containers as kilns

[richie47]

Hey there folks,
down on the other side [of the world] in Oz; sub-tropical area, avocado growers just to give you an idea of the climate.
Looking for info on making a container kiln if anyone has done it successfully before.

Also looking to dry an orchard of pecan for parquet flooring as the new owner doesn't want the trees and prefers the view.
The container is just one option as I can build a solar kiln or plastic house with timber frame almost as easily which would have larger doors.
Log length is not great however, and longer sticks could be bucked to fit in the container.

[Running a W/mizer LT 40 hydraulic, 34hp diesel, standard blades.]

Regards to all,

richie

[Ga_Boy]

First let me welcome you to the FF Richie.  Glad to have you and we hope you stay around.

Now to your question....

I have done what you are asking about.  If you decide to use a container, get an insulated sea container, the doors seal nicely and the interior is lined with Stainless Steel.

You can use the DH units or as I did and went conventional. 




Mark

[GregS]

Mark,
I am thinking about doing the same and I understand the insulated containers would be easier.  I was given a aluminum truck box that is 16'x8' that is currently being used as a giant tool box while I build my polebarn-shop.  I placed the truck-box in the future kiln location thinking it would be converted into an insulated container for the kiln.  I was going to have the walls spayed with icynene foam and build new doors.  It is one of those situations the price was right....$free  ;).  In your experienced opinion would you convert this box or is it too much trouble to seal it up correctly?  Thanks for any input.

Greg

[scsmith42]

I have a 45' hi cube shipping container kiln, with a Nyle 200 dehumidification unit and Wood-Mizer controller. Here are some of my lessons learned:

1. Purchase an insulated container if at all possible. High cube (9.5' ceiling height) is the best way to go. A 45' length will let you get two carts of 16' boards and one cart of 12' boards in the kiln, which works out to around 4500 bf.   If you're going to be drying hardwood exclusively, go with a smaller container or a larger DH unit.

2. If you can't get an insulated container, the following process is very effective: Glue 2" foamboard (R6.4) to the inside top, sides and ends of the container. Over this, glue FBBWP (foil, bubble, bubble, white poly) Tekfoil available from FarmTek (www.farmtek.com). It's about 3/8" thick, and has an R value of 10.

This insulation combination is unbelievably effective at retaining heat inside the kiln, and moisture will not easily condense on the white poly. On a seventy degree day, with an inside kiln temperature of 120 degrees, the steel outer shell of my container is about 72 degrees.

3. Build a track system inside the kiln, and even more importantly, extend the tracks outside the kiln. You will need to have about a 4' removable gap between the kiln and the outside tracks to allow the doors to close. The Nyle manual provides an example of an effective track system. Don't skimp on your kiln carts or cart wheels.

Inside track is important because the weight of the lumber can punch the cart wheels right through the wood floor of the container. Track outside the kiln is critical in order to use a forklift or tractor loader to load the kiln carts.

You can lose a lot of heat through the floor, so be sure to insulate the floor in between and outside of the tracks with 1" foam board and Tekfoil. 

4. Build a relief in the side of the container for the dehumidification unit to sit in. It provides for more consistent air flow through the kiln and you reduce the chance of damaging your dehumidifier during loading or load inspections.

5. Install one fan for every 8 feet of container length. I have 5 in my 45' container. Hang the fans on rubber mounts (Grainger's has them), otherwise the steel container will reverberate and you'll hear it humming 600' away.

6. If you live in a rural area that is subject to power outages or surges (such as when a tree strikes a power line), be sure to install a surge arrestor on your load center. The kiln controllers can be susceptible to voltage surges. You can get surge arrestors at an electrical supply center.   I've replaced about $700.00 worth of controllers before I invested in the surge suppressor...

7. If you purchase a Nyle unit, consider ordering the extended length cable from the controller to the dehumidifier. The standard 6' length is a little short.

8. Clean and paint all exposed metal surfaces inside the container, as moisture will condense and the metal will rust quickly (especially if you're drying oak - it produces an acid byproduct). This is especially important on the insides of the doors and bottom of the door frame.

The folks at Nyle are really great, and their products are top quality and reasonably priced.

