Repair of centrifugal pump rotors

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Rotor repair The rotor of a pump core pump is mainly composed of an impeller, a main shaft, and shaft sleeves, etc. Before repair, the rotor must be disassembled, cleaned, and inspected; careful attention should be paid to the wear of the impeller, the radial runout (not exceeding 0.05 mm), and the degree of eccentricity ； Wear and bending of shafts and bushings, etc. 　(1) Repair of the main shaft: The pump’s main shaft may become bent or cracked due to vibrations that occur during rotation or as a result of sudden impacts ； The surface of the shaft suffers severe indentations and wear due to friction or corrosion by the conveying medium, which leads to radial runout or reduced strength, affecting its performance and requiring repair. Slight surface damage can be smoothed out by polishing with oil-soaked sandpaper. The shaft needs to be straightened when it is bent ； Axes with severely damaged surfaces can be repaired using methods such as welding, spraying, electroplating, followed by grinding. After repair, the geometric accuracy and radial runout need to be retested (not exceeding ±0.05mm). 　(2) Repair of the shaft sleeve: During operation, the pump causes wear and radial runout at the part of the shaft sleeve that comes into contact with the packing. For less severe wear, repair can be carried out by welding and then turning; however, shaft sleeves with severe wear need to be replaced. 　(3) Repair of the impeller: The impeller is one of the vulnerable components of a pump. As it rotates, friction and corrosion can cause severe damage, leading to changes in its size and shape that affect the pump’s performance; therefore, it needs to be repaired or replaced promptly. For impellers with less severe damage, they can be repaired by patch welding. During repair, the impeller is first heated to 600°C, then rewelded, with care being taken to cool it slowly after welding to prevent the formation of new cracks. Cool it down and then turn it to the original size. If a loose key is detected, the keyway can be widened or re-cut if possible (at 90° or 180° to the original keyway), and a new key fitted. If the impeller has severe sand holes or is heavily damaged, it needs to be replaced. 　　The repaired impeller needs to be re-equilibrated. For the repaired impeller, the end-face deflection shall not exceed 0.2 mm, and the radial runout at the outer edge of the impeller and the seal ring shall also not exceed 0.05 mm.