Which centrifugal pump must be primed before operation?

• A. Submersible Pumps
• B. Vertical Turbine Pumps
• C. Centrifugal Pumps
• D. Prefabricated Pumps

Answer: (C)

Priming is about getting rid of air in the pump and its suction line so a liquid column can be established and the pump can develop suction. A centrifugal pump relies on that suction to draw water into the impeller eye and start moving it. If air remains in the pump or suction line, the pump can’t create the vacuum needed, so it will spin without pumping or cavitate.

Submersible pumps are designed to operate while submerged in the liquid, so the suction path is already filled with fluid and priming isn’t needed. Vertical turbine pumps sit below the water surface in a well or tank, with their suction line flooded by the liquid, so they don’t require priming for standard operation. Prefabricated or packaged pumps can vary in design, but many are built as self-priming or are used in configurations where the suction is already filled; however, a typical surface centrifugal pump that isn’t submerged must be primed to start pumping.