Distributing Dust and Shavings in a Long Bin

      Ideas from experience for augers, paddles, or blowers to spread out shavings from the dust collector system through an entire large bin. March 4, 2009

Question
It is time to plan for dust collection for our new building. Due to zoning restricts, we will have most, if not all, inside the building. 8,800 s/f, up to eight people, and mostly solid woods.

We currently have the biggest Oneida fan and filtration, and it has worked well for eight years (four man shop). We want to reuse it, put the fan before the cyclone, and use a rotary air lock to drop shavings into a big, roll-off type dumpster.

My questions are: Am I dreaming when I think about a horizontal auger under the RAL to distribute shavings along the 20' long dumpster, all under a shallow, gable tarped, close fitting cover? Where have I seen this? How would this large dumpster be rolled out for pick-up without destroying the floor? Does anyone have any other ideas or advice out there?

We have a four head molder than can generate four yards of shavings in a few hours, so the smaller 3-4 yard dumpsters are out. Besides, dumping them inside or outside the shop will defeat the purpose of good collection and eat up time.

We currently drop shavings into an airtight bin and auger out the bin twice a week. Two men, twp hours x 52 x 65/hr = $13,000/yr ! So, I'm looking for something with much less involvement on our part. I've already paid for it, so to speak.

Forum Responses
(Dust Collection and Safety Equipment Forum)
From contributor J:
When we designed our new indoor system I wanted to use a conveyer or auger to transfer shavings. Dantherm has a slick but expensive paddle conveyer to do this. They told me the less expensive screw conveyers can work under certain conditions but molders are always a problem with these. We transfer to two locations (briquette press in winter and outside bin in summer) so the conveyer was getting complicated and pricy. We ended up with Belfabs pneumatic transfer system. These can go into roll off dumpsters, but they have to be covered and pretty much airtight.

I assume with your inside system height is a problem, so you cannot put the dumpster under the RAL and keep moving it. Orange box makes a 10 yard fork able tilt dumper that can have wheels. Are you paying a trash service to haul the roll off? I have always tried to put the shavings to a use but in reality paying to have it hauled might be the most cost effective when you figure all costs.

I am still trying to decide about the outside bin and like you we have zoning, noise, height and appearance issues. We are in a rural area and can get rid of shavings if they can be hauled or loaded. I know millwork shops in the cities usually have people that will haul loaded semi trailer boxes or containers off. A lot of shops here use 12’ dump trailers with a 20 yard box. The trailer is connected to the pneumatic system. 2 trailers work best. These cost around 6K each with the box built. Less if you find a used trailer. One shop here bought a used dump truck and parks it under the RAL. Huge amount of height required for this. I found plans on the internet for a pneumatic fed bottom unloading clamshell door shavings bin. These are around 30 feet high but have 100 yard capacity.

I am even considering a 75 yard capacity concrete silo that I can drive our skid steer into for unloading. Like you mentioned about unloading five yard dumpers this gets time consuming and dusty. A self unloading silo is what I would like but these are out of the cost range for our size shop.

No good answers for you but maybe more things to think about. I would also like to hear some more ideas for 20 yard plus bins that can be unloaded or hauled easy.



From contributor S:
The best system will be the one that lets you handle the dust with by itself. Puts it where you want the dust to go without having anyone to move it, handle it, or clean it out. I have been through all types of dust collection. We have a blower cyclone combination. A rotary airlock installed under the cyclone. The dust goes through the airlock and drops into a small bin/pipe. On one end of the pipe we installed a small blower with a VFD to control the speed, and on the other a hose. The dust simply falls into the pipe and the aux blower blows the dust where ever you want - in our case a semi trailer. All I have to do is pull the hose out when the trailer is full. You could easily do the same. I have seen people just get a tarp and blow the dust into a dumpster.


From the original questioner:
Good ideas, all. We are hamstrung by local authorities that will not allow dumpsters, trailers, dust or shavings in their community, much less standing on our property. Dumping a 10 yard dumpster into a larger dumpster not only involves more handling than we want, but also will stir the dust up - inside or outside. But, they all want our products - a familiar story - eh?

My thought is for something that is as passive as possible, and gets hauled away on cue. A large, tight fitting tarp on frame, suspended over a dumpster, with something to distribute the shavings evenly inside the bin (passive - no remembering to move a hose around), all raised by a motor lift, and hauled away.

