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Author Topic: reefers for kilns  (Read 1560 times)

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Offline starmac

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reefers for kilns
« on: November 18, 2017, 12:27:30 PM »
I see a lot of guys using or asking about using old refer trailers, truck bodys or containers for kilns.
Reefer trailers are routinely replaced because the insulation retains moisture and are replaced when it gets to a certain level, many times the unit is saved and just installed on a new trailer. One reason is that as the insulation becomes saturated the trailer gains weight, but I understand it also affects it's efficiency.

Would this affect the efficiency of a kiln, or would the heat eventually dry it back out? Has anybody ever noticed a problem, as far as the insulation not working as well as you thought it should?
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Offline Peter Drouin

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Re: reefers for kilns
« Reply #1 on: November 19, 2017, 05:33:29 PM »
Good point, I had a call for a  40' one for $ 600.00. I have too much going on right now.
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Online mike_belben

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Re: reefers for kilns
« Reply #2 on: November 19, 2017, 07:53:52 PM »
Thats very cheap for anything 40' that isnt trash.  Especially insulated.  At that price id expect a banged up mold sponge with a busted door.
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Offline Gearbox

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Re: reefers for kilns
« Reply #3 on: November 19, 2017, 09:34:10 PM »
I was thinking that they were insulated with foam . Its been a while since I have seen one wrecked .
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Offline YellowHammer

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Re: reefers for kilns
« Reply #4 on: November 19, 2017, 10:09:24 PM »
If the insulation is taking on water, has broken down, and is generally unserviceable for refrigeration work, it will also be a poor choice for a DH kiln. 
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Offline GeneWengert-WoodDoc

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Re: reefers for kilns
« Reply #5 on: November 20, 2017, 11:40:41 AM »
Appreciate that heat will indeed help dry out wet insulation, but the environment in a kiln is often quite humid.  However, even if the kiln has a warm and moderately humid interior, as the humidiy (vapor) moves into the wall, which is cooler, then the humidity will increase and often will reach a condensation level.  So, it is critical that the walls, floor and roof all be sealed very well to prevent this migration.  Plastic sheets will do that for walls and roof, with the plastic or other sealer put on the inside so the moisture vapor cannot reach the insulation. 

As you mention, wet insulation weighs more and this weight can dislodge the insulation over time, so that ďsagging insulationĒ sections will have poor insulation qualities.  Also, wet insulation does not insulated well, even if it does not sag.  Poor insulation means higher drying costs...more energy and longer times.

When using a DH kiln, the price of heat to get the kiln hot enough to start and then to keep running suggests that we need about 8Ē of insulation...insulation that works correctly.  Adding insulation to a reefer might be a good idea, but again, avoid moisture.  So, adding it to the exterior is likely the best idea.  I also suggest painting the roof black on the outside to gain a small amount of solar heat.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline starmac

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Re: reefers for kilns
« Reply #6 on: November 21, 2017, 08:13:27 PM »
It seems like an old reefer would be a poor choice if 8 inches is needed to be efficient, I doubt they have over 2. If you have to add 6 more, might as well start from scratch and build it to your specs.
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Offline GeneWengert-WoodDoc

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Re: reefers for kilns
« Reply #7 on: November 21, 2017, 11:24:48 PM »
I would suggest you consider the cost of building your own kiln that will likely have better insulation; compare this cost to upgrading a used reefer.. A new kiln also will likely last longer than a converted reefer.  Both will work, so figure out the best economic approach...it is mainly an economic decision.

One additional thought is that if we have aluminum and are drying fresh oak, the acidity can quickly eat aluminum.  Small problem with air dried oak.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

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Re: reefers for kilns
« Reply #8 on: November 22, 2017, 07:51:15 AM »
I think id prefer a conex container.  Atleast theyre easy to pick up and move if you decide to relocate or sell it.  And you can weld structure right to them.  Cutting into and framing stuff in a reefer is a pain. 
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Offline YellowHammer

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Re: reefers for kilns
« Reply #9 on: November 22, 2017, 08:33:26 AM »
A well built kiln is a quite an undertaking, and it's important to make sure everything is right.  It just starts with the container or building.  I bought my high cube reefer while it was still in service, made sure it was in good shape, traded the refridgeration equipment for new seals, and love it.  It even had a few bonus packs of beef jerky still in it from the last load it hauled. It has a sealed, stainless steel interior, will not corrode and is still bright and shiny.   

