

24 BULLETIN 495, U. S. DEPARTMENT OF AGRICULTURE. 
STEEL OR WROUGHT-IRON PIPE. 
Steel or wrought-iron pipe with threaded joints which screw to- 
gether, used for main pipe lines, is the common water or steam pipe 
used exclusively in all plumbing. This comes in random lengths of 
about 18 feet long and in all diameters. It is the best to use for 
mains up to 5 inches diameter. Larger sizes are expensive and more 
difficult to handle in the field. It is advisable to use galvanized- 
steel pipe throughout. However, black-iron fittings cost less than 
galvanized and outlast the galvanized pipe. Some irrigators prefer 
black “ guaranteed ” pure wrought-iron pipe for mains. This costs 
about the same as galvanized steel and is more durable than black 
steel. Pipe 2 inches and over in size should be cut, threaded, and 
marked to fit each section in the shop, as it is difficult and expensive 
to do this in the field. Where a main intersects a nozzle line a tee is 
used in the main and the standpipe for the nozzle line is screwed into 
the tee direct (fig. 12). 
RIVETED STEEL PIPE. 
Riveted steel pipe, made of sheet metal either straight or spiral- 
riveted into a pipe, can be purchased in sizes of 3-inch diameter and 
over. The thickness of metal used depends upon the pressure which 
the pipe must withstand and somewhat upon the length of life de- 
sired. The riveted pipe is treated with an asphalt-tar solution of 
mineral paint or is galvanized. The unprotected steel pipe never 
should be used in irrigation construction. The small sizes, from 3 
to 8 inches, should be galvanized and the larger coated if not gal- 
vanized. 
Riveted pipe can be made in any lengths convenient to handle in 
the field; 20 to 25 feet is the usual section. Two types of joints are 
used for riveted steel pipe, 1. e., flange and gasket or bolted. ‘The 
flanged joint is rigid and the line must be straight, unless the pipe 
is made curved in the shop. The bolted joint permits a small angle 
in the line at each joint, and generally is the most adaptable for 
irrigation mains. The bolted joints also act as expansion joints, 
which is advantageous in long lines. In all straight mains of great 
length some design of expansion joint must be used to care for 
expansion and contraction caused by changes in temperature. 
Laterals or nozzle lines can be connected to riveted steel pipe mains 
by the use of a special tee. Where bolted joints are properly spaced 
in the mains the cast-iron collars of the joints can be tapped for 
the connections. It is also possible to have special flanges or saddles, 
into which the lateral can be screwed, riveted to the pipe in the shop. 
Riveted steel pipe is more economical where large sizes are needed 
and long shipments must be made, as this pipe is light in weight. 





, 


