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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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Conditions for dust explosions l.jpg

Conditions for Dust Explosions

Albert Ness

SAChE Workshop

Sept. 15, 2008


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Dust Explosion Pentagon

Combustible Dust

Confinement

(< 420 microns)

Turbulence (dispersed with

[C] > MEC)

Oxidant

Ignition Source


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Questions

  • Is this a dust explosion?

  • Why or why not?


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Venting


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Mental / Visual Exercise


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Remember Dispersion Limits?


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Minimum Explosible Concentration

  • Lower limit  10 – 30 g/M3

    • Polymethylacrylate  15 g/M3

    • Ground Dextrose  20 g/M3

    • Flour  60 g/M3


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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


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Why do we care?

Secondary Explosions


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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


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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


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Want Proof?

2008 - Imperial Sugar, GA

13 Dead, > 40 injured


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Q; Are these layers > 1/32 in?


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2003 - West Pharmaceutical, NC

6 Dead

37 Injured

West Pharmaceuticals, NC


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2003 – CTA Acoustics, KY

CTA Acoustics, KY

7 Dead

37 Injured


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Case Study – Mill / Cyclone / Baghouse

Organic chips ground to 10  (Kst = 150) Conveyed to cyclone and baghouse for collection


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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?


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Our Answer


  • Login