The handbook of Technical irrigaTion informaTion - Hunter Industries

Handbook of Technical Irrigation InformationBrake HorsepowerPumpsThis formula determines the amount of power required at the pump shaft based on the pump efficiency. It does nottake into account any losses in the engine or electric motor.BHP = Q x h3960 x E fWhere:BHP = brake horsepower (1 HP = 550 ft-lbs/sec)Q = pump discharge in gallons per minute (GPM)h = total dynamic head in feet3960 = constant for conversion of units to brake horsepowerE f = pump efficiency (decimal)Example:A pump with an efficiency of 85% is pumping 500 GPM with a total dynamic head of 230 feet. What is the brakehorsepower required to drive the pump?BHP = 500 x 2303960 x 0.85BHP = 34.17Horsepower Required in Pumping WaterThis formula is used to determine the brake horsepower requirements.BHP = ft x GPM3960 x E fWhere:BHP = Brake Horsepowerft = the number of feet the water is lifted from the surface of the water source to the discharge pointGPM = the gallons per minute being pumped3960 = constant for conversion to horsepowerE f = pump efficiency (decimal)Example:A pump system is needed to pump 500 GPM from a river 70 feet up to a golf course water reservoir. What is theminimum horsepower required to pump this water? This pump is rated at 75% efficient.HP = 70 x 5003960 x .75HP = 11.78≈12Brake horsepower is the power required at the pump shaft required to drive the pump.16