A Bell & Gossett Series e-80 4x4x13.5 pump has a 12.5-inch impeller and is operating at 1750 rpm. The pump is installed in a closed-loop pipe system. An analysis of the pump/pipe system at 400 gpm indicates a required pump head of 75 ft.

a. Determine the operating point of the pump/pipe system under these conditions.

After several years of service, engineers have decided to refit the pump with a 12-inch impeller. The engineers also decide to install a variable speed drive for the pump. The new impeller is installed and the operating speed is reduced to 1480 rpm.

b. Use the affinity laws to determine the new pump capacity and head for the operating point determined in part (a).

c. Determine the operating point of the pump/pipe system under the new operating conditions (capacity and head).

d. Explain why the points determined in parts

(b) and

(c) do not match.