Document v6X5mDV6J6g4jJZe1N2GNG2bm

'756 CHAPTER 32 a e!l GROOVED SEAM __JLl STANDING SEAM s SLIP DRIVE SUP ' 1956 Guide END SLIP DOUBLE SEAM PITTSBURGH SEAM BAR.. SLIP M. ANGLE SUP REINFORCED BAR SLIP N POCKET SLIP ANGLE CONNECTION OP FLUSH SEAM HEATER, FILTER, AND WASHER CONNECTIONS Fig. 15. Sheet Metal Duct and Arrangement Details offs should always be arranged to cut or slice into the air stream in order to reduce as far as possible the losses in velocity head. Wherever ducts pass through fire walls or connect two fire areas of s building, automatic fire dampers should be provided. For design of- such dmnpers and other fire protective details, see Pamphlet No. 90 of the NaTtihoenarel cBoomamrdeonfdFeidregaUgnedsefrowrristeteresli1*(or iron) and aluminum sheet metal rectangular ducts are given in Table 8. Steel or iron sheets are specified Air Duct Design 757 according to the manufacturers or U. S. Standard Gage System. Alu minum sheets are specified according to the American or Brown & Sharpe Gage System. Weights of black and galvanized steel and iron sheets per square foot of surface for various gages are given in Table 9. Similar data for 2S aluminum sheets will be found in Table 10. Weights of standard copper sheets are given in Table 11. In calculating the total weight of a given length of duct work from these tables, it is customary to aad 20 percent for the weight of joints and bracings. - Aluminum sheets of the 2S and 3S type alloy and % hard temper, are TABLE 9. 1LECOMMENDED SHEET METAL IMAGES FOB KECTANGTJLAB DtJCT CONSTBUCTION* AluMINUM B.AS. Gags Steel U. S. Std. Gage Maximum Side, Inches Type op Transverse Joint Connections1* Bracing 24 26 Up to S. Drive, Pocket or Bar Slips, on None 12 7 ft 10 in. centers 13 to 24 S, Drive, Pocket or Bar Slips, on None 7 ft 10 in. centers 22 24 25 to 30 S, Drive, 1 in. Pocket or 1 in. Bar 1 x 1 x f in. angles Slips, on 7 ft 10 in. centers0 4 ft from joint 31 to 40 Drive, 1 in. Pocket.or 1 in. Bar l x 1 x f in. angles 20 22 Slips, on 7 ft 10 in. centers0 4 ft from joint 41 to 60 1 in. Angle Connections, or 1j in. If x If x f in. angles . Pocket or 1 in. Bar Slips with. 4 ft from joint If in. x f in. bar reinforcing on 7 ft 10 in. centers 18 20 61 to 90 If in. Angle Connections, or If If x If x J in. diagonal in. Pocket or If in. Bar Slips angles, or If x If x f 3 ft 9 in. maximum centers with in. angles If x f in. bar reinforcing 2 ft from joint 16 18 91 and 2 in. Angle Connections or If in. If x If x f in. diagonal up Pocket or If in. Bar Slips 3 ft angles, or If x If x f 9 in. maximum centers with in. angles If x f in. bar reinforcing'1 . 2 ft from joint' For A1J uninsulat.ed d_u__c_t_s__1_8__in__.jand..l.a..r..g...e..rMsihcoaujuldii cblea, curuogsusj-baruoukueinu. ueCcroosnss-tbrurecatekdinogi mmaeytabi etwoomgiattgeeds'oHneauvnieinr.su lated ducts if two gages of heavier metal are used. Other joint connections of equivalent mechanical strength and air tightness may be used. . . c Duct sections of 3 ft 9 in. may be used with bracing angles omitted, instead of 7 ft 10 in. lengths with Joints indicated. Ducts 91 in. and larger require special field study for hanging and supporting methods. readily workable, and can be used.for practically all duct work. The 2S type (commercially pure aluminum) is suitable for all, except very large ducts. For large ducts, where more strength is desired, the 3S alloy with or y2 hard temper is frequently used. The higher tempers, particularly full hard, do not have the formability of the lower tempers. For very huge ducts, where considerable strength is required, aluminum sheets should be 2 gages heavier than indicated in Table 8, and should be amply stiffened. Joints can be of any of the standard designs, and can be fabri cated in the same manner as iron. Repeated sharp bending and rebending should be avoided, as aluminum has a tendency to crack under such treat-