PUMPING MACHINERY 26l 



A United States gallon contains 231 cubic inches. 



A cubic foot of water weighs 62.5 pounds. 



A gallon of water weighs 8J/3 pounds. 



A cubic foot contains approximately 7^2 gallons. 



The pressure of a column of water is equal to its 

 height multiplied by .434. Approximately the pressure 

 is equal to one-half of the height of water column or head. 



Formulas for pump capacity and power: 



D = diameter of pump cylinder in inches. 

 N = number of strokes per minute. 



H = total height water is elevated, figuring from the surface of 

 suction water to highest point of discharge. 

 S = length of stroke in inches. 

 Q =r quantity of water in gallons raised per minute. 



D 2 X .7854 X S == capacity of pump in cubic inches per stroke. 



D 2 X S 



capacity of pump per stroke in gallons. 



294 

 D'XS 



capacity of pump per stroke in pounds of water. 

 =. capacity of pump per minute in gallons. 



35-266 



D 2 XSXN 

 294 



D 2 X S X H X N 



7g = number of foot-pounds of work per minute. 



A rule which may be used to calculate roughly the 

 capacity of a pump is as follows: The number of gal- 

 lons pumped per minute by a pump with a lo-inch stroke 

 at 30 strokes per minute is equal to the square of the 

 diameter of the cylinder in inches. From this rule it is 

 easy to calculate the capacity of a pump of a longer or 

 shorter stroke and making more or less strokes per min- 

 ute. 



372. Friction of pumps. Pumps used to pump water 

 from wells are of rather low efficiency ; on an average, 

 35 per cent of the power is required to overcome friction 



