112 



IRRIGATION FARMING. 



FIG. 22 — RIVETED IRON PIPE. 



and malleability are more to be desired than great 

 tensile strength, it is customary to specify that the 

 plates in either iron or steel shall be annealed; in other 

 words, heated to a cherry, red in a close oven and then 

 slowly cooled, or what is better, cooled in lime or oil. 

 In this country riveted pipes come in sheets three 

 to three and one-half feet in width and of various 

 lengths. These sheets after being sized and punched 



in multiple punch- 

 ing - machines are 

 bent around rollers 

 to the required size, 

 taking care that the 

 grain of the iron or 

 steel shall lie around 

 the pipe. These 

 short cylinders are 

 then double-riveted along the straight seam, using a 

 guoa quality of Swedish or Norway iron. By means 

 of traveling cranes and numerous supports seven or 

 eight of the short lengths are afterward continuously 

 riveted, making a se(5lion of completed pipe of from 

 twenty to twenty-five feet long. A secftion of this pipe 

 may be seen in Fig. 22. 



Only one row of rivets is inserted in the end or 

 round seams, and the joint is made by expanding one 

 end by means of specially devised machinery, by 

 accomplishing the same objedl in riveting, or by mak- 

 ing an equal number of large and small cylinders so 

 that the end of the smaller can be driven into the end 

 of the larger and riveted. 



Spiral iron pipe, shown in Fig. 23, is made in much 



