Author Topic: Vacuum Kiln (Read 2324 times)

J_T · « **on:** March 01, 2002, 07:05:07 pm »

Any one every try to build one of these kilns for small operations say 100 or200 bf? What is the principal if i knew this i might give it a try . I have some pumps that will suck a beach ball through a 50 ft garden hose !!!

Ron Wenrich · « **Reply #1 on:** March 02, 2002, 03:54:05 am »

I worked a little with the Woodmizer vacuum kiln. In addition to the vacuum, you need to get some heat into the kiln. WM uses electric blankets between the layers of wood to give the heat.

Jeff_Green · « **Reply #2 on:** March 02, 2002, 05:44:36 am »

I have been looking at building a vacuum kiln also. After many hours of research and travelling around looking at what others have tried (everyone I saw eventually gave up!!), I have observed the following:

steel chambers stain many woods, aluminum is weak so you need stainless steel - and it needs to be very well braced.

seals cannot be cut from flat rubber or gasket material - use a well designed o ring seal.

use a liquid ring vacuum pump - not a diaphram or positive displacement type.

without a regulated source of heat between the layers of wood you will not be successful.

between the kiln and the pump you need to have a water trap (with a valve at both ends and a drain at the bottom) and a chiller to scrub the vapours so the pump will not be ruined by moisture and natural acids from the wood.

after all that you still need to guard against drying too fast and turning your load of good wood into firewood (I haven't figured this part out yet)

I still plan to build one myself to use on 3" and thicker oak, I will just take it slow and try to do it right the first time!!

Good Luck!!!

Bud Man · « **Reply #3 on:** March 02, 2002, 06:20:02 am »

Jeff G - Between you and J T -- There is no doubt there is a solution if the two of you get together. Let's see, Missouri and Kentucky, I figure about one month ought to be enough for youse two to make this happen. Make it big enough for 2000 bf. and I'll take the third one off the assembly line. Might ought to get Charlie involved , he'd be a source of Hot Air and will be available in just a few days after his retirement kicks in !!

Trc^ · « **Reply #4 on:** March 02, 2002, 06:34:14 am »

it seems to me that if ya wantin to make a vacumn kiln .. might as well go all the way and set up for pressure treatin .. the same chamber should work well ... both are pressure vessels .. and then you have another marketable item for the same equipment .. when i can get into sawing thats what i am really thinkin of doin .. pressure treated stuff is a big market around this area .. plus wouldnt really need to worry to much about certified gradein of material ... just a thought .. still researchin it tho

Trc^

Bud Man · « **Reply #5 on:** March 02, 2002, 07:15:38 am »

Trc^ I'll bet you got the attention of J T now. He like's to build things that have an element of Boom in them.

Tom · « **Reply #6 on:** March 02, 2002, 01:13:23 pm »

Trc^, my concern would be the Fed. requirements for environmental proteciton. You could end up on the short end of the stick since they change the rules so often. I thought about it to once because of the need for pressure treated wood around here. I didn't do it because the local treatment plants already practically have a resident Gov. official walking around with vials and flashlights and clipboards trying to find something wrong. Looks like CCA is on the way out....what next?

I have watched the vacuum drawn on the charge tank in preparation for introducing the chemical. They draw as perfect a vacuum on the wood as they can and you should see the steam coming from the pump or at least some valve in front of it. The moisture in the wood boils in the low pressure and insures that the pores are open and that the water is out of the wood. I can see how a vacuum kiln might would work but I wonder about its efficiency.

Trc^ · « **Reply #7 on:** March 02, 2002, 02:11:21 pm »

Well .. your right about the EPA issues usein CCA. I can see with the chromium and arsnic .. (to tell the truth wouldnt want to mess with any of it) but with the newwe stuff out they claim there is nothing in them that is a problem in any way. But then if a person was thinkin about it that would be one of the issues have to bring up with the chemical suppliers .. as i said .. im thinkin of goin that way myself .. but first .. need to get another truck .. a tractor .. and a sawmill ... (dang the wish list just keeps growin ...

)

Trc^

JoeyLowe · « **Reply #8 on:** March 02, 2002, 03:10:59 pm »

Pressure treating is an open invitation for all kinds of regulatory woes. The largest sawmill in East Texas shut down last year and auctioned off all of their equipment just to avoid suits brought on by their pressure treatment facility. Now solar kilns have my attention for the moment.

I went to several different web sites and they all have The Wood Doctor's taint on them regarding solar kilns. I did find one that sparked my interest out of Fayettville, Arkansas. Seems two professors, De Vore and Snow were recently awarded US patents for the completely passive solar kilns. Has anyone heard about this particular kiln? Any input at all on solar kilns in general? I'm considering installing two 2000BF solar kilns to get started. Any thoughts?

