Internal gear pump is a simple pump as the name suggests “Gear within a Gear”. Internal gear pumps are energy efficient, self priming, positive displacement rotary pumps.

When the pump shaft rotates, the fluid from pump inlet fills the gaps/spaces between the teeth of two gears i.e. rotor & idler according to the rotation.

Liquid is then transferred in the filled gaps/spaces to the discharge side/pump outlet. The walls of the pump casing & crescent create a seal that separates pump inlet from pump outlet.