Venting Dust Collection outside without a cyclone

[Eyrich Stauffer]

Hi- First post on Sawmill Creek. I have enjoyed and learned quite a bit reading the site over the last several years- thanks!- but I couldn't find an answer to the following. I am revamping my dust collection system to vent to the outside (I've have read all about the pros and cons from heat loss, to CO2 to air quality). Most folks who vent outside still seem to use a cyclone to collect the big chips. My plan is to forgo the cyclone / bags /barrels / change over and down time and blow big chips and all right into an enclosed trailer parked outside the shop. Is there any reason I need the cyclone? Any reason I can't just blow it all right on out? Currently a 3.5hp blower on a cyclone which I intend on reusing for this or I may jump up to a 5hp blower unit. I am a small 2 person professional shop. Thanks in advance for your thoughts and advice.

[Jamie Buxton]

What you may find is this. The dust-laden air goes into the trailer, and an equal amount of air has to get out of the trailer. If there's perfect separation between the air and the dust inside the trailer, that outgoing air stream will carry no dust. But it is unlikely that all the dust is just going drop out of the airstream inside the trailer, and some of it will travel out of the trailer in that outgoing air stream. The result is dust falling on your vehicles or yard or house or whatever. The cyclone increases the separation efficiency, so almost all the dust stays in the trailer, and cleaner air goes out to your environment.

[Bill Dufour]

Climate and any neighbors to complain about the pumped dust clouds on their property?
Bil lD

[Eyrich Stauffer]

Climate and any neighbors to complain about the pumped dust clouds on their property?
Bil lD

Thanks for the quick responses. No neighbors to worry about. Good point about the equal amount of air leaving the trailer. Any issues that you know of for the blower itself?

[Mike Kreinhop]

With a cyclone, all of the big stuff will be separated into a container at the bottom of the cyclone. About the only thing that goes through the blower impeller blades will be air and fine dust. If you don't use a cyclone separator, then everything will be going through the impeller blades. If a large piece manages to make it through to the impeller, who knows what may happen?

I think, based on other blowers I've seen, fine dust can accumulate on the impeller blades. This will reduce the efficiency of the blower.

[Eyrich Stauffer]

Thanks Mike-

[Bill Dufour]

Some impellers are not designed to pump strings and chips. They can load up the vanes and cause unbalanced forces very fast. Also some designs are not self cleaning of strings and chips so they can slowly plug up the fan.
Bill D

[Bill Dufour]

I have a feeling that California, and other states, would have something to say about a commercial shop dumping any visible substance into the air. A cloud of saw dust might be considered flammable waste. If it includes any thing other then natural wood the EPA will want to get involved. Do you know if 50 years from now all the synthetic wood products in that dust will be considered safe?
Bil lD
Bil lD

[Bobby Robbinett]

I live in the rural south and most of the local cabinet shops all vent outdoors. Some blow the dust into a garbage container or a trailer bed, but most just vent onto what becomes a large mountain of saw dust. We do the same and prefer this method. We sell our saw dust by the trailer load to people with farms and horses and such. It is a small insignificant revenue stream but it keeps our mountain from getting out of hand.

If you run air conditioning or heat you might loose some of the heat or cool air but for the most part it doesn’t matter as most shops are not heated and cooled. We find that our 10hp dust collectors work better not using the filter bags and instead just venting outside. Same with our smaller units. It’s nice not having to constantly change out bags. We have been doing this for years and never once damaged the impellers. (Knock on wood).

I think that a 5HP blower would be a big step up from a 3HP blower. Grizzly has a 10hp dust collector for around $1,800 which is a steal of a deal. I would snatch up one of those and ditch the filter bags to direct the exhaust outside. That would be a huge step up from either a 3HP or a 5HP unit.

[Keith Outten]

My DC vents everything directly to a 3000 gallon open top tank behind my shop. I have never had a problem with fine dust on the grass or on my shop siding.