I have about 12k invested in my container kiln, excluding labor. Breakdown is as follows:

Container, delivered: 1,500.00
Nyle (Wood-Mizer) 200 series kiln: 4,745.00
Three extra fans (Nyle): 725.00
Moisture meter: 410.00
Steel for kiln carts and tracks: 1,000.00
Kiln cart wheels (Nyle): 420.00
Insulation (1" foam) 90sheets @ 13.00 ea: 1170.00
Insulation (Tekfoil FBBWP) 1,500 sq. ft.: 600.00
Misc electrical (load ctr, boxes, wiring): 350.00
Plywood and hinges for baffles: 350.00
Misc hardware: 100.00
Metal and wood for side kiln chamber: 200.00

Total, excluding labor: 11,570.00

From a labor perspective, it took the following: Two men about 40 hours to glue in the insulation, with furring strips for extra support, and to build the side kiln chamber. It took two men about 40 hours to install the fans (including electrical) and fabricate the plywood baffles. Finally, it took two men about 50 hours to fabricate three kiln carts (two 16' carts, and one 12' cart), and the track system inside and outside the kiln.

[Ga_Boy]

Greg,

First let me frame my response.

My operation is a business like most others here we are doing this to turn a profit.  This is stated as I do not know what your intended purpose is.

As for your container, the doors are critical, you can loose a lot of heat and loose control of your humidity with an air leak thrugh your door.  For this reason I opted for the insulated shipping container.  Also by the break down SCSMITH 42 gave the labor required and cost of insulation to insulate a non-insulated container made it cost ineffective for me.  At that time I did not have any help, so all work was done alone.

To convert my container it took me about 6-7 eight hour days of labor working alone to hang the fans, pull electric, install and hook up the heating elements and wire my electronics.  My unit is a home  built conventional unit.  I run a out door wood fired furnance to supply the heat to the heat exchngers.  Now all of the work stated above was predicated on my attending a four day kiln operators course and about nine months of research on kiln theory and operation.   

The cost of a 20' insulated container ran me about $2500 each, I purchased two units, one is the kiln the other is storage for now but when I need a second kiln it will be converted.  The controler and support electoronics, heat exchanger and fans cost about $7,000.  My kiln cart material costs were $500, this includes wheels, steel, SS bolts and high temp greese.  I use a lab oven and scales to determine the MC, I have about $1000 tied up there with another $400 in a moisture meter. 

I did a cost analysis and determined it was cheaper to buy an insulated container rather than build one.  Depending on your intended use and market this is decission you will have to make for your operation.

If you have any more questions let us know.  If you plan onstarting this as a business you will be like the rest of us here waking up a 2 AM because you can not sleep and logging on to this place to answer question before you start your day.



Mark

[scsmith42]

Having been down this path, again Ditto what Mark said.  Go insulated. 

[Ga_Boy]

Scott,

I sent you a PM about the show.  If you do not have it let me know and I will resend.  I got a funny screen after I sent the message.  Just want to make sure you got it.




Mark

[GregS]

Thank you gentlemen for your Thank you gentlemen for the thought and details that went into your responses.  The experiences you have certainly could save many hours and dollars! 

I did a quick cost calculation based on the insulation recommendations from scsmith and I am at ~1200 for my small space (without new doors and floor).  I will only be drying hardwoods and limited to one stack up to 12 foot long and maybe 5ft high with this truck-box.  Most of my hardwoods are 8' long so this puts me under 1000bf per load.  This size load is fine for now but I see myself out-growing it as soon as I am done building the kiln.  I am leaning toward looking for a 24' insulated box now.  Considering I do not count labor as free I think this make sense.  It is so tempting to use what I have but I have learned this lesson before and I am trying not to repeat my mistakes.

Thanks again for you input(s).

Greg S

[scsmith42]

Greg - glad to help.

Mark - I got your PM - thanks a bunch.  Look forward to seeing you Friday. 

Scott

[asy]

Richie!

Hiya!

Where exactly are you?

Also, where are you getting your container from? I'm looking for a container, so if you have a cheap source, I'd VERY much appreciate knowing it!

asy :D

[amberwood]

how many do you want?? I am in Melbourne but buy a few for work from a national reseller so might be able to assist.


DTR

[asy]

Just one.

