🔍 Key Concepts

• Centrifugal pump operation – how does a centrifugal pump actually move liquid and what condition must be met at the suction side? • Priming requirements – what does "primed" mean for a pump, and what happens if air enters the suction? • Stuffing box and lantern rings – what are they for on a pump shaft: sealing, lubrication, or flow?

💭 Think About

• First, think about what happens inside a centrifugal pump casing if the eye of the impeller is not completely filled with liquid. Can the pump move water or just spin air? • Ask yourself what the main purpose of a lantern ring and stuffing box is: to improve bilge suction, to provide lubrication/cooling/sealing, or to change the flow pattern in the volute? • Consider which option is directly related to getting ALL the bilge water out, versus options that are more about mechanical sealing or flow characteristics inside the casing.

✅ Before You Answer

• Be clear on the definition of priming for a centrifugal pump and how loss of prime affects bilge pumping. • Verify the primary function of a stuffing box and lantern rings in marine pumps – what problem are they designed to solve? • Separate what is needed for hydraulic performance (actually moving water from the bilge) from what is needed only for shaft sealing or internal flow shaping.