Document 8528MB6ej3v5rnBgpGm56G7Me

HS5 298 CHAPTER 21 1959 Guide Table 9.... Recommended Construction for Rectangular Sheet-Metal Ducts High Medium low Pwtzra Sail Steel Steel U.S. Std. U.S. Std. U-S-Std. Goge Akslnon B & S Gage 22 24 26 24 (0.020) Csr RoOed 16 02 Duct DinenzioA in ladwi Recommended Construction Tronzverra Joarts and Bracing Up thru 12 S slip, drive slip, 1 iu. pocket lock on 8 ft centers. 20 22 24 22 (0.02S) 24 oz 13 thru 18 S slip, drive slip, 1 in. pocket lock on 8 ft centers. 19 thru 30 8 slip, 1 in. pocket lock on 4 ft centers. S slip, 1 in. pocket lock on 8 ft centers with 1 X 1 X H angles 4 ft from joint. S slip, 1 in. pocket lock on 8 ft centers with cross break 1 in. stand ing seam on 5 ft centers. 18 20 22 20 (0.032) 32 oz 31 thru 42 1 in standing S cleat, bar slip, pocket lock on 4 ft centers. 1 in. standing S eleat, bar slip, pocket lock on 8 ft centers with 1 X I X H in. angle 4 ft from joint. 1 in. standing seam on 4 ft centers. Longitudinal standing seam with 1 X 1 X H in. angles on 4 ft centers. 43 thru 54 1)4 in. standing S cleat, bar slip, pocket lock on 4 ft centers. 1)4 in. standing 8 cleat, bar slip, pocket lock on 8 ft centers with 1}4 X 1)4 X X in. angles 4 ft from joiot. 1)4 in. standing seam on 3 ft centers. 16 18 20 18 (0.040) 36 oz 55 thru 60 Longitudinal standing seam inside within X IX X H iu. angles on * 4 ft centers. 61 thru 84 1)4 in. standing S cleat, bar slip, pocket lock on 4 ft centers with 1)4 X 1)4 X X in. angles 4 ft from joint. 1)4 in. standing S eleat, bar slip, pocket lock on 8 ft centers with 1)4 X 1)4 X )i in. angles on 2 ft. centers. 1)4 in. standing seam on 3 ft centers. Longitudinal standing seams inside with IX X 1)4 X H in. angles on 2 ft centers. 14 16 18 16 (0.051) 48 os 85 thru 96 1)4 in. standing S cleat, bar slip, pocket lock reinforced with 1)4 X 1)4 X )4 in., or companion angles on 4 ft centers. t 1)4 in. standing S cleat, bar slip, pocket lock reinforced with 1)4 X 1)4 X He in- or companion angles on 8 ft centers with 1)4 X 1)4 X j, He in. angles on 2 ft centers. Longitudinal standing seams inside with 1)4 X 1)4 X H in. angles on 2 ft centers,. Over 96 1)4 in. standing S cleat, bar slip, pocket lock reinforced with 2 X 2 X H in. angles, or companion angles on 4 ft centers. 1)4 in. standing 8 cleat, bar slip, pocket lock reinforced with 2 X 2 X )4 in. angles, or companion angles on 8 ft centers with 2 X 2 X H in. angles on 2 ft centers. 1)4 in. standing seams with 2 X 2 X X in. angles on 2 ft centers. Longitudinal standing seams inside with 2 X 2 X H in. angles on 2 ft centers. Note: zpecisl rigidity or stiffms is required, duct* should be ooatruoted of metal tvo p{ numbers heavier .*use ZS me instead of S4 me- Ducta brcer -- M in- require special field study for and supportiat methods. Other joint construction of equivalent mrrhsninal strength and airtitfataets may be rrv.ttw^y of fmy<>n4PI bracing to ductwork include riveting. bolting. and tack welding. Bracing, stiffening members, or angle connectioua for copper duetwork, where exposed to the weather, should be of brass or aluminum, of suitable thickness for strength. DUCT CONSTRUCTION DETAILS pressures m the duct system for these classifications are: The recommended gages for steel (or iron), aluminum, and copper sheet-metal rectangular ducts are given in Table 9. No general agreement has yet been reached as to the exact limits of the classifications high pressure, medium pressure, and low pressure shown in Table 9. Suggested ranges ef static Low Pressure = up to IX in- water. Medium Pressure = IX in. to 4 in. water. High Pressure = 4 in. to 8 in. water. * It should be noted that these values are the pressures exist ing in the duct, not the total pressure at the fan. ft!L* v. Air Duct Design Table 10.... Recommended Duct Construction for Round end Hat-Oval Ducts*' b Sled U.S. SHI. Gag* Round 24 Flat-oval 22 Size Ota or Max Width To 10 in. firodag on Fid Surfoce None 22 20 ' 11 to 20 in. l)i X IX X H in. angle or IX X X X H in. channel on 4 ft centers. 20 18 21 to 40 in. IX X IX X X in. angle or 2 X X X X m. channel on 4 ft centers. 18 16 41 to 60 in. 2 X 2 X X in. angle or 2X X H X He in- channel on 2 ft centers. 