Correlation of centrifugal pump vibration to unsteady flow under variable motor speed

Abstract

Although condition monitoring of centrifugal pump bearings to infer faults is common practice, the relationship between a pump’s vibration level and the unsteady flow within has not been extensively researched. The latter, however potentially provides the foundations for further developments in, pump design to increase performance, advanced predictive maintenance programs and, vibration monitoring techniques that can permit inference of pump efficiency states. This paper investigates the correlation between pump vibration and unsteady flow at different motor speeds. A test rig and a numerical CFD model were employed. It was found that flow-induced vibration in general increases with pump speed and was clearly linked to pump efficiency. It therefore seems possible to construct a model to deduce a pump’s efficiency from its pressure and vibration levels, if the efficiency curve is known a priori. However, as the vibration levels are also dependent on the system’s structural natural frequencies and modes, it seems that knowledge of these may also be needed in some instances. The work confirms that utilising a variable speed pump at lower pump speeds allows greater deviations from the design BEP without jeopardising the safety of the pump and should be considered for industrial use.