If a pump is delivering 2,200 gpm against 150 feet of head with a brake horsepower of 100, how is efficiency calculated?

To calculate the efficiency of a pump, the most widely used formula takes into account both the hydraulic power delivered by the pump and the brake horsepower being used to operate it. The correct answer utilizes the relationship between flow rate, head, and horsepower to determine efficiency in terms of percentage.

The efficiency formula is based on the concept that hydraulic power is defined as the product of the flow rate (in gallons per minute) and the head (in feet) divided by a constant that converts these units into horsepower. In this instance, the constant is 3957, which is used to convert the product of flow rate and head into horsepower.

By using the formula where efficiency is expressed as (gpm x head) / (3957 x BHP), we ascertain the ratio of the hydraulic power produced by the pump to the input power (brake horsepower). This effectively gives us a measure of how well the pump converts input energy into useful hydraulic work.

This methodally illustrates why the option is correct: it combines the necessary parameters — flow rate, head, and brake horsepower — in a way that reflects the actual efficiency of the pump’s operation. The division by the brake horsepower normalizes the hydraulic output power against the mechanical input, yielding a straightforward interpretation of