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Summary of inspection points for centrifugal pump maintenance

1. Inspection of pump shaft 
• First clean the pump shaft with kerosene, polish the surface of the pump shaft with sandpaper, and check whether there are grooves and wear on the surface.
• At the same time, check the wear of the keyway on the shaft. If the wear of the keyway is too large, reopen the keyway at 1800 opposite the pump shaft.
• Runout inspection of pump main shaft: after the main shaft is installed in the bearing box, the runout of the flange surface of the main shaft and bearing box shall be checked. Required runout 1 < 0.05mm; 2,3<0.05mm。
• For key pumps, if necessary, ultrasonic or magnetic flaw detection or coloring can be used to check whether there are cracks in the pump shaft.
• Check the bending of the pump shaft. Generally, the pump shaft should be placed on the lathe at room temperature. The measurement is most convenient and the accuracy can meet the requirements. Generally, we use V-shaped iron as the support frame and place it on the platform for measurement. The levelness of the shaft itself should be maintained. The tolerance is less than 0.08mm.


2.Inspection of impeller
•Check the impeller ring for wear. If the wear of the impeller ring is within the range, the inner hole of the impeller can be expanded with a mould on the lathe to repair the worn part (ensure the concentricity of the outer circle of the impeller ring and the inner hole). However, if the mouth ring is seriously worn and exceeds the specified mouth ring clearance range, it must be replaced.
•Check the impeller blade and surface for cavitation damage. If the blade has only a small cavity and will not affect the flow and head, it does not need to be replaced. Otherwise, it must be repaired or replaced.
•Check the impeller keyway, key and the fit between the impeller and the shaft. The impeller is used for a long time and disassembled for many times. The fit between the impeller and the shaft or the impeller keyway and key becomes loose, which affects the concentricity of the impeller and causes vibration during pump operation. If it is found that the fit between the impeller and the shaft is too loose, check the wear of the impeller or shaft, and replace those with excessive wear. If the fit between the impeller keyway and the key is too loose, reopen the keyway 180 degrees away from the original keyway of the impeller and re match the key.


3.Bearing inspection
• Before the assembly of rolling bearing, first dig out the antirust oil or grease in the bearing, then put the bearing in hot oil to melt the residual oil, wash it with kerosene and dry it with white cloth or compressed air.
• After cleaning the rolling bearing, check the following items; Whether the bearing rotates flexibly, briskly and freely, and whether it is stuck; Whether the bearing clearance is appropriate; Whether the bearing is clean, and whether the inner and outer rings, rolling elements and isolation rings are rusted, burr, bruise and crack; Whether the inner ring of the bearing is precisely close to the shaft shoulder; Whether the bearing accessories are complete. Replace if there is a problem.
• When checking the journal and bearing body, mainly use a micrometer or vernier caliper to measure whether the ovality and conicity of the journal and bearing body hole and their fit with the bearing meet the requirements. In addition, check whether the journal fillet is consistent with the bearing inner ring. Check the end face runout of the shaft shoulder and bearing hole, and the value shall not exceed the specified value, otherwise replace it.

4.Inspection of fixings such as pump housing, housing mouth ring, bearing suspension, etc
• Crack inspection: after cleaning the pump housing and bearing suspension, check whether there are cracks. The inspection method is generally to tap the pump housing with a hammer. If there is a hoarse sound, it indicates that the pump housing has cracks.
• For further inspection, kerosene can be applied to the pump housing and bearing suspension to allow kerosene to penetrate into the crack, then wipe off the kerosene on the surface and apply a layer of white powder, and then knock the pump housing and bearing suspension again with a hammer. The kerosene in the crack will seep out and wet the white powder, showing a black line, so as to judge the end point of the crack. If the part of the crack is not under pressure or has no sealing effect, in order to prevent the crack from continuing to expand, a circular hole with a diameter of 3mm can be drilled at both ends of the crack to prevent the crack from continuing to expand. If the crack occurs in the pressure bearing part, repair welding must be carried out.


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Peter Tian
Phone/WA: +86 137 3018 7521

Email: [email protected]