I also have a stick built kiln and it has its advantageous, also.  Both kilns are in 24/7 service from the day they were installed, many years ago. 

Standard metal Connex containers are made from Cor-ten or similar, a "weathering" steel, designed to passivate in a corrosive environment.  So it has a limited design life and typical Connex shipping containers are taken out of after only 5 years of ocean transport service.  That's one reason there are so many used for sale.  After several years of use, my stainless high cube looks and works as good as the day it was put in service.   Kiln drying green wood produces significant corrosive vapors and the Nyle kiln guys have told me stories of standard Connex containers rusting out and pin holing in a just a few years of kiln service.   

I guess my point is that considering the effort taken to build and operate a proper kiln, the value of each load of wood processed in Nyke 200 or equivalent kiln, (4,000 bdft per load, average $4 per bdft retail sails, $16,000 per load, one load every 7 to 9 days), and the cost of electricity to operate a DH kiln (compressor plus 4 KW heat strips, on for days or longer if not properly insulated), then it can become painfully expensive to start out with some sort of container or building that isn't in top shape and try to save money up front.
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Offline starmac

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Re: reefers for kilns
« Reply #10 on: November 22, 2017, 02:48:03 PM »
40 ft containers here always bring anywhere from 3 to 4 thousand bucks at any auction, 20 footers are no cheaper, so would not be something I would want to start with.
I have a neighbor bought 4 brand new ones to the tune of 6500 bucks a piece. His intentions were to build a house out of them, which has since changed. Myself, I thought that was some pretty expensive walls.
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Re: reefers for kilns
« Reply #11 on: November 22, 2017, 08:31:11 PM »
Good lord.
Standard 40s are $1700 each in atlanta.
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Offline starmac

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Re: reefers for kilns
« Reply #12 on: November 22, 2017, 09:02:33 PM »
I know, but we get to pay that Alaska premium for things like them. lol
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Offline tule peak timber

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Re: reefers for kilns
« Reply #13 on: November 22, 2017, 09:39:21 PM »
I built a kiln by the Nyle book and it cost a fortune. Never used it once and sold the property with the kiln on it. When I moved to my present location I bought a refer container for 7000$ and put a Woodschmooser 4000 unit in it that has run more or less 24/7 for 11 years. I'm toying with the idea of another kiln with a wood fired boiler and the payback numbers are good, but other things keep popping up.The cost of containers where I'm at in SoCal is very high also and I just got a bid to move two of them to AK at a tidy 30 k give or take filled with equipment. Sadly Ak is out for me ! Rob
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Offline starmac

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Re: reefers for kilns
« Reply #14 on: November 22, 2017, 10:07:01 PM »
That bid may or may not be a good deal, where in Ak.  If it was on the road system anywhere south of Fairbanks, I would move them for you, but sadly California is out for me. lol
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Offline Geeg

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Re: reefers for kilns
« Reply #15 on: November 22, 2017, 11:43:10 PM »
I just finished my 20' reefer kiln and got one load in this year. I am happy with the way it operates and was not to hard to put together. I dried 2000bf of red pine that had been outside for a year. It took 3 days to finish the load down to 8%. Here is the link to my build. I just hope the paint that I used to seal the container works as advertised.

http://www.forestryforum.com/board/index.php/topic,86277.0.html
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Offline Cazzhrdwd

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Re: reefers for kilns
« Reply #16 on: November 23, 2017, 06:33:11 PM »
Iíve had my reefer container for at least a decade. It takes the same electric, the same time to heat up. Itís the most consistent kiln Iíve ever had. If the walls were saturated with water, I doubt it would hold heat very well at all. Itís also lined with stainless steel, so itís very easy to keep it sealed.
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Offline WLC

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Re: reefers for kilns
« Reply #17 on: November 23, 2017, 06:54:34 PM »
40 ft containers here always bring anywhere from 3 to 4 thousand bucks at any auction, 20 footers are no cheaper, so would not be something I would want to start with.
I have a neighbor bought 4 brand new ones to the tune of 6500 bucks a piece. His intentions were to build a house out of them, which has since changed. Myself, I thought that was some pretty expensive walls.

