Single and Double Volutes:
A Centrifugal pumps could also be constructed in a manner which results in two distinct volutes, every receiving the liquid which is discharged from an 180o region of the impeller at some given time.
Pumps of this kind are known as double volute pumps (they might also be referred to a split volute pumps). In a few applications the double volute minimizes radial forces imparted to the shaft and bearings because of imbalances within the pressure around the impeller. Comparison of single and double volute centrifugal pumps is displays on below figure.
Figure: Single and Double Volutes