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Workshop dust extraction plan

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TFrench

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One for the hive mind of UKW. My current DX setup is a kity 0.5hp with a thein seperator and fine bag. Just has a flexible duct so I can connect it to anything I put near it.
Kity extractor
It works very well - the baffle catches virtually everything. However, its taking up a lot of space and if I'm thicknessing the barrel fills quickly. I got this big 2hp jobby a while ago as part of a job lot, when I realised it was single phase I thought I'd keep it to upgrade mine.
New extractor
It's quieter and a lot more powerful. I've been thinking and I think I've come up with a way of making it work. Excuse the rough drawing, its not my strong point! :lol:
Extraction plan
My workshop is in 2 halves, I plan to put the extractor in the back corner mounted to the wall, with a bigger barrel and thein seperator beneath it, 5" galvanised duct around the walls to where I need it with blast gates on the ends. The exhaust side will go into the loft where I will mount the bag filter to the wall. My main worry is do we think a 2hp extractor is up to the job? Any other critique welcome!
 

Inspector

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To get an idea of what kind of losses your ducting would have I played with an online calculator. With 43' (13M) of ducting a couple elbows using 750 CFM which is close to what a 2hp can draw you have 5+ inches of static pressure, that doesn't include the separator losses of approximately 4+ inches or the effects of the filters. If you had a fan curve for that DC you'd see that at at that level of static pressure losses you would have under 200 CFM of airflow. For proper collection of dust at a machine you should have 800 CFM as a minimum and a 5" pipe can't support that flow. You need as a minimum a 3hp DC and 6" pipe with a 5hp cyclone being best.
http://www.freecalc.com/ductloss.htm

You've probably see people recommend reading Bill Pentz's site as he did extensive work on home shop sized dust collection. I suggest the same. There is the information there for fabrication of a cyclone yourself which will separate better than the Thein and you'll only loose a touch over a couple inches of static pressure to it. The spreadsheet will spit out the dimensions when you put in your impeller information. There is also a spreadsheet for calculating duct losses. http://billpentz.com/woodworking/cyclone/index.cfm

With the system you have and propose you should be wearing a cartridge mask almost all the time.

For what it's worth I am putting in a Clear Vue-Max 5hp, 16" impeller cyclone (Bill's design) and my hobby shop is 24' x 28' (-60 metres). I hate dust. :evil:

Pete
 

TFrench

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Damn. I thought it would be close but I might get away with it. The idea behind me exhausting in the loft space is to keep to fine particles from the filter out of the workspace - I only use it for storage up there. Can't vent to outside as I've got neighbours who probably wouldn't be impressed! Guess I'll have to look properly at making a cyclone.
 

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Sorry to be the bearer of bad news.

Having the filters in the attic is a good idea if the shop isn't heated with a furnace or wood stove etc. The air removed by the DC will have to come from somewhere unless there is make up air of some kind to keep from back drafting through the heater's exhaust bringing carbon monoxide with it.

If you do build a good cyclone you could have it all in the attic except for the collection barrel that can be in the shop below. Then you don't have to get the shavings out of the attic. If the headspace in the attic is restricted the cyclone can be mounted on an angle to match the roof. It will still work the same. The Pentz cyclone can be made of almost anything, not just sheet metal. I think bendy plywood or staved like a barrel would work and I know of a New Zealander that made one from fibreglass.

Pete
 

will1983

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I made the chamber of my Thien separator from 6mm ply strips all staved together.

It works pretty good but I may remake it at some point out of clear plastic just so I can see the muck spinning round inside!!
 

TFrench

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Thats why I put the window in mine! (1st pic) You can also see when the can needs emptying as well.
 
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