We do have 20' high ceilings in most places, so can accommodate a lot, height-wise. I don't know if the dust cover thing is imaginary or real, and I don't know how to move the large dumpster (6' x 20') in and out of the building. We will pay an as yet to be determined amount since the waste haulers want the shavings for absorption. But we still have dumpster rental and haul charges. Anytime you blow shavings (air) into a box/truck/bin you have to exhaust somewhere, and unless this exhaust is filtered, we will have dust coming out and the town will go beserk, the phone will ring, and we'll be back to the drawing board.



From contributor G:
You can blow your dust into an enclosed bin without a dusty mess. The bin needs to be fairly airtight. One hose directs the blower into the bin (how about a roll off) and another hose or pipe brings the return air back to the fan. It is called a closed loop system. The system is usually under a rotary air lock. It’s very simple and effective. We blow into a semitrailer with a 5hp blower and it works great! I will never mess with augers again. The trailer is outside but I don't know why it wouldn't work in an indoor application if you have the room.


From contributor J:
Contributor G is correct that a pneumatic closed loop transfer system is clean if done right. In the case of our Belfab the V shaped airtight hopper under the collector drops the shavings into the closed loop. If the pipe, bin or trailer are tight it should be dust free. I think when this system is used with a RAL the collection hopper under is sealed off also. The shop I mentioned that pipes alternatively to 20 yard trailers get a little dust on the ground when they change hoses. Not enough to worry about. The enclosed paddle conveyer system from Dantherm is slick but will cost two to four times more than the closed loop transfer.

Enclosed roll off dumpsters are available. I don’t know about moving or loading these in a shop. They would have to back the semi into the shop. Belfab said I could have up to 100 feet plus of total pipe. Maybe you could place the roll off in front of a door.

Contributor G – when loading the semi trailer do you have to move the pipe or hose as it fills? Do they dump it by loading on to a flatbed dump truck? This could be a possibility for my outside bin. Just don’t know how I would get it moved or dumped.



From the original questioner:
This is getting better. When I think of a blower into a bin, I see the various shops around here that just blast it out, with no enclosures, and it goes everywhere. We don't think we can park a roll-off outside, but we have both a dock and level overhead door for ins and outs. I'm thinking about a large roll off pushed far enough into the building so as to not block the flow, but easy to winch out for hauling. This would be easy to utilize a closed loop system as you describe.

This brings up further questions: How does one move around one of these big dumpsters? I picture a little fork truck spinning tires. Won't the dumpster rollers (only on one end) scar up our virginal new floor?

Can I buy one of these things? We used to get random four yard dumpsters, but some really were - shall we say - odiferous? I protested and worked it out where we have the same, clean dumpster every time. This would become more important once we move this baby inside and get to live with it.



From contributor G:
We blow into a 48" semi trailer. A spiral pipe is fastened to the ceiling on the driver’s side that extends half way to the front. I am surprised how well the small 5hp blower (most use a lager blower) fills it up. We thought we would have to remove the pipe as the trailer fills but the airflow changes and circles towards the back of the trailer. The person who owns the trailer empties it and I do not know how. Most sawdust trailers have a walking floor that move the dust out the back. His does not. Small wheels on a roll off could be a problem. They are not made to actually move it around. I would begin by talking to the hauler. Off course a straight truck size would be easier to handle than a semi sized. The hauler should have some suggestions. Worst case is to have one custom built. May sound pricey up front but may be best in the long run. I was involved with the local county recycling program when they switched to roll offs distributed to various sites. They were custom built for the county by a local metelfab shop and work great.


From contributor S:
We have built something similar to what you describe in your posted question. I took an old dump truck box and it is mounted on an different dump truck frame that was modified so that a tractor could pull it. The box actually dumps as well with the Tractor Hydraulics.

We then mounted an open auger flighting just under the ridge poles of the dump truck box. We then had a custom made tarp that has an attached "sock" that we slide up over our 10" downspout from our Rotary Air Lock on our NR Murphy Baghouse.

When the wood shavings come down the spout, the first build a pile and then the open auger flighting continually pushes them forward until the entire wagon/box is full. We also installed a Lexan viewing window at the front upper corner of the box so that we could monitor its level.

I hope this info helps; I realize though that you are using slide off boxes. Another option would be to contact MacDonald Steel; they offer slide off box covers that do exactly what you are wanting to do.



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