A positive displacement pump is a liquid or gas to move by trapping a fixed amount of fluid or gas and then forcing (displacing) that trapped volume into the discharge pipe. Positive displacement pumps can be further specified as either rotary-type (for example the rotary vane) or lobe pumps same to oil pumps used in car engines. These pumps give a non-pulsating output or displacement unlike the reciprocating pumps. Hence, they are known as positive displacement pumps.