3090648 Original Excavator Main Pump Retainer Plate for ZX870-6

Part number 3090648 is the original main pump fixing plate provided by Hitachi for large mining hydraulic excavators such as ZX870-6. As shown in the picture you provided, this component is a key installation substrate that connects the hydraulic main pump with the engine flywheel housing or gearbox, responsible for achieving high-precision alignment and rigid connection between the power end and the hydraulic end. Its universal models mainly cover ZX870-6 and its derivative models in the same series. It is strictly prohibited to use this component for other equipment of unspecified tonnage or model, in order to avoid serious faults such as bearing damage, abnormal noise, or oil leakage caused by poor alignment of the main pump due to installation hole position and thickness deviation.

This product is an installation flange made of high-strength alloy steel (such as 42CrMo) or ductile iron precision machining. The main body is a circular plate with a large shaft hole in the center, and ten bolt through holes are evenly distributed on the outer edge for connecting with the body. The threaded holes on the inner edge are used to fix the main pump. Its thickness is usually 20-30mm, and it undergoes quenching and tempering heat treatment as a whole to obtain high strength and toughness. The surface is treated with phosphating or blackening to prevent rust, presenting a dark gray color as shown in the picture. The dimensional accuracy (H7 level) and end face runout (≤ 0.05mm) of the central large hole require extremely high precision, which is the core to ensure the coaxiality between the main pump drive shaft and the engine crankshaft.

Installation specifications: 1 Cleaning: Before installation, both sides of the fixing plate, the engine joint surface, and all bolt threads must be thoroughly cleaned with cleaning agent and a lint free cloth. 2. Center placement: Place the fixing plate firmly on the engine installation surface and pre tighten all bolts by hand. 3. Final tightening: A calibrated torque wrench must be used to tighten the bolts in 2-3 steps according to the cross sequence specified in the maintenance manual to the specified torque (usually 120-150 N · m level, specific values need to be referred to in the ZX870-6 maintenance manual). Inspection and replacement: Every 2000 working hours or when disassembling the main pump, check this fixing plate for cracks, deformation (measure flatness with a ruler), and whether the threaded holes are intact. Once any permanent deformation or crack is found, it must be replaced immediately and cannot be repaired for use.