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Thread: Dust collection design for trunk line and branches

  1. #16
    Join Date
    Apr 2010
    Location
    Nashville, TN
    Posts
    1,532
    This is a larger than normal home/hobby system but is still a very small dust collection system in terms what we see in industrial applications.

    I read the other thread related to this on on the ducting. Between this thread and the other one I have a better idea of your situation.

    Since you stated in the other thread this is a one-person shop. I would suggest you run the 10HP system for the edgebander that takes the high flow, then use a smaller system for the rest of the tools. If that doesn't work for you, consider making several collection areas that would all run at the same time. Maybe you only have 3 or 4 of these areas with one of them being the edgebander.

    It doesn't make sense to use a 3000 CFM collector to exhaust an 800 CFM tablesaw. You will starve the collector and may cause surging, but its only a 10HP fan so may not be a big deal? Instead, connect maybe the jointer, planer and another tool or two so this collection area approaches your collector CFM?

    Use metal ducting whether spiral, welded, or quick clamp. You can get flanges for the spiral and welded and you should be able to get them in 10' lengths.

    I have designed numerous dust collection systems in my day job. Start with a map of your shop with the tools listed with CFM, SP, and port size. Then show your collector(s) location. Start at the tool and work back from there to the collector for each area, summing the combined airflows of the tools that would be operating for each scenario. Having 4 or 5 tools in a scenario reduces your number of scenarios versus have 17 individual considerations.

    Remember Q=VA where Q is the flow, V=duct velocity, A=duct area for any branch, submain, or main. The minimum velocity for planers, jointers, and maybe your edgebander if it produces stringy material is 4500 FPM+. For sanding dust, use 3500 FPM+, everything else falls in between. Don't worry about resizing for vertical vs horizontal runs, these velocities should work regardless. Static pressure required varies with the square of the velocity so it is also linked to duct sizing, and tool requirements.

    Typically the fan is picked last, the tools and minimum velocity determine flow and static pressure which is what is needed to select the fan. If you make a sketch, the ducting companies may be able to give you a quick static pressure calculation so you can compare to your existing fan.

    Also, Kevin is right about your filter area. It is kind of low unless you are only moving about 1200 CFM or so (10:1 AMR). It will be fine on the coarse dust, but if you do a lot of sanding, may have to change the filters sooner than you think.

    Good luck!

    Mike

  2. #17
    If it were me, I'd do 12 on the trunk and the branches, and reduce to the tool port size as close to the tool as is convenient.

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