If the fault diagnosis is in the working unit hydraulic system and the boom and swing are not working properly. There are many reasons for this failure. In addition to the boom spool valve leakage and other fault causes, the main safety valve, hydraulic pump, oil filter, hydraulic oil and distribution valve inlet and return oil circuit faults may all cause this fault phenomenon. Since there are many possible causes of failure, it can be checked from easy to difficult and from key points. Check the most intuitive reason first. Check the cleanliness, color, viscosity, consistency and smell of the hydraulic oil if the oil in the oil tank is insufficient. When the hydraulic oil flows from the high-pressure side to the low-pressure side without doing mechanical work, heat will be generated in the hydraulic system. Too high temperature of hydraulic oil will deteriorate the seals and oxidize the oil to failure. It will cause corrosion and deposit formation, which may block the damping hole and accelerate the wear of the valve. Too high temperature will make the valve and pump stuck. If the above parts have faults, remove them first. Then check the following key parts. The possibility of internal leakage of boom cylinder and swing cylinder at the same time is relatively small. First, check the system pressure. Install a 40MPa pressure gauge at the pressure measuring point. Raise the boom to the highest position at rated engine speed. At this time, the gauge shows the maximum pressure, and the reading should be 27~28MPa. If the reading is low, check and eliminate it in detail from the distribution valve, working pump, boom cylinder, bucket cylinder, working oil pressure, etc.
