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4th June 2017, 01:21 PM #196Senior Member
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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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4th June 2017 01:21 PM # ADSGoogle Adsense Advertisement
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4th June 2017, 02:19 PM #197Woodworking mechanic
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- Jan 2014
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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
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4th June 2017, 04:36 PM #198.
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- Perth
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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.
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
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4th June 2017, 04:39 PM #199Woodworking mechanic
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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
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4th June 2017, 07:34 PM #200
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4th June 2017, 08:38 PM #201.
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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.
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4th June 2017, 08:44 PM #202Woodworking mechanic
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4th June 2017, 08:54 PM #203Woodworking mechanic
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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.
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4th June 2017, 09:40 PM #204.
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5th June 2017, 08:06 AM #205Woodworking mechanic
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5th June 2017, 09:22 AM #206.
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12th August 2017, 12:01 AM #207
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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