![]() ![]() To support rapid combustion, the dust must consist of very small particles with a high surface area to volume ratio, thereby making the collective or combined surface area of all the particles very large in comparison to a dust of larger particles. In special effects pyrotechnics, lycopodium powder and non-dairy creamer are two common means of producing safe, controlled fire effects. Enclosed paper mill areas subject to such dangers commonly maintain very high air humidities to reduce the chance of airborne paper dust explosions. Īlthough not strictly a dust, paper particles emitted during processing – especially rolling, unrolling, calendaring/slitting, and sheet-cutting – are also known to pose an explosion hazard. Efforts are underway not only to build this knowledgebase within the industry but also to share it with local fire departments, who do periodic fire-safety inspections of businesses in their districts and who can expect to answer alarms at shops or plants where AM is now part of the production mix. For example, in machining operations downstream of the AM build, excess powder liberated from porosities in the support structures can be exposed to sparks from the cutting interface. Since the advent of industrial production–scale metal powder–based additive manufacturing (AM) in the 2010s, there is growing need for more information and experience with preventing dust explosions and fires from the traces of excess metal powder sometimes left over after laser sintering or other fusion methods. A similar problem occurs in sawmills and other places dedicated to woodworking. Powdered metals (such as aluminum, magnesium, and titanium) can form explosive suspensions in air, if finely divided.Ī gigantic explosion of flour dust destroyed a mill in Minnesota on May 2, 1878, killing 14 workers at the Washburn A Mill and another four in adjacent buildings. ![]() In addition, many otherwise mundane organic materials can also be dispersed into a dangerous dust cloud, such as grain, flour, starch, sugar, powdered milk, cocoa, coffee, and pollen. Many common materials which are known to burn can generate a dust explosion, such as coal dust and sawdust. ![]() Conditions required Īftermath of 2008 explosion at Imperial Sugar in Port Wentworth, Georgia, US Historically, fatalities from dust explosions have largely been the result of secondary dust explosions. Secondary dust explosions are the result of dust accumulation inside a building being disturbed and ignited by the primary explosion, resulting in a much more dangerous uncontrolled explosion that can affect the entire structure. Primary dust explosions may occur inside process equipment or similar enclosures, and are generally controlled by pressure relief through purpose-built ducting to the external atmosphere. If the spread of flame is at subsonic speed, the phenomenon is sometimes called a " deflagration", although looser usage calls both phenomena " explosions".ĭust explosions may be classified as being either "primary" or "secondary" in nature. The sudden release of energy from a " detonation" can produce a shockwave, either in open air or in a confined space. If rapid combustion occurs in a confined space, enormous overpressures can build up, causing major structural damage and flying debris. These weapons are the most powerful non-nuclear weapons in existence. Thermobaric weapons exploit this principle by rapidly saturating an area with an easily combustible material and then igniting it to produce explosive force. They are also commonly used by special effects artists, filmmakers, and pyrotechnicians, given their spectacular appearance and ability to be safely contained under certain carefully controlled conditions. In cases when fuel plays the role of a combustible material, the explosion is known as a fuel-air explosion.ĭust explosions are a frequent hazard in coal mines, grain elevators, and other industrial environments. Dust explosions can occur where any dispersed powdered combustible material is present in high-enough concentrations in the atmosphere or other oxidizing gaseous medium, such as pure oxygen. Lab demonstration with burning lycopodium powderĪ dust explosion is the rapid combustion of fine particles suspended in the air within an enclosed location. ![]()
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