🔍 Key Concepts

• Centrifugal pump working principle – how the impeller moves liquid (not air) outward by centrifugal force • Priming – what it means in terms of filling the casing and suction line with liquid before starting • Suction lift vs. discharge head – what the pump can and cannot do when there is air in the casing

💭 Think About

• Think about what a centrifugal bilge pump needs to have inside its casing in order to create flow when it first starts • Ask yourself: can a centrifugal impeller grab and move air the same way it moves water? What happens if the eye of the impeller is full of air? • Consider whether the main startup problem is on the suction side (lifting water into the pump) or on the discharge side (pushing water out)

✅ Before You Answer

• Verify that priming means filling the pump and suction line with liquid, not just reducing pressure or lubricating parts • Check which option correctly focuses on the pump’s inability to handle air on the suction side, rather than issues with discharge pressure or seal lubrication • Eliminate any choice that treats priming as mainly a mechanical lubrication or pressure balancing step, instead of solving the “air in the pump” problem