Definition - What does Volute mean?
A volute is a spiral-shaped pump casing frequently used in centrifugal pumps. The purpose of the volute is to convert the liquid's velocity to pressure as the impeller discharges the liquid through the casing nozzle. This is achieved via a gradually increasing cross-sectional area in the volute that increases the fluid’s flow-through area, thus increasing the static pressure of the fluid.
Corrosionpedia explains Volute
As the impeller of the centrifugal pump rotates, it increases the velocity of the liquid in the pump casing. This impeller is located off-center of the volute, resulting in a varied and gradually increasing flow-through area in the pump casing.
The fluid flow due to the action of the impeller starts at the area of the volute closest to the impeller, which has the smallest cross-sectional area. As the fluid makes its way around the casing to the discharge area, it gains pressure as it fills the increased area of the volute. The fluid, therefore, gains maximum pressure at the discharge area, where the area of the volute is greatest.