Document daJ85LZ1ZQB9qxzvkDOLqgmLG

308 W. N. WITHEBIDGE Successful application of very high-velocity, low-volume local exff been reported by British investigators, which is of special interest to,| fronted with the control of dust from portable devices.11 Tables 9 and 10 are recommendations from the American Standardj tion on the fundamentals of exhaust systems.12 TABLE 9 Range of Capture Velocities Condition of dispersion of contaminant Released with no velocity into quiet air Released at low velocity into mod erately still air Active generation into zone of rapid air motion Released at high initial velocity into zone of very rapid air motion Examples Evaporation from tanks; degreasing, plat ing, pickling Spray booths; intermittent container filling; low speed conveyor transfers; welding Spray painting in shallow booths; barrel fill ing; conveyor loading; crushers Grinding; abrasive blasting, tumbling TABLE 10 Capture Velocities for Specific Operations (Velocity at furthest point of source unless otherwise specified.) Operation Abrasive blasting Cabinets Rooras__ Bagging' Paper bags Cloth bags Barrel filling Bins and hopper Bottle washing Cfifl.v.eyot-tranafer.points Core sanding Forge (hand operated) Foundry screens Cylindrical ^.Flotdeck___ Capture velocity (l.f.m.) Remarks 500 60-100 100 200 400 75-100 150-200 150-250 . ... -150-200-- 100 ' 200 400 200 .... Virtually complete enclosu, Downdraft in room Booth or enclosure Booth or enclosure At point of origin (local!! Point of origin Face of enclosing hood Face of booth --Face-of-enclOfling-hob Point of origin (Wham Face of enclosure " ' Openings in enclosure ..Openingsdn-enclosuier- " W. B. Lawrie, A. T. Holman, and E. B. James, Proceedings of the Conjere c Ventilation and Dust Control, Harrogate, England, 1955. The British Cast Iron' ciation, Birmingham, 1956, pp. 245-54. , "American Standard, Fundamentals Relating to the Design and Operateu.v Systems, Z9. American Standards Association, New York, 1936 (revision in process! VENTILATION 309 TABLE 10 (continued) Capture velocity (l.f.m.) Remarks 200 Openings in enclosure 250 Cold castings, downdraft 600 Hot castings, downdraft 150-200 200-250 Openings in enclosure Openings in enclosure 500 Face of enclosing hood 200 1500 1500 Point of origin--suspended hood Point of origin Face of enclosing hood 200-400 100-150 100-150 100-150 125-200 Downdraft grilles in bench or floor Face of booth Face of canopy Face of hood, door open Downdraft through bench grille 200 125 '200 100-200 50-100 75-150 100-400 100-200 100-200 500 750 100-150 - 150-200 75-100 100 150 50 150 75-100 50-100 100 75-100 100-200 100 Face of enclosing booth Face of enclosing booth Face of local hood Face of enclosure Face of booth Downdraft Openings in complete enclosure At face of booth. Depends on size and depth of booth, Bize of work At point of escape (opening of pan) Point of origin Point of origin Face of booth Face ofboothrVaries with size work Hood opening Point of origin Face of canopy Point of origin Openings in partial enclosure Point of origin Point of origin Face of hood opening Point of origin Point of origin (suspended hood) Face of enclosing booth