① The hydraulic pumps of Hitachi excavators are mostly variable piston pumps. After working for a certain time, the internal parts of the pump will inevitably be worn, resulting in internal leakage, and the data of various parameters are inconsistent, resulting in insufficient flow, high oil temperature, slow speed and unable to establish high pressure. Therefore, the action is slow and unable to establish high pressure. For such problems, the hydraulic pump must be removed for data measurement to confirm the problem and replace the parts that can not be used anymore, Or repair the accessories that can continue to be used, and conduct bench commissioning after reassembly to match the parameters of each circuit (pressure, flow, power, variable, etc.).
② An important hydraulic component on the excavator is a multi-channel distribution valve, which has main safety valve, secondary valve, overflow valve, oil makeup valve, etc. if the pressure set by these valves does not reach the standard pressure, it will lead to weak excavation In addition, if the clearance between the valve stem and the valve hole is too large due to wear, the valve stem return is incomplete and the reversing is not in place, a large amount of internal leakage will lead to insufficient flow and slow speed For such problems, remove the multi-channel distribution valve, send it to the test bench for commissioning, reset the pressure of all valves to the standard pressure, and eliminate the gap between the valve stem and the valve hole.
③ All hydraulic pumps on imported excavators are equipped with pilot gear pump, which is mainly used to participate in the variable of hydraulic pump and open the valve rod of multi-channel distribution valve as pilot oil to reverse it If the gear pump is excessively worn and cannot establish a certain pressure, or the safety valve on the gear pump cannot be set to a certain pressure, the hydraulic pump will always be in a low flow state, and the valve rod cannot be completely reversed, resulting in insufficient flow, slow action, insufficient pressure and weak excavation. For such problems, just replace the pilot gear pump or reset the pilot safety valve.
④ When the engine is cold - everything is normal, when the engine is hot, the action is slow and the excavation is weak. Such problems indicate that the internal accessories of the hydraulic pump are seriously worn, and the vulnerable parts in the pump must be replaced, reassembled, adjusted and calibrated on the test bench.
Another - main reason for the slow and weak operation of the excavator is the deterioration of the hydraulic oil. Therefore, pay attention to monitoring the quality of the hydraulic oil (viscosity, fluidity, presence of suspended solids, etc.), and replace the hydraulic oil in accordance with the regulations on time, so as to avoid such faults to a great extent.
