Document B8R12QGrm0LmaOaNoRD5zgGbm

American Society of Heating and Ventilating Engineers Guide mains should be a certain percentage greater area than the sum connections, and still lower power consumption can be obtained bv * larger branches and mains of equal area. While the rule of thumb of determining size of mains works" very well in. many cases, yet always desirable to figure the mains and branches of the proper size ^ give the velocity which has been found best suited to the work to be d ^ In certain special cases where explosive or poisonous dusts such*1** aluminum buffings, grain dust, powdered sugar, or lead dust are handled increasing the size of the mains unduly would introduce a serious hazard The maintained resistance of the exhaust system is composed of thr factors: (1) loss through the hoods; (2) collector drop; and (3) frjc, 66 drop in the pipes. ^ The collector drop in inches of water is given roughly by equation ( Table 4. Cubic Feet of Air Handled Per Minute Through Average Collecting Hoods Based on Coefficient of Orifice of 0.71 with 10 Per Cent Added for Leakage Diameter op Connection Pipe In. 1 Maintained Suction--In. Water Gage 1H 2 2H 3 4 5 m 2 VA 3 m 4 4Vi 5 6 7 8 9 10 38 68 107 153 209 273 345 427 614 . 835 1092 1381 1705 47 84 131 188 256 334 423 523 751 1023 1337 1694 2090 54 97 161 217 296 386 488 605 867 1181 1546 1953 2409- . 61 108 168 243 330 431 546 676 970 1322 1727 2184 2695 67 118 185 266 362 473 598 741 1062 1448 1892 2387 2959 76 136 214 306 418 546 690 854 1228 1670 2184 2762 3410 86 153 238 343 466 609 775 955 1373 1870 2440 3091 3806 but where possible the resistance of the particular collector to be used should be ascertained from the manufacturer as these resistances differ quite widely. Drop = c{tw)' (2) where C -- a constant which depends upon the type of collector and ranges from 0.065 to 0.145. V = velocity in feet per minute of air entering the collector. . Friction drop in the pipes must be computed for each section where there is a change in area or in velocity. Find the velocities in each section of pipe starting with the branch most remote from the fan. The friction drop for these sections can be determined by reference to Table 5. Total friction loss in the piping system is the friction drop in the most remote branch plus the drop in the various sections of the main, plus the drop in the discharge pipe. 388 b2 --Exhaust Systems for Dust and Refuse TYPICAL layout and calculations ft strate the method of laying out and calculating the elements of ''E st system, assume a small wood-working shop, having one 16 in. cxhau one 12 in. diameter cut-off saw, one band saw with 2 in. Ir^nd one planer with 10 in. knives, and with the general arrange- ^VolThe machines and exhaust system as shown in Fig. 1. % (jgtermine the sizes to be used for the branch connection to the These sizes can be taken from Table 1 giving due consideration type and size of machines as well as the class of work handled. Table 6). - Frictional Resistance of Straight Conveyor Pipe Table 5. To Flow of Air Per 100 Feet of Pipe VSI-OfA flw 22200- 2400 22726!8f 0000 3000 3200 3400 3600 3800 4000 4200 4400 4800 5200 5600 6000 1.92 I 2.32 I 2.77 3.26 3.76 4.33 4.93 5.56 6.23 6.95 7.69 8.48 9.26 11.05 13.00 15.25 17.30 1.53 1.85 2.22 2.60 3.01 3.46 3.94 4.45 4.98 5.55 6.15 6.78 7.41 8.85 10.50 12.05 13.85 1.28 1.55 1.84 2.17 2.52 2.88 3.28 3.71 4.15 4.62 5.13 5.65 6.18 7.38 8.66 10.05 11.52 0.962 1.16 1.39 1.63 1.89 2.08 2.47 2.78 3.12 3.48 3.85 4.25 4.63 5.55 6.50 7.55 8.66 0.770 0.932 1.01 1.30 1.51 1.73 1.97 2.22 2.49 2.78 3.08 3.49 3.71 4.43 5.21 6.03 6.92 0.640 0.778 0.924 1.08 1.26 1.44 1.64 1.85 2.08 2.32 2.57 2.83 3.09 3.69 4.34 5.05 5.76 0.482 0.582 0.693 0.810 0.932 1.08 1.23 1.43 1.56 1.74 1.92 2.12 2.33 2.77 3.25 3.78 4.33 0.428 0.578 0.617 0.722 0.838 0.961 1.09 1.24 1.38 1.54 1.71 1.88 2.06 2.46 2.89 3.35 3.85 0.385 0.465 0.553 0.650 0.754 0.865 0.985 1.11 1.25 1.39 1.54 1.70 1.85 2.22 2.61 3.02 3.46 0.350 0.423 0.504 0.590 0.685 0.788 0.895 1.01 1.13 1.26 1.40 1.54 1.68 2.02 2.36 2.74 3.14 0.320 0.388 0.462 0.542 0.628 0:722 ! 0.820 0.925 1.04 1.16 1.28 1.42 1.54 1.85 2.16 2.52 2.89