Centrifugal Pumps
These liquid handling machines embody the same principles as centrifugal fans used to move air and other gases. Both forms of equipment when in operation follow the same general laws. Centrifugal pumps are relatively high speed machines and are generally direct connected to a steam turbine or an electric motor; V belt drives or internal combustion engines may also be used. Water enters the impeller, at the center flows radially outward, and leaves the periphery of the impeller at a velocity
that is the resultant of the tip velocity of the impeller blade and that of radial flow of the liquid ahead of the backward curved impeller blade. The velocity of the liquid is gradually decreased, and the energy of motion is converted into pressure head in the pump casing in which the impeller rotates. The liquid being handled is under pressure and will flow out of the pump against the resistance to be overcome. The design of a centrifugal pump is generally directed towards converting the energy of velocity into potential energy without loss, minimizing the friction of impeller rotation, and balancing the end thrust of the impeller shaft. The groupings below are applicable to commercial centrifugal pumps.
Volute
Turbine (diffuser)
Axial-flow units
Numbers of stages are single suction, double-suction; open and enclosed impeller; and horizontal and vertical.
Multistage Centrifugal Pumps
The liquid involved passes through two or more impellers in multistage centrifugal pumps. Each stage consists of separate compartment in which an impeller, mounted upon a shaft common to all stages revolves. Each stage delivers its discharge to the inlet of the next stage impeller with the exception of the last stage, which sends its output to the pump outlet. The final liquid pressure is dependent upon the number of stages involved as well as upon features of the pump design and its speed of operation. Commercial multistage pumps may have two, three, four, five, six, seven, eight, nine, ten, or eleven stages, depending upon the design and the builder. The casing may be either of the volute or the diffuser construction, and the impellers may be either single inlet or the less frequently used double inlet type.
Sampling theory
Main information page
High pressure water pump, Rotary pumps.