16 14 61 in. and 2 X 2 X X in. angle or 2X X over- H X He in. channel on 2 ft centers. All fitting! should be of him gage u pipe or heavier. b Satisfactory for pressure in duct up to 10 la. water. The recommended gages for steel (or iron) sheet-metal round or flat-oval ducts are given in Table 10. Steel or iron sheets are specified according to the manufac turers or U. S. Standard Gage System'. Aluminum sheets are specified according to the American or Brown & Sharpe Gage System. Copper sheets are usually specified by the weight in ounces per square foot. Weights of black and galvanized-steel and -iron sheets per square foot of surface .for various gages are given in Table 11. Similar data for 2S aluminum sheets will be found in Table 12. Weights of standard copper sheets are given in Table 13. In calculating the total weight of a given length of ductwork from these tables, it is customary to add 15 percent to the weight to cover hangers, slips, and scrap. Duct bracing or stiffening members should be calcu lated separately. Rectangular ducts are generally constructed by breaking the corners and grooving the longitudinal seam, although some fabricators still use the standing seam. Elbows and transformation sections are generally formed with Pittsburgh comer seams because this seam is easier to lock in place than the double seam, but double.seams are equally acceptable. The constructions of these various seams, as well as the types of girth connections, are shown in Fig. 16. The application of the various slips, connections, and bracing is outlined in Table 9. The end dip may be used wherever 5 slips are recom mended. Designs Af to P of Fig. 16 are for flush-type apamg on duct work where joints are to be concealed. For smooth external appearance the seams may be filled with suitable filler. Screws or rivets used should be of oven-head type. Round and flat-oval ducts should be fabricated in accord ance with the recommendations given in Table 10. Sections may be assembled using beaded couplings, swaged ends, or beaded and crimped small ends. Sections are held in place, using suitable sealers, with sheet-metal screws or rivets, or are welded together. Spiral conduit is acceptable in place of round or flat-oval duct, with recommended gages shown in the following table: Diameter. tathet 3 to 8 . 9 to 24 Recommended U. S. Sid. Gog* Not lighter than 26 gage Not lighter than 24 gage 299 Table 11 .... Weights of Black and Galvanized Sheets U S. Std. Gage 30 28 26 24 i 22 20 e 18 16 14 12 11 10 Approximate Thtdenem, In. Sieel 0.0123 0.0153 0.0184 0.0245 0.0306 0.0368 0.0490 0.0613 0.0766 0.1072 0.1225 0.1379 In*. 0.0125 0.0156 0.0188 0.0250 0.0313 0.0375 0.0500 0.0625 0.0781 0.1094 0.1250 0.1406 Weight Per Square foot Ounce* 8 10 12 16 20 24 32 40 50 70 80 90 Pounds 0.500 0.625 0.750 1.000 1.250 1.500 2.000 2.500 3.125 4.375 5.000 5.625 30 28 26 24 f 22 20 18 16 <5 14 12 11 10 0.0163 0.0193 0.0224 0.0285 0.0346 0.0408 0.0530 0.0653 0.0806 0.1112 0.1265 0.1419 0.0165 0.0196 0.0228 0.0290 0.0353 0.0415 0.0540 0.0665 0.0821 0.1134 0.1290 0.1446 10.5 12.5 14.5 18.5 22.5 26.5 34.5 42.5 52.5 72.5 82.5 92.5 0.656 0.781 0.906 1.156 1.406 1.656 2.156 2.656 3.281 4.531 5.156 5.781 * Galvanized sheet! era caged before galvanizing and are therefore approzjtnately 0.004 in. thicker. Table 12 .... Wrights and Thicknesses of 2S Aluminum (Density 0.098 Ib/ai in.) . * S. Thrricnea. Indies Decimal Nearest Fraction Weight per Square foot Ounces Pounds 28 0.012 28 0.016 24 0.020 22 0.025 20 0.032 18 0.040 16 0.051 14 .0.064 He H4 He X2 X* X* He . He 2.7 3.6 4.5 5.4 7.2 9.0 11.5 14.4 0.1 0.226 0.282 0.353 0.452 0.563 0.720 0.903 Aluminum sheets of the 2S- and 3S-type alloy and V* hard temper are readily workable, and can be used for practically all ductwork. The'2S type (commercially pure aluminum) is suitable for ail, except very large ducts. For large ducts, where more strength is desired, the 3S alloy with Ye or Yt hard / temper is frequently used. The higher tempers, particularly full hard, do not have the formability of the lower tempers. Joints can be of any of the standard designs, and can be fabricated in the same manner as iron. Repeated sharp bend ing and rebending should be avoided, as aluminum has. a tendency to crack under such treatment. Aluminum of 16 B. & S. gage or heavier can readily be welded by the metallic arc or acetylene process. Riveting is done in the same manner as in iron or steel sheet. Self-tapping screws tend to loosen be cause of the softness of aluminum. The construction of elbows and changes of shape cannot be definitely outlined, because of the varied conditions en-