In a two-stage centrifugal pump, Volume mode corresponds to which arrangement?

• A. Parallel arrangement, where each impeller handles half the water
• B. Series arrangement, where water goes through both impellers
• C. Stand-alone single impeller
• D. Off

Answer: (A)

In a two-stage centrifugal pump, how the impellers are arranged changes the pump’s performance curve: in series the water passes through both impellers, boosting head (pressure) but not increasing the total flow, while in parallel the flow is split and then recombined, increasing the overall flow while keeping the head more or less the same as a single stage. Volume mode aims to move as much water as possible, so the two impellers are used in parallel. Each impeller handles part of the total flow, and together they deliver a higher flow rate than a single impeller at the same speed. The alternative of putting the impellers in series would raise pressure rather than volume, and a stand-alone single impeller wouldn’t take advantage of the second stage.