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Forum topic by dpjeansonne posted 02-11-2010 10:17 PM 1490 views 0 times favorited 15 replies Add to Favorites Watch
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dpjeansonne

72 posts in 2678 days


02-11-2010 10:17 PM

I built an air filtration unit from a surplus furnace blower with three inlet filters. The first filter is a coarse inexpensive washable filter followed by a pleated 3M 700 rated filter and last by an electrostaic pleated 3M 1200 rated filter. The unit is mounted overhead on a side wall about 1/3 of the way down and still closest to the biggest dust generator ( a 6×80 horizontal belt sander). It seems to work well—meaning it collects alot of dust.
I run it every time I am generating some sort of dust. I do use my Delta AP400 dust collector connected to each machine I have one at a time. I am trying to catch the dust at the machine before it gets air borne.

My problem is that I still seem to have a fine dust covering the entire shop. I just can’t seem to get rid of it.

What can I do to improve my situation? Do I need a better dust collector than the AP400, ie. better collection efficiency?

-- Cajun Don, Louisiana


15 replies so far

View Paul M Cohen's profile

Paul M Cohen

86 posts in 3242 days


#1 posted 02-11-2010 10:39 PM

My guess is the AP400 is letting fine dust into the air because it is not filtering it well enough due to its 30 micron standard filter bag. You might want to look into a 1 or .5 micro filter canister for the AP400 (I don’t know if they are available as I have a Jet).

-- Paul, Beaverton OR, www.TravelbyPaul.com

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Sawkerf

1730 posts in 2533 days


#2 posted 02-11-2010 10:53 PM

A couple of things are probably at work here.

1. Some of the dust particles you’re generating are small enough to pass thru the filters you’re using. You can reduce (but never completely eliminate) this by using tighter (higher effeciecny) filters – but they also cost much more. Even the filter bag on your DC can’t stop everything. If it did, your system air flow would become so low that it wouldn’t work at all.

2. Some dust will escape at the point of creation (saw blade, planer knives, etc.). We all wish that weren’t so, but….......... – lol

3. Unless you’ve totally sealed up the joints in the positively pressurized parts of your DC system, you’ll get some leakage. I always have a bit of very fine sawdust on my Jet 1100 cfm DC because the cartridge filter doesn’t make a perfectly sealed connection to the DC body. I could slap on some duct tape, I suppose, but that would make emptying and cleaning even more aggravating than it already is. I can live with it. – lol

-- Adversity doesn't build character...................it reveals it.

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a1Jim

115202 posts in 3042 days


#3 posted 02-11-2010 10:55 PM

You have to start by not letting most of the dust get in the air by collecting it at the source.

-- http://artisticwoodstudio.com Custom furniture

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PaulfromVictor

224 posts in 2810 days


#4 posted 02-11-2010 11:08 PM

Don,

I think Jim has the main issue, getting the dust at the source is the single best thing that you can do.

I built an air filtration unit that sounds similar to yours. I used a high velocity Patton fan, built a plywood frame around it, and installed a furnace air cleaner (Trion Air Bear) filter behind it. I am not familiar with 3M’s microparticle rating system (1200?). There are many measurements for effectiveness, but a commonly used measurement for filter efficiency is a MERV rating http://www.furnacefiltercare.com/merv-ratings.php . Initially I had hoped to use a 15 rated filter in both my home furnace and also my air cleaner. Unfortunately there is a tradeoff – loss of airflow on higher rated filters. I now use MERV 8 rated filters, but they are 5 inches deep, so there is a great deal of filter media, and in my opinion that makes a huge difference. As the filter fills with dust, it will be more effective at trapping dust, but eventually drops in airflow. The filters are about $35 a piece, but they can be vacuumed with a shop vac periodically, so they will last a long time.

I would suggest catching as much dust at the source as possible, and also getting a filter with deep baffles of media. If you can, keep the air intake side of the filter towards the dust source that will keep it from being blown before it is filtered.

Finally, get a broom. Dust happens.

Good luck.

View Ole's profile

Ole

67 posts in 2541 days


#5 posted 02-11-2010 11:21 PM

From what you’ve written it seems that you only have it running while you’re generating dust. This might be redundant, but do you let it run after you’ve finished using power tools? Commercial models often come with a timer.

View dbhost's profile

dbhost

5607 posts in 2697 days


#6 posted 02-11-2010 11:24 PM

To boil it down for you, dust control consists of, dust collection (getting it at the source, and keeping it out of the air) and cleaning up what you missed…

Now first priority is to keep it out of the air in the first place, start at proper dust hood designs. If you are necking down the 4” port on a cabinet saw, chances are REALLY good you won’t be moving enough air to do any good at all for example… Make sure your dust hoods are configured to best capture the dust, and get it in a big enough duct…

Next is the hose / duct itself. Assuming you are moving machine to machine, use as short of a hose as physically possible, every rib in the hose slows the air down… Also keep it as straight as possible. Bends slow air down too…

Once you get to the dust collector, you need to keep the air flow going, while not allowing the dust and debris load to get simply pumped back out in the air, which is where I think you are having trouble. As others have said, the AP400 has a 30 micron filter. This is then simply a dust pump, moving that fine dust back up and spreading it in the air… Add a proper 1micron or better filter and you will notice a huge difference… In order to keep air flow up, you will want to separate dust / debris out as much as possible prior to getting to the filter. A Thien separator works great for that…

