The balance device on the centrifugal pump is designed to fully or partially compensate the axial thrust generated by the pump rotor. Designs containing a single balance drum or double drums require thrust bearings to absorb residual thrust.
If the balance device consists of a balance disc, the entire axial thrust of the pump rotor is usually balanced. In this case, no additional thrust bearing is required.
When the pump is running, the balancing device requires a certain amount of balancing flow to pass through the gap between the rotating and non-rotating parts of the balancing device. The balance flow is considerably throttled during its passage through the gap.
This pressure loss results in an axial force acting on the balancing device, which counteracts the axial thrust of the impeller and achieves the required balance. When the axial thrust involved is extremely high (such as overpressure pumps), a balancing device will be used.