Repair of Gear Pump Shaft Wear
The wear of the gear pump shaft is mainly due to frictional wear between the shaft ends and the supporting needle rollers, causing the shaft diameter to decrease. For minor wear, a layer of hard chrome plating can be used to increase the diameter of this part of the shaft, thus repairing it. If the shaft wear is severe, it should be remanufactured using 45 steel or 40Cr steel. After rough and finish machining of the shaft blank, the bearing area should be heat-treated to a hardness of HRC60-65, followed by grinding to ensure the surface roughness Ra of the bearing mating area is no greater than 0.32μm; the roundness and cylindricity tolerance of the shaft is 0.005mm; and the surface roughness Ra of the mating area with the gear should be no greater than 0.63μm according to h7/h6.
Repair of Gear Pump Body Wear
The wear on the inner surface of the pump body mainly occurs on the arc-shaped working surface of the oil suction section. If minor wear occurs, it can be repaired and deburred with an oilstone before use. The pump body is formed from a cast iron blank; if severe wear occurs, it should be replaced with a new part. If the two end faces of the gears inside the pump are repaired by grinding, the width of the pump body must also be changed to match the dimensions removed during grinding. The re-machined end faces of the pump body should meet the technical requirements.
Repair of Worn End Covers of Gear Pumps
The end covers of gear pumps are made of cast iron. Minor wear can be repaired by grinding on a flat plate, while more severe wear should be repaired by grinding on a surface grinder. The contact surface between the repaired end cover and the pump body should be no less than 85%. The allowable tolerances for flatness, perpendicularity of the end face to the hole centerline, parallelism of the two end faces, and parallelism of the two shaft hole centerlines are all 0.01 mm. The surface roughness ra after grinding should not exceed 1.5 μm.
Repair and Replacement of Needle Roller Bearings in Gear Pumps
After repairing parts in the pump, the needle roller bearings should be replaced. The requirements for needle rollers are as follows: the dimensional error of the diameter of all needle rollers should not exceed 0.003mm, the length tolerance is 0.1mm, and the clearance with the shaft should be around 0.01mm; when assembling the needle rollers, the bearing housing should be filled with the required quantity, and the needle rollers should be arranged in parallel to each other.
