Design of a New Type of Balance Drum to Reduce Axial Loading in Centrifugal Pumps

In centrifugal pumps, axial thrust bearings are required to compensate for the axial loading on the pump impeller(s). These forces are mainly the result of unequal distributions of pressure on projected areas at both sides of the impeller(s). Axial loading tends to be highest in multistage pumps in which all impellers face the same direction. Balancing devices are often used to reduce the loading of the axial bearings. Common types of balancing devices are the balance drum and the balance disc. Both of them have their advantages and disadvantages. A stepped balance drum is a new concept for a balancing device that can be used in any type of turbomachinery. It combines the benefits of the balance drum and the balance disk without the drawbacks of both. In this paper, the new concept is presented along with a semi-empirical model of its performance. A CFD analysis is also presented which serves to verify the analytical model. An optimization procedure of a stepped balance drum is given using a multistage centrifugal pump as an example.