Regarding the issue of centrifugal pump seizure

It’s not necessarily due to the bearings; it could also be caused by a misaligned rotor, friction between the moving and stationary parts, or impurities that have entered the impeller seal ring and caused a blockage.

The original poster may be misunderstanding things; when a centrifugal pump seizes, it does not mean that the inner ring of the bearing seizes to the shaft. Generally, there is an interference fit between the inner ring of the bearing and the shaft, and the bearing needs to be heated in order for the inner ring to be fitted onto the shaft. Therefore, the inner ring and the shaft are already in a sealed fit; if they do not seize, there is something wrong with the assembly process. What the original poster meant by the centrifugal pump seizing might refer to the phenomenon of the pump’s shaft getting stuck, which prevents the pump from rotating. This shaft seizure usually occurs due to a lack of oil in the bearings or poor lubrication, as well as burned-out bearings; in such cases, the inner and outer rings of the bearings, along with the retainers and rolling elements, stick together, preventing the pump from rotating. A centrifugal pump getting stuck and failing to rotate can be caused by various factors: it may be due to the entry of foreign objects or the impeller getting jammed. It might be that the bearing lacks oil, causing it to stick to the shaft; the bearing is stuck ； It could be that the mechanical seal is damaged and the rotating and stationary rings are stuck together; it might also be due to axial movement of the shaft, with the impeller ring and the volute ring becoming stuck. The material may have better flow properties when it is hot, but if insulation is inadequate and the temperature is low, the material becomes viscous, causing the impeller to get stuck. It’s also possible that the pump has not been used for a long time and regular rotation of the shaft has not taken place, resulting in the rotating and stationary parts sticking together (such as the rotating and stationary rings). There are other reasons as well.

The answer on the third floor is quite comprehensive; the original poster should take a closer look

It might be due to improper assembly; the clasp is stuck. Disassemble it and reassemble it

Your analysis is quite accurate; I give you a thumbs up.

A problem identified on site: before starting the new pump, the motor wires were connected in the wrong order, causing the impeller to rotate in the opposite direction; moreover, the nut securing the impeller was loose, which led to the impeller coming off its shaft and getting stuck

Yes, what’s happening to us is likely due to a lack of oil. Thank you for such a detailed explanation

I have another question: if all four parts of the shaft and bearing stick together, it can be considered that the bearing and shaft are integrated as one unit. In that case, the outer ring should also be able to rotate. The only situations I can think of in which rotation wouldn’t be possible are when there is sliding friction between the outer ring and the bearing housing, with the friction being too high to allow rotation; or, even worse, when a part of the outer ring sticks directly to the bearing housing due to a lack of oil. I’m not sure if my reasoning is correct.