Industrial Division

Combustible Dust Testing & Remediation Consulting

Maintenance and Housekeeping

  • Develop and maintain a housekeeping program (this is something OSHA inspectors are checking for).
  • Replace mops, brooms and blow guns with more effective cleaning tools/practices. These products push dust around without removing it and can create dangerous dust clouds.
  • Limit/reduce the amount of overhead horizontal surfaces (racks, piping, ductwork, drop ceilings). These areas are hard to clean and trap dust.
  • Make sure equipment is grounded to avoid electrical and static sparking.

NFPA 654 (2013 version) will include a Safe Housekeeping Hierarchy

  1. Vacuum dust with a certified vacuum that is bonded and grounded, so it doesn't become an ignition source.
  2. Where the vacuum cannot reach, conduct a water wash down or carefully sweep with a broom in a manner that does not stir up dust.
  3. Finally, if the previous two measures are not effective, cleaning with compressed air is permissible only in small areas with operating equipment shut down.

Source: Feed & Grain, 2012

  • vacuuming horizontal surfacesUtilize vacuums for source capture and as portable suction devices to prevent fugitive dust from accumulating.
  • Make housekeeping as easy and ergonomic as possible by using lightweight, adjustable tools, flexible hoses, and overhead cleaning accessories.
  • Keep dust below 1/32" on horizontal surfaces as directed in OSHA's NEP.
  • Inspect all equipment (especially older) for possible ignition sources and for needed deflagration venting upgrades.

Duct Design

  • Ductwork should be as short and straight as possible
  • Ductwork must be made of conductive material and have a smooth interior
  • Duct velocities must be 4500 FPM
  • There cannot be any unused capped outlets, pockets, or dead end spaces
  • Additional branch ducts cannot be added unless a redesign of the system is performed
  • Duct system along with machinery, hoods and collector must be bonded and grounded
Particles are suspended
Air velocity at least 4,500 ft/min
particles suspended and flowing
Entrainment is what you need!
Build-up of dust particles
Air velocity less than 3,500 ft/min
particle build-up and not flowing

Make sure that your collector systems are capable of moving all dust under all conditions. Velocity flow of 4,500 feet per minute is considered adequate to keep dust moving and also pick up any dust that falls out due to unexpected interruption of operation like a breakdown or power outage. This kind of velocity pressure will also keep the density of the dust below explosive concentrations. Sufficient air velocity in ducts will ensure: particles remain suspended and reach the dust collector and that if particles fall out the velocity will be sufficient to provide re-entrainment. Insufficient duct velocity will result in particle build-up in ducts.

Poor duct designDucts should be kept short and straight to get the maximum flow of air through them. Do not add additional branches unless you do a management of change redesign of the system. No dead ends or unused caps that could cause an accumulation of combustible aluminum dust. The whole system must be grounded and bonded to ensure dissipation of static electricity.

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