Explosion dust explosions

See also vapour cloud explosions, dust explosion incidents GLASS INCIDENTS... 

A series of explosions in silos of an acrylonitrile/butadiene/styrene resin plant appears to have been a conventional dust explosion. dust explosion incidents (reference 22)... 

Caution for all dust explosions dust explosion potential for particle dia. <200 pm. Minimum ignition temperature >300°C minimum ignition energy 10 to 30 mJ. 

Combustible dusts may be present in many different types of facilities. Common places for combustible dusts to be found are in grain elevators, flour mills, woodworking shops, and dry-bulk transport trucks. Dusts in facilities have caused many explosions over the years that have killed and injured employees. An explosion occurred in a facility on the East Coast that had many hazardous materials on site. At first, it was thought that one of the chemicals had exploded. The hre department and the hazmat team were called to the scene. Investigation revealed that the explosion occurred in a dust-collection system it was a combustible-dust explosion. Dust explosions can be prevented by proper housekeeping and maintenance practices at facilities where these types of dusts are present. 

Dust explosions most often occur in containers with dust distributed in the atmosphere. They can also occur when some activity suddenly creates a cloud of airborne dust in the presence of an ignition source. Similar to gas and vapor explosions, dust explosions show effects related to the L/D ratio of the container. 

Just use a search engine with the term chemsafety.gov or CSB and you can find hours of research. The investigation topics include major petroleum fires and explosions, dust explosions, nitrogen asphyxiation, chlorine releases, hydrogen sulfide releases, vapor elouds, and far too maiy others to list here. 

Chapter 3 Explosives Dehnition of Explosion Categories of Explosions Phases of Explosions Mechanical Overpressure Explosions Mechanical/Chemical Explosions Chemical Explosions Dust Explosions Nuclear Explosions Components of an Explosion Types of Explosives... 

The two main methods of explosion hazard control are explosion prevention (e.g. preventing formation of explosible dust clouds, removing all possible ignition sources, creating an atmosphere that cannot support combustion) and explosion protection (e.g. venting, suppression, containment and/or isolation). Quite often it is difficult to guarantee explosion prevention (e.g. due to equipment/instrumentation failure and/or human error). Explosion protection usually is pursued to protect personnel and minimise plant damage. Despite the similarities with gas explosions, dust explosions can be quite different ... 

When dispersed as a dust, adipic acid is subject to normal dust explosion hazards. See Table 3 for ignition properties of such dust—air mixtures. The material is an irritant, especially upon contact with the mucous membranes. Thus protective goggles or face shields should be worn when handling the material. Prolonged contact with the skin should also be avoided. Eye wash fountains, showers, and washing faciUties should be provided in work areas. However, MSDS Sheet400 (5) reports that no acute or chronic effects have been observed. 

Dust Filter. The cloth or bag dust filter is the oldest and often the most reHable of the many methods for removing dusts from an air stream. Among their advantages are high (often 99+%) collection efficiency, moderate pressure drop and power consumption, recovery of the dust in a dry and often reusable form, and no water to saturate the exhaust gases as when a wet scmbber is used. There are also numerous disadvantages maintenance for bag replacement can be expensive as well as a sometimes unpleasant task these filters are suitable only for low to moderate temperature use they cannot be used where Hquid condensation may occur they may be hazardous with combustible and explosive dusts and they are bulky, requiring considerable installation space. 

The most important polyhydric alcohols are shown in Figure 1. Each is a white soHd, ranging from the crystalline pentaerythritols to the waxy trimethylol alkyls. The trihydric alcohols are very soluble in water, as is ditrimethylol-propane. Pentaerythritol is moderately soluble and dipentaerythritol and tripen taerythritol are less soluble. Table 1 Hsts the physical properties of these alcohols. Pentaerythritol and trimethyl olpropane have no known toxic or irritating effects (1,2). Finely powdered pentaerythritol, however, may form explosive dust clouds at concentrations above 30 g/m in air. The minimum ignition temperature is 450°C (3). 

K. N. Palmer, Dust Explosions and Fires, Chapman and Hall, London, 1973. 

Uncured resins are skin sensitizers and contact should be avoided, as weU as breathing the vapor, mist, or dust. Novolak-based pulverized products generally contain hexamethylenetetramine, which may cause rashes and dermatitis. PhenoHc molding compounds and pulverized phenoHc adhesives must be controUed as potentially explosive dusts. In addition, they contain irritating or toxic additives. 

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. 

Dust explosions usually occur in pairs. The first explosion involves dust already in suspension. This jars dust from beams, ledges, etc, creating a second cloud to which the explosion propagates, resulting in a secondary explosion. Dust clouds have been ignited by open flames, electric sparks, hot... 

Proper ventilation and housekeeping minimizes secondary explosions. Dust coUectors of the dry type should be located outside the building, and provided with conduction bags and adequate explosion venting to a safe location. 

Succinic acid is Generally Recogni2ed As Safe (GRAS) by the U.S. PDA (184) and is approved as a flavor enhancer, as a pH control agent in condiments, and for use in meat products. It causes irritation to the eyes (185), skin, mucous membranes, and upper respiratory tract. LD q in rat is 2260 mg/kg. Succinic acid, like most materials in powder form, can cause dust explosion. 

OSHA and ACGIH have not estabhshed specific airborne exposure limits for PVB and PVF resias however, some products may contain sufficient fines to be considered nuisance dust and present dust explosion potential if sufficient quantities are dispersed ia air. Unformulated PVB and PVF resias have flash poiats above 370°C. The lower explosive limit (lei) for PVB dust ia air is about 20 g/m. ... 

Because biphenyl is often transported in the molten state, a moderate fire ha2ard does exist under these circumstances. Biphenyl, with a flash point of 113°C, has a lower flammability limit of about 0.6% (by volume) at the flash point to an upper limit of 5.8% at 166°C (42). Dust explosions are a ha2ard when vapors from a hot Hquid surface condense in air in a confined space. 

According to the National Board of Fire Underwriters, activated carbons normally used for water treatment pose no dust explosion ha2ard and are not subject to spontaneous combustion when confined to bags, dmms, or storage bins (64). However, activated carbon bums when sufficient heat is appbed the ignition point varies between about 300 and 600°C (65). 

Cellulose esters, like most dry organic materials in powder form, are capable of creating dust explosions (133). The explosion at Bayer s cellulose acetate plant at Dormagen, Germany in 1976 can attest to the explosive potential of dust. Damage to the plant was estimated at between DM 5—10 million (134). 

Frevention of Fire and Dust Explosions in the Chemical, Dje, Fharmaceutical, andFlastics Industrj, NFFM 654, National Fire Protection Association, Quiucy, Me., 1982. 

Whereas an explosion from methane tends to be localized, it may start coal dust explosions resulting in more widespread injury and loss of life. AH coal breaking operations result in formation of fine coal particles some are controlled with water during the mining operation. Breakage associated with hauling disperses dust, and dust accumulations can be made safe by rockdusting. Powdered limestone is spread over the mine surfaces to cover the dust. 

Dust Explosion Prevention-Plastics Industy, Code No. 654, NFPA, 1988. 

Richard Siwek/ M S / Explosion Protection Manager, Corporate Unit Safety and Environment, Ciba-Geigy Ltd., Basel, Switzerland. (Dust Explosions)... 

Prevention and Protection Concept against Dust Explosions. 26-61... 

Dust Explosions Static Electricity Hazards of Vacuum Hazards of Inert Gases Gas Dispersion... 

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