Flow Recirculation In Centrifugal Pumps

Abstract

Recirculation in centrifugal pumps is a flow reversal at the inlet or at the discharge tips of the impeller vanes. Through analysis and tests, it is now possible to determine the flow patterns that must exist to produce the observed results. All impellers exhibit a point of suction recirculation and a point of discharge recirculation at some specific capacity, and depending on the size and speed of the pump, the effects of recirculation can be very damaging, not only to the operation but also to the life of the impeller and casing. The symptoms associated with recirculation are very specific and are listed along with the diagnoses of the cause. Many of these problems can be avoided by specifying and designing pumps for lower suction specific speeds and limiting the range of operation to capacities above the point of recirculation,