That's what gets me.  They have them at the port in Anchorage all the time, but we still pay the Alaska premium for them.  They are a bit cheaper down here than in FBX though, but not by much.  I had a friend in Delta that told me not long after we moved up here that I would find that in AK they charge freight on a haircut.  That's not too far off the truth.
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Offline starmac

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Re: reefers for kilns
« Reply #18 on: November 23, 2017, 09:41:02 PM »
Supply and demand, supply and demand. Anchorage gets them, but not near, as in not even 1 % of what major ports do down south, and they are quick handy shelters to keep stuff out from under blue tarps here, so bring a premium.
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Re: reefers for kilns
« Reply #19 on: November 24, 2017, 09:04:12 AM »
Yeah im sure theres hardly a person in alaska who doesnt want one.  Hawaii was similar with everything having a huge markup.  It cost about $1200 at the time to matson a vehicle from LA but the dealer markup was $10k vs the mainland.

Conversely, NYC has great prices on old construction equipment.  Other than the handful of contractors in the area who must run pretty looking machines to remain credible among the bankers theyre working for, who wants a beat up old dozer in brooklyn?  And who outside of NYC wants to deal with going there to see one and worse, arranging to truck it out. 

No demand = cheap
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Offline tule peak timber

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Re: reefers for kilns
« Reply #20 on: November 24, 2017, 09:15:11 AM »
This summer In Las Vegas I happened to strike up a conversation with a guy that buys and sells used containers. The bar tender later mentioned he was a regular and worth millions. He lives in a high rise on the strip. Is there a substantial markup on containers, it would appear so.  Rob
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Re: reefers for kilns
« Reply #21 on: November 24, 2017, 09:43:14 AM »
When the railroad or freight carrier is switching the fleet from say 40 to 40hc, or 40 to 48, 48 to 53 ..  You know.. The constant push toward bigger better faster..  Theyll want to unload tremendous volumes of containers all at once to clear the yards for delivery of new containers.  Someone with deep enough pockets to buy them all and actually move them off site is gonna get quite the deal.  If you can afford to wait for the money back at market price, then yes profit margin will be substantial. 

At port in NJ a 40' will bring maybe $1800.  Few hours north in springfield i was selling them for $2500-4000 based on condition, delivered to end user.  If youre hiring out the transport then there is no savings but if you are the transporter, and youre buying bulk diesel and the truck is paid, then you get to pocket the markup.
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Offline jaciausa

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Re: reefers for kilns
« Reply #22 on: November 26, 2017, 05:21:41 AM »

I have been planning a kiln in my Great Dane reefer trailers for some time. I was not aware of the problem oak and aluminum have. How big of problem if the oak or other wood is air dried?
I was going to re insulate over the frp sidewalls and ceiling inside.

Offline YellowHammer

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Re: reefers for kilns
« Reply #23 on: November 26, 2017, 08:44:13 AM »
Air dried is better.  However, the inside of my reefer is stainless steel.  Is yours aluminum clad on the inside?
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Re: reefers for kilns
« Reply #24 on: November 26, 2017, 12:10:51 PM »
Wouldnt insulation and vapor barrier pretty well cure the corrosivity issue?
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Offline starmac

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Re: reefers for kilns
« Reply #25 on: November 26, 2017, 01:53:45 PM »
I may be wrong, but I thought all refers had an aluminum floor, no matter what the walls were lined with.
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Re: reefers for kilns
« Reply #26 on: November 26, 2017, 02:13:08 PM »
I always thought my units were stainless on the floor, I need to go check the serial number and find the specs. Also take a magnet. I am in the process of finding another reefer trailer and I have found one with 3 side doors that is aluminum. I believe in any case I can retrofit and come out well ahead. I plan on spraying the foam and covering or using r board. I would already be started but received loads of dry lumber this summer that I need storage for. Any advise on the insulation or other is appreciated. Thanks

Offline jaciausa

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Re: reefers for kilns
« Reply #27 on: November 26, 2017, 05:08:55 PM »
I am now sure that the floor and the outside must be aluminum. They did a fantastic job polishing the outside when this was built. It will just be another obstacle to contend with. Would ERC be any more corrosive then white oak, and are there any more woods that would cause problems?
Insulating the floor from the top and using a taller inverted track could work, but that gets me  to thinking that building from scratch would be the best option! Any steel placed inside also would corrode from the moisture.

