The Effect Of Specific Speed On The Efficiency Of Single Stage Centrifugal Pumps

Abstract

A chart relating the efficiency of centrifugal pumps to the specific speed and capacity at the maximum efficiency capacity has been in use in the pump industry for almost forty years. While it has been useful to both the manufacturer and the user of centrifugal pumps its initial formulation was based on some generalizations that require a more precise definition today. For example, the data for the chart reflect hydrodynamic designs before 1945. Improvements in both the deign procedures and in the manufacturing process have been achieved in the intervening years. An additional reason for a diminishing utility of the chart is that with the introduction of high speed pumps, the use of capacity alone as a criterion of pump size is no longer valid. The procedures outlined herein are an attempt to resolve some of these discrepancies while, at the same time, retaining the basic simplicity of the original chart. To say this is not to discredit the value or reliability of the original chart, but rather to enhance its ability to predict pump efficiencies based upon today’s procedures and capabilities.