Document N2mZOybq69qLpnBwmRaVGYkVQ

HOT WORKING OF METALS maximal acceptable concentrations, and physiological effects of these materials Also see Chapter 41, "Table of Chemical Haz ards," for summaries of their physical prop erties Dust is generated in m?ny foundry proc esses and presents a two-fold problem oleanmg to remove deposits and control at the point of origin to prevent further ac cumulation Some foundries have found water under pressure or mixed with steam to be a good cleaning agent A combination water and compressed air hose with a special nozzle also does a good job With this method, however, workers should wear approved respirators In any case, water cleaning should not be done during or immediately before melting and pounng These opera tions should be started only after all equip ment has been allowed to dry thoroughly Vacuum cleaning is probably the most satisfactory method used for dust removal in foundries, and the special equipment needed is well worth the investment Once dust has been removed, further ac cumulation can be prevented by local ex haust systems (Fig 27-1) which remove it at the point of origin Installations which follow the recommendations of Chapter 28, "Local Exhaust Systems, General and Com fort Ventilation," will control dust effec tively Solvents include many different sub stances, each of which must be evaluated on the basis of its chemical ingredients Proper labeling, limitations on quantities m use, and other methods of control as detailed in Chapter 39, "Industrial Hygiene," can help minimize the toxic and flammable hazards involved in solvent use Acroletn occurs in foundry operations as a result of the thermal decomposition of core oil Aluminum is not usunllv a toxic hazard in casting processes, but docs present a fire and explosion hazard m dust-collecting sys tems Antimony is usually an unimportant con taminant in foundry operations Beryllium may produce a typical pulmo nary disease, such as reported in one plant casting a 1 per cent beryllium-copper alloy Carbon, as sea coal, is a common ingredi ent of molding sand used for facing Carbon dust may cause anthracosis, which produces characteristic lung shadows in an X-ray, but is a relatively harmless condition Caibon monoxide is generated during some cycles m the operation of a cupola Chromium is encountered m stainless steel casting as the element or the oxide Exposures occur during melting, gate and head burning, and grinding Fluorides, sometimes in the form of cryo lite (sodium aluminum fluonde), are used in the manufacture of ductile iron and mag nesium castings Iron oxide fumes and dust are created during melting, burning, pounng, grinding, welding, and machining of ferrous castings Exposure may be particularly high where manganese steel castings or oxygen-lancmg of the furnace is involved Lead is the greatest health hazard m nonferrous foundries It forms the oxide m melting, pounng, and welding operations Elemental lead dust is produced in cleaning and machining operations Magnesium dust or chips create senous fire and explosion hazards Physiological effects are confined to a form of "metal fume fever" from the inhalation of finely divided magnesium Manganese is usually associated with steel c-stmgs and bronze alloys in foundry work and presents no special control problem Phosphorus is used in the production of phosphor-copper Acute cases of poisoning have not been reported and chronic cases are rare The drying of phosphor-copper shot may produce phosphine gas Resins--phenol-formaldehyde and ureaformaldehyde--are used in shell molding and create several hazards The phenol-for maldehyde type contain hex.imeth> lenetetramine ("hex") which is a skin irritant and h ghly explosive This type of resin also decomposes on heating to give a mixture of phenol and formaldehyde vapors Urea de composes to give ammonia and carbon diox.de In practice, however, fumes from resins are a nuisance, because the concentra tions needed to produce toxic effects cannot usually be tolerated by man Resin dust, especially "hex," is highly 27-3