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American Society of Heating and Ventilating Engineers Guide, igjj Table 1. Size of Connections for Wood-Working Machinery <i Type of Machine Circular Saws, 12-in. diam_______ Circular Saws, 12-24-in. diam._ Circular Saws, 24-40-in. diara._ Band Saws, Blade under 2 in. wide.___ Band Saws, Blade 2-3 in. wide._______ Band Saws, Blade 3-4 in. wide............... Band Saws, Blade 4-5 in. wide._______ Band Saws, Blade 5-6 in. wide._______ Small Mortisers--- ---- ------------------------Single End Tenoners._________________ Double End Tenoners. Double End, Double Head Tenoners................................ Planers, Matchers, Moulders, Stickers, Jointers, etc.-- With Knives, 6-10 in............... .................................. With Knives, 10-20 in................... ....... ...................... With Knives, 20-30 in........... ...................................... Shapers, Light Work............................................................ Shapers, Heavy Work___________________ ____________ Belt Sander, Belt less than 6 in. wide--............................. Belt Sander, Belt 6-10 in. wide....... ........ ........................ Belt Sander, Belt 10-14 in. wide......... ............................... Drum Sander, 24 in........... ....... .................... ..................... Drum Sander, 30 in..................... ........................................ Drum Sander, 36 in-------- ............ ...................................... Drum Sander, 48 in..................... ........................................ Drum Sander, over 48 in._.................................................. Disc Sander, 24 in. diam..................................................... Disc Sander, 26-36 in. diam............................................. ... Disc Sander, 36-48 in. diam......................................... ...... Arm Sander..... ............... ...................................................... where it would not be sufficient to carry the material from the machines still in operation, and thus result in clogging the pipes. Accordingly, it is sometimes desirable to use velocities higher than the minimum to allow a factor of safety to cover this contingency. In some states codes have been issued specifying suctions to be main tained for the more common dusts. A suction standard should always be considered in conjunction with the shape of hood, and size connection, as these factors together determine the volume of air exhausted and its velocity, which in turn are a measure of the effectiveness of the exhaust .system. The volume of air of standard density taken into the system at each connection is given by the formula: Q = 4,0004 }^~ (1) where Q =`cubic feet of air per minute. A = area of connection in square'feet. / = orifice or restriction coefficient. = static suction measured in inches of water. 386 KTi;/Chapter 25--Exhaust Systems fob Dust and Refuse gTABLB 2. Size of Connections for Gri_nd_i_ng__an--d--B-u-f-f--in-g--W---b---_, _= MW. Diam. of Branch Pipes in Inches Diameter or Wheels a .i' to le9ssi,nn.,oitnoclvuesriv1ei,nn. otht iocvke.-r--1--)-4---i-n-.---th--i-c--k-.-, Hup>- to 16 in;, # u a 2 fSin/to 19 m., o grin.to24m., fl ,, ,,,, to 30 _______________ m* otor l1e2ssi,nn,,oitnoclvuesriv1ei,nn.otht iocvke..r..1...)4..i.n......t.h..i.c..k... Eg fe. to 16 in.. " ` * 2 in. * . ZKmRlli in. ttoo2207 iinn..,, $7 in. to 33 in., a" "" "" 34 iinn.. "" " " 5 in. " i-The orifice coefficient / is dependent upon the shape and construction the hood and will range from 60 to 90 per cent. An average value is iKnowing the suction at each hood and the diameter of each connection, gf$fiepevrocluemnte. of air passing tip each branch can be taken from Table 4. jBfhe;Sum of all these volumes gives the total volume to be handled by fiHe2i0&etmeox2ihm5aoupsentr fcpaernan.ct tiinceexicsestos provide a of the sum main of the suction areas of pipe, having the branches an area entering sit between the point in question and the dead end of the main. Similarly ifthe discharge pipe leading from the fan outlet to the collector is frequently fmade the same diameter as the large end of the main suction pipe. The |reason for this increase in size is that a considerable power saving results ffrom the lower air velocity. However, there is no technical reason why Sr'-4 Table 3. Suction Pressures Required at Hoods for Connections of Usual Proportions Static Sdctiom is Inches or Wateb Exhausting from grinding and buffing wheels........................ 'EExxhhaauussttiinngg ffrroomm twuomobdl-inwgorbkainrrgelms.a..c..h..i.n..e. .r.y..--....l.i.g..h...t..d...u..t.y....-..-.-.-.Exhausting from wood-working machinery--heavy duty.... Shoe machinery exhaust....... ................. ................. :.............. Exhausting from rubber manufacturing processes------------Flint grinding exhaust--......................................................... Exhausting from pottery processes........................................ Lead dust and fume exhaust....... ........................................... Fur and felt machinery exhaust.........................,.................. Exhausting from textile machinery..... ................................. Exhausting from elevating and crushing machinery.......... Conveying bulky and heavy materials................................. 387 2 2 2 2-4 2r3 2 2 2 2-4 2-3 2-3 2 3--5