Why is specific speed important?
Specific speed is defined as the speed in revolutions per minute at which an impeller would operate if reduced proportionately in size so as to deliver a unit of capacity against a unit of total head. The performance of a pump can be determined by stating its speed, the head it generates and the rate of discharge. Yet, when comparing one pump to another, it is more useful to use one term which will provide a general description of the pump’s performance characteristics. Different types of impellers and flow patterns can best be compared by means of the specific speed. A pump can be classified as axial flow, mixed flow, or radial flow depending where the impeller discharges the liquid. An axial flow pump discharges the liquid in the axial direction compared to the pump shaft centerline, a radial flow pump discharges the liquid in the radial direction and a mixed flow pump is one that is a combination between a radial and an axial flow pump design. Pumps have to be selected with the righ
