly stop and accompanied by a sound, the operation efficiency will decline, and in serious cases, it will not work normally, and even have potential safety hazards.
The hydraulic system of wheel excavator working device is mainly composed of oil tank, two parallel variable pumps, control valve group, hydraulic cylinder, pilot servo pump and pilot control mechanism. The variable displacement pump sucks the hydraulic oil from the oil tank into the control valve group. When the right pilot control handle is pulled backward, the pilot servo pump controls the control valve group to input the hydraulic oil into the boom cylinder, and the boom rises. Conversely, when the joystick is pushed forward, the boom lowers.
Due to the long-term operation of the equipment in a complex and harsh environment, the performance degradation of the assembly is the main cause of the failure. In addition, improper operation and use or untimely maintenance can also cause similar failures. According to experience, more than 75% of hydraulic system faults are caused by the quality of hydraulic oil in the process of system circulation
1. The brand of the replaced hydraulic oil is not suitable. In addition to the selection according to the mechanical operation manual, the special hydraulic oil should be considered first, and then the alternative hydraulic oil should be considered according to the actual use conditions of the machine.
2. Oil pollution deterioration, which is easy to cause oil pollution are impurities entering the oil tank during refueling, untimely or lax sealing, deterioration of hydraulic oil due to long-term circulation under high temperature and high pressure, etc. Contaminated hydraulic oil enters into the hydraulic system, which accelerates the wear, corrosion and blockage of hydraulic components, and finally leads to failure.
In addition, the hydraulic oil tank filter and the oil tank cover vent are blocked, the hydraulic oil is insufficient or the air enters into the system, the pressure of the pilot system and the main safety valve is insufficient, the efficiency of the variable displacement pump is too low and the hydraulic cylinder leaks, which will cause the flow of the hydraulic system to drop and the pressure to drop, thus making the boom slow and weak.