What should be noted during the maintenance of multi-stage centrifugal pumps?

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When performing maintenance on a multi-stage pump, if possible, it is best to first review the manufacturer’s maintenance instructions and general assembly drawings to identify any special considerations. I. During disassembly: 1. Before removing the thrust bearing, use a dial indicator to measure the clearance of the balance disk and record it ； 2. When disassembling a multi-stage pump, it is necessary to mark each component in its original assembly order to avoid confusion and incorrect installation during reassembly ； 3. Small components that are difficult to mark (such as keys) can be placed together with impellers or vanes of the same level (in the middle section), etc. 4. During disassembly, one can visually check whether there are any abnormal components, such as loose fits, etc. II. Part inspection: 1. Visually check whether the surfaces of all parts are in good condition; all mating surfaces must be free from dents, scratches, or rust ； 2. Use measuring tools to verify whether the tolerances of key mating parts are acceptable ； 3. Check whether the clearances at the impeller seal ring, casing seal ring, guide vane seal ring, inter-stage shaft sleeves, etc., are within the allowable range; those that are excessively worn need to be replaced ； 4. Check whether the bearings are in good condition ； 5. It is best to replace all seals and gaskets with new ones ； III. Reinstallation: 1. First, install the rotor and conduct a dynamic balance test again ； 2. Reassemble all components in the reverse order of disassembly. When reassembling, be sure to measure the clearance at each seal ring again to ensure accuracy ； 3. The total rotor string length should be measured before installing the balance disk ； 4. After installing the balance disc, measure the rotor’s half-string length. 5. When compared with the total string length and half-string length specified in the manufacturer’s general assembly diagram, it should generally meet the requirements of the drawings. Under normal circumstances, the half-string quantity is roughly half of the total string quantity. 6. Tighten all the main bolts evenly, making sure to do so diagonally ； 7. Attach a dial indicator to the shaft and rotate it to measure the balance disc; the tolerance shall meet the requirements specified in the drawings, and generally should not exceed 0.06 ； 8. When installing the thrust bearing, attention should be paid to adjusting the clearance of the balance disk; the adjustment ring in front of the bearing should be used to set the balance disk clearance to the value specified in the drawings.