[2][3] A pump is a mechanical device generally used for raising liquid from a lower level to higher one.
Due to low inlet pressure, the liquid rises from where it is to be stored or supplied.
It can be classified into two types: Positive-displacement rotary pump move the fluid by using a rotating mechanism that creates a vacuum that captures and draws in the liquid.
Rotary positive-displacement pumps can be classified into two main types: Reciprocating pumps move the fluid using one or more oscillating pistons, plungers or membranes, while valves limit fluid motion to the desired direction.
With this pump type, the volume of the liquid delivered for each cycle depends on the resistance offered to flow.
A simplest type of pump comprises an impeller fitted onto a shaft, rotating in a volute casing.
[6] Rotodynamic pumps can be classified by various factors such as design, construction, applications, service etc.
Due to centrifugal force, both pressure and kinetic energy of fluid will increases.
As the centrifugal force occurs in the fluid particles, at the inlet nozzle (at the suction) side the pressure will decreases.
This situation is very dangerous for the pump because the fluid starts to boil and form the bubbles.
The fluid pressure inside the casing is very high, a proper sealing arrangement is required.