[Alan Lightstone]

My DC vents everything directly to a 3000 gallon open top tank behind my shop. I have never had a problem with fine dust on the grass or on my shop siding.

3000 gallon tank??!!!??? :eek:

Picture, please. Sounds impressive, to say the least.


Have you ever had to empty it? How?

[Prashun Patel]

Your external bin will be a separator. The air has to go somewhere. Unless there is a big enough distance between the inlet and outlet, or you have a baffle or cyclone, the outlet will eject some heavy particles too. You could also put a coarse filter screen on the outlet of the collection bin lid.

People usually put the separator before the impeller to protect the impeller from heavy pieces of wood or worse an errant screw that could cause a spark(!) but a post impeller separator can also work.

[Jamie Buxton]

Cyclones can be used either as push or pull. In the pull case, the impeller is downstream of the cyclone, so air is being pulled through the cyclone. In the push case, the impeller is upstream of the cyclone, so air is being pushed through the cyclone. Most small-shop cyclones are pull systems, so most dust is removed from the air stream before it gets to the impeller. That is, the cyclone protects the impeller. However, with the impeller sucking air out of the cyclone, the cyclone needs to be connected tightly to the chip-collection bin, otherwise air gets sucked into the cyclone from the bottom, and destroys the separation process. If you want the cyclone to drop dust into an open container, you want to run the cyclone in the push configuration. The downside is that you may get big shavings (think handplane curlies) wrapping around the impeller, or big things (bolts or measuring tapes) banging into the impeller.

[Clarence Martinn]

Years ago, there was a man that built a house not far from where I used to live. In the back of the house, he built a Wood Cow Barn Next to the Barn, he built an old fashioned upright Silo out of stone and lined the inside walls with Cement. Traditional Silo roof cap , Outside Ladder on the Silo and a small Silo unloader . He used that barn that he built, for his wood shop, and the Stone Silo was used for Sawdust and wood chips. Worked out perfectly .

[William Hodge]

Venting dust outdoors works for me, in New England. I have 11" and 6" dust collectors, and a central vac. The dust goes into a trailer on the north east corner of the building. The trailer is a 4" wide by 4' tall by 8' long box, with metal roofing on it. There are 2x4 posts up the walls and ceiling to act as baffles. The large stuff stays in the trailer. Some of the fine dust comes out. I have a meadow that catches the fine stuff. Because I don't use plastic or sheet goods, all the dust is able to degrade. Sending plastic particles from plywood and other sheet goods out into the woods is despicable. An organic meat farmer takes the sawdust to use for bedding, because there is no plastic in it.

The heat loss depends on the number of people in the shop, and the machinery being used. One person shops have less runtime on the blower. I need to open an up wind window for make up air. Milling when it's below zero can be cold, down into the 50's. Having radiant heat in the slab helps. One thing that has helped a lot with heat loss is to put blast gates on the exit pipes. When the blowers aren't being used, the cold is kept out. In the summer, a medium air conditioner keeps the place cool. I also have 10" of insulation in the walls, and 24" in the attic.The attic is kept cool with a large fan.

The costs for all this are offset by the state laws in Massachusetts that allow me to have solar panels, and sell the surplus to the power company. Electric heat and cooling make sense, and they are solar powered.

[Frank Pratt]

It seems so odd to go to the expense of insulating well & then blowing all that conditioned air outside. Filters work very well at cleaning that air & saving the energy.

[Keith Outten]

This tank was originally an ultrasonic inspection tank at NASA Langley that I purchased as scrap. I sold the aluminum bridge and all of the precision rails and recouped my total cost of the tank plus a few bucks. In the picture you can see that I was in the process of installing vinyl siding so it matches my shop. I was originally going to fabricate a removable top but after putting it in service I decided it wasn't necessary.

I built the first two chip boxes from plywood, the first one was in the early 1980's. The boxes were 4 by 4 by 8 foot long and they lasted about ten years each. When I got the opportunity to acquire the steel tank I knew it would outlast me so I jumped at the deal...I think I gave 250 bucks for the tank with all of the attachments and it cost me a hundred bucks to get a rollback wrecker to move it to my home.

