Filter dust without losing heat?

[shenandoahsawmill]

You might consider dumping all of the dust and or fumes outside, without a return to the inside, and installing radient heaters. 

[Don_Papenburg]

A grain vac will have an airlock under the cyclone .  I t has a set of vanes that are rotated , incoming waste is dropped into the first  V as it rotates another set opens and the first set turns down to the opening on the bottom the waste falls out  without pressure or vac .  Also think of a rotating door setup , you walk into a cylinder behind a door and push as the door behind follows you and then you exit as you get to the inner opening. Google air lock . 
 Check into a heat exchanger  .  You might have to make one up yourself that would work for wood dust and with the larger opening needed it would not be as effective as one on a furnace . but what the heck if you could get the incoming air 20 to 40 degrees warmer that would help.

[mike_belben]

All our lead blowers and also polishing wheels used solenoid controlled air blasts for shaking the junk out of the pleat.  Lead and polishing dust/abrasive/glue turn to rock so im sure itll work for wood chip and dust. Nylon lines to nozzles, and parker 110AC valves on timers.. Maybe every 15mins a one second bang of air hit them.  Worked pretty fair

[Satamax]

Satamax, do you have any pictures of what your talking about.  I know what a helical or rotary screw air compressor is, but now sure what you are talking about?

Well rotary airlock from Google
https://www.google.fr/search?q=airlock+rotary&prmd=sivn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj-qf_RypTeAhUBLBoKHVtABDoQ_AUIEigC&biw=360&bih=560
Ans the compressor one i have seen, was nearly like a three lobe straight roots compressor.  Except that there some play 
Ans the back shape of the lobe is different to accomodate for chips and sawdust. 

[Ben Cut-wright]

Satamax, do you have any pictures of what your talking about.  I know what a helical or rotary screw air compressor is, but now sure what you are talking about?

Well rotary airlock from Google
airlock rotary - Google Search
Ans the compressor one i have seen, was nearly like a three lobe straight roots compressor.  Except that there some play
Ans the back shape of the lobe is different to accomodate for chips and sawdust.

Lots of differences between a Roots Blower/Compressor and a rotary screw compressor, especially compared to the fan blowers used on cyclone separators.  And nearly no comparison between a rotary airlock and those devices.


An airlock installed below a cyclone separator does little to nothing in retaining room/area heat or cool.  In normal operation, air flow used to transfer material goes out the cyclone exhaust, no matter if a rotary airlock is used or not. The airlock does control the release of collected dust particles into containers or can be used for measuring purposes.

[Satamax]

Ben cut Wright. 

I don't think you know what i am talking about. 

I am not talking about a rotary screw compressor. 

I am talking about airlocks. The vane type, is one, and yes, it keeps hot air in the workshop, in the case of an external dust container. 

And i have seen another type of airlock, which is like a three lobe roots compressor, but with more slack. Which compresses and amalgamates the sawdust and shavings, into some sort of  flat chips. Which were carried by a conveyor belt in one of the cases i have seen it. 

But shavings and sawdust could also be compressed with a screw compressor. Providing it is désigned for it. 

[Andries]

 

Brad; when you talk about heat loss, its funny how the folks located in the hotter than H zones don't seem to understand how that could be an issue. ;) 
Cyclones are your friend. Filters are a PITa. Been there. . . .
I recalled another thread which discusses some of of what you need:
New Sawdust Removal Bin in Sawmills and Milling 
I think most of us would agree that Robert (aka @Yellowhammer) has unrivalled research ability.
There's few on the Forum that figure it out better than him. 
However, he lives in Alabama. 
Clearly, Robert doesn't waste much time on thinking about how to stay warm.  :D
In the very last photo of his system, it shows the cyclone exhaust venting outside.
What you'll want to consider is: how to direct that air back into your shop.

This video by April Wilkerson shows us how to bring the cyclone cleaned and heated air BACK into the shop:
Installing A Dust Collection System - YouTube 
You'll want to have a Yellowhammer's waste bin located outside under the cyclone, to handle the volume of sawdust you've described. 

Combine the Yellowhammer with the April, and you've got a winner winner.
Keep us up to date as you move forward on this.

[samandothers]

My thoughts had been to have the DC unit in a separate room in the workshop with cyclone and filters.  The air returned to the main room via a door or wall with furnace style filters.  Issue with this is much of the noise is still in the workshop.  The video of Amy's workshop solved by moving the noise maker outside. I just did not want to cut through my exterior wall since my shop will be in my basement, though the basement will be walk out on the back side.

