Dust explosion
A dust explosion is the rapid
Dust explosions are a frequent hazard in
Terminology
If rapid combustion occurs in a
Dust explosions may be classified as being either "primary" or "secondary" in nature. 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. 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. Historically, fatalities from dust explosions have largely been the result of secondary dust explosions.[2]
Conditions required
There are five necessary conditions for a dust explosion:[3]
- A combustible dust
- The dust is dispersed in the air within certain flammability limits
- There is an oxidant(typically atmospheric oxygen)
- There is an ignition source
- The area is confined – a building can be an enclosure
Sources of dust
Many common materials which are known to burn can generate a dust explosion, such as
) can form explosive suspensions in air, if finely divided.A
Since the advent of industrial production–scale
Although not strictly a dust, paper
In
are two common means of producing safe, controlled fire effects.To support rapid combustion, the dust must consist of very small particles with a high
Concentration
Below a certain value, the lower explosive limit (LEL), there is insufficient dust to support the combustion at the rate required for an explosion.[7] A combustible concentration at or below 25% of the LEL is considered safe.[8] Similarly, if the fuel to air ratio increases above the upper explosive limit (UEL), there is insufficient oxidant to permit combustion to continue at the necessary rate.
Determining the minimum explosive concentration or maximum explosive concentration of dusts in air is difficult, and consulting different sources can lead to quite different results. Typical explosive ranges in air are from few dozens grams/m3 for the minimum limit, to few kg/m3 for the maximum limit. For example, the LEL for sawdust has been determined to be between 40 and 50 grams/m3.[9] It depends on many factors including the type of material used.
Oxidant
Typically, normal atmospheric oxygen can be sufficient to support a dust explosion if the other necessary conditions are also present. High-oxygen or pure oxygen environments are considered to be especially hazardous, as are strong oxidizing gases such as
Sources of ignition
There are many sources of ignition, and a naked flame need not be the only one: over one half of the dust explosions in Germany in 2005 were from non-flame sources.[7] Common sources of ignition include:
- electrostatic discharge (e.g. an improperly installed conveyor belt, which can act like a Van de Graaff generator)
- friction
- electrical arcingfrom machinery or other equipment
- hot surfaces (e.g. overheated bearings)
- fire
- self-ignition
However, it is often difficult to determine the exact source of ignition when investigating after an explosion. When a source cannot be found, ignition will often be attributed to static electricity. Static charges can be generated by external sources, or can be internally generated by friction at the surfaces of particles themselves as they collide or move past one another.
Mechanism
Dusts have a very large surface area compared to their mass. Since burning can only occur at the surface of a solid or liquid, where it can react with oxygen, this causes dusts to be much more flammable than bulk materials. For example, a 1 kilogram (2.2 lb) sphere of a combustible material with a density of 1 g/cm3 would be about 12.4 centimetres (4.9 in) in diameter, and have a surface area of 0.048 square metres (0.52 sq ft). However, if it were broken up into spherical dust particles 50
When this mixture of fuel and air is ignited, especially in a confined space such as a warehouse or silo, a significant increase in pressure is created, often more than sufficient to demolish the structure. Even materials that are traditionally thought of as nonflammable (such as aluminum), or slow burning (such as wood), can produce a powerful explosion when finely divided, and can be ignited by even a small spark.
-
Experimental setup
-
Finely-ground flour is dispersed
-
Cloud of flour is ignited
-
Fireball spreads rapidly
-
Intenseradiant heathas nothing to ignite here
-
Fireball and superheated gases rise
-
Aftermath of explosion, with unburned flour on the ground
Effects
A dust explosion can cause major damage to structures, equipment, and personnel from violent overpressure or shockwave effects. Flying objects and debris can cause further damage. Intense
Protection and mitigation
Much research has been carried out in Europe and elsewhere to understand how to control these dangers, but dust explosions still occur. The alternatives for making processes and plants safer depend on the industry.
In the
Some industries exclude oxygen from dust-raising processes, a precaution known as "inerting". Typically this uses
Good housekeeping practices, such as eliminating build-up of combustible dust deposits that could be disturbed and lead to a secondary explosion, also help mitigate the problem.
Best engineering control measures which can be found in the National Fire Protection Association (NFPA) Combustible Dust Standards[12] include:
- Wetting
- Oxidant concentration reduction
- Deflagration venting
- Deflagration pressure containment
- Deflagration suppression
- Deflagration venting through a dust retention and flame-arresting device
Notable incidents
Dust clouds are a common source of explosions, causing an estimated 2,000 explosions annually in Europe.[13] The table lists notable incidents worldwide.
