Drying to 160 F

[GeneWengert-WoodDoc]

This is a brand new requirement (December 18 ) for ash lumber going to Europe.  Although most FF readers are not heavily involved in this specifically, I believe it does show what the future is likely going to be for shipment of all species of lumber outside the U.S.  (...and maybe even within the U.S. eventually?).  Most important is the 160 degrees F requirement when kiln drying.  Most of our FF readers to not have proper equipment to meet this requirement.  This is also going to affect vacuum drying.  I can see that soon many customers within North America will as for such sanitized lumber too.

Will there soon be requirements that all wood products (furniture, cabinets, flooring) will also have to have this heat requirement?

All Ash originating from Canada or the United States and traveling to the European Union must be in the "systems approach". The "systems approach" is defined below. 


Shipments must have a PHYTO with the accompanying NHLA KD Certificate with clip id numbers.The Shipments must also meet all of the following requirements:

*   10% or less in MC
*   Dry bulb temperature must reach 160 degrees F for 20 hours minimum.
*   Lumber must be debarked, small residual pieces less than the size of a credit card are  acceptable.
*   Lumber drying time of 14 days, this includes air drying time.
*   Lumber must be stenciled with KD - HT on both ends of the packs. (bottom right corner)
*   Treatment durations, dry and wet bulb temperatures, and final moisture contents will be recorded for each specific lot, and maintained for a minimum of 3 years.

[WLC]

Sounds similar to the requirements many years ago for pine wood chip exports to the UK due to pine wood nematode.

[longtime lurker]

Yeah well I can't blame them: EAB is coming for them out of Russia but it'll take a while to get there... current projections put it at around 2030. However much can happen in 10 years in terms of biological or other controls being developed, so I guess all they can do really is tighten up quarantine regulations and hope.

The reality is that if proper quarantine was observed it would never have left East Asia in the first place right? But theres always someone somewhere wants to cut a few corners. Depressing really... I got no doubt our overworked customs guys here dont have much hope of checking every pallet, skid, and crate for exotic insect pests either. The world was a much larger place when everything was loaded over the rails of a ship by hand.

[PA_Walnut]

Not an issue here. Usually get to those temps to sterilize anyway. Don't get the 20hours specification though.
Does any known critter survive past even 1 hour at 160?

[GeneWengert-WoodDoc]

A lot of critters can survive an air temperature of 160 F for a brief time if they are inside the wood.  

As one example, if the air is 160 F, but the WB is 125 F, the maximum wet wood temperature will be 125 F.  

Another example: Wood at 100 F that is then exposed to 160 F air will not heat up to even 130 F in four hours, depending on thickness, air flow, MC and humidity of the air.

[PA_Walnut]

My kiln creeps up in temp, so assuming the wood does too. It takes hours to go from 120-160. I'm going to probe the wood so see the correlation of kiln temp to actual wood temps. Will report back.

[btulloh]

I'm going to probe the wood so see the correlation of kiln temp to actual wood temps

Good plan.  I did this a while back and it provided some good information and understanding.  I can't put my hands on the data at the moment, but my test was not comprehensive anyway.  Running a test like this with different species and thickness would be best.  Looking forward to seeing your results.

[btulloh]

This could all be calculated instead of collecting emperical data.  Material properties, thermal conductivity, etc.  These data are known and published - somewhere.  Just need the right scientist to chart this our for us.  

[LeeB]

Not sure, but I would almost bet someone has compiled this data before. I have no idea where to tell you to find it.

[nybhh]

I'm building a solar kiln next summer and am going to double glaze it and insulate well but are there any good techniques to add supplemental heat to a solar kiln to help push it up to the sanitation temps for a sustained period of time?  I'm just a hobby sawyer so its hard to justify a big expense since there is no ROI.

• I've thought about trying to rig up an old wood stove or something where I could blow in some supplemental heat through ducts but the logistics of that get complicated pretty quick.  

• Hot water off a wood-fired boiler piped through old fin-tubed baseboard radiators would probably be more efficient but that can get dangerous real quick without pressure relief valves and everything, not to mention the cost of the boiler.

• If I had electricity at the site, electric baseboard heating elements would be an option as well but the wattage of solar panels required just to run the circulation fans is adding up quick, heating with electricity via solar would require lots of expensive batteries and would be crazy expensive.
• An evacuated-tube solar panel might be an option and can get water real hot pretty quick but would still require electricity to run the pumps and you still have the problem of holding temps at night or when cloudy.

