Which type of pump generally has a greater capacity?

• A. Rotary pump
• B. Reciprocating pump
• C. Centrifugal pump
• D. Diaphragm pump

Answer: (C)

Capacity means how much fluid the pump can move per unit time (flow rate). Centrifugal pumps generally provide higher flow because they accelerate fluid with a rotating impeller and then discharge it through a volute, giving a steady, continuous stream. There’s no fixed volume per stroke to limit the flow; increasing the impeller size or the rotational speed raises the flow substantially, up to mechanical limits. In contrast, the other common pump types move a specific amount of fluid with each cycle or revolution (positive-displacement). Rotary pumps have a set displacement per revolution, reciprocating pumps push a fixed volume with each stroke, and diaphragm pumps also displace a defined volume each cycle, which limits their maximum flow compared to a centrifugal pump. For large capacity, centrifugal pumps are typically the better choice.