1. check the filter and clean or replace it if it is blocked Observe the oil and replace it if it is deteriorated.
2. check the pipeline in the hydraulic system If the conduit or joint is damaged, it shall be replaced or repaired by welding.
3. check whether the piston sealing ring of hydraulic cylinder loses sealing function Retract the hydraulic cylinders of the working device, i.e. boom, stick and bucket one by one, remove the high-pressure oil pipe at the outlet joint of the large cylinder of the hydraulic cylinder, and continue to operate and control the joystick of the corresponding hydraulic cylinder to further retract the piston rod of the hydraulic cylinder Since the piston rod has been fully retracted at this time, it cannot be moved again to increase the oil pressure. Carefully observe whether there is oil flowing out at the outlet of the large chamber of the hydraulic cylinder If only a small amount of oil flows out from the outlet, the sealing ring of the hydraulic cylinder does not fail; If a large oil flow is formed, the piston sealing ring of the hydraulic cylinder is invalid. The hydraulic cylinder should be overhauled and the sealing ring should be replaced.
4. under the condition of high-speed idling of the engine and unloading of the stick, gradually measure the overflow pressure of the control pump and the front and rear main pumps, and measure the pressure of the torque control valve The specified value: the overflow pressure of the control pump is 3~3.8mpa, the overflow pressure of the front and rear main pumps is 31~34.5mpa, and the pressure of the torque control valve (TVC valve) is 1.8~2 OMPa.
When the overflow pressure of the control pump, the front and rear main pumps and the set pressure of TVC valve are within the specified value, and the front and rear main pumps overflow, the main pump has internal leakage, and the main pump should be repaired.
When the measured overflow pressure of the control pump and the front and rear main pumps is within the specified value, but the measured TVC valve set pressure is not within the specified value, adjust the TVC valve set pressure to the specified range, and the fault is eliminated If the pressure of TVC valve cannot be adjusted and TVC valve is faulty, disassemble and clean the TVC valve If the main valve core of TVC valve is stuck, grind and repair the valve core hole until it can be pushed freely. Otherwise, replace the TVC valve.
5. the overflow pressure of the control pump is within 3~3.8mpa, while the overflow pressure of the front and rear main pumps is not within 31~34 Within SMPA, adjust the overflow pressure of the main overflow valve of the front and rear main pumps to the specified value, and the fault is eliminated If the pressure of the main overflow valve cannot be adjusted, the main overflow valve is faulty, and the main overflow valve shall be disassembled and cleaned If the main overflow valve is stuck, clean the main valve core so that it can be pushed freely When the valve core cannot be pushed freely, grind and repair the main valve core hole, or replace the main overflow valve.
6. if the overflow pressure of the control pump is not within 3~3.8mpa, adjust the overflow pressure to the specified value and eliminate the fault.
When the overflow pressure of the control pump cannot be adjusted, cut off 1~6 circuits respectively Measure the overflow pressure of the control pump. If the value is within 3~3.8mpa, the corresponding control elements have serious internal leakage, and the corresponding control elements should be overhauled; If the pressure is not within 3-3.8mpa, check whether there is iron powder and foreign matters in the oil discharged from the filter at the outlet of the control pump If any, repair or replace the control pump; If not, clean the main valve core of the overflow valve of the control pump, grind the main valve core hole or replace the main overflow valve of the control pump.
7. when the PPC valve hydraulic control element is found to be faulty, the valve core and valve body of the main control valve control device shall also be cleaned At the same time, check the clearance between the valve core and the valve body. The normal value is 0.015-0.025mm, and the maximum clearance shall not exceed 0.04mm If the clearance is too large or the valve element is seriously worn, this group of control valves shall be replaced; Check the spring. If it is deformed, softened or broken, replace it.
