Principles of Pumps and Pumping Systems

Brake horsepower is also plotted on the curve. Note that brake horsepower decreases with decreasing flow, but does not reach zero at zero flow. There will be a noticeable and sometimes troublesome heat effect in cetrifugal pumps operating with the discharge throttled to abnormally low flow rates. Pump efficiency is also indicated on the curve. 

Pump curves should never be extrapolated beyond the limits shown by the equipment supplier. Pump curves often terminate abruptly, with very little capacity increase at discharge heads lower than those shown by the vendor. 

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