how long to sterilize reclaimed timbers?

[forrestM]

Hello, 

I have a customer wanting to sterilize some very old and already dry 8x8 beams that have been reclaimed. Just wanting to kill the bugs. My search on the forum shows a similar question has been asked before but I didn't get a clear answer from it. Is it still 24 hours per inch, at 140*? meaning it would take 8 days at 140* to kill the bugs in these beams? or does the timing change when things get over a certain size?

is it wise to keep the humidity throughout, even if the beams have been drying for decades? Just to make sure they stay around 12 percent or whatever they may be when they go into the kiln?

I have a Nyle L200 M

thanks,
forrest

[doc henderson]

I am shooting a bit from the hip.  I have knowledge, but no experience.  I think if you can get the humidity up so the EMC stays at the presumed 12%, then you can poss. go higher on the temp and shorten the time.  are these rustic?  if so, can you place a temp probe at the core?  then you go till the core is over 133° I think.  If they are really dry, it should reduce the number of potential invaders.  will they be used outside?  @GeneWengert-WoodDoc   @YellowHammer   @WDH 

[scsmith42]

Table 7-31 from the USDA Kiln operators manual has some good information for up to 3" material.  The line appears linear so you should be able to extrapolate out.

I finish up most of my drying cycles at 120F in the Nyle.  Once I start the sterilization cycle and increase the temp to 160F, I'll allow at least 12 hours for sterilization of 4/4 lumber, and follow the increase times below at an additional 2 hours per inch of thickness.  So dry 8x8 would be at least 26 hours.



 

[GeneWengert-WoodDoc]

Doc is correct.  

If you do this at 150F and have dry wood, once you reach 150 F for 8/4 or thinner, the entire process can take less than six hours. It depends on how much heat you have.  133 F throughout the wood is the target amd you get there faster at 150 F.

[YellowHammer]

It will take a day for the kiln to reach 150F, once it’s there, let it sit for a day, them turn it off, let it cool by itself, and come back the next day to unload.

Look for dead bugs.  

When in doubt, (when I dry thick mantels) I drill a little hole, and stick in a bar b que meat probe or even a meat thermometer.  It doesn’t have to be fancy, I got mine as a present years ago for cooking meat, but use it for my kiln.  

Use the chicken setting

[firefighter ontheside]

Isn't chicken supposed to be cooked to 165.

[GeneWengert-WoodDoc]

And chicken eggs are cooked at 212F to make hard boiled eggs. 

This reminds me that there is an enzyme between the egg and the shell.  Slowly warming the egg when boiling, or warming the eggs first for maybe a day, or just not using fresh eggs, allows the enzyme to loosen the shell from the egg, so it will peel easily and cleanly.  Fresh bought eggs, but in water with the heat on high to boil means difficult peeling.  (80 year old guys usually either preach or reminisce.)

Anyway, heating wood to 133 F is suppose to kill all insects and their eggs, larva, etc.  when I first started in the wood business, it was 130 F.  I guess the insects are tougher now.  Or maybe it is about politics.

It is good to also know that the temperature of WET WOOD will be at the wet-bulb temperature, not the dry bulb.  So, when sterilizing wet wood, we need to consider the wet-bulb of the air.

[doc henderson]

slow roasting maple with a meator! in Drying and Processing (forestryforum.com)