Event | Date | Location | Country | Source material | Fatalities | Injuries | Notes |
---|---|---|---|---|---|---|---|
Tradeston Flour Mills explosion | July 9, 1872 | Glasgow, Scotland | United Kingdom | grain dust | 18 | 16 | Destroyed the mill building and damaged surrounding buildings, and started a fire that killed others. The investigation into the explosion was published across Europe and the Americas. |
Great Mill Disaster | May 2, 1878 | Minneapolis, Minnesota |
United States | grain dust | 18 | Destroyed the largest grain mill in the world and leveled five other mills, effectively reducing the milling capacity of Minneapolis by one-third to one-half. Prompted mills throughout the country to install better ventilation systems to prevent dust build-up. | |
Husted Mill and Elevator Disaster | June 24, 1913 | Buffalo, New York | United States | grain dust | 33 | 80 | This workday afternoon explosion destroyed a grain elevator and mill complex. The engineer of a passing railroad switch engine was blown from the cab and died. Windows of a passing Nickel Plate Road passenger train were broken, but no passengers were injured.[14][15] |
Milwaukee Works explosion | May 20, 1919 | Milwaukee, Wisconsin | United States | Feed grinding plant | 3 | 4 | The blast was felt for miles around and completely leveled the plant owned by the company. |
Douglas Starch Works explosion | May 22, 1919 | Cedar Rapids, Iowa | United States | corn starch | 43 | 30 | The blast was felt for miles around and completely leveled the plant owned by the company. |
Port Colborne explosion | August 9, 1919 | Port Colborne | Canada | grain | 10 | 16 | Blast also destroyed the steamer Quebec, which was near the grain elevator |
Large terminal grain elevator in Kansas City | September 13, 1919 | Kansas City, Missouri | United States | 14 | 10 | Originated in basement of elevator, during a cleanup period, and travelled up through the elevator shaft | |
Mount Mulligan mine disaster | September 19, 1921 | Mount Mulligan, Queensland | Australia | coal dust | 75 | The series of coal dust explosions within a mine rocked the close-knit township and was audible as far as 30 kilometres (19 mi) away. | |
Benxihu Colliery explosion | April 26, 1942 | Benxi, Liaoning | Manchukuo (now China) | coal dust and gas | 1,549 | 34% of the miners working that day were killed. This is the world's worst-ever coal-mining accident. | |
Pillsbury Explosion and Fire | January 2, 1972 | Buffalo, New York | United States | wheat flour | 3 | 8 | New Year's weekend explosion at what was then the world's biggest flour mill. The blast occurred in a series of 500-foot-long, 10-story-tall concrete-and-steel bulk flour storage bins. Repairs took a year to complete.[16] |
Westwego grain elevator explosion |
December 22, 1977 | Westwego, Louisiana | United States | grain dust | 36 | 13 | [17] |
Galveston grain elevator explosion | December 27, 1977 | Galveston, Texas |
United States | grain dust | 20 | [17] | |
Bird's Custard factory explosion | November 18, 1981 | Banbury | United Kingdom | corn starch | 9 | [13][18] | |
Metz malt factory explosion | October 18, 1982 | Metz | France | barley dust | 12 | 1 | [19] |
Ingeniero White Silo Nº 5 explosion | 13 March 1985 | Ingeniero White | Argentina | grain dust | 22 | [20] | |
Harbin textile factory explosion | March 17, 1987 | Harbin | China | flax dust | 58 | 177 | [21] |
Sukhodilska–Skhidna coal mine accident | June 9, 1992 | Sukhodilsk | Ukraine | coal dust and firedamp | 63 | 37 | [22][23] |
Blaye grain explosion | August 1997 | Blaye | France | grain dust | 11 | 1 | Explosion in a grain storage facility at the Société d’Exploitation Maritime Blayaise killed 11 people in nearby offices and injured one.[13] |
Debruce elevator explosion | June 1998 | Wichita, Kansas | United States | grain dust | 7 | 10 | Multiple explosions occurred in what was then the world's largest grain elevator. Dust collection systems were not properly maintained.[24] |
West Pharmaceutical Services explosion | January 29, 2003 | Kinston, North Carolina | United States | polyethylene dust | 6 | 38 | |
Imperial Sugar explosion |
February 7, 2008 | Port Wentworth, Georgia | United States | sugar dust | 14 | 42 | [13] |
2014 Kunshan explosion | August 2, 2014 | Kunshan | China | metal powder | 146 | 114 | |
Formosa Fun Coast explosion |
June 27, 2015 | New Taipei |
Taiwan | colored starch powder | 15 | 498 | Explosion when Holi-like colored powder was released at an outdoor music and color festival at the Formosa Fun Coast. |
Bosley wood flour mill explosion | July 17, 2015 | Bosley, Cheshire | United Kingdom | wood flour |
4 | 4 | [25][26] |
See also
- Air to fuel ratio
- Power tool
References
- ISSN 0261-3077. Retrieved 2019-01-19.
