Reduction of Radial Thrust by Using Triple-Volute Casing

Abstract

Radial thrust in a single volute centrifugal pump, which is a result of pressure variation in the volute casing, is investigated in order to avoid failures caused by this thrust force. Two ideas are introduced to avoid or to minimize this thrust force, the first is a double volute, and the second is a triple volute. A complete centrifugal pump design was manufactured. The volute was designed such that partition vanes could be added to change the number of volutes. Experiments were performed on single volute centrifugal pump, double volute centrifugal pump and triple volute centrifugal pump at 500, 800, and 900 rpm for each case. The thrust values of the double volute pump are always lower than that of the single volute pump specially when operating far from the best efficiency point where, the radial thrust is reduced by more than 55% at shut off and more than 40% at high discharges, while the thrust values of the triple volute are always lower than that of the single volute and double volute pumps specially when operating far from the best efficiency point where, the radial thrust is reduced by more than 70% at shut off and more than 50% at high discharges comparing to single volute and the radial thrust is reduced by more than 40% at shut off and more than 20% at high discharges comparing to double volute. However, it is to be mentioned that the best pump efficiency is always obtained for the single volute pump, compared with the other alternatives.