To be honest, the AP400 is a bit on the smallish side, you might want to upgrade to a 50-760 or similar DC to get the performance you want…

-- My workshop blog can be found at http://daves-workshop.blogspot.com

View dpjeansonne's profile

dpjeansonne

72 posts in 2678 days


#7 posted 02-12-2010 08:50 PM

To respond to various comments made,
Before building my filtration unit I did some digging into filter ratings. I was able to finally get someone at JDS to say that the filters they use are equivalent to a MERV rating of 6 and 14 in their two stages. I also found that the 3M Filtrete pleated filters that are sold for home ac/furnaces are :
3M rating equivalent MERV
600 8
1000 – 1250 11
The HEPA filters are in the range of MERV 17 – 20 which I think is way beyond what is needed in a shop environment.

I do run the filtraion long after I stop generating dust but still have this light accumalations.

I am using some short runs of 4” pipe for a few tool collection but only one at a time. I think it is okay even though not the best practice.

I really suspect that the Delta AP400 is marginal for me and the problem is the poor collection efficiency ie. 30 micron particle size. I don’t have any confirmation of what the bags provided can actually do.
I think I will look into upgrading to a 5 or even a 1 micron bag or filter.

-- Cajun Don, Louisiana

View MedicKen's profile

MedicKen

1610 posts in 2927 days


#8 posted 02-12-2010 09:16 PM

These are probably some of the best on the market. http://store.oneida-air.com/retrofitfilterbags.aspx

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View Bob42's profile

Bob42

456 posts in 3255 days


#9 posted 02-12-2010 09:36 PM

One other thing to consider is how well are filters sealed in the frame you made? some smaller particles may be by passing the filters. You should run the system for hours after your done. Most have the right idea of capturing at the source with the proper sized filtration unit and filters. dbhost seems to be right on. The more efficient filters do clog faster and need to be changed more often. I had my own air filtration co. years ago and would help you along but I will be away the week of 2/14. PM me If you want and when I get back we can talk.

-- Bob K. East Northport, NY

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ardbeg

102 posts in 2492 days


#10 posted 02-12-2010 10:11 PM

I would look here http://www.highlandwoodworking.com/search.aspx?find=shaker+felt for some nice replacement filters that are far cheaper than the Oneidas.

-- You may delay, but time will not. --Ben Franklin

View TomHintz's profile

TomHintz

207 posts in 2863 days


#11 posted 02-12-2010 10:36 PM

The best thing I ever did for my shop was lose the 30-micron bag DC unit and replace it with my Powermatic with a 1-micron canister filter. The dust in my shop went from awful to nearly nothing all at once. I have much better DC performance at my machines as well because the PM DC has way more capacity inhaling and it’s canister actually keeps the dust in, not just spr4ead it around like the 30-micron unit did.

-- Tom Hintz, www.newwoodworker.com

View dbhost's profile

dbhost

5607 posts in 2697 days


#12 posted 02-12-2010 10:42 PM

Those Powermatics are really nice, but you don’t have to spend that much. A Harbor Freight #97869 2HP DC, fitted with a Wynn 35A paper blend filter will do just fine. ($140.00 for the DC after coupon, $110.00 I think for the cansiter filter). I have that setup but with the spun bond filters instead of paper (the paper filters at .5 micron, the spun bond at 1 micron, but it releases dust better…), and my dust went from awful, to nearly non existent once I went that route… (I keep forgetting to hook up my shark guard, not the DCs fault…).

-- My workshop blog can be found at http://daves-workshop.blogspot.com

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Bob #2

3809 posts in 3486 days


#13 posted 02-13-2010 02:41 AM

I note your tag line suggests you are in Louisiana.

Open a door or a window and blow the place out once in a while.

I’d kill for that but it’s -19 ° C today.

-- A mind, like a home, is furnished by its owner

View 459fitter's profile

459fitter

30 posts in 2530 days


#14 posted 02-13-2010 08:06 AM

If you can relocate the DC outside temporarily to determine if the fine dust in the air is coming form the DC or lack of collection at the source. Also even though your air filtration unit seems to move a lot air it may be not enough. Most residential furnace fans move at best with the filtration you described maybe 1000 CFM, seems like a lot until you figure the volume of your shop. 20’ x 20’ 10’ ceiling is 4000 Cubic feet or 4 minutes to process the same volume or air. That said in 4 minutes of run time you are far from processing ALL of the air in your shop, maybe something like 30 min to an hour to effectively filter the entire volume. I am sure that there have been many a wood worker try to calculate the half-life of sawdust (how many times you can divide a given amount of sawdust in half until you have a negligible amount) with little luck. Even the finest cabinet shops will have that fine dusting on top off their shelves. By the way are we all just trying to make a little dust anyway? Good luck with catching the elusive floaties!

Andy

-- Andy ---- Missoula, MT

View AWood's profile

AWood

49 posts in 3211 days


#15 posted 02-13-2010 02:05 PM

I am now looking at my dust situation in my basement shop. I have been weighing the cost and benefits of something like the 2 hp Oneida system (dealing with single micron numbers for dust particles). I spoke with a retired cabinet maker and he referred the Oneida to me.It is pricey but I am assessing the cost, the benefits, and the comforts of a clean shop over the frustration and time spent on the “conventional blower bag system”.

-- AllWood

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