[YellowHammer]

Here's what things looked like without the cyclone to separate dust from the air, high speed sawdust goes everywhere.  Some of it even gets into the trailer. :D 

[YellowHammer]

I looked at rotary air locks for vacuum side cyclone duct collection systems.  Basically, in order for a suction side cyclone to work, the sawdust centrifuged from the cyclone must fall out into a sealed, airtight bin, usually a drum.  Since the system must be sealed, emptying the drum is a pain, because it must be broken down and reinstalled with an airtight seal.  So lots of handling of spring seals.  With the rotary airlock Satamax talks about, a paddle wheel system meters the sawdust out of the collection bin into another disposal hopper or pile, all the while maintaining the airtight seal.  Here's a link:
Rotary Air Lock - Airex Industries

These work well and are used on more of the larger commercial systems.  They are also relatively expensive, and the ones I looked at were a couple $grand each.  Also, the sawdust must exit the airlock and fall into an open air hopper that must be dumped.

So as Andries says, (Thanks for the complements Andries) I decided to convert over to a pressure system to do away with the intermediate catch drum and airlock altogether.  And also, having owned a couple suction side bag units, I knew that much of the performance of the system is controlled by the mesh of the filters.  The tighter the mesh, the lower the performance due to head losses.  So I went with a virtually zero head loss pressure system, and exhausts outside, so that I could get more effective performance out of the blower and zero dust in my work area and lungs.  

I've been using the system for a while now and love it.  When I called up Oneida and told them what I had planned they said, "Well, it ought to work, but we won't guarantee it."  All the dust falls into the outside self dumping forklift hopper, and the hopper geometry itself doesn't matter.  I could just as easily be dumping in a larger bin, a semi trailer, etc.  

I don't worry much about cold air losses as during the winter, we have to open the doors routinely to move pallets of lumber in and out, and we use a thermostat controlled diesel fired 70,000 BTU torpedo heater to reheat the building after we open the doors or to make up heat lost from the dust collector.

One of the best things is we don't lose any space inside the building.  The blower is mounted outside under the roof eave, so is quiet, and the cyclone is mounted outside on the wall.  

   

[Brad_bb]

Yes YH, that is what I saw too.  That in order to recycle the air you need an airtight bin, which is a pain.   Are you pulling milling dust and planer chips too with your collection system?

If I were to take the beam planer and board planer out of the system, a smaller system that would fit inside would probably work for the mill dust and cabinet shop tools.  That would mean that when planing, I'd have to Perhaps set up a seperate blower to blow chips outside to a bin.  This would not be good in cold weather.  So I'd have to restrict my planing for 5 months of the year.  I don't know.  It's giving me things to think about.

[YellowHammer]

My dust collector system collects sawdust from all of our tools, the wet sawdust from the mill, the dry sawdust from the planer, the straight line rip saw, 20" jointer, chop saw, and the edger.  The hopper holds a couple thousand pounds of sawdust, and we have to dump it several times a week.  Since its a gravity self dumping hopper, all I have to do is pick it up with the forklift or tractor, drive it out to the pile, pull the lever and it dumps with no muss no fuss.   

[Don P]

If your bin is a relatively well sealed box with a sock from cyclone bottom to bin. Then the air exiting the cyclone top, which is 99% clean, goes to a baghouse or some filter  and then returns to the building.

[Satamax]

Brad, have you seen this one, with the airlock? 

5HP High Vacuum Dust Collector w/ Air Lock & SMART Boost | Oneida Air Systems

[ButchC]

Thanks everyone for the responses so far...



ButchC, that unit doesn't look very big.  I would assuming you'd need a lot more filter area than fits in that cabinet for mill dust?



I need a big capacity for chips- at least a minimum of three 55 gallon cans I'd say.  I do not want to have to manually shack or knock a fine filter, automatic is needed.  
I'd like to be able to plane for  a 6 hour day with only needing to dump chips etc at the end of the day, not multiple times a day.  

Brad,
Those units can be had that are the size of a small house. The size of them is deceiving due the large amount of surface area of the multiple bags. Having used one of the commonly seen and used home shop type dust collectors I would guess that my DustVent has 3-4 times the air capacity in the same physical size with much finer filtration. The picture I posted isn't my unit but a similar sized one. The type of bags will of course determine the filtration. They are available with augers to remove the dust and electrically operated and timed bag knockers.  I have also seen them for sale with augers or small conveyors to remove chips but a cyclone in front of the vent is much less spendy way to do it and if you dont want to be bothered with emptying the cyclone you can add an auger under the cyclone that is sealed with a boot.  My cyclone came from a junk New Holland feed grinder @$25 and my 5 x 12' auger came from a farm auction @$42.50 but the auger is not installed yet and I have to shut down to manual empty the cyclone.  I have run the planer heavily for several days at a time and as long as I dont let the cyclone over fill I dont have to mess with the bag house at all.
Here is a link to the dealer in Cleveland I mentioned. Punch in dust collector in the search box to see the inventory. HGR Equipment  

[ScottCC]

I have spent two days trying to solve this problem because I'm am about to have same issue.  The answer is simple and cheap and easy, use make-up air that is from outside that is injected at the extraction site.  Basically making a "slip steam for sawdust" thus virtually eliminating the effects of exhaust on the general shop air.  The set-up for each machine would be a head scratcher but winter is coming and you might have extra time.

