Document 2q57k3VmR7VqRbB1Kqxy1JyMp

American Society of Heating and Ventilating Engineers Guide, 1936 fittings are given in Table 7, whereas the dimensions for 125 lb cast-iron flanged fittings are given in Tables 8 and 9. For low temperature service not to exceed about 220 F, a number of paper or vegetable fiber gasket materials will prove satisfactory; for plain Table 9. American Standard Dimensions of Elbows for 125 Lb Cast-Iron Flanged Fittings Nominal Pipe Sox a A Bc Center to Face Elbow b-o-d Center to Face Long Radius Elbow b-o-d Center to Face 45 Deo Elbow c Diameter op Flange Thickness op Flange, Min. Metal Thickness op Boot, Min. i ih m' 2 2M 3 3K 4 5 6 8 10 12 14 O.D. 16 0.D. 18 O.D. 20 O.D. 24 O.D. 30 O.D. 36 O.D. 42 O.D. 48 O.D. 314 3H 4 4H 5 5\4 6 714 8 9 11 12 14 15 16H 18 22 25 28 31 34 5 5M 6 f>/4 7 7H m 9 10H 11H 14 16H 19 21M 24 26J4 29 34 41H 49 56 ]4 64 m 2 m 2H 3 3 3H 4 m 5 514 , 614 714 714 8 8/4 9H 11 15 18 21 24 N 4H m 5 6 7 7)4 814 9 10 11 1314 16 19 21 23H 25 27 ]4 32 38h 46 53 5914 He Yt He H `He H `He `He `He 1 m lHe 1H . m lHe lHe l`He 1H 2H 2% 2% 2H . He Ke K6 He . Ke ^6 K6 H He H H `He % l lHe 1H 1H lHe lHs l`He 2 AU dimensions given in inches. Size of all fittings listed indicates nominal inside diameter of port. bReducing elbows and side outlet elbows carry same dimensions center to face as straight size elbows . corresponding to the size of the larger opening. - - -\ eSpedal degree elbows, ranging from 1 to 45 deg, inclusive, have the same center to face dimensions as given for 45 deg elbows and those over 45 deg and up to 90 deg, inclusive, shall have the same center to face dimensions as given for 90 deg elbows. The angle designation of an elbow is its deflection from straight line flow and is the angle between the flange faces. dSide outlet elbows shall have all openings on intersection center-lines. raised face flanges, rubber or rubber inserted gaskets are commonly employed. Asbestos composition gaskets are probably the most widely used, particularly where the temperature exceeds 250 F. Jacketed asbestos and metallic gaskets may be used for any pressure and tern- 620 Chapter 34--Pipe, Fittings, Welding perature conditions, but preferably only with a relatively narrow recessed facing. WELDING Erection of piping in heating and ventilating installations by means of fusion welding has been commonly accepted in the past few years as a competitive method to the screwed and flanged joint. Since the question of economy of welding as against the use of screwed and flanged fittings is dependent on the individual job, the use of welding is generally recom mended on the basis of a greatly reduced cost of maintenance and repair, of less weight resulting from the use of a lighter-weight pipe, and of increased economy in pipe insulation, hangers, and supports rather than on the basis of any economy that might be effected in actual erection by welding. Fusion welding, commonly used in erection of piping, is defined as the process of joining metal parts in the molten, or molten and vapor states, without the application of mechanical pressure or blows. Fusion welding embraces gas welding and electric arc welding, both of which are com monly used to produce acceptable welds. Welding application requires the same basic knowledge of design as do the other types of assembly, but in addition, requires a generous know ledge of the sciences involved, particularly as to welding qualities of metal, their reaction to extremely high temperatures, and the ability to determine and use only the best quality welding rods. This requirement applies equally to employer and employee with the employer accepting all of the responsibility. Thus the employer should select his welding mechanics with good judgment, provide them with first-class equipment and tools, arrange for their training and use of acceptable workmanship standards, and at regular intervals subject their work to prescribed tests. Industry will not accept the employment of mechanics of undetermined ability nor on the basis of past experience. Neither does industry accept the statement that a weld is only as good as the workman who makes it. The control Codes now in process of adoption will be the law governing the use of the welding process. These Codes prohibit individual practices contrary to their specified procedure and rules of control, and this is predicated upon the sound requirement that the employer must assume full responsibility for the deposited weld. It is advisable that this management responsibility be included in all welding specifications and that, authoritative standards of workmanship also be specified. The standards of workmanship for this industry are as set forth in the Standard Manual on Pipe Welding of the Heating, Piping and Air Conditioning Contractors. National Association. A complete line of manufactured steel welding fittings is now available with plain ends machine beveled for welding and with radii similar to short and long radius flanged fittings. Some typical types of these fittings are shown in Fig. 3. They are made in pipe sizes % to 24 in., standard and extra heavy, in steel, wrought iron, brass, copper, and special alloys.- Socket welding, fittings of forged steel are also commercially available. These fittings have a machined recess into which the pipe slips. A fillet weld between the pipe and socket edge provides a pressure-tight-joint. A 621