WOOD PIPE FOR CONVEYING IRRIGATION WATER. 5 



purpose of this bulletin. Such discussion may be found in published 

 transactions of engineering societies and in engineering journals. 

 But some points relative to practice in design and use of materials 

 will be given in the following pages. 



SIZE OF PIPE. 



Continuous stave pipes have been built in sizes from 10 inches in 

 diameter up to 13.5 feet, but this form of construction is not common 

 at present in pipes of diameter less than 20 inches. Pipes smaller 

 than this are usually machine banded. Sizes greater than 8 feet in 

 diameter are exceptional. The size of pipe to use in any particular 

 place must be governed by conditions. For gravity lines the quantity 

 of water to be carried and the available head are the controlling 

 factors. If for conducting water from pumps, the size must be 

 determined with reference to the economic relation between velocity 

 or permissible friction head and power requirements. A pipe which 

 is too small may involve an excessive expense for power, while 

 too large a pipe would require initial investment greater than 

 necessarjr. 



The capacity of wood pipe is generally computed according to 

 Kutter's formula, in which a value of " n," the coefficient of rough- 

 ness, is selected somewhere between 0.010 and 0.013, depending upon 

 conditions and the judgment of the engineer. Just what value of 

 " n " to assume is a debatable question. Experiments are now being 

 made to determine the carrying capacities of wood pipes and 

 the proper coefficient of roughness to apply in such formulas as 

 Kutter's. 



As a result of measurements of flow in pipes, the following values 

 for " n " for specific cases have been determined by various writers : 

 Schuyler, 30-inch pipe, 0.0096; Gutelius, 24-inch pipe, 0.01; Adams, 

 18-inch pipe, 0.01; Adams, 14-inch pipe, 0.011; Marx, Wing, and 

 Hoskins, 72-inch pipe, 0.012 to 0.015. Smaller values for "n" are 

 usually assumed for small pipes than for larger ones, and there ap- 

 pears to be reason for believing that " n " may vary also with velocity. 

 Moritz, 1 from measurements of pipes 4 inches to 55 inches in diame- 

 ter, found V=1.72 D - 7 H - 555 and Q=1.35 D 2 - 7 H - 555 , where (^dis- 

 charge in second-feet; V, the mean velocity of flow in feet per sec- 

 ond; D, diameter of pipe in feet; and H, friction loss per 1,000 feet 

 of pipe. 



Based either on Kutter's formula or on one of the exponential type, 

 various tables have been prepared for convenient use in estimating 

 the capacity of pipes, loss of head in friction, etc. Such tables may 

 be obtained from the leading manufacturers of wood pipe. 



iEngin. News, 68 (1913), No. 24, p. 668. 