[scsmith42]

Brad, when I built my shop ten years ago I was unaware of the rotary air locks.  Hands down, if I ever have to rebuild my system I'll use one.

What I did was include a room specifically for dust collection.  It has a tandem axle dump truck parked inside with a 10' tall sleeve of filter cloth that attaches to the top of the dump truck bed.  The top end of the filter cloth terminates into a solid ceiling with penetrations for the dust collectors shavings and dust to enter.

In-between the dust collection room and the main shop is a wall that is covered with additional filter cloth.  What my system does is allow me to keep all conditioned air inside the shop, but capture all of the shavings and dust in the attached room with two levels of filtration in place.

It works as designed, but a rotary air lock would be superior.  If I had it to do over again, I would allocated the floor space in the dust collection room as additional shop space, duct my dust collection outside under a shed overhang using a cyclone with an air lock at the bottom (suspended above a dump truck bed), and then vent the discharge from the cyclone back into my shop via a couple of HEPA filters.

This design would allow for my conditioned air to be returned to the shop, yet the bulk of the dust and fines to be managed outside.

[mike_belben]

, use make-up air that is from outside that is injected at the extraction site.  Basically making a "slip steam for sawdust" thus virtually eliminating the effects of exhaust on the general shop air.  

Are you talking about creating a venturi effect by blowing outside air through the shop via a siphon nozzle type of pipe layout?  Like a paint or sandblast gun?

[Ben Cut-wright]

Brad, when I built my shop ten years ago I was unaware of the rotary air locks.  Hands down, if I ever have to rebuild my system I'll use one.

What I did was include a room specifically for dust collection.  It has a tandem axle dump truck parked inside with a 10' tall sleeve of filter cloth that attaches to the top of the dump truck bed.  The top end of the filter cloth terminates into a solid ceiling with penetrations for the dust collectors shavings and dust to enter.

In-between the dust collection room and the main shop is a wall that is covered with additional filter cloth.  What my system does is allow me to keep all conditioned air inside the shop, but capture all of the shavings and dust in the attached room with two levels of filtration in place.

It works as designed, but a rotary air lock would be superior.  If I had it to do over again, I would allocated the floor space in the dust collection room as additional shop space, duct my dust collection outside under a shed overhang using a cyclone with an air lock at the bottom (suspended above a dump truck bed), and then vent the discharge from the cyclone back into my shop via a couple of HEPA filters.

This design would allow for my conditioned air to be returned to the shop, yet the bulk of the dust and fines to be managed outside.

I can understand a benefit of controlling the acceptance particles using an airlock below the cyclone separator (inside) the building.   I would appreciate if you could explain how the added cost of an airlock would be worthwhile or necessary when discharging the cyclone dust into the truck outside. 

[YellowHammer]

Airlocks are only necessary on vacuum system to maintain a seal.
They can be handy on pressure systems to go from one bin to another.  

I don't have an airlock because I go straight into my final dump bin.  

I'm a big fan of outdoor bins. I've learned is that emptying sawdust bins by hand is not fun at all.  I used to get more dust exposure emptying the bags and bins than actually using the tools.  As my sawdust generating went up, so did the inconvenience.  Just last week I saw a guy on one of my local shops in the process of emptying his indoor bins wearing a full set of coveralls, a motorcycle set of goggles and a resistor mask.  He had so much dust on him he looked like the abominable snowman.  I thought it was hilarious, he was not so amused.  He was emptying a big 6 drum and bag indoor dust collector.  Once he got all the spring clamps loose, bags disconnected and fluffed, bottom barrels on rollers moving, he had to tote the full barrels of sawdust out the door and dump them.  They were too heavy to lift, and I watched him get madder and madder, and by the time he got to drum number 6 it was time for me to leave! :D :D

I emptied mine yesterday. 
Drive under, lift it, drive to the pile, pull the chain to dump the load, drive back, and done.  All from the comfort of the air conditioned cab, listening to the radio.

My point is, sometimes collecting the sawdust is only half the problem, getting the system emptied can be a significant problem too.  


