A positive displacement pump makes a fluid move by trapping a set amount and forcing (displacing) that trapped volume in to the discharge pipe. … Liquid flows in to the pumpas the cavity on the suction side expands and the liquid flows out of the discharge because the cavity decreases.

The most typical type among centrifugal pump is the radial flow pump. … The primary difference between these types of pumps and centrifugal can be that positive displacement pumps will move liquid at the same speed regardless of the pressure on the inlet end and centrifugal pumps will not