I need one 20ft container to use as storeage so I can turn the downstairs of my house back into a downstairs, not a storage bunker.

I'll PM you my phone number, and would really appreciate any help.

asy :D

[Warren]

I just bought two 48 ft insulated reefer trailers to use for a dry kiln and dry storage. I've looked thru previous posts and the galleries.  It looks like both Ga_Boy and Scsmith have both gone down this road. I have a couple questions:

1) Both units are 96" to 98" inside width (102" outside width) and about 98" inside height.  What size stacks (height and width) are you running ?  I'm thinking I should be able to get a 4ft wide by 6 ft tall lift of lumber on a 6" or 7" tall cart and with 18" to 20" drop down from the ceiling for fans / baffles.  This sound right ?

2) With 3 kiln carts, I am thinking I should be able to get about 44 ft of usable length in the unit.  With a 4 ft by 6 ft cross section, 3/4" stickers and 4/4 lumber I am thinking this should get close to 6,000 bf in a single charge.  With 2" stock, it should be pushing 8,000 bf per charge.  Does this sound right ?

3) Originally, I was thinking a Nyle L200 unit.  But looking at the potential board footage, I am concerned that I may need to step up to an L300 or similar unit.  I will only be drying hardwoods.  Primarily oak, some poplar, cherry and walnut.  What are your thoughts ?

4) Ga_Boy,  I am intrigued by your choice to go with a conventional heat / venting set up versus DH.  Can you share a little of the knowledge that you picked up in the drying class that swayed you in that direction ?

I am a total newbie to drying.  I had expected to start off a little smaller, 20 ft container, 2000 bf DH unit.   But the price was right ($1,700 for both units).  So, I'm going to take the plunge. All helpful advice is greatly appreciated.

Warren

[Ga_Boy]

Hi Warren,

First I do not believe I have welcomed you to the forum, so, Welcome to the FF.

Now to your question.

My decission to go conventional was based on economics of drying.  The cost of running a DH unit compared to the cost of a conventional unit made my decision.  For my operation heat is free energy, I burn my wood waste.  I am also able to heat my work shop and house from the one out door furnance. 

I made the decission to dry green from the saw, this provides the best quality material.  My only electrical expense is for the fans.  But you have fans in a DH unit as well, to set the pitch and kill insects in a DH unit you use electrical strip heaters.  It is cost ineffective to dry green 8/4 or thicker stock in a DH unit; thick stock is a market sector I wanted to capture, so I needed a conventional unit.

My analysis showed that the economics of a conventional unit worked better for my buinsess plan.  The up front costs were more as I had to buy the stove and accessories to hook it up, but the big pay off is I now heat my home and get hot water  for my home for free.

Let me know if you have any more questions.

Oh yes, I like the science behind using a conventional unit, I have the lab oven to bake my samples and do my daily mosture checks.  I like the math involved in determining the daily MC.   Fun stuff, for me at least.





Mark

[scsmith42]

Warren, your math looks good.  A few comments.

First - ask yourself how long it will take you to cut the amount of bd footage to fill your kiln.  In a perfect world, you would log on day one, mill on day two, and get it into the kiln on day 3.  All delays beyond this usually result in some type of reduction in your total quality lumber.

2 - airspeed through the stacks is very important.  Too little, and you will get mold.  Too much, and you'll get checking.  Buy, and use a good airflow guage.

3 - you need enough DH kiln to take the appropriate amount of moisture out of the air from the total board footage that you're drying.  Consult with Nyle (or your kiln manufacturer) about the specific quantities and species that you'll be drying, and follow their recommendations.

4 - different species dry at different rates, so it's "usually" a bad idea to mix species or thicknesses in the same load.

You may want to consider building a couple of portable "end walls" that you can move around in your large containers, to allow you to effectively dry smaller loads.   I'd also suggest building some smaller solar kilns to augment your setup, and perhaps to run small loads through them.

I've seen Mark's setup (GA_Boy) and it's pretty slick.  Using his waste wood to fire his boiler really allows him to control costs.

Good luck.

Scott

[Warren]

Mark,  Scott,

Thank you for your input.   Regarding timing, I will not be sawing 6,000 bf of grade lumber per day by myself.  This will probably take me 6 to 10 days of sawing since the common lumber will go another route.  I am planning to stack and sticker grade lumber off of the saw and then load the kiln when I have a full charge.  I like the idea of a moveable end wall.