Anyway, I don't blame the Europeans one bit and wish we would have done more.  I'm cutting all the ash off my 40-acres this winter and the whole *DanG process ranks up there as one of the most depressing things I've ever had to do.  I'm milling/salvaging as much as I can but most of them are in the 12"-14" DBH range so there isn't a lot of good wood left once you shave off the borer and woodpecker damage.  Another decade or two would have made a huge difference with these trees.   :embarassed:

[Don P]

Not sure, but I would almost bet someone has compiled this data before. I have no idea where to tell you to find it.

The Wood Handbook, Table 3-11. I'm sure you could get in the ballpark but nothing like a probe reading what you actually get.

[LeeB]

@Don P Do you dream about wood when you sleep?  :D

[Don P]

Doesn't everyone?  ;D
I bought my first copy of that book with lawn mowing money, the pages are falling out :D
Hmm, I'm not seeing that table in the current online version; (warning huge file)
https://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf

Here is a scan from my '99 copy, that isn't the lawn mower edition, this one was from an engineer friend when he retired. If it isn't readable holler and I'll try again tonite.

[btulloh]

Probes leave no room for doubt.  

One thing I was concerned with (over-thinking?) when I did the probe was thermal conductivity of the wires going to the probe.  ??  Not sure if that's a valid concern.  I filled the hole with fiberglass insulation after inserting the probe.  It was an interesting exercise.   Of course I was just using the solar kiln, so it's really not going to work  for sterilization.

[DR Buck]

I thought 160º was normal for most except solar kilns.    I've always run the last 24 hours of my drying at 160º.    I use a Wood-Mizer DH-4000 (Nyle-200) and I read or was told way back before I got it up and running that I needed to do that to sterilize and kill everything.     I even run air dried stuff in it at 160 for 24 hours if its going to be used inside anyplace.

[LeeB]

(warning huge file)
https://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf

I actually downloaded it today. No easy feat over here at work with the crappy internet we have. Had to restart twice due to dropped connection.

@Don P Thye page you posted is in the newer download; 4-13.

[GeneWengert-WoodDoc]

The problem with trying to calculate the heat rise is threefold: 

1.  The thermal conductivity and heat capacity (or specific heat) changes with MC and with grain angle, esp. around knots.  Remember that the entire piece needs to reach 133 F or other indicated temperature.
2.  The heat transfer rates air to wood is not well known.  Velocity plays a roll,
3.  The wood temperature is held at the wet bulb temperature where the MC is greater than 30% MC.

[longtime lurker]

I'll admit to being mystified about this the more I think about it.

If you really really are serious about not importing pests with your wood wouldnt you specify a chemical treatment rather then a heat/ MC level specification? Problem with specifying a heat treatment and moisture level is that wood gets wet and next thing you know its back to being borer friendly. A couple atmospheres of pressure in a cylinder of H3 though and shes good for the duration. And pressure treatment is actually cheaper then heat treatment anyway, or at least it is here.

[nybhh]

Full disclosure, I'm not a scientist and didn't stay at a Holiday Inn last night either.

However, my experience with EAB is that it only attacks the trees just below the bark.  I think once milled there is nothing left to attract them, even air dryed, much less kiln dried below 10%

[GeneWengert-WoodDoc]

Pressure treating is expensive.  The chemical must be active after treating to be better than heat treating.  But what chemical do you want that will not affect the user in contact with the wood, will not affect someone sanding the wood with poisoned dust, will not change the wood color, will not harm the environment, will not affect gluing or finishing?

Fumigation with a gas like methyl bromide kills existing insects, just like heat, but heat can affect products that are already glued.  Heat without humidity control can dry and check wood.  Methyl bromide harms the environment.  Fumigation and heat do not provide lasting protection.

Indeed, heat treating is inexpensive.  

Even drying does not protect against all insects.

[Escavader]

  I believe the key is recording.you just cant write it down.my nyles kilns have the recording devices built in,although i have never used them.and the kilns have to be certified by an outside agency duch as Nelma,Who certify and check kilns for heat treatment.
  I Think there is alot more to it,then just having a kiln that can get to 160.
 My Nelma inspectors that come around and inspect our grading,have a ton of places they go just to check on heat treatment facilitys

[GeneWengert-WoodDoc]

The new regulation I quoted only allows the NHLA.  Indeed, NeLMA and others can do shipping certification for undried wood.

