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Combustible Dust National Emphasis Program

Ignition Source. Dispersion. Confinement. Deflagration. Explosion. FIRE. Combustible Dust. Oxygen in Air. Combustible Dust National Emphasis Program. Combustible Dust. Background. History of Combustible Dust Incidents Overview of Combustible Dust NEP Hazard Mitigation Techniques

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Combustible Dust National Emphasis Program

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  1. Ignition Source Dispersion Confinement Deflagration Explosion FIRE Combustible Dust Oxygen in Air Combustible Dust National Emphasis Program Combustible Dust

  2. Background • History of Combustible Dust Incidents • Overview of Combustible Dust NEP • Hazard Mitigation Techniques • Resources

  3. Select Catastrophic Combustible Dust Incidents since 1995

  4. Combustible Dust Explosions History Malden Mills

  5. Malden Mills • 12/11/1995 • Lawrence , MA • 13 hospitalized • No citations • Made nylon fibers and suspected the static electricity ignited the fibers that were glues to make fibers stand on end in the fleece making process.

  6. Firefighting efforts following the explosion at Malden Mills (Methuen, Massachusetts, December 11, 1995).

  7. Combustible Dust Explosions History Jahn foundry

  8. Jahn Foundry • 2/25/1999 • Springfield, MA • 3 fatalities, 9 hospitalized • General duty, electrical and housekeeping. $115k • Secondary explosion ignited phenol formaldehyde resin. Initial cause is not sure. • Heavy deposits of resin dust were found in the flexible exhaust ducts serving the ovens in the shell molding stations

  9. Combustible Dust Explosions History Ford River Rouge: Killed six workers and injured 36

  10. Ford River Rouge Power Plant • 2/1/1999 • Dearborn , MI • General Duty egregious, 1.5M • Natural gas boiler explosion triggered secondary coal dust explosion that had accumulated on building and equipment surfaces

  11. Combustible Dust Explosions History Rouse Polymerics

  12. Rouse Polymerics • 5/16/2002 • Vicksburg, MS • 5 fatalities, 7 injured • 23 serious, 2 unclassified 210K to 187k • Fire in the baghouse, then rubber dust explosion

  13. Combustible Dust Explosions History • January 29, 2003 - West Pharmaceutical Services, Kinston, NC • Six deaths, dozens of injuries • Facility produced rubber stoppers and other products for medical use

  14. West Pharmaceutical facility destroyed by polyethylene dust

  15. West Pharmaceutical Services • Combustibledust was ignited by some ignition source causing an initial explosion in the Milling Room, which dislodged ceiling tiles, steel beams, and wall panels, and also putting a large quantity of combustibledust from these areas into suspension, which was added fuel to the blast wave from the first explosion, creating a second and larger explosion.

  16. CTA Acoustics • 02/20/2003 • Corbin , KY • 7 fatalities, 37 injured • 4 serious including 1910.307b, 28k • Fiberglass fibers and excess phenolic resin powder probably went to the oven while workers were using compressed air and lance to break up a cogged bag house filter.

  17. Combustible Dust Explosions History • October 29, 2003 - Hayes Lemmerz Manufacturing Plant • Two severely burned (one of the victims died) • Accumulated aluminum dust • Facility manufactured cast aluminum automotive wheels

  18. Hayes Lemmerz International • 10/29/2003 • Huntington IN • One fatality, one injured • 6 serious, 42k • General duty and 1910.307b cited • A dust collector attached to the recycling equipment exploded. The explosion propagated through piping to a furnace where the burned employees were working

  19. Types of Dust Involved in incidents Coal Food Plastic Wood Metal

  20. Types of Industries Involved in Dust Incidents

  21. Dust Incidents, Injuries, and Fatalities

  22. What Combustible Dustsareexplosible? • Some Metal dust • Wood dust • Coal and other carbon dusts. • Plastic dust • Biosolids • Organic dust such as sugar, paper, soap, and dried blood. • Certain textile materials

  23. B – 110 MEC g/m3 Mg – 15.7 AL – 80-120 Si – 200 S – 100 Ti – 70 Cr – undetermined Fe – 220-500 Ni - NF Zn – 300 to NF Nb – 420 to undetermined Mo – NF Sn – 450 Hf – 180 Ta – 400 W – 700-undetermined Pb - NF What metal dusts are explosive?

