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Wet Dust Collectors

Safety in collection of hazardous dust is of prime importance to your employees as well as your facility investment. Whether the application is combustible dust of aluminum, titanium or magnesium or your are just tired of fires from heavy grinding, w wet collector is most likely the best economical answer. Standard systems range from 800 to 10,000 CFM with options such as conveyors, cyclones, and liquid filtration systems. Wet dust collectors include stand alone unites to self contained downdraft tables to wet environmental dust booths.

Advantages of a wet dust collector include:

  • Safety. The best reason for using a wet dust collector in a metal finishing operation is peace of mind. Dry dust collector can and do catch fire. Work environments always include dust and lint that is pulled into hoods and ducting during normal use. At any time a ball of lint that is set fire by just a spark can travel to the filter system and ignite more fuel as the fan supplies abundant oxygen.
  • No replacement filters required.
  • No compressed air required.
  • Dust collectors for volatile dust may be placed inside building.
  • filtered air may be re-circulated for savings on cooling and heating costs

The NFPA 484 standard applies to the production, processing, finishing, handling, recycling, storage, and use of all meta and alloys that are in a form that is capable of combustion or explosion, as well as, operations where metal or metal alloys are subjected to processing or finishing operations that produce combustible powder or dust.

 

Here are some of the “Do’s and Don’t’s” relating to dust collection systems and collector design:

  • Do connect all dust producing equipment to hoods that capture and transport the dust.
  • Do keep your duct velocity at 4500 feet per minute.
  • Do use metal, not plastic, dust and keep the dust system simple and smooth, with seams downstream and as straight as you can.
  • Do bond and electrically ground all the machines, the dust, and the dust collector itself.
  • Do not mix the buffing-polishing with the grinding.
  • Do not allow the minimum explosive concentration (MEC) of the dust to occur. (This is a problem with vacuum cleaners)
  • Do not install any dead spots or ports for future use.
  • Do not mix any other metal with Aluminum in a dry collector or in any ducting.

Wet Dust Collector – Minimum Design Features:

  • The blower must be on the clean side.
  • The collector cannot have any un-vented pockets (hydrogen)
  • The efficiency must be high if you plan to recirculate the air.
  • The wet unit should be as close to the dust generation as possible.
  • No after-filter are allowed (for Aluminum)
  • Mix the sludge with dry clay (kitty litter) to make sure it is safe, i.e., to prevent it from overheating and giving off hydrogen.

What are the basic dangers?

The dangers involve the risk of fires and explosions. Here are a few real world examples:

  • A dry downdraft table used for Aluminum finishing is set on fire when a employee sharpens a knife on lunch break.
  • A young man is burned badly when he uses a bench grinder normally used for Steel to grind away aluminum rivets.
  • While sanding Aluminum parts, a worker is badly injured when a small collector with a Steel blower wheel on the dirty side of the filter explodes.

Other examples of potential dangers include:

  • Aluminum and Steel together burn very hot and are used in the military to melt away Steel parts in the field. Mixing the two metals can be very dangerous.
  • Steel parts or Steel grating in the workplace where Aluminum or Magnesium grinding occurs provide a high risk of sparks.
  • Common shop vacuum cleaners can be very dangerous due to the likelihood of creating an explosive fuel/air mixture in the vacuum hose and in the canister. If a static charge spark occurs, the risk of explosion is high.

 

The Importance of Wet Dust Collectors is highlighted by the NFPA Article Below:

Summary of NFPA 484 Standard for Combustible Metals 2009 edition