Dust explosions precautions

Eventually it was realized that coal dust presents a far greater danger than methane insofar as dust explosions are far more violent in character and widespread in effect than firedamp explosions (Torrent et al., 1991). These latter are usually fairly localized in their effect but the danger lies in the fact that a relatively minor firedamp explosion may initiate a far more serious coal dust explosion. Precautions taken against the occurrence of coal dust explosions include the deposition of incombustible rock dust on the mine surfaces to suppress propagation of the explosion. 

Health and Safety Factors. Both pyromellitic acid and its dianhydride irritate skin, eyes, and mucous membranes, and they cause skin sensitization (156). When it comes in contact with moist tissue the dianhydride converts to the acid. Direct contact with should be avoided and protective clothing should be worn in areas where it is used. The LD q for intergastric administration in rats is 2.2—2.6 g/kg (157). In 6-mo experiments, the maximum nontoxic dose was 0.07 mg/kg/d, and it affected the fiver, kidney, and reproductive tract. Precautions against fire and dust explosions as explained in the terephthafic acid section should be foUowed. 

Hazard, i.e. the potential of the material to cause injury under certain conditions (flammability, explosion limits in air, ignition and autoignition temperatures, static electricity (explosions have occurred during drying due to static electricity), dust explosion, boiling point, fire protection (specification of extinguishers, compounds formed when firing), R S (nature of special risk and safety precautions). Table 5.2-5 lists hazards associated with typical chemical reactions. 

Precautions recommended include use of cold zinc and total enclosure of such processes [2]. The possibility of explosions of zinc dust suspended in air is presented as a serious hazard [3], A serious dust explosion in the air filter unit of a zinc grinding mill was initiated by a spark from an explosion relief panel [4], See Zinc chloride, below... 

The new US fire code covers precautions to prevent fires or dust explosions in... 

Use of a steel chisel to open a drum of carbide caused an incendive spark which ignited traces of acetylene in the drum. The non-ferrous tools normally used for this purpose should be kept free from embedded ferrous particles [1]. If calcium carbide is warm when filled into drums, absorption of the nitrogen from the trapped air may enrich the oxygen content up to 28%. In this case, less than 3% of acetylene (liberated by moisture) is enough to form an explosive mixture, which may be initiated on opening the sealed drum. Other precautions are detailed [2]. Use of carbon dioxide to purge carbide drums, and of brass or bronze non-sparking tools to open them are advocated [3]. The dust explosion characteristics of calcium carbide powder in air have been studied [4]. 

The chart below presents MIE results (in mJ) for a select sample of APIs produced at Merck and Co., Inc. It is clear that while not every compound poses a severe dust explosion risk, 20% of the compounds in this set have MIEs of lOmJ or less and require special handling precautions (Fig. 2). 

Observe normal precautions appropriate to the circumstances and quantity of material handled. Measures should be taken to minimize the potential for dust explosion. Eye protection is recommended. 

There Is a danger of dust explosions special safety precautions are required (see Preventive Measures). 

Environmental Not expected to cause any adverse environmental effect Precaution May present a dust explosion hazard static charges may ignite flamm. atmospheres melts in proximity to tires causing slippery floors/stairs spillages may be slippeiy incompat. with strong oxidizing agents... 

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