Steve · « **Reply #9 on:** March 02, 2002, 03:32:47 pm »

I will second JoeyLowes request for help in sorting out all the information on solar kilns. I would love to put one up as well.

Thanks
Steve

Tom · « **Reply #10 on:** March 02, 2002, 03:36:01 pm »

Yep, Solar Kilns trip my trigger too. I have ideas but nothing tested.

DanG · « **Reply #11 on:** March 02, 2002, 04:23:00 pm »

I've been thinking along these lines, too. It seems to me that you would need several of them to be commercially feasible. I can't see waiting 30-60 days for every mbf of dry lumber, when you're trying to make money. I'm thinking of building one using a "hoop house", much like a greenhouse, with a chamber inside for the boards. I'll just use the solar heat to do the cooking, and a little fan for ventilation. I can build it for cheap, so, if it works, I can build more of them.

jwood · « **Reply #12 on:** March 03, 2002, 11:23:15 am »

BEEN READING ALL I CAN ON SOLAR KILNS AND I CAME UPON A SHORT ARTICALE BY ANDY DAVENPORT ON THE WOODWORKING HOBBYIST PAGE...AT WWW.MYBLDG.COM..ITS A SMALL KILN, ABOUT A 1000 BD.FT. .HE ALSO SAYS YOU CAN EMAIL HIM WITH QUESTIONS.IT MIGHT BE THAT IT COULD BE MADE LARGER....ITS NOT SOLAR ITS BUILT INSIDE HIS SHOP......

jwood · « **Reply #13 on:** March 03, 2002, 11:26:26 am »

BUMMER MY TYPING LACKS.. THATS WWW.MYBLDG.COM

Jeff · « **Reply #14 on:** March 03, 2002, 12:11:09 pm »

I just found the direct link to that article.

http://www.mybldg.com/hobbyist/homekiln.html

psychotic1 · « **Reply #15 on:** March 03, 2002, 08:46:51 pm »

I had an e-mail conversation with him a few months back. Very helpful fellow. Helped me figure out how to use ocean water as the cooling water in a wood-fired kiln. Not doing it yet, but "someday"

Steve · « **Reply #16 on:** March 03, 2002, 11:50:53 pm »

To follow up on DanG's comment. I once made a tyvek/visqueen covered 2 x 2 frame over 2MBF of stickered Mango 4/4" lumber. I put in one dehumidifier and a couple of simple fans. No introduced heat. After two months most of the wood tested out 10% moisture content although I had some areas that had poor air circulation and a higher moisture content. I really didn't have it sealed totally so was undoubtedly dehumidifying the outdoors a bit. A futile endeavor here for sure.
All in all I was amazed at how well the jury rigged setup worked. I think I'd still like about three 2mbf solar kilns.

Steve

Don P · « **Reply #17 on:** March 04, 2002, 02:55:33 pm »

Solar has the same pluses and minuses as air drying.
Plus...its cheap
Minus...you're at the mercy of nature
As long as you can afford to take the long view in your wood needs it seems like it would work fine, they effectively stop in the winter, and obviously on cloudy days (although diffusion towards the surface is still happening). I've wondered about it for cabin logs, shed dry one season...winter cut so the thick stock stays bright and dries slower in the early check prone phase. Continue the year in the open shed "pre-dryer" then load in a solar kiln for another year. It could get me where I want to be MC wise on a thick, slow, specialty load without a tremendous fuel cost, just a tremendous time and structure cost (although it's the least critical kiln type, BTU's are free, sort of). Fine for pine I hope, too much degrade for oak I imagine. I've always heard the more passive a system the more active the operator.
As time in the kiln increases the cost of running the fans becomes prohibitive. I saw an Amish solar kiln with a small waterwheel under the spring pipe, shafted to the kiln and fan inside. I gotta creek

.
For me its that or DH, vacuum just hasn't shown itself yet, I'm not sure it can be done cost effectively, J-T it sounds like you have all the fixins for DH. Stainless coils in a duct with your compressor,motors and guts outside would sidestep the acid corrosion I would think.

CCA is gone, they have 3 years to use it all up. ACQ from Chemical Specialties in Charlotte,NC is the new stuff, same equipment can be used though.

One log home co is doing a PEG/ Borate treated log in a large pressure vessel. "Treated" niches might be worth exploring

JoeyLowe · « **Reply #18 on:** March 04, 2002, 03:09:23 pm »

I know what you mean about the costs of running a fan or two or three in a solar kiln. I found an article on a solar kiln that is completely self-contained. They used a photoelectric fan to push the air across through the kiln. In Arkansas they were able to dry 2000 BF of 4/4 oak to 8% MC in under 30 days. That's pretty good in my limited, unexperienced opinion.

woodman · « **Reply #19 on:** March 04, 2002, 07:57:11 pm »

J T I just want to see the beach ball after it goes throu 50 feet of garden hose

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Author Topic: Vacuum Kiln (Read 2324 times)