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Compressors, Pumps, and Turbines 249

employed where it is required to deliver a high flow rate at a medium pressure. To
achieve higher discharge pressures with centrifugal pumps, several stages are in-

Inlet

Radial-Flow Centrifugal Peripheral
Source: Reference 5.45 Source: Reference 5.45

Propeller
Shaft

Axial How

Figure 5.27 Dynamic pumps.

stalled on one shaft or the pumps are installed in series. Centrifugal pumps are not
self priming. Methods of priming centrifugal pumps are discussed by Kern [48].
A centrifugal pump operating at a constant speed will develop the same head in
feet regardless of the specific gravity of the fluid being pumped, provided that the
viscosity of the fluids do not differ significantly. For this reason, it is usual to plot
the pump characteristic curve as head against volume flow rate for a given rota-
tional speed. Viscosities of less than 50 cp (0.05 Pa-s) will not affect the head
appreciably. The effect of viscosity is to change the internal friction of the pump
and thus the head developed by the pump. Although the head developed by dif-

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