  24. Which Industries have Potential Dust Explosion Hazards? • Agriculture • Chemical • Textile • Forest and furniture products • Metal Processing • Paper products • Pharmaceuticals • Recycling operations (metal, paper, and plastic recycling operations.) • Coal Power plants and coal processing facilities

  25. CSB Recommendations To OSHA 1) Issue a standard designed to prevent combustible dust fires and explosions in general industry 2) Revise the Hazard Communication Standard (HCS) (1910.1200) to clarify that the HCS covers combustible dusts • Communicate to the United Nations Economic Commission (UNECE) the need to amend the Globally Harmonized System (GHS) to address combustible dust hazards • Provide training through the OSHA Training Institute (OTI) on recognizing and preventing combustible dust explosions. • While a standard is being developed, implement a National Special Emphasis Program (SEP) on combustible dust hazards in general industry

  26. Definitions and Terminology NFPA 654 (2006) Definitions Combustible dust. A combustible particulate solid that presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations, regardless of particle size or shape.Combustible Particulate Solid. Any combustible solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition.Hybrid Mixture. A mixture of a flammable gas with either a combustible dust or a combustible mist. What is Combustible Dust?

  27. Definitions and Terminology What is Combustible Dust? NFPA 69 (2002), and 499 (2004) Definitions • Combustible Dust.Any finely divided solid material 420 microns or less in diameter (i.e., material passing through a U.S. No 40 Standard Sieve) that presents a fire or explosion hazard when dispersed 1 micron (µ) = 1.0 x 10-6m  = 1.0 x 10-4 cm = 1.0 x 10-3 mm  420 µ = 420 x 10-4 cm = .042 cm = 0.4mm A typical paper thickness is approximately 0.1mm

  28. Particle Size of Common Materials

  29. Definitions and Terminology Class II Locations Class II locations are those that are hazardous because of the presence of combustible dust. The following are Class II locations where the combustible dust atmospheres are present: Group E. Atmospheres containing combustible metal dusts, including aluminum, magnesium, and their commercial alloys, and other combustible dusts whose particle size, abrasiveness, and conductivity present similar hazards in the use of electrical equipment. Group F. Atmospheres containing combustible carbonaceous dusts that have more than 8 percent total entrapped volatiles (see ASTM D 3175, Standard Test Method for Volatile Matter in the Analysis Sample of Coal and Coke, for coal and coke dusts) or that have been sensitized by other materials so that they present an explosion hazard. Coal, carbon black, charcoal, and coke dusts are examples of carbonaceous dusts. Group G. Atmospheres containing other combustible dusts, including flour, grain, wood flour, plastic and chemicals.

  30. Deflagration Vs. Explosion Definitions and Terminology Deflagration. Propagation of a combustion zone at a speed that is less than the speed of sound in the unreacted medium. Detonation. Propagation of a combustion zone at a velocity that is greater than the speed of sound in the unreacted medium. Explosion.The bursting or rupture of an enclosure or a container due to the development of internal pressure from deflagration. Deflagration Explosion Detonation

  31. The minimum concentration of combustible dust suspended in air, measured in mass per unit volume that will support a deflagration. Lower Flammable Limit (LFL) The lower flammable limit is the lowest concentration of a combustible substance in an oxidizing medium Upper Flammable Limit (UFL) The upper flammable limits is the highest concentration of a combustible substance in an oxidizing medium that will propagate a flame. How are MEC and LFLDifferent? Definitions and Terminology Minimum Explosible Concentration (MEC)

  32. Explosible Range Source: Dust Explosions in the Process Industries, Second Edition, Rolf K Eckhoff

  33. Definitions and Terminology • Minimum Ignition Temperature (MIT). The lowest temperature at which ignition occurs. • Lower the particle size – Lower the MIT • Lower the moisture content - Lower the MIT • Minimum Ignition Energy (MIE). The lowest electrostatic spark energy that is capable of igniting a dust cloud. • Energy Units (millijoules) • Decrease in particle size and moisture content – decreases MIE • An increase in temperature in dust cloud atmosphere - decreases MIE • Deflagration Index, Kst – Maximum dp/dt normalized to 1.0 m3 volume. • Pmax – The maximum pressure reached during the course of a deflagration.

