When using a pump graph, if you find that the impeller that is needed is about 10% smaller than the one you have, what options do you have to maintain the same steady volume of flow and head?

Choosing an impeller that is 10% smaller than what is needed typically results in a decrease in the volume of flow and head generated by the pump. To maintain the same steady volume of flow and head with a smaller impeller, several options can be considered.

Machining the impeller can be a viable solution, as it allows for modifications to the impeller that can help achieve the desired performance characteristics. By altering the impeller, adjustments can be made to enhance the flow and head output. This can include increasing the diameter or optimizing the blade shape to improve performance, which can compensate for the reduction in size.

Throttling the discharge is another effective method. By partially closing the discharge valve, resistance in the system is introduced, which helps increase the pressure at the pump's output. This can help maintain the desired flow rate even when the impeller is smaller.

Since both machining the impeller and throttling the discharge can work together to help achieve the required flow and head, choosing the option that includes both actions is justified. This combination provides a comprehensive approach to addressing the performance limitations of a smaller impeller. Hence, confirming both provided methods as correct ensures that the needed flow and head can continue to be achieved effectively.