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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

Conditions for Dust Explosions

Albert Ness

SAChE Workshop

Sept. 15, 2008

dust explosion pentagon
Dust Explosion Pentagon

Combustible Dust

Confinement

(< 420 microns)

Turbulence (dispersed with

[C] > MEC)

Oxidant

Ignition Source

questions
Questions
  • Is this a dust explosion?
  • Why or why not?
minimum explosible concentration
Minimum Explosible Concentration
  • Lower limit  10 – 30 g/M3
    • Polymethylacrylate  15 g/M3
    • Ground Dextrose  20 g/M3
    • Flour  60 g/M3
questions9
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

what is the effect
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
housekeeping
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
case study mill cyclone baghouse
Case Study – Mill / Cyclone / Baghouse

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

questions18
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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