Dust Collecter / Air Filter - A Design For My Shop

MTBob

Well-Known Member
For a long time I've been frustrated with dust collection and general shop air filtration. I've used the common box Delta filter that often hangs from a ceiling with limited success. A fixed shop evacuation system with ducting doesn't work for me, much of my equipment is on wheels and too mobile to have adequate dust collection.
So, I designed a combination portable dust collector that also acts as a whole-shop air filter. Obviously, this isn't for everyone, but it's worked in my shop for over a year. Perhaps some of you will find the design concept something useful in making a filter for your shop.

Here's the unit set up for whole-shop general air filtration. It is a 6 sided box with 18"x18"x1" paper pleated Merv 8 and 13 filters in each face., except the dust collection face on the left. I chose the filter size to allow the assembly to easily fit through a door in my shop and based on needed filter surface area for particulate capture. It has a 1250 CFM commercial grade fan, exchanging the whole shop air volume in about 10 minutes. The pressure drop across the filters is monitored with a differential pressure gauge, and the fan run time is set on a 0-6hr timer. The DP gauge tells me when it's time to blow out or change the filters.
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This view shows the dual filters in each face. In the general whole-shop air cleaning mode air borne particles are first captured in the vertical face & top filters and then, secondarily, in the two lower horizontal final filters just upstream of the fan inlet. The dust collection filter face uses a stainless steel washable filter that also serves as a spark arrestor. Behind it is a Merv 8 catch filter. The catch filter is the primary collection surface for point-source capture of grinding dust or fumes from welding. I clean that filter routinely with compressed air (outside).
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This is the point-source dust collection mode, in this case sitting behind the 2x72 grinder platen, capturing grinding material coming off the belt, not direct hot sparks from the belt. Note that in this mode cardboard pieces are placed in 4 filter faces (3 side & top) to increase air flow suction at the nozzle. This arrangement also works well to capture plasma torch and welding fumes.
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In the black section of the filter is where hot sparks are stopped from entering the filter - first the intake air hits a perforated baffle to deflect and slow air flow so there's is less direct air flow on the filter face. Each hole in the baffle holds neodymium magnets as a first catch for ferrous grindings. If hot sparks get past that point, the secondary catch point is the stainless filter. I periodically pull the magnets and clean them and blow material off the paper filter with compressed air. I use this point-source mode to catch metal grindings and handle grinding materials. Most important is capturing G-10 or other hazardous particles.
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Initially I was concerned about hot sparks and fire issues with the paper pleated filters. That hasn't been a problem because the baffle, magnets and metal filter stop ferrous material before it gets to the pleated filter. I've tested the fire concern several times by having a full stream of hot sparks enter the nozzle. The magnets and metal filter stop anything from getting to the paper filter.
Typically I'll use the point-source dust catcher for various jobs during the day and then convert it to the whole-shop cleaning mode at night, letting it run for several hours after I've left the shop. This whole -shop air filter has significantly reduced fugitive dust throughout my shop.
WIP photos available.
 

Abbott

Well-Known Member
That looks real good, Bob, love the magnet idea. Damn, your a pro, nice shop!

I am working on a dust collector for my new grinder today, right after this break I am going to go cut a hole in the back wall of the shop. I like to keep the dust collector motors outside in a small water tight shed so I don't have to listen to them.

Thanks for posting the pics, shop pics are always enjoyable and informative.
 
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REK Knives

Well-Known Member
That looks amazing! I would love to hear/see more about the fan and controller and how it's fixtured on the bottom!

Which fan did you get?
 

MTBob

Well-Known Member
That looks amazing! I would love to hear/see more about the fan and controller and how it's fixtured on the bottom!

