Explosion Protection in the Food Industry

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  • Grain Standard 29CFR 1910.272There've been explosions involving, coca, spices, meat powder, sugar, flour, starch, vitasmins, supplements, pet foods
  • Ignition source must have sufficient energyMEC must be reached (fuel)
  • Common Inerting materials can’t be used
  • Grain Handling Facilities Standard[29 CFR 1910.272]
  • $17 million in damages
  • Explosion Protection in the Food Industry

    1. 1. Explosion Protection in the Food Industry Teresa Long November 2012
    2. 2. OSHA Standards According to OSHA statistics, the food industry has twice as many combustible dust related fires and explosions than any other industry  74 incidents between 1980 and 2008  There is no OSHA Combustible Dust Standard  2
    3. 3. NFPA Standards NFPA 61 “Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Production Facilities”  NFPA 68 “Guide for Venting of Deflagrations”  NFPA 69 “Standard on Explosion Prevention Systems”  NFPA 654 “Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids”  3
    4. 4. You Can Eat It, So It’s Safe  Often, the hazard isn’t recognized  Food is perceived to be safe Minimum Explosible Concentration (MEC) of many food products is <100mg / m3  4
    5. 5. Combustible Products Egg white Milk, powdered Milk, nonfat, dry Soy flour Starch, corn Starch, rice Starch, wheat Sugar Sugar, milk Parsley(dehydra ted) Green coffee Hops (malted) Lemon peel dust Lemon pulp Locust bean gum Xanthan gum Wheat grain dust Peanut meal and skins Raw yucca seed dust Sunflower seed dust Oat flour Oat grain dust Olive pellets Onion powder Peach Potato Potato flour Sugar (10x) Potato starch Rice dust Rice flour Rice starch Rye flour Semolina Soybean dust Spice dust Spice powder Tapioca Sunflower Walnut dust Wheat flour Wheat starch Malt Whey Sugar, beet 5
    6. 6. Recipe for a Dust Explosion Five elements, which form the explosion pentagon, must occur simultaneously for a dust explosion to occur. 6
    7. 7. Simultaneous Conditions Required for Dust Explosions The dust must be combustible  The dust must be dispersed  The dust concentration must be within the explosible range (above the Minimum Explosive Concentration, MEC)  The dust must have a particle size distribution capable of propagating flame  The atmosphere in which the dust cloud is present must be capable of supporting combustion (oxygen)  Ignition source must have sufficient energy to initiate combustion (Minimum Ignition Energy, MIE)  7
    8. 8. Dust Explosion Protection Principles (Ebadat, 2012) Risk of an explosion is minimized when one of the following measures is ensured:      An explosible dust cloud is never allowed to form The atmosphere is sufficiently depleted of oxidant (normally the oxygen in air) that it cannot support combustion All ignition sources capable of igniting the dust cloud are removed People and facilities are protected against the consequences of an explosion by “protection measures” such as explosion containment, explosion suppression or explosion relief venting Housekeeping activities must ensure that secondary fuel sources are not available. Of key importance is the evaluation of dust release points and exhaust ventilation needs – It is much easier to replace a gasket, install local dust aspiration systems, etc., than to spend the time cleaning up the dust that has escaped 8
    9. 9. Explosion Protection Measures Explosion relief venting  Explosion suppression  Explosion containment  Explosion isolation  Inert gas purging, if needed  9
    10. 10. Housekeeping and Ventilation System Design        Most serious dust explosions are not caused by a primary explosion inside the plant, they are caused by a secondary explosion within the building An initial event causes pressure and shock waves to propagate into the workplace, and dust deposits form a cloud, which ignites. If this happens in a series of connected rooms, a chain reaction occurs and the result can be devastating Secondary dust explosions are common in industries such as the food industry where the material are perceived to be safe. Dust is often present outside the process equipment due to the perception the material is toxic and cheap Fugitive dust outside equipment must be minimized. Evaluation of dust release points and exhaust ventilation needs is critical Preventing dust is much easier than cleaning up after it has escaped. Venting inside a building can cause harm to people, damage the facility, and poses an increased risk of a secondary explosion 10
