Volute type pump

The volute type pump has its impeller mounted eccentrically within the volute. The degree of eccentricity governs the pressure that the pump can generate. If the impeller were concentric inside the volute, or equidistant, the pump would generate flow, but not much pressure or head (Figure 9-1). 

Multistage pumps may be of the volute type (Fig. 10-41), with single- or double-suc tion impehers (Fig. 10-42), or of the diffuser type (Fig. 10-43). They may have horizontahy split casings or, for... 

Unless otherwise specified, except for volute sump pumps (Type VS4), the first stage impeller shall be located between bearings. 

Some feed problems have been resolved by using a volute type of eentrifugal pump and feed tank ... 

This type of pump is similar to others exeept that the impellers diseharge into a diffuser hell ty pe housing instead of the volute. The diffuser has multiple veins or ribs that direct the pumped liquid through a eolumn or into the next impeller (Figure 6-10). 

For open system sump pump service, the pressure containing components Types VS4 and VS5 pumps are the volute casing, suction cover, and discharge fine. For closed system pressurized or vacuum tank service, the outer stuffing box or seal housing, pump cover plate, and tank cover also become pressure containing components. 

Vertically suspended double casing pumps are designated Type VS6 for diffuser construction and VS7 for volute construction. 

Wet pit, vertically-suspended, single-casing volute pumps with discharge through the column are designated pump type VS2. 

Double-casing volute vertically-suspended pumps shall be designated pump type VS7. 

Figure 7.9. Some types of centrifugal pumps, (a) Single-stage, single suction volute pump, (b) Flow path in a volute pump, (c) Double suction for minimizing axial thrust, (d) Horizontally split casing for ease of maintenance, (e) Diffuser pump vanes V are fixed, impellers P rotate, (f) A related type, Ihe turbine pump.

FIGURE 4.5 Various types of pump impellers, continued (a) lobe type (b) internal gear type (c) vane type (d) impeller with stationary guiding diffuser vanes (e) impeller with volute discharge and (f) external gear type impeller. 

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