Measuring the bend degree of the shaft of deep well submersible pumps

Shaft is a crucial part of deep well submersible pumps.

If the shaft bends, it will cause imbalance of the rotor and friction between the dynamic parts and the static parts. Therefore, the bend degree of the pump shaft should always be measured during overhaul.

1. Put the two ends of the shaft on the V shaped iron. The V shaped iron should stand stable and firmly.
2. Set up the dial indicator. Let the measuring rod point to the head of the shaft.

Then, turn the shaft of the deep well submersible pumps slowly. If the shaft is bent, the dial indicator will have a max reading and a minimum reading in every circle the shaft turns. The difference between the two readings show the bending degree of the shaft.

In conclusion, the process is actually measuring the radial run-out of the shaft, or flutter.

3. Half of the flutter is the bending value of the shaft.

The common request on radial run-out is that the middle part shall not run out more than 0.05 mm, while the two ends shall not run out more than 0.02 mm.

Another crucial part of the deep well submersible pumps is impeller.  Therefore, we will talk about the maintenance of impellers as follows:

1. Clean and check the surface of each stage of impeller. The impeller surface should not have such defects as cracks, wear, etc. The surface of the flow channel of the impeller should be smooth, with no lime scale or burr. The vanes shall not have such defects like cracks, being thin as a result of flushing.
2. Check the seal ring at the suction inlet and discharge outlet of each stage of impellers. The ring shall not be loose and its surface shall be smooth, with no burrs. The coarseness value of the surface shall not surpass 0.8μm. The assembly clearance between the ring and the impeller shall be 0.05~0.10 mm.

Check the radial run-out of the impellers basing on its internal diameter. The checked value shall not be larger than 0.05 mm

End surface run-out no larger than 0.04 mm.

3. The impellers and the shaft adopt interference fit, usually H 7/h 6.

The interference value between key and key slot is 0.09~0.12 mm. After assembly, the clearance at the top of the deep well submersible pumps key will be 0.04~0.07 mm.

4. The impeller should be statically balanced.