Water-Lifting Devices – Pumps - Practices of Irrigation and On-farm Water Management - page 455

a high velocity and the casing converts this velocity head into pressure head due to
volute design. Volute pumps usually employ closed type of impeller for irrigation,
which has curved vanes for smooth flow of liquid. There are other kinds of impellers
like open, semi-open, and nonclogging impeller, but these are used for purposes
other than irrigation.
A generalized specification of the reciprocating pump is given below

Impeller
diameter
(mm)

Suction size
(mm)

Delivery
size (mm)

Total head
(m)

Discharge
(l/s)

Revolution
per min

Motor
rating (kW)

50-125 40-125 185-300 4-45 1.4-73 1,380-1,480 1.5-7.5

12.5.3.2 Uses

Monoblock pumps are used for agricultural purposes. These are also suitable for
domestic and industrial applications of pumping water.

12.5.4 Radial-Flow Pump

Basically, a centrifugal radial-flow pump has two main parts: (1) a rotating element
(impeller and shaft) and (2) a stationary element (casing, stuffing box, and bearings).
Water enters the pump near the axis of the high-speed impeller, and by centrifugal
force is thrown radially outward into the pump casing. The velocity head imparted
to the fluid by the impeller is converted into pressure head by means of a volute
(Fig. 12.4 ) or by a set of stationary diffusion vanes surrounding the impeller.

Fig. 12.4 Schematic of a
radial flow pump