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Conditions for Dust Explosions

Conditions for Dust Explosions. Albert Ness SAChE Workshop Sept. 15, 2008. Dust Explosion Pentagon. Combustible Dust. Confinement. (< 420 microns). Turbulence (dispersed with [C] > MEC). Oxidant. Ignition Source. Questions. Is this a dust explosion? Why or why not?. Venting.

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Conditions for Dust Explosions

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  1. Conditions for Dust Explosions Albert Ness SAChE Workshop Sept. 15, 2008

  2. Dust Explosion Pentagon Combustible Dust Confinement (< 420 microns) Turbulence (dispersed with [C] > MEC) Oxidant Ignition Source

  3. Questions • Is this a dust explosion? • Why or why not?

  4. Venting

  5. Mental / Visual Exercise

  6. Remember Dispersion Limits?

  7. Minimum Explosible Concentration • Lower limit  10 – 30 g/M3 • Polymethylacrylate  15 g/M3 • Ground Dextrose  20 g/M3 • Flour  60 g/M3

  8. Questions 18,000 • Given a 10M x 10M x 3M room • How many grams of flour are needed to be above the MEC? • How many 2.2 kg (~ 5 lb) bags of flour are needed to exceed the MEC? • How many bags of flour are needed to exceed the MEC in this room? • Does that seem like a lot of flour on the floor? 8

  9. Why do we care? Secondary Explosions

  10. What is the effect? • Poor housekeeping, and secondary explosions, heighten the damage potential • Larger portion of facility, and more people, potentially involved • Longer duration events è greater impulse è more damage to structures and equipment

  11. Housekeeping • Importance stressed and guidance provided in NFPA 654 • Dust layers >1/32 inch deep are a concern • Can be hazardous if >5% of floor area covered • Beams, ductwork, cabling, piping, walls all gather dust and should also be considered • Construct buildings and equipment for ease of cleaning

  12. Want Proof? 2008 - Imperial Sugar, GA 13 Dead, > 40 injured

  13. Q; Are these layers > 1/32 in?

  14. 2003 - West Pharmaceutical, NC 6 Dead 37 Injured West Pharmaceuticals, NC

  15. 2003 – CTA Acoustics, KY CTA Acoustics, KY 7 Dead 37 Injured

  16. Case Study – Mill / Cyclone / Baghouse Organic chips ground to 10  (Kst = 150) Conveyed to cyclone and baghouse for collection

  17. Questions • Do the conditions exist for a dust explosion? • Where? • What are potential the ignition sources? • If yes, how would you protect the system? • If there were 10 of these units in a building, how would you protect them?

  18. Our Answer

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