What should be paid attention to when repairing multistage centrifugal pump

For the maintenance of multistage pump, if conditions permit, it is better to read the maintenance manual and general assembly drawing of the manufacturer first to see what special points need attention.
1、 During disassembly:
1. Before removing the thrust bearing, use a dial gauge to measure the clearance of the balance plate and make records;
2. When the multistage pump is disassembled, all parts must be marked according to the original assembly order to avoid confusion and wrong assembly during reassembly;
3. Small parts (such as keys) that are not convenient for marking can be placed together with the impeller or guide vane (middle section) of the same level.
4. During disassembly, you can intuitively feel whether there are abnormal parts, such as loose fitting.
2、 Parts maintenance:
1. Visually check whether the surface of each part is normal, and all mating surfaces must be free of collision, scratch, corrosion, etc;
2. Check whether the tolerance of key fitting parts is qualified by measuring tools;
3. Measure whether the clearance of impeller seal ring, shell seal ring, guide vane seal ring, interstage shaft sleeve, etc. is within the allowable range, and replace it if it is excessively worn;
4. Check whether the bearing is in good condition;
5. All sealing rings and gaskets shall be replaced with new ones;
3、 Reassembly:
1. Install the rotor and conduct dynamic balance test again;
2. Reassemble all parts in the reverse order of pump disassembly. During reassembly, pay attention to measuring the clearance value of each sealing ring again to ensure there is no error;
3. Before installing the balance disk, the total rotor runout shall be measured;
4. After installing the balance plate, measure the half string quantity of the rotor.
5. Compared with the total string quantity and half string quantity required on the general assembly drawing of the manufacturer, it shall basically meet the drawing requirements. Generally, the half string amount is about half of the total string amount.
6. Tighten all main bolts evenly, paying attention to the diagonal;
7. Suck a dial indicator on the shaft, rotate the shaft to mark the balance plate, and the tolerance shall not exceed 0.06 as per the drawing requirements;
8. When installing the thrust bearing, attention shall be paid to adjusting the clearance of the balance disc. The adjustment ring in front of the bearing shall be used to adjust the clearance of the balance disc to the requirements of the drawing.

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