13.2.2 Types of pumpsPumps may be classified as rotodynamic (radial (centrifugal), axial or
mixed-flow type)) and reciprocating (positive displacement) pumps. Also,
there exist several other types such as air-lift (pneumatic) and jet pumps,
screw and helical rotor pumps, etc.
In the rotodynamic-type pump water, while passing through the
rotating element (impeller), gains energy which is converted into pressure
energy by an appropriate impeller casing (Fig. 13.1(a) and Fig. 13.1(b)).
The reciprocating pump (Fig. 13.1(c)) utilizes the energy transmitted by a
moving element (piston) in a tightly fitting case (cylinder). The applica-
tions of positive displacement pumps, air-lift, and jet pumps are very much
limited nowadays and most pumping stations utilize centrifugal-type
PUMPS AND THEIR CLASSIFICATION 549
Fig. 13.1 Rotodynamic and reciprocating (piston) type pumps