The Difference Between Rotary Pump And Centrifugal Pumps

Rotary pumps operate in a circular motion and displace a constant amount of liquid
with each revolution of the pump shaft. In general, this is accomplished by pumping
elements (e.g., gears, lobes, vanes, screws) moving in such a way as to expand
volumes to allow liquid to enter the pump. These volumes are then contained by the
pump geometry until the pumping elements move in such a way as to reduce the
volumes and force liquid out of the pump. Flow from rotary PD pumps is relatively
unaffected by differential pressure and is smooth and continuous. Rotary PD pumps
have very tight internal clearances which minimize the amount of liquid that slips
back from discharge to suction side of the pump. Because of this, they are very
efficient. These pumps work well with a wide range of viscosities, particularly high
viscosities.
Centrifugal pumps differ from rotary pumps in that they rely on kinetic energy rather
than mechanical means to move liquid. Liquid enters the pump at the center of a
rotating impeller and gains energy as it moves to the outer diameter of the impeller.
Liquid is forced out of the pump by the energy it obtains from the rotating impeller.
Centrifugal pumps can transfer large volumes of liquid but efficiency and flow
decrease rapidly as pressure and/or viscosity increases.