What performance aspect is most directly affected by impeller wear?

• A. head
• B. flow rate
• C. efficiency
• D. noise

Answer: (C)

Impeller wear mainly alters how effectively a pump converts motor power into hydraulic energy. When the blades are worn, their geometry changes and roughness increases, which raises internal hydraulic losses due to turbulence, leakage around the impeller, and less area to push the fluid. That means, for the same shaft power, less hydraulic power is delivered to the fluid, so the efficiency drops. Head and flow can be affected as the operating point shifts on the pump curve, but the direct, primary effect of wear is a decrease in efficiency because energy transfer becomes less effective. Noise and changes in flow can accompany wear, but they are secondary to the efficiency loss.