🔍 Key Concepts

• Centrifugal pump internal parts – especially the impeller, casing, and wear/wearing rings • Purpose of clearances between rotating and stationary parts in a pump • How leakage between suction (inlet) and discharge (outlet) affects pump efficiency

💭 Think About

• Think about where wearing rings are physically located in relation to the impeller and casing. Are they on the suction side, the discharge side, or between them? • Ask yourself: if fluid can slip back from high-pressure side to low-pressure side inside the pump, what simple replaceable part could limit that without major machining of the whole casing or impeller? • Consider which choice describes something that would logically be done by a small, replaceable ring at a close-running clearance rather than by a seal or by the shape of the casing/volute.

✅ Before You Answer

• Verify whether wearing rings are stationary, rotating, or both, and how they fit between impeller and pump casing • Check which option best matches reducing internal leakage across a small clearance rather than sealing the external shaft or changing flow turbulence at discharge • Eliminate any options that confuse shaft seals/packing/glands with the function of wearing rings inside the pump casing