What restricts the flow between the impeller discharge and suction areas in a centrifugal pump to prevent excessive water circulation between the two?

• A. Impeller clearance devices
• B. Gaskets
• C. Wear rings
• D. Check valves

Answer: (C)

Wear rings restrict the flow between the impeller discharge and suction areas by forming a very tight clearance between the impeller and the casing. This small annular gap minimizes the internal leakage that would otherwise allow fluid to short-circuit from the high-pressure discharge side back toward the suction side, reducing recirculation inside the pump. Keeping this leakage low helps maintain the designed head, efficiency, and stable flow. Wear rings are replaceable because they wear over time, which increases clearance and increases internal leakage, degrading performance. Gaskets seal external joints, not the internal clearance around the impeller; check valves prevent backflow in the discharge line rather than controlling internal leakage; “impeller clearance devices” isn’t a standard term for this function.