Document O3BQ1q4awjVJ2a4zea796R9oe

EXHAUST SYSTEMS, GENERAL ir COMFORT VENTILATION TABLE 28-N EXHAUST HOODS FOR GRINDER AND CUTOFF WHEELS Wheel Diameter (in.) Width (in) Good Enclosure Duct diameter (in.) Cfm Poor Enclosure Duct Cfm diameter (in.) Up to 9.............................1% Over 9 to 16 .................... 2 Over 16 to 19.................... 3 Over 19 to 24.................... 4 Over 24 to 30.................... 5 Over 30 to 36.................... 6 3 220 3% 330 4 390 5 600 4% 500 5% 750 5 610 6 920 6 880 7 1,300 7 1,200 8 1,600 Note These figures should be considered adequate only for nontoxio metals, such os gray Iron Whore toxic metals or alloys are encountered, these types of hoods ore not adequate for control From American Standards Association, 20 East 40th St, New York City Grinding, Polishing, and Bnglng Equipment Sanitation ZiS, mills, sandblast cabinets, sandblast rooms, and automatic cleaning machines, the re quired air volumes and duct sizes axe speci fied * Grinding operations Health, comfort, and good housekeeping demand that grinding, buffing, and polish ing equipment be equipped with local ex haust systems Many state codes require them, and where such codes exist, the safe ty director should obtain a copy Its regu lations should be met Hoods on grinding and cutting wheels serve a dual purpose they protect the op erator from hazards of bursting wheels, and they provide for removal of dust end dirt generated Most such wheels today are made of artificial abrasives containing no free silica in order to eliminate silicosis hazard There is no hazard from iron or steel dust Uncleaned castings, on the other hand, may have mold sand adhering to them, which can be ground to dust, causing a sili cosis hazard In addition, grinding of some alloys, such as high-manganese steel, ce mented tungsten-tipped tools, and spark-re sistant tools, presents other occupational disease hazards Furthermore, all grinding operations need local exhaust hoods to remove the dust and gnndings that would otherwise cause poor housekeeping in the shop The exhaust hoods must have sufficient structural strength, and must enclose the wheel sufficiently Details are given in state codes, industry codes, and codes of the American Standards Association The hoods for a floor stand, pedestal, or bench grinder should have an adjustable tongue, which can be placed within % m of the periphery of the wheel at all times This is an important adjunct, because it tends to "peel" off the dust as it is earned around the wheel in the air stream set up by the wheel's rotation. No more than 25 per cent of the wheel should be exposed Minimum velocity m the branch ducts should be 4,500 fpm, and m the mam duct, 3,500 fpm The branch duct should attach to the hood at a tapered connecting piece It should be inclined in the direction that material is thrown off the wheel Chip trays may be provided if desired for heavy grind ing Exhaust requirements of Amencan Stand ard code Z43, Grinding, Polishmg, and Buffing Equipment Sanitation, are given in Table 28-N "American Foundrymen's Society, Des Plaines, HI. Engineering Manual for Con trol of In-Plant Environment *n Found ries, 1958 28-37