  34. Deflagration Index - Kst Kst = (dP/dt)max V1/3 (bar m/s) where: (dP/dt) max = the maximum rate of pressure rise (bar/s) V = the volume of the testing chamber (m3)

  35. Initial Internal Deflagration Process Equipment 0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec. The “Typical” Explosion Event

  36. Initial Internal Deflagration Shock Wave Process Equipment 0 25 50 75 100 125 150 175 200 225 250 300 325 The “Typical” Explosion Event Time, msec.

  37. Initial Internal Deflagration Elastic Rebound Shock Waves Process Equipment 0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec. The “Typical” Explosion Event

  38. Initial Internal Deflagration Dust clouds caused by Elastic Rebound Process Equipment 0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec. The “Typical” Explosion Event

  39. Containment Failure from Initial Deflagration Dust Clouds Caused by Elastic Rebound Process Equipment 0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec. The “Typical” Explosion Event

  40. Dust Clouds Caused by Elastic Rebound Process Equipment Secondary Deflagration Initiated 0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec. The “Typical” Explosion Event

  41. Secondary Deflagration Propagates through Interior Process Equipment 0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec. The “Typical” Explosion Event

  42. Secondary Deflagration Vents from Structure 0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec. The “Typical” Explosion Event Process Equipment

  43. Secondary Deflagration Causes Collapse and Residual Fires 0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec. The “Typical” Explosion Event Diagrams Courtesy of John M. Cholin, P.E., FSFPE, J.M. Cholin Consultants, Inc.

  44. Dust Handling Equipment

  45. Typesof Equipment Used in Dust Handling • Bag Openers (Slitters) • Blenders/Mixers • Dryers • Dust Collectors • Pneumatic Conveyors • Size Reduction Equipment (Grinders) • Silos and Hoppers • Hoses, Loading Spouts, Flexible Boots

  46. Equipment Involved in Dust Explosions USA 42% Source: Guidelines for Safe Handling of Powders and Bulk Solids, CCPS, AICHE

  47. Heat Generation due to Rubbing of Solids Rubbing of internal parts Electrostatic Charging of the Solids Dust Formation inside of the equipment Blenders/Mixers Source: http://www.fedequip.com/abstract.asp?ItemNumber=17478&txtSearchType=0&txtPageNo=1&txtSearchCriteria=ribbon_mixer

  48. Dust Collectors 42% • Presence of easily ignitable fine dust atmosphere and high turbulence • Experienced many fires over the years due to broken bags. • Ignition source is electrostatic spark discharges • Another ignition source is entrance of hot, glowing particles into the baghouse from upstream equipment Fabric Filters (Baghouses)

  49. Aluminum Dry Dust Collector • Dry Type collectors located outside • Explosive Dust Warning sign on collector • Collectors or cyclone have temperature alarms • No recycling of air from powder collectors • Collector ductwork blanked before repairs • Filter cannot be synthetic • Dust removed AT LEAST once a day • Dust put in sealed tight metal containers

  50. Pneumatic conveying system • Downstream equipment have high rate of risk for fires and explosion • Static electricity is generated from particle to particle contact or from particle to duct wall contact. • Heated particles which are created during grinding or drying may be carried into the pneumatic conveying system and fanned to a glow by high gas velocity. • Tramp metal in the pneumatic system may also cause frictional heating. • Charged powder may leak from joints to the atmosphere and electrostatic sparking can occur resulting in an explosion. Figure source:www.flexicon.com/us/products/PneumaticConveyingSystems/index.asp?gclid=COa2kKWK4o8CFQGzGgodikc9Dg

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