Friday, June 7, 2013

V4.23 - Collecting dust from all over

I got a question past week that might be good to pass along to my readers. Here’s the issue: “Samples are being cut from defective units. Once the employee rough trims the pieces to approximate sizes with a circular saw they use a tile saw to finish trim them and a belt sander to clean up the edges. The samples are made from Gel-Coat, resin, wood and ½” X 1” metal bar stock. What would be the best dust collection system for this?”

In his email, he gave 3 separate issues. #1-wood, #2- not wood, #3- metal. Each of these need separate consideration. The easiest is wood. Both Delta, Jet and many others make wood dust collectors. Most units are now the single-stage style- meaning the incoming material travels right thru, and impacts, the wheel. Steel is more resistant to the material’s impact and steel wheels are what is found in the single-stage units.

With that in mind, let’s look at each: wood would be fine with single-stage units and standard bags- no issues, however, with ‘not wood’, you’d need to be concerned about the bags themselves. At its most basic, wood is a porous material- meaning if the airflow was hard enough, *some* air could pass thru it. Not so with ‘not wood’. If the inside of the bag was coated with Gel-coat or resin, the airflow would stop and either it just wouldn’t work, or the pressure would build up and cause a bag seam to rupture. Your best bet here is to just collect it in a two-stage system like Cincinnati Fan has. This was the company that Delta used to get their 50-180-series units from. You’d want your dust to just drop into the barrel and not get to the bag to clog it up. Now for metal; metal is a whole different ballgame. If you are collecting wood and metal at the same time and using a single-stage, STEEL wheel, once the wood dust got to the critical ‘lower explosion level’ of 40 grams per cubic meter of air, and a metal spark was injected into the mix, a dust explosion is a real possibility. It would be safer to use the Cincinnati Fan style, two-stage collector as they use cast aluminum radial wheels so sparking is not as much of a concern; however, if you have a pile of wood dust in the bottom of the barrel and a grinding spark of metal made it thru to that pile, you could have a smoldering fire occur. Mixing metal and combustible material is never a good thing. Metal dust collection is best handled by a dedicated unit such as Delta’s old 49-826. (for those who’ve read this far and might need a good ferrous metal dust collector, I happen to have a brand new one- never used- $4000.00 value for only $1500.00) But it will not do the multi-material collecting either. It’s not good for anything but ferrous metals.

Send your questions or comments to: and we’ll see what we can do to help you.

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