HYDRAULICS 351 



It is not advisable to use bands less than f in. in diameter, 

 as they are likely to cut into the wood. By reducing the dis- 

 tance between the bands, stave pipes can be made to stand very 

 heavy pressures, but above about 85 Ib. per sq. in., the cost of 

 construction is equal to or greater than for steel pipe. 



POWER REQUIRED FOR PUMPING 



In calculating the power required in pumping water through 

 a height h, the work performed in overcoming the resistances to 

 flow must be taken into account. Let Q be the discharge in 

 cubic feet per second; /, the coefficient of resistance due to 

 friction; c, the sum of the coefficients of resistance due to 

 entrance, bends, valves, etc. ; d, the diameter and / the length 

 of the pipe, both in feet. Then, the work performed by the 

 pump in a second, in foot-pounds, is 



7 = 62.50 



and the number of horsepower is 



H. P. = .11360 /i + .0252(/X- 

 L d 



EXAMPLE 1. It is desired to raise 15 cu. ft. of water per sec. 

 by pumping to a reservoir 300 ft. above and 2 mi. distant from 

 the pumping well. What horsepower will be necessary to do 

 this work through a main 24 in. in diameter, having four bends, 

 assuming a value of /as .018, a value of .5 for the coefficient of 

 resistance at entrance, and the value of the coefficient for each 

 bend as .9. 



SOLUTION. Here, = 15, h = 300, 1 = 5,280X2 = 10,560, d 

 = f* = 2,/=.018, c = .5 + .9X4 = 4.1. Substituting these values 

 in the formula 



H. P. = .1136X15X I 300 + .0252X I .018X ' +4 



/ 

 300 + .0252X (.018X 



Cost of Pumping Water. The cost of pumping water is 

 approximately as follows: In a general way, the cost of watet 

 may be estimated at a certain amount per million or per 

 thousand gallons. It is found by experience that, in the best 