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Re: reefers for kilns
« Reply #28 on: November 26, 2017, 08:08:43 PM »
Paint it.  Works on bridges and battleships.

Btw stainless is nonmagnetic other than 400 series.


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Offline YellowHammer

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Re: reefers for kilns
« Reply #29 on: November 26, 2017, 08:34:08 PM »
Steel will rust pretty bad in a kiln, galvanized steel even worse, but I don't think aluminum is in any real threat from corrosion failure in a kiln. 

I have two Nyle kilns, and both of the chassis of the units appear to be constructed of aluminum sheet metal maybe 1/8" thick.  Nyle wouldn't use it if it was a significant problem.

Also, I know the floor runners I can see are extruded alumimun and is one of the reasons I bought the reefer.  This structure makes the floor dead flat, and I look at it every time I load and unload the kiln, and I have seen no degradation at all.  It looks as good as the day I put it into service, more than two years ago.  In that time, I have had it running 24/7 and pump a load out every 7 to 9 days.

I would not hesitate to build more of these, they are maintenance free, and work extremely well.  Due to the total lack of chamber degrade and zero maintenance I prefer it over my stick built. 

Reply #26 has some pics of the floor
http://www.forestryforum.com/board/index.php/topic,82071.100.html

BTW, eastern red cedar is a lot tougher on the kiln machine than the chamber.  When dried, it vaporizes some of its oils and it condenses in the drip pan as a white crystal mashed potato looking material, and clogs up the drip tube and sometimes the drip pan. 
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Re: reefers for kilns
« Reply #30 on: November 27, 2017, 08:01:37 AM »
I am glad I have the experienced help from all of you. My floor is not a duct aluminum floor, more of a continuous probably alum sheet metal.Metal only goes up about 18 inches on sides. The plastic coating most likely is glued on plywood- frp as it is fastened only on top/bottom. I am now going to use this the way it came, no insulation added except under floor. Outside probably is 300 grade stainless like one of you mentioned.
The food service industries use these type of trailers and many are available when they update there fleets. The units I bought were taken out of service because diesel emission rules outlawed there use in some states. Being a portable kiln could be a plus in some cases. It also means there are most likely some in every state ready to become kilns. Tell them its for cheap storage or they will up the price! 

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Re: reefers for kilns
« Reply #31 on: November 29, 2017, 10:55:01 PM »
Steel will rust pretty bad in a kiln, galvanized steel even worse, but I don't think aluminum is in any real threat from corrosion failure in a kiln. 

I have two Nyle kilns, and both of the chassis of the units appear to be constructed of aluminum sheet metal maybe 1/8" thick.  Nyle wouldn't use it if it was a significant problem.

Also, I know the floor runners I can see are extruded alumimun and is one of the reasons I bought the reefer.  This structure makes the floor dead flat, and I look at it every time I load and unload the kiln, and I have seen no degradation at all.  It looks as good as the day I put it into service, more than two years ago.  In that time, I have had it running 24/7 and pump a load out every 7 to 9 days.

I would not hesitate to build more of these, they are maintenance free, and work extremely well.  Due to the total lack of chamber degrade and zero maintenance I prefer it over my stick built. 

Reply #26 has some pics of the floor
http://www.forestryforum.com/board/index.php/topic,82071.100.html

BTW, eastern red cedar is a lot tougher on the kiln machine than the chamber.  When dried, it vaporizes some of its oils and it condenses in the drip pan as a white crystal mashed potato looking material, and clogs up the drip tube and sometimes the drip pan.

Same with mine, never had a problem with the aluminum floor.
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