Which type of pump uses closely meshed gears, vanes, or lobes?

• A. rotary pump
• B. centrifugal pump
• C. piston pump
• D. diaphragm pump

Answer: (B)

Rotary pumps are positive-displacement devices that trap a fixed amount of fluid between closely meshed gears, vanes, or lobes and carry it to the discharge as they rotate. This meshing creates sealed cavities that move fluid with each rotation, producing a steady flow and relatively high pressure at low to moderate speeds.

This differs from centrifugal pumps, which rely on an impeller to fling fluid outward and convert velocity into pressure rather than trapping a fixed volume per rotation. Piston pumps use a reciprocating motion of a piston in a cylinder to draw in and push out fluid, while diaphragm pumps use a flexible membrane that expands and contracts to achieve the same effect. So the feature of tightly intermeshing rotating parts points to the rotary pump.