The hydraulic cartridge type pressure relief valves as a replacement parts for Hitachi Ex220 excavator series. If the hydraulic crawler excavator sometimes appears the weakness of operation, which due to the failure of cartridge type pressure relief valves in the hydraulic system.
There are two reason leads to the low pressure:
Hitachi Ex220 excavator use double swash plate axial variable piston pump. Under normal circumstances, the main pump output hydraulic pressure ≥ 30MPa. If more than the standard amount of wear between the plunger and the cylinder of the main pump or between the end face of the cylinder valve plate (the gap between the plunger and the cylinder should be less than 0.02mm, between the cylinder end face of the valve plate the contact area should not be less than 90%) , it will cause the main pump output pressure is low , reflected in a mechanical device, there will be the phenomenon of the working of weakness.
To achieve the best match in the main pump and engine power, it should be given the full pay to the role of the engine for the output of the pump flow varies with the change of engine power. The hydraulic cartridge type pressure relief valve is used to adjust the main pump flow volume, for example, the valve spool stuck, valve spring broken, which will cause the main pump is always in a constant flow. If the main pump has been in a state of the small flow machine at work will weakness, low pressure and slow action.
Hitachi Excavator EX220 Hydraulic Cartridge Type Pressure Relief Valve
