What component is NOT part of an external gear pump?

An external gear pump operates on the principle of moving fluid through the mechanical rotation of two gears that mesh together within a pump housing. The main components of an external gear pump include the driving gear and the idler gear, which work together to create pockets of liquid that facilitate the movement of fluid from the inlet to the outlet.

The driving gear is the gear that is powered by an external motor, causing it to rotate. This rotation of the driving gear causes the idler gear to also turn, resulting in the creation of suction that draws fluid into the pump, filling the pockets formed between the gears. As the gears continue to rotate, these pockets decrease in volume, forcing the liquid out of the pump.

In contrast, an impeller is a component typically found in centrifugal pumps, not in external gear pumps. Impellers are designed to impart energy to the fluid primarily through rotational motion, but external gear pumps utilize gears instead of impellers to achieve fluid movement. The presence of an impeller in this context does not conform to the design principles of an external gear pump, confirming that it is indeed not a component of such a pump.