Hydraulic Performance Comparison of Centrifugal Pumps

The purchase of large water pumps, requiring a high capital investment, necessitates, in addition to the economical evaluation, a thorough analysis of the hydraulic performance of the pumps. Thus, capacity, head, rotative speed, efficiency, and the related performance curves must be compared. To simplify the comparison of those variables for different pumps, the specific speed deviation method is introduced. This method, which is based on the specific speed criterion, compares the designed operation point of the pump with its best efficiency point, expressing it in the form of the deviation parameter, δ. To illustrate the use of this method, a group of seven pumps is analyzed and evaluated. The paper includes also a short examination of the dimensionless specific speed criterion, and the computation of the capacity-head curve.