Rotary Vane Pump Operation uses which internal mechanism?

• A. A rotor with movable vanes mounted off-center inside a housing to trap air/water and compress it, forcing it out the discharge
• B. A diaphragm that flexes with pressure
• C. A piston in a cylinder
• D. A rotor with fixed blades

Answer: (A)

Rotary vane pumps rely on a positive-displacement mechanism created by a rotor with movable vanes that ride against the inner wall of a housing mounted off-center. As the rotor turns, the vanes slide outward to contact the housing, forming sealed pockets that trap a small amount of fluid or air between two vanes and the housing. Those pockets are carried from the suction side to the discharge side; when they move past the discharge, the pocket volume decreases and the trapped fluid is compressed and expelled. The off-center (eccentric) arrangement continually changes the volume of these pockets, producing suction on the inlet and discharge on the outlet in a continuous cycle.

This is why the described mechanism is the best fit. A diaphragm pump uses a flexible membrane instead of a rotor and vanes. A piston pump relies on reciprocating motion of a piston in a cylinder. A rotor with fixed blades would not seal or trap fluid effectively, so it wouldn’t perform as a vane pump.