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.
- 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!
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.
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.
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.
