Hazard control dust explosions

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 ... 

Inherently safer approaches to dust explosion hazard control include inerting and building equipment strong enough to contain an explosion. 

Dust explosions usually occur in two stages a primary explosion which disturbs deposited dust followed by the second, severe, explosion of the dust thrown into the atmosphere. Any finely divided combustible solid is a potential explosion hazard. Particular care must be taken in the design of dryers, conveyors, cyclones, and storage hoppers for polymers and other combustible products or intermediates. The extensive literature on the hazard and control of dust explosions should be consulted before designing powder handling systems Field (1982), Cross and Farrer (1982), Barton (2001), and Eckhoff (2003). 

Also according to Van Dolah ammonium nitrate-oil mixtures offer a certain dust explosion hazard and any electric equipment (switches controls, motors, lights) located in the plant should conform to the safety requirements or should be installed outside the plant. In order not to increase the dust explosion hazard no liquid hydrocarbon fuel with higher volatility than No. 2 Diesel fuel (minimum flash point of 145°F, ASTM closed-cup procedure) should be used as an admixture to ammonium nitrate. More volatile fuels, such as gasoline, kerosine or No. 1 Diesel fuel cannot be recommended according to Van Dolah, as they would seriously increase the hazard of a vapour explosion. 

Controlling dust emissions and explosion hazards in powder handling plants... 

The intent of this document is to provide the readers with basic information on how to identify, assess, and eliminate/control potential dust explosion hazards in their facilities. More detailed information on the topics that are covered in this document may be obtained from Bibliography. 

Safety aspects, e.g., combustion and dust explosion, fire hazard, toxicity, etc. Value of the product Need for control... 

Currently (May 2014) webinars like Changes to PSM Standard Executive Order 13650 Webinar Series, Operating Discipline, LNG Webinar Series, Storage Tanks The Hidden Threat Webinar Series are available. White papers are also available on a wide spread of topics from Safety Cirlture, Reducing the Risk of Dust Explosion Hazards, Control System Cyber Security, etc. Other information is available on risk management, security, integrity marragemerrt arrd other topics. 

In this chapter, the basics of combustion are outlined followed by the fundamentals specific to dust explosions. The measurement and application of dust explosion characteristics, such as ignition temperature, range of flammable concentrations minimum ignition energy are covered. Finally the available methods for control of dust explosion hazard are discussed. 

Examination of this list reveals that it is not simply a list of six hazards for which plans must be developed. It refers to both specific hazards (e.g. spontaneous combustion) and general control systems (e.g. ventilation management), which may be applicable to more than one hazard. The principle hazards are to some extent implicit in this list. They include methane gas explosions (which may or may not trigger coal dust explosions), carbon monoxide poisoning, roof or wall collapse, and the long latency period dust disease, pneumoconiosis, which has probably killed more miners in the long run than anything else. 

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