8051275 Original HITACHI Excavator Hydraulic Pump Piston Assy for ZX330

The original Hitachi excavator hydraulic pump plunger (part number: 8051275) is the core moving component inside the Hitachi excavator hydraulic main pump (usually Kawasaki K3V series variable displacement plunger pump). According to publicly available procurement information, the part is clearly compatible with the Hitachi ZX330-5G excavator model. As an original plunger component, it is usually supplied in sets, and each main pump requires multiple sets (such as 9 or 11) of plungers and corresponding cylinder bodies, sliding shoes, etc. to form a plunger pair.

This plunger is the core component of an axial piston pump that achieves oil suction and pressure functions. Its core function is to perform reciprocating linear motion within the cylinder bore, converting the rotational mechanical energy of the engine into pressure energy of hydraulic oil through cooperation with the inclined plate (or inclined shaft). The plunger is usually made of high-strength alloy steel (such as GCr15 bearing steel or similar materials) through precision forging, turning, grinding, and heat treatment processes such as carburizing, quenching, and precision grinding. The surface has extremely high hardness and smoothness to withstand system pressures of up to 350 bar and frequent friction. Its head is connected to the slider ball joint, and there are oil holes or grooves at the waist.

The maintenance core of this plunger is to ensure the cleanliness of hydraulic oil, regular monitoring, and preventive replacement. Daily monitoring: It is necessary to ensure that the cleanliness of the hydraulic oil meets NAS 1638 level 8 or higher standards, check the oil quality every 500 working hours, and replace the hydraulic oil and filter element every 2000 hours or annually. The plunger is a precision component and cannot be repaired separately. Once worn, it must be replaced in groups. Disassembling the pump assembly should be carried out in an absolutely clean environment, thoroughly cleaning all parts. During installation, it is necessary to ensure that the assembly clearance of components such as plungers, sliding shoes, and return discs meets the standards of the maintenance manual.