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April 12, 2021
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Dust Explosion Prevention Hierarchy

The Dust Explosion Prevention Hierarchy provides effective strategies to prevent combustible dust explosions.

The strategies are listed in order of effectiveness.

Eliminate

  • Avoid installation of horizontal surfaces where dust can accumulate.
  • Eliminate hidden areas where dust can accumulate.
  • Eliminate the use of compressed air for cleaning surfaces.
  • Eliminate point sources for fugitive dusts (i.e., leaks, patches, etc.).

Substitution

  • Install smooth ceiling and wall surfaces (instead of rough finish) to minimize dust accumulation and allow effective cleaning.
  • Install enclosed conveyance systems to replace open systems.

dust_hierarchy.jpg#asset:153181

Engineering Controls

  • Install dust collection systems at transfer points, truck receiving/loadout areas, inside bucket elevators, conveyance, etc.
  • Locate dust collectors (baghouses) on the exterior of structures/buildings. If located inside a structure, ensure dust collectors and baghouses are adequately vented and have adequate fire separation and/or explosion suppression. Always direct deflagration venting away from areas that are occupied by employees.
  • Ensure proper electrical classifications are used when installing or retrofitting equipment (i.e. Class II).
  • Install hazard monitoring (motion detection, belt alignment, bearing temperature monitoring) on bucket elevator legs and conveyance.
  • Install deflagration suppression systems on bucket elevator legs.
  • Install deflagration suppression systems on interior dust collection (i.e. baghouses).
  • Install oil-addition systems (food grade) to reduce dust levels.
  • Pressurize interior areas to reduce fugitive dust.
  • Prevent tramp metal from entering the product stream by using magnets and properly-sized grating at receiving areas.
  • Install magnets to remove metal from the process flow.

Administrative Controls

  • Develop and implement a combustible dust inspection program to identify housekeeping opportunities.
  • Develop and implement a written housekeeping program that defines the responsibility, frequency, and acceptable methods for cleaning.
  • Develop, implement, and enforce a hot work program.
  • Develop, implement, and enforce the "No Smoking" policy.
  • Educate employees, contractors, visitors, and drivers on the hazards of combustible dusts including common ignition sources such as smoking.
  • Implement cleaning techniques that minimize placing dust in suspension.
  • If using compressed air for cleaning, implement a permit system that requires the elimination of ignition sources during cleaning activities.
  • Develop and implement a documented preventive maintenance program that defines the types of equipment inspected (bucket elevator leg, drying equipment, conveyance, dust collection, etc.), frequency of inspection, inspection elements, etc.
  • Develop and implement a routine inspection program to identify point sources of fugitive dust to include bucket elevators, distributors, conveyance enclosures, dust collection equipment, spouting, etc.
  • Develop and implement a program for inspecting and cleaning magnets.

- Originally published Sept. 24, 2018.


Source: Joe Mlynek is president of Progressive Safety Services LLC, Port Clinton, OH: joe.mlynek@progressivesafety.us, and content creation expert for Safety Made Simple Inc., Olathe, KS; joe@safetymadesimple.com.


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