The passage area of the pump casing that increases in size as it gets closer to the discharge is known as what?

• A. Diffuser
• B. Volute
• C. Impeller
• D. Casing

Answer: (B)

The volute is the snail-shaped pump casing whose cross-sectional area increases as you move toward the discharge. This widening path collects the high-velocity flow leaving the impeller and gradually slows it, converting kinetic energy into static pressure so the fluid exits smoothly into the discharge line. The volute’s shape helps gather flow from all parts of the impeller and directs it efficiently to the outlet, reducing turbulence and losses. This differs from a diffuser, which uses stationary vanes to decelerate flow in a separate section; here the emphasis is on the expanding casing that broadens toward the discharge.