The spiral chamber of a centrifugal pump in which the velocity given to water by the impeller is converted into pressure is called the

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

Answer: (B)

Volute is the term for the spiral chamber. It surrounds the impeller and has a gradually enlarging cross-section, which slows the water’s velocity as it moves through the chamber and converts that velocity energy into pressure energy, delivering a steady discharge. This spiral design distinguishes the volute from other parts. A diffuser accomplishes velocity-to-pressure conversion too, but it uses stationary vanes to slow the flow within a separate stage, not the spiral casing itself. The casing is the outer shell of the pump, not the specific channel that turns velocity into pressure. So the spiral chamber where velocity is converted to pressure is correctly called the volute.