When I started the sign shop at CNU we purchased a ShopBot CNC Router and I converted the shipping box to a chip box. I cut rectangular holes in the end of the box and used baby diapers for filters. We only had to empty the ShopBot chip box once each year and I used four 30 gallon plastic trash cans to transfer the chips to one of our dumpsters on campus.

The first two chip boxes I built from plywood were larger, even so I was filling the chip box about once every couple of months. At that time I lived in a neighborhood and just about a mile away was a horse stable that purchased all of my chips, I made enough to pay the electric bill for the shop. The only down side to this deal was that when i needed to plane walnut I had to empty the chip box because walnut in a horse stall will cause problems with their legs and feet.

I live in a rural area now. If I live long enough to have to empty the tank I will probably use plastic trash cans again but I now own a front end loader that is able to empty half of the tank. The last option is to wait for a hurricane, it will empty the box in a matter of minutes :)

My dust collector a 1.5hp Grizzly that I bought well over twenty years ago. I scrapped the bags and the rolling cart, set the DC on the floor in the corner of my shop and ran the exhaust line directly through the wall into the tank. I estimate that the performance of my DC is much higher than the original specs because there isn't any back pressure or restriction from bags or filters. All of my piping is 4" PVC. In addition to the normal machines I also run a CNC Router and a Laser Engraver so the DC gets plenty of hours on it every month.

I live on the East Coast of Virginia. The temperature here is pretty mild in the Winter but hot and humid in the Summer. Except for the very few extremely cold periods over the years I have not experienced any serious problems cooling or heating my shop. Most of the heat is stored in the machines and the concrete floor and that provides a pretty stable temperature. I have a small wall mounted heat pump that keeps the temperature very comfortable, I prefer 65 to 70 degrees. Hundreds of people have visited my shop though the years, most were here for the ADA sign training I used to offer. They all experienced the performance of my dust collection and the comfortable temperatures, never had one complaint.

[Bill Dufour]

It seems so odd to go to the expense of insulating well & then blowing all that conditioned air outside. Filters work very well at cleaning that air & saving the energy.

The OP made no mention of heat or cooling . I assume he lives where they are not needed.
Bil lD

[Brice Rogers]

The OP, Eyrich Stauffer, didn't mention what material he would be sucking up. If it is just sawdust, then no separator is needed.

If Eyrich is sucking up long strings of shavings (e.g., from a jointer/planer) then he needs a separator. Why? because the impeller of the dust collector will get plugged up.

I have a 2 HP Harbor Fright DC and put a separator in front of it. It captures 100% of the big things. The rest is blown outside. I'm in a semi-rural area so there are not any issues with neighbors.

[David L Morse]

If Eyrich is sucking up long strings of shavings (e.g., from a jointer/planer) then he needs a separator. Why? because the impeller of the dust collector will get plugged up.

I have a 2 HP Harbor Fright DC...

Interesting. Did you plug up the impeller itself? Or perhaps not remove the intake screen and have a clog there?

[Rod Sheridan]

Is the blower designed to be in the dirty airstream?

The blower on my cyclone has a fan that would be damaged by wood scraps...



Rod.

[Andrew More]

I have a feeling that California, and other states, would have something to say about a commercial shop dumping any visible substance into the air.

They don't. I contacted the Ohio EPA and did a detailed analysis of our 2 HP Penn Station cyclone for the local maker space. The rep from the EPA was very detailed, but could care less about the vented dust. Might be an issue for a large commercial facility, but at the smaller shop level it wasn't an issue. I specifically asked about exactly this situation since we had a couple of members who were very concerned about this, and opposed venting outdoors for this reason.

The truth is that the air is already pretty awful in most places, or at least more fouled that any contribution from a dust collector, which would probably produce cleaner air.