    11. 11. Process Equipment Design Source: New Zealand Department of Labor 11
    12. 12. Ventilation Ducting       Ducting carrying product + air is vulnerable to primary explosions Four elements of the explosion pentagon are present: fuel, oxygen, confinement, and suspension All that is needed is an ignition source Ducts to transport dust are designed to operate at ~4,000 ft/min (~45 mph or ~20 m/s ) in order to keep the dust entrained In a closed vessel, such as a duct, expansion cannot occur and pressure rises In a long duct, an explosion can propagate. Expansion of the dust increases turbulence, which increases combustion rates, and the explosion accelerates (2km per second) until a detonation is reached 12
    13. 13. Safety Measures      Do not locate dust collectors inside buildings Rooms, buildings, and dust collectors should have explosion relief venting distributed over the exterior wall of buildings and enclosures Explosion venting is directed to a safe location away from employees The facility should have isolation devices to prevent deflagration propagation between pieces of equipment connected by ductwork Dust-containing systems (ducts and dust collectors) should be designed in a manner that fugitive dusts are not allowed to accumulate in the work area 13
    14. 14. The Dilemma “The food industry has potentially conflicting requirements for food safety (hygiene, cleanability and prevention of foreign matter contamination) and explosion safety (venting, suppression, isolation). Finding a safe path through these requirements is not easy, and the blanket application of non-food industry solutions to food processing is often not practical” Dr. Christopher Bloore, Dairy Industry Systems Consultant to the New Zealand and Australian Dairy Industries 14
    15. 15. The Dilemma Explosions are costly and can be just as devastating to a company’s image as contaminated food in the supply chain "Relying on housekeeping as a first line of defense against explosion and fire is a false economy - not only is there a greater risk to the workers, but the maintenance costs for machinery are higher, due to increased abrasion from dust getting into the moving parts of machinery"--Eric Anderson, P.E, Ventilation Engineering 15
    16. 16. Imperial Sugar (February 7,2008)    14 killed, 36 injured, extensive damage to the plant Resulted from ongoing releases of sugar from inadequately designed and maintained dust collection equipment, conveyors, and sugar handling equipment Minimum explosible concentration in air: 0.045 g/l Source: CSB 16
    17. 17. DeBruce Grain Elevator Explosion June 8,1998 7 killed, 10 injuries Grain dust accumulation in pneumatic dust collecting duct North silo complex as seen from the headhouse South end of north silo complex viewed from the west 17
    18. 18. DeBruce Grain Elevator Explosion June 8,1998 Wall damage on East side of headhouse Headhouse with truck dump, lean-to, and dust collection system 18
    19. 19. DeBruce Grain Elevator Explosion Possible transition from deflagration (subsonic burning) to detonation (supersonic burning) in the combustion process 19
    20. 20. LiHua Starch Co. Qinghuangdao, China 21 killed, 47 Injured February 24, 2010 20
    21. 21. LiHua Starch Co. Qinghuangdao, China 21 killed, 47 Injured February 24, 2010 21
    22. 22. Lucky Day Tapioca Explosion Thailand July 7, 2011 9 injured 22
    23. 23. References Anderson, E. (10, 28 2012). [Personal Interview]. Bloore, C. (10/15/2012). [Personal Interview]. Zeeuwen, P. "Explosion Risks in Silo Filling and Discharge." Chilworth Technology. N.p.. Web. 27 Oct 2012. Ebadat, V. "Dust Explosions In The Food Industry." Food Manufacturing. 2012: n. page. Web. 27 Nov. 2012. <http://www.manufacturing.net/articles/2012/03/dust-explosions-in-the-food-industry>. New Zealand. Department of Labor. APPROVED CODE OF PRACTICE FOR THE PREVENTION, DETECTION AND CONTROL OF FIRE AND EXPLOSION IN NEW ZEALAND DAIRY INDUSTRY SPRAY DRYING PLANT ISSUED. 1993. Print. Haywood, B. "Dust Explosions In The Food Industry." SAFTENG.net. N.p., n. d. Web. Web. 03 Nov. 2012. <http://www.safteng.net/index.php?option=com_content&view=article&id=2000&Itemid=4>. Grain Elevator Explosion Investigation Team, . United States. OSHA. DeBruce Grain Elevator Explosion - Report. 2003. Web. <http://www.osha.gov/SLTC/grainhandling/geeit/index.html>. 23

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