🔍 Key Concepts

• Centrifugal pump casing and shaft passage and where leakage or air entry can occur • Purpose of sealing arrangements (stuffing box, mechanical seal, sealing water) in pumps • Effect of air entering the suction side of a centrifugal pump on priming and discharge pressure

💭 Think About

• Think about what would happen to pump performance if air were allowed to travel along the shaft into the casing while the pump is running. • Which option describes a function that is different from simply ‘replacing’ another component (like a mechanical seal or slinger ring) and instead focuses on protecting pump operation? • Consider which part of the pump is most sensitive to the presence of air compared to a small amount of liquid leakage.

✅ Before You Answer

• Identify where the shaft passes through the casing and what needs to be controlled at that point (liquid leakage vs. air entry). • Decide which options describe a primary design purpose of sealing lines versus something that sounds like a substitute for another device. • Ask yourself which situation would most quickly cause loss of suction / loss of prime in a centrifugal pump and match that to the option that addresses it.