[farmfromkansas]

The ash borers we have here in Kansas must bore deeper into the log once it is cut down.  A sawyer told me to spray the bark on some logs I took to him with malathion. Those boards were ok, but I sawed some myself and did not spray them, stacked the boards in the barn and went back in a few months to get some, and those boards were totally ruined by big nasty borers.

[longtime lurker]

The reality is that yard degrade of logs - insect attack, fungal decay, drying defects -can be a significant operating cost to any sawmill. And its one that largely goes uncounted. I've got an old mate who used to be a serious sawmiller, and he told me that they calculated their yard degrade as being around $300k a year - in the late 1980's. That was a lot of money back then, and they were big enough that they were doing things right in terms of prevention and minimisation. My degrade bill (by back of my head calculation) is around 9% of gross - which is to say that between straight up loss, and more importantly loss of grade - I think I'm losing about 9% of the potential value of my logs. It's part of the cost of business but its one that I lose sleep for sure. Faster saws and a log pond seem to be my best option, but that all comes at a cost too: straight up dollars for the saws, but ponded storage has a dollar operating cost that I dont fully know how to calculate. 

Anything sprayed on logs is better then nothing. And anything that will kill a termite will kill a borer. Malathion works, but its a nasty stuff. The pick of them for insect decay in a  log pile is a stuff called Pounce 500 which is a synthetic pyrethrin with a whole lot of rain fast capability.

[longtime lurker]

Pressure treating is expensive.  The chemical must be active after treating to be better than heat treating.  But what chemical do you want that will not affect the user in contact with the wood, will not affect someone sanding the wood with poisoned dust, will not change the wood color, will not harm the environment, will not affect gluing or finishing?

Fumigation with a gas like methyl bromide kills existing insects, just like heat, but heat can affect products that are already glued.  Heat without humidity control can dry and check wood.  Methyl bromide harms the environment.  Fumigation and heat do not provide lasting protection.

Indeed, heat treating is inexpensive.  

Even drying does not protect against all insects.

I think Gene that its a case of horses for courses, which is to say that the intended application of the wood product should determine the best treatment schedule.
Pressure treatment at commercial rates here runs at approximately 1/3 the cost per cubic meter of commercial kiln charges, plus chemical costs. Including chemical you're looking at around half the cost of kiln drying. Having said that for a product that has to be dried anyway its an over and above. The question then becomes does the wood product have to be dry? Some do, some dont : used to be a lot of things built with green ( no free water) wood once that arent now.
I'm still a believer in borax. It's cheap, effective, environmentally benign, although it does have drawbacks around leeching which limit its use in weather exposed situations.
General weather exposed the current darlings here are ACQ for timber in the rough, and H3 clear (which is permethrin and anti fungals in LOSP) for finished articles. H3 clear is applied after machining, the LOSP not drawn out during the negative pressure at the end of the treament cycle evaporates off fast resulting in no dimensional change to the profile so it suits things like mouldings, DAR etc.
There is some research being done around using vegetable type oils as a "pre oil" type treatment. Oil finished woods of course have high resistance to most decay organisms in the mid term.
The big one in all of this is the millions of tons of wood used every year in low grade applications like single use skids and packaging. Thats the stuff that transports pests and diseases all around the world, and it needs to be cheap. Although when you start to look at the economic impact of importing pests like EAB in the United States, you really have to wonder about whether cheap packaging wood is really cheap at all. As it stands thats the one I really feel we need to be asking questions about.... its fine it leaves the factory as HT spec... but then it goes to Joes warehouse where it gets stood up in the rain on the hardstand next to a termite mound for three days and next thing you know the HT stamp and treatment process was worthless. Its physically impossible for customs agencies the world over to check every single skid in every single container. I dont know the answer to that one but I'm just a sawmiller and I'm not paid to think but.... yanno I wonder about just pressure impregnation of plain old salt water, pre kiln cycle. Relatively cheap, no great environmental concerns at the end of the products very short life cycle, some issues with the in kiln environment and fixings and fittings but most of that stuff is single use so it doesnt matter if the screws are rusty at the other end.