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Centrifugal

pumps

1.1 The pump

A pump is an item of mechanical equipment that moves liquid from one
area to another by increasing the pressure of the liquid to the amount
needed to overcome the combined effects of friction, gravity and
system operating pressures. In spite of the wide divergence of pump
types available, over 80% of all pumps used in industry are of the single
stage, end suction, centrifugal pump.

The centrifugal pump moves liquid by rotating one or more impellers
inside a volute casing. The liquid is introduced through the casing inlet
to the eye of the impeller where it is picked up by the impeller vanes.
The rotation of the impeller at high speeds creates the centrifugal force
that throws the liquid along the vanes, causing it to be discharged from
its outside diameter at a higher velocity. This velocity energy is
converted to pressure energy by the volute casing prior to discharging
the liquid to the system.
Two pump types are more commonly used than all the others put
together. They are the ANSI pump that is designed and built to the
standards of the American National Standards Institute, and the API
pump that meets the requirements of the American Petroleum Institute
Standard 610 for General Refinery Service. While other countries have
their own designations, such as the International ISO Standards, the
German DIN Standards and the British BS Specifications, the pump
styles are still very similar to either the ANSI or the API pump.
Over the years, ANSI designs have become the preferred style of end
suction pumps, not only for chemical process applications, but also for
water and other less aggressive services. The ANSI Standard provides
for dimensional interchangeability of pumps from one manufacturer to
another.

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