Which fan did you get?
I bought a 10" 1266 CFM FanTech fan from Zoro.com, the internet outlet for Grainger, list $591. They will often have promotions of 10-20% discounts.
https://www.zoro.com/fantech-inline-centrifugal-duct-fan-10-in-dia-fkd-10xl/i/G1419503/
I have had other centrifugal fans that have not had motors that can withstand the nasty grit environment that this setup needs. For that reason, I decided to spend more money on a commercial grade, high volume fan.
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The fan is supported in an inverted position on two hangers below the filter box. and those supports take all the fan weight. There is a transition ring between the fan and the floor of the filter box. I got the transition ring from Zoro also. I also bought a speed controller made by FanTech, though I don't often use it, mostly runs at high speed all the time.
One thing I've discovered that is an added benefit with this design is that with the fan exhaust blowing horizontal near the floor, it will tend to circulate air in the shop floor and that provides for more particulate removal when in the whole-shop cleaning mode. It also acts as a great air mover when I've really crapped up the shop with fumes, or need to move air either into or our of the shop.
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Here are a few build photos
The filter box is simply 5 angle iron frames welded into a cube.
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The Dwyer manometer has a tube that enters the fan box inside the filter cavity to measure differential pressure across the filters, giving an indication of clogging. Keeping a low* air flow rate through the filters is important for particulate removal.
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* Edit: I stated this wrong initially, the flow rate through the filters should be low for good particulate removal.
 
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REK Knives

Well-Known Member
Wow that's amazing! Thanks for sharing those wip pics... Really helps me see how it all works!

So did it have to fabricate those hangers or did you get it at zoro as well?
 

MTBob

Well-Known Member
So did it have to fabricate those hangers or did you get it at zoro as well?
I fabricated all the frame assembly including the fan supports, but bought the fan, switch, controller & DP unit. There are mounting tabs on the fan body that comes with the fan.
Here's a better photo of the fan support, one on each side.
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MTBob

Well-Known Member
I've got one of these on hand already... you think it would work?
That fan may work, but I'd be concerned about 2 things. First, the motor must be fully enclosed without the possibility of any material entering the windings. This kind of application will ruin a motor quickly, been there... done that. Next, the rated flow of the fan you referenced is 1,650 CFM, at no load. That should be more than adequate. But, the question is whether that axial flow fan (blade type) and motor have can move sufficient air through the filters. There is no pressure drop information with that fan, so it's hard to tell.
You could try mounting that fan on the side of the filter box frame instead of the bottom.
 

REK Knives

Well-Known Member
I fabricated all the frame assembly including the fan supports, but bought the fan, switch, controller & DP unit. There are mounting tabs on the fan body that comes with the fan.
Here's a better photo of the fan support, one on each side.
View attachment 76343
Thanks!! Cool I didn't even notice the tabs there on the side... I was meaning that circular fixture for the 'mouth' to fit in. Not sure how to bend angle iron haha.
 

REK Knives

Well-Known Member
That fan may work, but I'd be concerned about 2 things. First, the motor must be fully enclosed without the possibility of any material entering the windings. This kind of application will ruin a motor quickly, been there... done that. Next, the rated flow of the fan you referenced is 1,650 CFM, at no load. That should be more than adequate. But, the question is whether that axial flow fan (blade type) and motor have can move sufficient air through the filters. There is no pressure drop information with that fan, so it's hard to tell.
You could try mounting that fan on the side of the filter box frame instead of the bottom.
Ahhh good points!! Glad I had you look at it!

I emailed them to see if I can get that info...

It said it's "Totally enclosed and thermally protected motor" - wouldn't that mean it's protected from steel dust in the winding?
 

MTBob

Well-Known Member
Thanks!! Cool I didn't even notice the tabs there on the side... I was meaning that circular fixture for the 'mouth' to fit in. Not sure how to bend angle iron haha.
That is a transition fixture that I bought from Zoro when I got the fan. I can try to find the part number if that helps.
 

MTBob

Well-Known Member
Ahhh good points!! Glad I had you look at it!

I emailed them to see if I can get that info...

It said it's "Totally enclosed and thermally protected motor" - wouldn't that mean it's protected from steel dust in the winding?
If they are saying the motor is totally enclosed (like TEFC), then that should be OK.
 
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