- ^ ISBN 0-7506-3270-4.
- ^ "OSHA Fact Sheet: Hazard Alert: Combustible Dust Explosions" (PDF). osha.gov. Archived from the original (PDF) on 2020-11-01. Retrieved 2018-01-23.
- ^ Nathanson, Iric. The 1878 Washburn A Mill Explosion. Archived from the original on 2014-04-08. Retrieved 2014-04-08.
- ^ a b c Simpson, Timothy W. (2017-08-17), "Will My AM Part Explode? Not if you're careful. Parts built from metallic powder require extra precautions", Modern Machine Shop.
- ^ "Detonation Films – Why Coffee Creamer?". Archived from the original on November 12, 2020. Retrieved March 20, 2011.
- ^ a b "Dust explosion protection" (PDF). bartec.de. 2005. Archived from the original (PDF) on 2006-12-10.
- ^ NFPA 69 8.3.1
- ^ "Dust explosion concentration – Physical meaning and use in risk assessment of powder minimum explosive concentration (MEC)". PowderProcess.net.
- ^ Murray, Charles Edward Robertson; Wilberforce, Daniel; Ritchie, David (1903), "Mount Kembla Colliery Disaster 31 July 1902 – Report of the Royal Commission, together with minutes of evidence and exhibits", Historical and Cultural Collections – Publications, New South Wales Legislative Assembly: xxxvi, retrieved 19 May 2019
- hdl:1842/5365
- ^ "List of NFPA Codes & Standards". NFPA.org.
- ^ a b c d Hought, Julian (28 February 2011). "Dust to Dust". Retrieved 2015-07-02.
- ^ "Buffalo, NY Grain Elevator Explosion, June 1913 | GenDisasters ... Genealogy in Tragedy, Disasters, Fires, Floods Page 1". www.gendisasters.com. Retrieved 2022-02-28.
- ^ Henry H., Baxter (1980). Grain Elevators (PDF). Buffalo, NY: Buffalo and Erie County Historical Society. p. 14.
- ISSN 0362-4331. Retrieved 2022-02-28.
- ^ a b "Explosion suits settled". The Day. New London, Connecticut. 24 April 1980. p. 26.
- ISBN 0-11-883673-0
- ^ Explosion dans un silo d'une malterie(in French)
- ^ "En un emotivo acto presentaron el documental "Elevador 5 – 35 años"". La Nueva (in Spanish). 13 March 2020. Retrieved 17 November 2021.
- ^ "47 Die, 179 Injured in Blast at Linen Mill in Northeast China". Los Angeles Times. March 17, 1987. Retrieved 2015-07-02.
- ^ "Взрыв на шахте «Суходольская-Восточная»". 25 March 2016.
- ^ "Самые масштабные аварии на шахтах за годы независимой Украины". 2 March 2017.
- ^ OSHA report on the Debruce explosion
- ^ "Bosley explosion: Four missing in Wood Flour Mills blast". BBC News. July 17, 2015. Retrieved 2015-12-02.
- Mirror Online. Retrieved 2015-12-02.
- Barton, John, ed. (2002). Dust Explosion Prevention and Protection: A Practical Guide. Institution of Chemical Engineers. ISBN 0-85295-410-7.
- Eckhoff, Rolf K. (1997). Dust Explosions in the Process Industries (2nd ed.). Butterworth-Heinemann. ISBN 0-7506-3270-4.
- Price, David J. (1921). "A Disastrous Explosion of Starch Dust". American Miller and Processor. 49 (1–6). National Miller Publications.
External links
Incidents in France and the US:
- Combustible dust explosion investigation products from the Chemical Safety Board
- Combustible Dust Policy Institute-ATEX
- OSHA case studies of dust explosions
Protecting process plant, grain handling facilities, etc. from the risk of dust hazard explosions: