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OSHA Combustible dusts


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OSHA Combustible dusts

  1. 1. Combustible Dust National Emphasis Program March 10, 2008 Combustible Dust Oxygen in Air Ignition Source Dispersion Confinement Explosion FIRE Deflagration
  2. 2. Background <ul><li>History of Combustible Dust Incidents </li></ul><ul><li>Overview of Combustible Dust NEP </li></ul><ul><li>Hazard Mitigation Techniques </li></ul><ul><li>Resources </li></ul>
  3. 3. <ul><li>Catastrophic Combustible Dust Incidents since 1995 </li></ul>
  4. 4. Malden Mills Methuen, MA December 11, 1995 37 Injured Nylon Fiber Combustible Dust Explosions History
  5. 5. <ul><li>Firefighting efforts following the explosion at Malden Mills (Methuen, Massachusetts, December 11, 1995). </li></ul>
  6. 6. Combustible Dust Explosions History Jahn foundry Springfield, MA February 26, 1999 3 dead 9 Injured Phenolic resin dust
  7. 7. Ford River Rouge: Secondary Coal Dust Explosion February 1, 1999 Combustible Dust Explosions History Killed six workers and injured 36
  8. 8. Combustible Dust Explosions History May 16, 2002 Rouse Polymerics Vicksburg, Ms 5 dead, 7 injured Rubber Dust
  9. 9. Combustible Dust Explosions History <ul><li>January 29, 2003 - West Pharmaceutical Services, Kinston, NC </li></ul><ul><ul><li>Six deaths , dozens of injuries </li></ul></ul><ul><ul><li>Facility produced rubber stoppers and other products for medical use </li></ul></ul><ul><ul><li>Plastic powder accumulated above suspended ceiling ignited </li></ul></ul>
  10. 10. West Pharmaceutical facility destroyed by polyethylene dust
  11. 11. Combustible Dust Explosions History <ul><li>February 20, 2003 – CTA Acoustics, Corbin, KY </li></ul><ul><ul><li>Seven Workers died </li></ul></ul><ul><ul><li>Facility produced fiberglass insulation for automotive industry </li></ul></ul><ul><ul><li>Resin accumulated in production area that got ignited </li></ul></ul>
  12. 12. Combustible Dust Explosions History <ul><li>October 29, 2003 - Hayes Lemmerz Manufacturing Plant </li></ul><ul><ul><li>Two severely burned ( one of the victims died ) </li></ul></ul><ul><ul><li>Accumulated aluminum dust </li></ul></ul><ul><ul><li>Facility manufactured cast aluminum automotive wheels </li></ul></ul>
  13. 13. Types of Dust Involved in incidents
  14. 14. Types of Industries Involved in Dust Incidents
  15. 15. Dust Incidents, Injuries, and Fatalities
  16. 16. What Combustible Dusts are explosible? <ul><li>Metal dust such as aluminum and magnesium. </li></ul><ul><li>Wood dust </li></ul><ul><li>Coal and other carbon dusts. </li></ul><ul><li>Plastic dust </li></ul><ul><li>Biosolids </li></ul><ul><li>Organic dust such as sugar, paper, soap, and dried blood. </li></ul><ul><li>Certain textile materials </li></ul>
  17. 17. Which Industries have Potential Dust Explosion Hazards? <ul><li>Agriculture </li></ul><ul><li>Chemical </li></ul><ul><li>Textile </li></ul><ul><li>Forest and furniture products </li></ul><ul><li>Metal Processing </li></ul><ul><li>Paper products </li></ul><ul><li>Pharmaceuticals </li></ul><ul><li>Recycling operations (metal, paper, and plastic recycling operations.) </li></ul>
  18. 18. CSB Recommendations To OSHA <ul><ul><ul><li>1) Issue a standard designed to prevent combustible dust fires and explosions in general industry </li></ul></ul></ul><ul><ul><ul><li>2) Revise the Hazard Communication Standard (HCS) (1910.1200) to clarify that the HCS covers combustible dusts </li></ul></ul></ul><ul><ul><ul><li>Communicate to the United Nations Economic Commission (UNECE) the need to amend the Globally Harmonized System (GHS) to address combustible dust hazards </li></ul></ul></ul><ul><ul><ul><li>Provide training through the OSHA Training Institute (OTI) on recognizing and preventing combustible dust explosions. </li></ul></ul></ul><ul><ul><ul><li>While a standard is being developed, implement a National Special Emphasis Program (SEP) on combustible dust hazards in general industry </li></ul></ul></ul>
  19. 19. Definitions and Terminology <ul><li>Combustible Dust </li></ul><ul><li>Combustible Particulate Solid </li></ul><ul><li>Hybrid Mixture </li></ul><ul><li>Fugitive Grain Dust </li></ul><ul><li>Class II Locations </li></ul><ul><li>Deflagration </li></ul><ul><li>Detonation </li></ul><ul><li>Explosion </li></ul><ul><li>Minimum Explosible Concentration (MEC) </li></ul><ul><li>Lower Flammable Limit (LFL) </li></ul><ul><li>Upper Flammable Limit (UFL) </li></ul><ul><li>Minimum Ignition Temperature (MIT) </li></ul><ul><li>Minimum Ignition Energy (MIE) </li></ul>
  20. 20. <ul><li>NFPA 654 (2006) Definitions </li></ul><ul><li>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. </li></ul>What is Combustible Dust? Definitions and Terminology
  21. 21. Definitions and Terminology <ul><ul><li>NFPA 69 (2002), and 499 (2004) Definitions </li></ul></ul><ul><ul><li>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 </li></ul></ul>1 micron (µ) = 1.0 x 10 -6 m  = 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 What is Combustible Dust?
  22. 22. Particle Size of Common Materials
  23. 23. 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 . Class II Locations Definitions and Terminology
  24. 24. Deflagration Vs. Explosion 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. Explosion Deflagration Detonation Definitions and Terminology
  25. 25. How are MEC and LFL Different? <ul><li>Minimum Explosible Concentration (MEC) </li></ul>Definitions and Terminology The minimum concentration of combustible dust suspended in air, measured in mass per unit volume that will support a deflagration . The lower flammable limit is the lowest concentration of a combustible substance in an oxidizing medium Lower Flammable Limit (LFL) 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.
  26. 26. Source: Dust Explosions in the Process Industries, Second Edition, Rolf K Eckhoff Explosible Range
  27. 27. Definitions and Terminology <ul><li>Minimum Ignition Temperature (MIT). The lowest temperature at which ignition occurs. </li></ul><ul><ul><li>Lower the particle size – Lower the MIT </li></ul></ul><ul><ul><li>Lower the moisture content - Lower the MIT </li></ul></ul><ul><li>Minimum Ignition Energy (MIE) . The lowest electrostatic spark energy that is capable of igniting a dust cloud. </li></ul><ul><ul><li>Energy Units (millijoules) </li></ul></ul><ul><ul><li>Decrease in particle size and moisture content – decreases MIE </li></ul></ul><ul><ul><li>An increase in temperature in dust cloud atmosphere - decreases MIE </li></ul></ul><ul><li>Deflagration Index, Kst – Maximum dp/dt normalized to 1.0 m 3 volume. </li></ul><ul><li>Pmax – The maximum pressure reached during the course of a deflagration. </li></ul>
  28. 28. Deflagration Index - Kst Kst = (dP/dt) max V 1/3 (bar m/s) where: (dP/dt) max = the maximum rate of pressure rise (bar/s) V = the volume of the testing chamber (m 3 ) Very strong explosion >300 St 3 Strong explosion >200 and <=300 St 2 Weak explosion >0 and <=200 St 1 No explosion 0 St 0 Characteristic Kst (bar.m/s) Dust explosion class
  29. 29. The “Typical” Explosion Event Process Equipment Initial Internal Deflagration Time, msec. 0 25 50 75 100 125 150 175 200 225 250 300 325
  30. 30. The “Typical” Explosion Event Time, msec. Process Equipment Initial Internal Deflagration Shock Wave 0 25 50 75 100 125 150 175 200 225 250 300 325
  31. 31. The “Typical” Explosion Event Process Equipment Initial Internal Deflagration Elastic Rebound Shock Waves Time, msec. 0 25 50 75 100 125 150 175 200 225 250 300 325
  32. 32. The “Typical” Explosion Event Time, msec. 0 25 50 75 100 125 150 175 200 225 250 300 325 Process Equipment Initial Internal Deflagration Dust clouds caused by Elastic Rebound
  33. 33. The “Typical” Explosion Event Process Equipment Containment Failure from Initial Deflagration Dust Clouds Caused by Elastic Rebound Time, msec. 0 25 50 75 100 125 150 175 200 225 250 300 325
  34. 34. The “Typical” Explosion Event Process Equipment Secondary Deflagration Initiated Dust Clouds Caused by Elastic Rebound Time, msec. 0 25 50 75 100 125 150 175 200 225 250 300 325
  35. 35. The “Typical” Explosion Event Process Equipment Secondary Deflagration Propagates through Interior Time, msec. 0 25 50 75 100 125 150 175 200 225 250 300 325
  36. 36. The “Typical” Explosion Event Process Equipment Secondary Deflagration Vents from Structure Time, msec. 0 25 50 75 100 125 150 175 200 225 250 300 325
  37. 37. The “Typical” Explosion Event Diagrams Courtesy of John M. Cholin, P.E., FSFPE, J.M. Cholin Consultants, Inc. Secondary Deflagration Causes Collapse and Residual Fires Time, msec. 0 25 50 75 100 125 150 175 200 225 250 300 325
  38. 38. Dust Handling Equipment
  39. 39. Types of Equipment Used in Dust Handling <ul><li>Bag Openers (Slitters) </li></ul><ul><li>Blenders/Mixers </li></ul><ul><li>Dryers </li></ul><ul><li>Dust Collectors </li></ul><ul><li>Pneumatic Conveyors </li></ul><ul><li>Size Reduction Equipment (Grinders) </li></ul><ul><li>Silos and Hoppers </li></ul><ul><li>Hoses, Loading Spouts, Flexible Boots </li></ul>
  40. 40. Equipment Involved in Dust Explosions Source: Guidelines for Safe Handling of Powders and Bulk Solids, CCPS, AICHE
  41. 41. Blenders/Mixers <ul><li>Heat Generation due to </li></ul><ul><ul><li>Rubbing of Solids </li></ul></ul><ul><ul><li>Rubbing of internal parts </li></ul></ul><ul><li>Electrostatic Charging of the Solids </li></ul><ul><li>Dust Formation inside of the equipment </li></ul>Source:
  42. 42. Dryers <ul><li>Direct-Heat Dryers </li></ul><ul><ul><li>Convective Drying System </li></ul></ul><ul><ul><li>Heat provided by heated air or gas </li></ul></ul><ul><ul><li>Moisture is carried by drying medium </li></ul></ul><ul><li>Indirect–Heat Dryers </li></ul><ul><ul><li>Heat transfer by Conduction </li></ul></ul><ul><ul><li>Steam for Jacketed Dryers </li></ul></ul>
  43. 43. Dust Collectors <ul><li>Cyclone Separators </li></ul><ul><li>Electrostatic Precipitators </li></ul><ul><li>Fabric Filters </li></ul><ul><li>Wet Scrubbers </li></ul>
  44. 44. Dust Collectors <ul><li>Presence of easily ignitable fine dust atmosphere and high turbulence </li></ul><ul><li>Experienced many fires over the years due to broken bags. </li></ul><ul><li>Ignition source is electrostatic spark discharges </li></ul><ul><li>Another ignition source is entrance of hot, glowing particles into the baghouse from upstream equipment </li></ul>Fabric Filters (Baghouses )
  45. 45. Pneumatic conveying system <ul><li>Downstream equipment have high rate of risk for fires and explosion </li></ul><ul><ul><li>Static electricity is generated from particle to particle contact or from particle to duct wall contact. </li></ul></ul><ul><ul><li>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. </li></ul></ul><ul><ul><li>Tramp metal in the pneumatic system may also cause frictional heating. </li></ul></ul><ul><ul><li>Charged powder may leak from joints to the atmosphere and electrostatic sparking can occur resulting in an explosion. </li></ul></ul>Figure
  46. 46. Pneumatic conveying systems (Cont.) <ul><li>Prevention and Protection systems </li></ul><ul><ul><li>Venting </li></ul></ul><ul><ul><li>Suppression </li></ul></ul><ul><ul><li>Pressure Containment </li></ul></ul><ul><ul><li>Deflagration Isolation </li></ul></ul><ul><ul><li>Spark detection and extinguishing system </li></ul></ul><ul><ul><li>Use of inert conveying gas </li></ul></ul>
  47. 47. Size Reduction System <ul><li>Size reduction equipment is regarded as a possible ignition source because of friction and hot surfaces arising from grinding </li></ul><ul><li>Entrance of metal into the equipment </li></ul><ul><li>Too slow feed rate can increase the possibility of fire/explosion hazard </li></ul>
  48. 48. Silos and Hoppers <ul><li>No inter-silo Venting </li></ul><ul><li>Silos and hoppers shall be located outside the buildings with some exceptions </li></ul><ul><li>Air cannons not to be used to break bridges in silos </li></ul><ul><li>Detection of smoldering fires in silos and hoppers can be achieved with methane and carbon monoxide detectors </li></ul><ul><li>Pressure containment, inerting, and suppression systems to protect against explosions </li></ul><ul><li>Venting is the most widely used protection against explosions </li></ul>
  49. 49. <ul><li>Hazard Mitigation </li></ul>
  50. 50. Hazard Mitigation <ul><li>Dust control </li></ul><ul><li>Ignition source control </li></ul><ul><li>Damage control </li></ul>
  51. 51. Dust Control <ul><li>Design of facility & process equipment </li></ul><ul><li>Contain combustible dust </li></ul><ul><li>Clean fugitive dust </li></ul><ul><ul><li>Regular program </li></ul></ul><ul><ul><li>Access to hidden areas </li></ul></ul><ul><ul><li>Safe cleaning methods </li></ul></ul><ul><li>Maintenance </li></ul>
  52. 52. Dust Layer Thickness Guidelines <ul><li>1/8” in grain standard </li></ul><ul><li>Rule of thumb in NFPA 654 </li></ul><ul><ul><li>1/32” over 5% of area </li></ul></ul><ul><ul><li>Bar joist surface area ~ 5% </li></ul></ul><ul><ul><li>Max 20,000 SF </li></ul></ul><ul><ul><li>Idealized </li></ul></ul><ul><li>Consider point in cleaning cycle </li></ul>
  53. 53. Ignition Source Control <ul><li>Electrical equipment </li></ul><ul><li>Static electricity control </li></ul><ul><li>Mechanical sparks & friction </li></ul><ul><li>Open flame control </li></ul><ul><li>Design of heating systems & heated surfaces </li></ul><ul><li>Use of tools, & vehicles </li></ul><ul><li>Maintenance </li></ul>
  54. 54. Damage Control Construction <ul><li>Detachment (outside or other bldg.) </li></ul><ul><li>Separation (distance with in same room) </li></ul><ul><li>Segregation (barrier) </li></ul><ul><li>Pressure resistant construction </li></ul><ul><li>Pressure relieving construction </li></ul><ul><li>Pressure Venting </li></ul><ul><li>Relief valves </li></ul><ul><li>Maintenance </li></ul>
  55. 55. Damage Control Systems <ul><li>Specialized detection systems </li></ul><ul><li>Specialized suppression systems </li></ul><ul><li>Explosion prevention systems </li></ul><ul><li>Maintenance </li></ul>
  56. 56. NEP/ Industry Application <ul><ul><li>Agriculture </li></ul></ul><ul><ul><li>Chemicals </li></ul></ul><ul><ul><li>Textiles </li></ul></ul><ul><ul><li>Forest and furniture products </li></ul></ul><ul><ul><li>Metal processing </li></ul></ul><ul><ul><li>Tire and rubber manufacturing plants </li></ul></ul><ul><ul><li>Paper products </li></ul></ul><ul><ul><li>Pharmaceuticals </li></ul></ul><ul><ul><li>Wastewater treatment </li></ul></ul><ul><ul><li>Recycling operations (metal, paper, and plastic.) </li></ul></ul><ul><ul><li>Coal dust in coal handling and processing facilities. </li></ul></ul>
  57. 57. Other Programs <ul><li>State plan participation in this national emphasis effort is strongly encouraged but is not required. </li></ul><ul><li>does not replace the grain handling facility directive, OSHA Instruction CPL 02-01-004, Inspection of Grain Handling Facilities, 29 CFR 1910.272. </li></ul><ul><li>not intended for inspections of explosives and pyrotechnics manufacturing facilities covered by the Process Safety Management (PSM) standard (1910.119) </li></ul><ul><li>does not exclude facilities that manufacture or handle other types of combustible dusts (such as ammonium perchlorate) covered under the PSM standard. </li></ul>
  58. 58. CSHOs Safety and Health <ul><li>PPE and Nonspark Producing Clothing </li></ul><ul><li>Use of Cameras </li></ul><ul><li>Use of Safe Practices when collecting dust samples </li></ul>
  59. 59. Primary Applicable OSHA Standards <ul><ul><li>1910.22 General – Housekeeping </li></ul></ul><ul><ul><li>1910.307 Hazardous (Classified) Locations </li></ul></ul><ul><ul><li>1910.178 Powered Industrial Trucks </li></ul></ul><ul><ul><li>1910. 263 Bakery Equipment </li></ul></ul><ul><ul><li>1910.265 Sawmills </li></ul></ul><ul><ul><li>1910.272 Grain Handling </li></ul></ul><ul><ul><li>General Duty Clause </li></ul></ul>
  60. 60. Lab Tests and Results <ul><li>Percent through 40 mesh </li></ul><ul><li>Percent moisture content </li></ul><ul><li>Percent combustible material </li></ul><ul><li>Percent combustible dust </li></ul><ul><li>Metal dusts will include resistivity </li></ul><ul><li>Minimum explosive concentration (MEC) </li></ul><ul><li>Minimum ignition energy (MIE) </li></ul><ul><li>Class II test </li></ul><ul><li>Sample weight </li></ul><ul><li>Maximum normalized rate of pressure rise (dP/dt) – Kst Test </li></ul><ul><li>Minimum ignition temperature </li></ul>
  61. 61. Laboratory Testing
  63. 63. Initial Sample Preparation <ul><li>Samples are sieved </li></ul>
  64. 64. Sieve stack
  65. 65. Sample Loading
  66. 67. Sieved Sample
  67. 68. <ul><li>At this point (if appropriate) moisture content, combustible fraction and resistivity are determined </li></ul>
  68. 69. Explosibility Testing Paths <ul><li>Two main branches of testing are available </li></ul><ul><ul><li>Class II </li></ul></ul><ul><ul><li>Kst </li></ul></ul><ul><ul><li>Note – the CSHO must pick ONE branch of testing </li></ul></ul>
  69. 70. Class II Testing <ul><li>Class II tests must be requested if electrical issues are in play </li></ul><ul><li>Testing uses an electrical arc for ignition source (2.4 joules) </li></ul><ul><li>Results must not be used for engineering calculations </li></ul><ul><li>It is much more likely to prove that a dust is explosive, than class II </li></ul>
  70. 71. Class II Dust Chamber
  71. 72. Dust Loaded
  72. 73. Chamber Assembled
  73. 74. Kst Testing <ul><li>Unless electrical considerations exist, this is the superior test </li></ul><ul><li>Ignition source is a chemical igniter (2500 joules) </li></ul><ul><li>Chamber configuration allows for some engineering calculations </li></ul><ul><li>Note that the Lab uses a low turbulence chamber – results are lower than high turbulence by 4-5 X Use for rough comparisons only </li></ul>
  74. 75. 20 Liter Chamber
  75. 76. Loaded
  76. 77. Prepared for Firing
  77. 78. Conclusion <ul><li>Two basic explosibility tests run at the Lab </li></ul><ul><ul><li>Class II – for electrical </li></ul></ul><ul><ul><li>Kst – to demonstrate explosiveness </li></ul></ul><ul><ul><li>CSHO must determine which test will best serve their needs, as only one or the other will be performed </li></ul></ul><ul><ul><li>Lab will always discuss options with the CSHO to help decision making </li></ul></ul>
  78. 79. <ul><li>Resources </li></ul>
  79. 80. Safety and Health Information Bulletin <ul><li>Purpose </li></ul><ul><li>Background </li></ul><ul><li>Elements of a Dust Explosion </li></ul><ul><li>Facility Dust Hazard Assessment </li></ul><ul><li>Dust Control </li></ul><ul><li>Ignition Control </li></ul><ul><li>Damage Control </li></ul><ul><li>Training </li></ul><ul><li>References </li></ul>
  80. 81. NFPA Standards – Dust Hazards <ul><li>654 General </li></ul><ul><li>664 Wood </li></ul><ul><li>61 Agriculture </li></ul><ul><li>484 Metal </li></ul><ul><li>480 Magnesium </li></ul><ul><li>481 Titanium </li></ul><ul><li>482 Zirconium </li></ul><ul><li>485 Lithium </li></ul>
  81. 82. NFPA Standards – Electrical & Systems <ul><li>70 National Electric Code </li></ul><ul><li>499 Classification of Combustible Dust </li></ul><ul><li>68 Deflagration Venting Systems </li></ul><ul><li>69 Explosion Prevention Systems </li></ul><ul><li>91 Exhaust Systems </li></ul>
  82. 83. Viewing NFPA Standards <ul><li> </li></ul><ul><li>Point to “Codes and Standards” </li></ul><ul><li>Click “Document List” </li></ul><ul><li>Click on standard desired, NFPA XXX </li></ul><ul><li>On bottom, click “Preview this Document” </li></ul><ul><li>Below disclaimer, click “I Agree” </li></ul><ul><li>Click “Open NFPA XXX” </li></ul><ul><li>After standard opens, the “1-2-3” button gives you the Table of Contents </li></ul>
  83. 85. Combustible Dust NEP <ul><li>Any Questions? </li></ul>