What is a proper airspeed ?  Is it measured on the pressure side of the stack, or the vacuum side of the stack ?

I spoke with Trip at Nyle.  He indicated the L200 system would be sufficient.  His experience was that a 48 ft van was more likely to net out about 5,000 bf.  Since I am drying primarily oak, some maple, cherry, walnut, he did not think the removal rate would be a problem.

Again, I appreciate your help.

Warren

[stevareno]

I've pondered the idea of using a shipping container as a condenser kiln.  My idea was to use an outdoor (hot water) wood furnace as the heat source.  If the chamber was uninsulated, one could actually take advantage of the cold temps in the winter time where the walls would naturally serve as a condenser.  It really wouldn't matter if you lost heat through the uninsulated walls since it's a sealed container, you're not venting heat, and like GA_Boy sais it's free energy.  Since atmospheric pressure rises as the humidity in the chamber rises, one could utilize a pressure relief valve to control humidity.  In the summer time, a cooling tower and copper finned tubing could be used for condensation..  My only concern was the air being too dry during the initial stages of drying since the walls would condense very fast.  However, the dew point of the walls would rise as the kiln temperature went up thus slowing down condensation.  The only energy used for this system would be circulation fans. 

We use a PC Specialties vacuum kiln which I'm extremely happy with.  If you don't already have one of these, I highly recommend picking one up!  So far, we've dried  walnut, red and white oak, cherry, hickory, ash, and hard maple in a variety of thicknesses ranging from 1/2" strips to 16/4.  A big thanks to Den, it's one of the most prized possessions in our facility. 

Regards,
Steve

[Don_Lewis]

One advantage of using the uninsulated walls as a condener is that within a few months you'll have pretty good holes and can switch from condenser to heat and vent kiln.

Seriously, I have some customers who have tried using uninsulated containers for heat treaters and they lasted about 6 months. They were heat treating Oak and the temperatures were higher and acid in Oak is higher but the condensate is still as acidic though the rate of reaction is somewhat temperature sensitive.

[serg]

I offer to look as rotation air without fans in Russia is used free. From photos it is possible to receive the interesting information  :Pon a design of the drying chamber on base of the container.
Sergey.


http://tm.fromby.ru/index/p13.htm

[serg]

Don Lewis hi!
You are right. The case of the drying chamber quickly will receive rusts.

[stevareno]

Don,
Serg uses uninsulated walls for his kiln chambers.  He doesn't have rust because he's heating the kiln walls which raises the due point thus eliminating corrosion.  He also has excellent ideas for transfering heat without the use of circulation fans.  Although he's drying in a vacuum atmosphere, there is no reason it wouldn't work at 750.062 torr or slightly above.  Imagine having a kiln that required very little investment with a free heat source, free condenser, and no cirulation fans!  Calculate energy cost on that one!  Even if corrosion was a factor, with todays advances in polymer technology one could simply paint the interior with a corrosion resistant polymer or coal tar.  

Steve

[Warren]

Speaking of interior coatings...  The two vans I purchased, one has a plastic or fiberglass panel type interior.  I am assuming this should be O.K. for kiln use.  The second one has a type of plywood lining.  I am assuming the plywood would need some type of coating to seal/preserve it before being used as a kiln chamber.  But, I am not certain what to use.

I've heard of aluminum roof paint.  I've heard of coal tar (tho I don't really know what it is). I would guess that putting another layer of foil based insulation on the inside and taping it might help.

What are the folks currently in operation using ?   And if you had to change, what would you do differently ?

All help appreciated,

Warren

[serg]

  Warren Hi!
1. I put metal for aircraft construction - dearly!
2. I put a board of a pine thickness of 20 mm, I paint a black varnish.
Plywood quickly fails. Examples look under this reference.

< http: // www.vacuums.ru/index.php? id=12 >
Sergey.

[Warren]

For the folks who are actually using vans / containers for drying, What did you use for a base to set the van/container on to keep it level and to keep it from settling "not level" ?

Also, any problem with critters wanting to make their home under the box ?

Warren

[Ga_Boy]

Railroad ties...