Container-Bin Dust Collection Setup

      Shop owner describes a site-built rig for capturing dust and shavings using filters and a tarp on top of a shipping container. January 21, 2007

Question
I run a small lumber manufacturing company with 2 moulders, a planer and a rip saw. Our DC is a 10,000 cfm central blower system which discharges into a 8'x20' shipping container at the top of the container's rear wall. I cut two 2'x2' exiting air vent holes in that rear wall but I'm getting way too many wood chips and finer sawdust, too. I'm considering installing about 15 to 20 of the filter bags (24" diameter x 42" high) on the flat roof of the container and building a roof on top of them to keep the rain off. We don't have a cyclone and don't want one. I'm hoping the bags will be all the filtration we'll need. I guess the whole thing will look kind of like a shoe box with a bunch of upside down cups on the top. Any ideas?

Forum Responses
(Dust Collection and Safety Equipment Forum)
From contributor D:
And why don't you want a cyclone? Sounds like the issues you're addressing would be solved by one properly set up. Having that container with bags under positive pressure must be a pain.



From contributor B:
Doesn't add up - a cyclone would be so much easier. Maintaining the bags even if covered from the rain would not be easy. For starters, they need to be shaken to keep the stuff off the sides and then there will be a mildew problem. With a cyclone separating the material, most likely you could simply exhaust the air. Sounds like you are not re-claiming it anyway.


From the original questioner:
I wouldn't mind a cyclone except for the following problems:

- The wood shavings bin is very close to the property line (hidden by a tall fence) and installing a 20' high cyclone on top of the 9' high container would draw a lot of attention in my city location.

- I'm told that cyclones alone are not allowable in city locations anymore and must be combined with some sort of secondary filter.

- A cyclone would dump the shavings into one pile in the container, which would require periodic spreading by someone with a shovel to prevent a big clogging backup; the big baghouse design we're working on shoots the shavings in at 4500 fpm so they can be dispersed more evenly throughout the 8x20 container. Down the road, we may even have to add another 8x20 container to the front of this one for additional storage capacity if the shavings accumulate before we can get people to haul them off.

- We've talked to the folks at American Fabric Filter Co. in Florida and they say they have a polyester fabric bag that looks like a heavy linen tablecloth which has excellent airflow (90 cfm per sq.ft.) and is very slick and will not retain moisture, although it will require at least a shed roof over the container. They say the bags last about 4-5 years. Your thoughts please!



From Curt Corum, forum technical advisor:
Everything that the guys have mentioned previously is proper and valid. I have had customers in rural areas in similar situations. Sounds crude, but they covered the escape opening with burlap. It's inexpensive, weathers well, holds in all the chips, and emits some fines.

Ten thousand CFM through the 2'x2' opening is discharging around 2,500 FPM velocity. If you make it 1' larger, the discharge velocity would be around 1,750 FPM, which would be a little less restrictive.



From the original questioner:
Here's what I've done so far. I've ordered 12 metal rings of 24" diameter x 6" high and we'll bolt them to the roof of the container and then cut out the center portion. While waiting for the 12 filter bags to arrive, we'll cover each hole with a high durability vinyl-like insect screen from Home Depot. That should get us by for a while. Who knows, it may be enough surface area so that the screens don't clog up (plus they'll be on the ceiling of the container) and the dust particles may be small enough to live with.


From the original questioner:
Okay, here's what has happened! It worked pretty darn good! Since I last wrote, I tried the insect screen material at Home Depot... no good. It let through way too much dust. I went to a fabric store and bought a nylon sheer window curtain material (about $4/sq.yd) and covered each of the 12 holes, securing them with really large hose clamps. It worked great!

Just fine dust was coming out, so to dampen that a little bit more and rainproof the holes, we put a tarp over the top of the container and tied it off with ropes. So now, when we run the blower, it poofs the tarp up about 12" and the dust that comes through the fabric settles down on the sides of the container instead of drifting all over the business park.

What's good about this solution is that the filter material is very cheap and I didn't have to build a roof structure over the vent holes, just drape a tarp! Some clogging has occurred in the fabric, but we brush that from time to time and no big deal.

By the way, I did finally get some of the bags from the supplier today via UPS and some are still on backorder. Once I get them all and a chance, we will build a covered wagon style roof over the container and install them, but I'm not in a big rush anymore because I can function.

Regarding wood shavings disposal, I placed a free ad in the local classified section of our newspaper last week and have had two people come by to load (themselves) at least a pickup truck load of our cypress/pine wood shavings. The only drawback so far is that they won't be able to load shavings when we're running the blower.

Oh, one other thing I learned. Our 25hp blower motor was drawing way too much amps because it had way too much airflow, we estimated about 10,000 cfm. I blocked all the unused pipes off, effectively cutting the cfm in half, and the amps went way down, from 128 to 90, which is barely acceptable for that size motor. The long term solution I'm told is to get a bigger motor to handle the 10,000 cfm that the blower and pipes will allow.



From the original questioner:
We've been using the dust collection container for a month or so and it's been doing pretty well. The 8x8x20 container fills up pretty quickly though! We placed a free classified advertisement in the two local papers and have found a couple of good ole boys who are more than happy to keep the container cleaned out.

The filters have worked pretty well, although they do get clogged. We finally got our real filter bags in the mail but haven't installed them yet because we have to build the little 4' high shed roof over the container first. I think the temporary filters get clogged quicker when there's more wood shavings in the container. Just an update to let ya'll know that this system will work if you don't want to or can't build a cyclone style where you work.



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