Volute casing & Impeller

Volute casing & Impeller

Volute of a centrifugal pump is the casing that receives the fluid being pumped by the impeller
As liquid exits the impeller it has high kinetic energy and the volute directs this flow through to the discharge.
As the fluid travels along the volute it is joined by more and more fluid exiting the impeller but, as the cross sectional area of the volute increases, and velocity is gradually reduces.

Volute casings come in three different types:

Single volute and Double volute

The fundamental benefit of a double volute over a single volute is the equalization of the pressure distribution within the volute.
Radial thrust can substantially increase the pump shaft deflection

Types of Pump Casings

Pressure distribution comparison

for non diffuser volute casing

The motional energy of one or more driven rotors, known as impellers, is transferred to power a centrifugal pump.
The fluid is directed toward the pump output by the impeller's movement, which raises its pressure and velocity.
Depending on the flow line pattern in the impeller, impellers are subdivided into the following types:

Radial Impeller
Mixed flow impeller
Axial flow impeller
Peripheral flow impeller

Fig. 5 Impeller: Axial impeller (axial propeller)

a

Fig. 1 Impeller: Radial impeller with purely radial vanes, stagnation point S (shown with front shroud removed)

b

Fig. 3 Impeller: Mixed flow impeller (diagonal impeller) (shown with front shroud removed)

c

Fig. 15 Impeller: Peripheral impeller

d

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