 

 

[mike_belben]

Now make that guy sweating his butt off in tyvek marshmallow suit with a fullface backpack respirator in a baghouse full of lead or oil, polishing jack clumps and pidgeon fur and thatd be my life as a maintenance mechanic.  

Ill take the hopper and new holland any day!

[Brad_bb]

That is a very interesting Oneida system Satamax posted with the airlock. I am wondering, how fast does the airlock rotate?  Is it 1 RPM or 1500 RPM or ?

I understand that the purpose of the airlock is to maintain a seal in the system so that the exhaust air doesn't escape with the sawdust.  By the airlock maintaining the seal, it sends the exhaust air to the filters or baghouse.  The Oneida system is meant to be an all indoor system. I'm sure you could mount the cyclone and dust bin outside if you insulate the cyclone so you don't lose heat.  I'm not sure if you'd have sweating or condensation issues.  I'm also not sure if the bearings of the motor would be adversely affected by the cold?  In any case, this system is meant to be compact enough to be inside obviously.  

The other question I have is, when planer chips go through there, will chips get pinched between the seal and the housing of the airlock?  While it may be strong enough that it doesn't get jammed, will it cause seal problems and allow the escape of exhaust air? 

[Brad_bb]

The last step in my process is burning the dust/chips with the double vortex burn barrels.  Virtually no smoke and a fast efficient burn with this method.  I don't mind at the end of 6 hours of milling or planing emptying 3 to 6  42 gallon rubbermaid garbage cans of dust/chips and burning them.  I can keep up with that.  Two garbage cans worth will fit into one burn barrel.  Then you put the top chimney barrel on and it will burn down in 30 minutes to 1.5 hours.  Then fill again for one more burn and you're done.  Again, in the future I'll have to do this on average once a week or slightly less.
Burning as we go in Sawmills and Milling
So changing out the barrel below the airlock would not be an issue for me.  

When I first started milling 4 years ago, I started putting my dust in a pile in my back pasture.  Then when conditions were right, I'd open burn it. It was a lot of smoke and a pain in the butt.  The pile ended up being pretty big by the time I had conditions I could burn.  Even then it took a long time to burn, didn't get everything due to some being wet.  I couldn't stand the messiness of a big pile sitting permanently.  It seems to take mill dust forever to decompose.  

[mike_belben]

Itll break down to beautiful compost in as little as 3 weeks with enough nitrogen.  Via manure or grass clippings etc.  

[Satamax]

That is a very interesting Oneida system Satamax posted with the airlock. I am wondering, how fast does the airlock rotate?  Is it 1 RPM or 1500 RPM or ?

I understand that the purpose of the airlock is to maintain a seal in the system so that the exhaust air doesn't escape with the sawdust.  By the airlock maintaining the seal, it sends the exhaust air to the filters or baghouse.  The Oneida system is meant to be an all indoor system. I'm sure you could mount the cyclone and dust bin outside if you insulate the cyclone so you don't lose heat.  I'm not sure if you'd have sweating or condensation issues.  I'm also not sure if the bearings of the motor would be adversely affected by the cold?  In any case, this system is meant to be compact enough to be inside obviously.  

The other question I have is, when planer chips go through there, will chips get pinched between the seal and the housing of the airlock?  While it may be strong enough that it doesn't get jammed, will it cause seal problems and allow the escape of exhaust air?

Brad, the very nice advantage of an airlock, is that you make a "half room" a sort of box, inside your workshop, open to the great outsides, in which you can park a trailer or huge wheelie bin.  You tuck your cyclone, as high up as you can, and make that box bellow, which has a cutout in the workshop wall. And a hole to the airlock in it's ceiling. You obviously can insulate the walls of such a "room, so your workshop doesn't get cold.  And since you have an airlock, you don't send your hot air outside, or, it is minimal. In the case of a push through cyclone, or you don't suck cold air in, in case of a suck through cyclone.  IIRC, airlocks are usually in the range of 30 rpm. But can be regulated, with a potentiometer. So if you exceed the capacity of the airlock, you can run it faster, so it can cope better with your chip production. the advantage with the half room, also, is if you forget to empty your trailer of bin, it falls to the sides, and you can shovel away the excess chips. It doesn't fill your cyclone and filters up. I can't remember if it's at Bill Pentz site, or at the MIMF, that some guy devised a system to tell you when to empty the bag sor bins.  A tiny DC motor with a model boat propeller, and an amperage  checking circuitry, affixed to the bin lid, inside. The little motor runs full blast, until the bag  or bin is too full of dust or chips, then it gets slowed down by the chips, and amperage goes up. This is when a flashing light or sound alarm starts.