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  1. #196
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    Quote Originally Posted by Lappa View Post
    Just make sure the neighbours washing is off the line when using the DC
    We can joke about it, but unfiltered venting of wood dust should not be done, especially in a domestic environment. In NSW the remedy for private nuisance is usually through the courts, in some other states there are acts of parliament that provide remedy and may be administered by councils. Either way, if it can be shown that you should have been aware of the possible impacts and failed to mitigate them, you won't have a leg to stand on should a complaint be made.

    12 metres of 400mm duct creates another problem, that is as the air velocity drops dust will drop out of the airstream and build up in the duct. This principle is actually used in large commercial dust systems, where a very large main duct is used with a conveyor at the bottom to collect these particulates and feed them through a rotary valve to collection hoppers. I don't know what kind of 400mm duct was considered but the affordable choice is Flexi duct for aircon, and they use filters on aircon return air inlets for a reason.

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  3. #197
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    Quote Originally Posted by thumbsucker View Post
    Lappa I think a small box on the end of the 400mm ducting may be a good idea.

    I do not understand what you are saying here:
    I am thinking about a large box/enclosure with baffles and a catch tray at the base. A manometer attached during the build will allow me to adjust the baffles to minimise back pressure.
    Re the wok. Jet added a deflection plate in the dust separator body to reduce the amount of dust and chips reaching the top filter. It looks like an upside down wok. A number of people have adapted woks and added them to their dust collectors like shown in these pictures.

    IMG_0252.JPGIMG_0251.JPG

    By all accounts they appear to work.

    I bought a wok some time ago to have a go but haven't got around to it yet.

    As to the comments that all dust collectors leak on the pressure side, I have used clamps and duct tape on all my joints and there are still small signs signs of fine dust in some areas near the filter bag but the joints away from the bag seem clean. Whether this fine dust evident is still from the filter being conditioned, or whether the filter bag will always pass fine dust, I'm not sure. Most of these bags only filter down to 5 micron.
    .IMG_0708.jpgIMG_0706.jpg

  4. #198
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    Perth
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    Quote Originally Posted by Lappa View Post
    I am thinking about a large box/enclosure with baffles and a catch tray at the base. A manometer attached during the build will allow me to adjust the baffles to minimise back pressure.
    I'm not sure why you want to adjust the back pressure? why not just go for the least back pressure possible.

    As to the comments that all dust collectors leak on the pressure side, I have used clamps and duct tape on all my joints and there are still small signs signs of fine dust in some areas near the filter bag but the joints away from the bag seem clean. Whether this fine dust evident is still from the filter being conditioned, or whether the filter bag will always pass fine dust, I'm not sure. Most of these bags only filter down to 5 micron.
    Once conditioned most needle felt bags and Pleated filters bags perform quite well even below this particle size.

    In my DC study I found that on average, Needlefelt (NF) bags and Pleated Filters (F) filtered just as well (at sometimes better) down to 0.7 microns, as they did at 5 microns
    The purple line, FFM = full face masks, the darker blue line is for RAF - Room air filters.

    Note how poorly on average cloth bags (CBs - mid blue line) and vacuum cleaners (VCs orange line) performed - their efficiencies at were negative meaning they pumped out more fine dust than they pulled in.
    Their efficiencies should be read off on the Right hand axis (RHA) where as the others should be read on the left hand axis.

    Please note that these are average vales across some 65 dust collection machines and individual results vary markedly.
    Newer, fixed in place, well maintained machines performed better than older, mobile, poorly maintained machines
    Screen Shot 2017-06-04 at 1.24.21 PM.png

  5. #199
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    Bob, please notice that I said "adjust baffles to minimise back pressure" in my post not "adjust back pressure".

    The idea being to get as much particle separation as possible with the least back pressure - hopefully none.
    Last edited by Lappa; 4th June 2017 at 04:48 PM. Reason: Additional comments

  6. #200
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    Adelaide Hills, South Australia
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    Quote Originally Posted by BobL View Post
    Very informative graph, thanks Bob.

    Sent from my ZTE T84 using Tapatalk
    Stay sharp and stay safe!

    Neil



  7. #201
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    Quote Originally Posted by Lappa View Post
    Bob, please notice that I said "adjust baffles to minimise back pressure" in my post not "adjust back pressure".
    How is minimal back pressure going to be adjustable? surely the widest opening is going to be the lowest back pressure.

    The reason for baffles is presumably to reduce noise emission or is it something else?
    If it's noise then I can understand there will be a trade off between noise and back pressure.

    The idea being to get as much particle separation as possible with the least back pressure - hopefully none.
    I'm missing something here, what exactly are you hoping to separate?

  8. #202
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    Quote Originally Posted by BobL View Post
    How is minimal back pressure going to be adjustable? surely the widest opening is going to be the lowest back pressure.

    The reason for baffles is presumably to reduce noise emission or is it something else?
    If it's noise then I can understand there will be a trade off between noise and back pressure.


    I'm missing something here, what exactly are you hoping to separate?
    I mean this in a nice way Bob.

    Rather than confusing you more, I suggest you google inertial separator - baffle design

  9. #203
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    If the baffle in the chamber is too restrictive, then back pressure will rise - not good. If the baffle is too small, then chip and dust separation will be minimal so it's a balance between the two.

  10. #204
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    Quote Originally Posted by Lappa View Post
    If the baffle in the chamber is too restrictive, then back pressure will rise - not good. If the baffle is too small, then chip and dust separation will be minimal so it's a balance between the two.
    Are you talking about inside or outside the DC ?

  11. #205
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    Quote Originally Posted by BobL View Post
    Are you talking about inside or outside the DC ?
    post #187 then #189

  12. #206
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    Quote Originally Posted by Lappa View Post
    post #187 then #189
    Thanks

    Instead of cluttering up TS interesting SHED thread I propose this discussion be take up the dust forum.

    BTW I do know about inertial separators and have used several for many years to size dust and made one last year and posted that in the dust forum.

  13. #207
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    Hi Thumbs

    2 months on, can you report how your garage shed is working out.

    Anything you would really like to change?
    regards from Alberta, Canada

    ian

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