STEAM 99 



FLOW OF STEAM 



Weight of Steam Discharged. The number of pounds of 

 steam that will flow continuously through a pipe of given 

 diameter in 1 min. at specified pressure may be calculated 

 by the formula 



in which W = weight of steam discharged , in pounds per minute ; 



w = weight of 1 cu. ft. of steam at the pressure Pi ; 

 Pi = pressure of steam at entrance to pipe, in pounds 



per square inch; 



P 2 = pressure of steam at discharge, in pounds per 

 square inch; 



L = length of pipe, in feet; 



d = diameter of pipe, in inches. 



In applying the preceding formula in determining the diam- 

 eter of the steam pipe for an engine, it must be remembered 

 that, in steam-engine work, the steam is drawn intermittently 

 from the pipe. Thus, assume that an engine of 100 H. P., con- 

 suming 30 Ib. of steam per horsepower per hour, cuts off at J 

 stroke. In that case, the steam consumption per hour would 

 be 100 X 30 = 3,000 Ib. But as the steam used at each stroke is 

 drawn into the cylinder during only one-fourth of the time 

 required to complete the stroke, the 3,000 Ib. of steam flows 

 through the pipe in J hr. Then, in order to determine the 

 quantity of steam that would flow continuously at the same 

 velocity at which it flows during admission to the cylinder, 

 the actual steam consumption per hour should be divided by 

 the fraction representing the cut-off and the quotient should be 

 taken as the weight of steam discharged per hour. This value, 

 divided by 60, should be substituted for w in the formula. 

 Thus, in the case mentioned, the amount of steam discharged 

 per hour, flowing continuously at the same velocity as during the 

 admission period, is 3,000 -f- i = 12,000, and the value of W to 

 be used in the formula is therefore 12, 000 -=-60 = 200 Ib. per 

 min. Knowing the pressures, the length of pipe, and the 



