Influence Of Impeller Suction Specific Speed On Vibration Performance

Abstract

The most commonly used hard limitation for pump suction specific speed is 11,000 (US units). This hard limit grew out of the recommendations from a 1982 reliability study by J.L. Hallam (Hallam 1982). Concomitant testing of the vibration performance of an OH2 4x6-11 pump was made with impellers designed for different suction specific speeds (Lobanoff and Ross 1985). This study showed that all things being equal, a strong relationship existed between suction specific speed and the pump vibration at off BEP operation. Given the significant changes in impeller design methods and computational tools in the subsequent three decades, this paper seeks to investigate how these new methods/tools have affected the relationship between suction specific speed and the pump vibration. Experiments are performed using a series of impellers designed for different suction specific speeds using modern design techniques. These impellers are mounted in a subject test pump which is also an OH2 4x6-11 in order to achieve equivalency with the prior testing. Vibration performance over the pump operating range is recorded. The results are complemented with computational fluid dynamic (CFD) analysis to further examine the performance of each impeller.