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American Society of Heating and Ventilating Engineers Guide, 1937 first cost can be justified on the basis of longer life expectancy. Wroughtiron pipe may be identified by the spiral line marked into each length either knurled into the metal or painted on it in red or other bright color! Otherwise, there is little difference in the appearance of wrought-iron and steel pipe, although microscopic examination of polished and etched specimens will readily disclose the difference. Cast Ferrous Pipe. There are now available several types of cast ferrous-metal pipe made of a good grade of cast-iron with or without additions of nickel, chromium, or other alloy. This pipe is available in sizes from in. to 6 in., and in standard lengths of 5 or 6 ft with external and internal diameters closely approximating those of extra-strong wrought pipe. Cast ferrous pipe may be obtained coupled, beveled for welding, or with ends plain or grooved for the several types of couplings. It is easily cut and threaded as well as welded. The fact that it is readily welded enables the manufacturers to supply the pipe in any lengths practicable for handling. Alloy Metal Pipe. Steel pipe bearing a small alloy of copper or other alloying element and iron pipe bearing a small alloy of copper and moly bdenum have been claimed to possess more resistance to corrosion than plain steel pipe and they are advertised and sofd under various trade names. Copper Pipe and Fittings. Owing to its inherent resistance to cor rosion, copper and brass pipe have always been used in heating, venti lating, and water supply installations, but the cost wi$h standard dimen sions for threaded connections has been high. The recent introduction of fittings which permit erection by soldering or sweating allows the use of pipe with thinner walls than are possible with threaded connections, thereby reducing the cost of installations. The initial cost of brass and copper pipe installations generally runs highei than the corresponding job with steel pipe and screwed connections in spite of the use of thin-wall pipe, but the corrosive nature of the fluid conveyed or the inaccessibility of some of the piping may warrant use of a more expensive material than plain steel. The advantages of corrosionresisting pipe and fittings should be weighed against the correspondingly higher initial cost. COMMERCIAL PIPE DIMENSIONS The IPS dimensions of commercial pipe universally used at the present time conform to the recommendations made by a Committee of the A.S.M.E. in 1886. Pipe up to 12 in. in diameter is made in certain definite sizes designated by nominal internal diameter which is somewhat different from the actual internal diameter, depending on the wall thick ness required. There are three weights of wrought-iron and steel pipe commonly used, known as standard-weight, extra-strong, and double-extra strong. Because of the necessity of maintaining the same external dia meter in all three weights for the same nominal size, the added wall thickness is obtained by decreasing the internal diameter. The term full-weight, when applied to sizes below 8 in., means that the pipe is up to the nominal weight per foot. When applied to sizes between 8 and 12 in.,' inclusive, it often indicates that the pipe has the heaviest of several wall 624 Chapter 34--Pipe, Fittings, Welding thicknesses listed. In sizes 14 in. and upward, pipe is designated by its outside diameter (O.D.) and the wall thickness is specified. While the demands for pipe for the heating and ventilating industry are reasonably well served by the standard-weight and extra-strong pipe, demands for pipe for higher pressures and temperatures in industry resulted in the use of a multiplicity of wall thicknesses for all sizes. Even in heating installations, the erection of piping by welding was deemed to Table 1. Dimensions op Welded and Seamless Steel Pipe Nokh'm. Pipe Snx Nominal Wall Thicknesses toe Schedule Nuhbehb OursmB 10Duu. Schedule Schedule 20 Schedule 30 Schedule 40 Schedule 60 Schedule SO Schedule] Schedule 100 120 Schedule 140 Schedule 160 x X H H lX iH 1X 2 2X 3 3H 4 5 6 8 10 12 14 O. D. 16 0. D. 18 O.D. 20 0. D. 24 0. D. 300. D. 0.40S 0.068' 0.540 10.088' 0.675 0.091' 0.840 0.109 1.050 0.113 1.315 1.660 0.133*1 0.149*! 1.900 0.145* 2.375 [0.154* 2.875 10.203* 3.500 [0.216*1 4.000 226' 4.500 0.237 5.563 0.258*| 6.625 0.280*1 8.625 0.250 0.277*] 0.322* 10.75 0.250 0.307 0.365* 12.75 0.250 0.330* ,0.406 14.0 0.250 0.312 0.375 |0.437 16.0 0.250 |0.312 0.375 0.500 18.0 10.250 0.312 0.437 0.562 20.0 0.250 0.375 0.500 0.593 24.0 0.250 0.375 0.562 0.687 30.0 0.312 0.500 0.625 406 500* 562 593 656 .718 .812 .937 095 119 126* 147* 154* 179' 191* 200' 218' 276 300*1 318*1 337* 0.437 375* |0.500 432* 0.562 .500* 10.593 0.718 0.812 .593 0.718 0.843 1.000 .687 0.843 1.000 1.125 750 [0.937 1.062 1.250 .843 1.031 1.218 1.437 937 1.156 1.343 1.562 .031 1.250 1.500 1.750 .218 1.500 1.750 2.062 0.187 0.218 0.250 0.250 0.281 0.343 0.375 0.437 0.531 0.625 0.718 0.906 1.125 1.312 1.406 1.562 1.750 1.937 2.312 All dimensions are given in inches. The decimal thicknesses listed for the respective pipe sizes represent their nominal or average wall dimensions and include an allowance for mill tolerance of 12.5 per cent under nominal thicknesses. *Thicknesses marked with asterisk in Schedules 30 and 40 are identical with thicknesses for standardweight pipe in former lists; those in Schedules 60 and SO are identical with thicknesses-for extra-strong pipe iu former lists. ' --------------J----IJWk _ D/C warrant the use of pipe lighter than standard weight. For these reasons, a Sectional Committee on Standardization of Wrought Iron and Wrought Steel Pipe and Tubing functioning under the procedure of the American Standards Association was appointed to standardize the dimensions and materials of pipe. The proposed pipe standard recommended by that sectional committee has set up several schedules of pipe including standard-weight and extra strong thicknesses which are now included in Schedules 40 and 60, re spectively. The schedules approved by the Sectional Committee are given in Tables 1 and 3 and the corresponding weights in Tables 2 and 4. Standard-weight pipe is generally furnished with threaded ends in 625 i