Which senior expert can provide guidance on multi-stage pumps?

This post was last edited by qwl on 2020-8-22 08:58: The bearing cannot be positioned. The bearing shifts within its bearing housing. Axial movement is controlled by the balance disc. In a running multi-stage pump, due to the presence of axial forces and the action of balancing devices, the pump rotor remains in a state of dynamic balance, that is, the rotor keeps moving back and forth. The pitch momentum is approximately between 0.1 and 0.15 mm, with a pitch frequency of 10 to 20 times per minute. The high-pressure liquid in the high-pressure chamber where the balance disc is located always causes the balance disc to move away from the balance ring. This effect occurs even if no pressure is established inside the pump at startup, due to the axial force resulting from the backflow of the liquid. The second is that the balancing device is designed to allow for wear. It is through its wear that the impeller is protected from being worn; in fact, due to the effect of high-pressure liquid, the minimum gap during normal operation remains at around 0.1 mm, leaving little opportunity for direct grinding. Severe grinding is often caused by poor installation and manufacturing, as well as deviations from the specified processes.

Multi-stage pumps with balance discs cannot be positioned by external forces. If your disc wears out frequently, it’s because the balance isn’t adjusted properly. This problem is not difficult to solve.

Unless you have previously determined the exact axial clearance position of the balance disc through calculations and tests, it is possible to fix the position of the balance disc directly; however, this approach is not recommended. As the various clearances within the pump (such as those in the sealing rings) wear out, as operating conditions change, and as the operating point shifts, the balanced position of the balance disc will also change. Once the position of the balance disc is fixed, it loses its ability to self-balance, which leads to increased load on the bearings and eventual damage to them.

Stop thinking about this issue – it’s not possible. The balance disc functions like a floating lubricated bearing that automatically balances the axial forces; once you set a position, it has to change, and without a pressure difference, there is no balance.

Theoretically, multi-stage pumps equipped with balance discs do not require positioning bearings, but in practice all multi-stage pumps have such bearings. The presence of a balance disc gap resolves the conflict between theory and practice: lol