107 

 Capacity of engine. 



The power necessary to lift water is indicated in horse powers. A horse 

 power represents the energy required to lift 33,000 pounds 1 foot high 

 in one minute; this is equivalent to 3960 gallons of water per minute 

 raised 1 foot high. This relation enables one to find the horse power 

 required in any case by multiplying the discharge of the pump in gallons 

 per minute by the total lift in feet frnd dividing by 3960. The result 

 obtained represents the useful water horse power necessary to lift the 

 water. The horse power delivered by the engine to the belt or gears when 

 the pump is belted or geared to the engine, or to the pump itself when 

 direct connected, is the brake horse power and must be greater than the 

 useful horse power to allow for the loss of energy in the pump and trans- 

 mission. The horse power developed within the engine itself is the indi- 

 cated horse power and must be greater than the brake horse power to allow 

 for the energy loss in the engine itself. Gasoline engines and motors are 

 rated on brake horse power. Steam engines are rated on indicated horse 

 power. 



The combined efficiency of a pumping plant represents the ratio of the 

 useful water horse power to the rated horse power of the engine, and will 

 vary considerably with the type of pump, method of connection of engine 

 with pump and the care taken in operating both pump and engine at the 

 proper speed. In ordinary field practice a good pumping plant, properly 

 installed, should easily reach the efficiency given in the following table: 



Efficiency of Centrifugal Pumping Plants. 



No. of centri- is ch ?; r ?, e ln Water horsepowei Brake horse - 



P- <oot o fll . e y . , P 



The efficiency of power plunger pumps varies with the size of the pump 

 and with the lift. A greater efficiency is obtained with the higher lifts and 

 with the larger sizes. The efficiencies of properly installed plunger pumps 

 and the horse power for various lifts are given in the following table: 



