Heat Treating Wood for Overseas Shipment

      The rules for heat-treating lumber for shipment overseas are impracticable because of the likely damage to both the lumber and the treating kiln. January 12, 2015

Question
I have a customer in India that wants me to heat treat 8/4 and 10/4 green red oak before it goes in the container. How is this possible?

Forum Responses
(Commercial Kiln Drying Forum)
From Gene Wengert, forum technical advisor:
Heat treating is done to kill any insects. Presently, the requirement is to heat the wood, including the core, to 133 F. To achieve this, often an air temperature of 160 F is used. Due to the risk of checking the oak lumber, you would have to do the heating at 100% RH (not even 99% RH), as the heat will certainly make checking likely if there is any drying at all. Getting a kiln to 160 F and 100% RH is next to impossible using common industrial equipment. Our present equipment is not designed to achieve such conditions. Even if you could achieve them, the conditions are rather severe and would make the structure subject to rapid deterioration. What might work is using a durable plastic bag that can withstand steam heat.

Overall, the request does not make sense, as when you customer opens the load when it arrives you will have mold and maybe even decay. The best idea is for you to dry it to around 20% MC before shipping. Due to the risk of defects, especially in 10/4, it would also be necessary for the customer to appreciate that some pieces will have a bit of honeycomb and perhaps some warp too. Have you ever dried 10/4 oak? If not, you might be surprised by the length of time involved. If your customer is in a hurry, then go with vacuum drying.



From contributor A:
I agree with everything Dr. Gene says and can add some more. I had to deliver some previously KD material to a customer overseas and had to heat treat to the exact same degree you mentioned in order for the material to get a Phyto Sanitary certificate from the USDA. Your customer isn't necessarily being difficult, they are using information provided by USDA. That information can cause a lot of trouble, as I found out the hard way. We got an overseas order for a variety of woods. The material was 12/4 padouk, 8/4 ziracote, some santos rosewood, and other stuff, most of it previously kiln dried. The material was clean going into the heat treatment, and looked ok upon inspection after heat treating. We then bundled the wood on a pallet and shipped it. By the time it got to the customer, it was all checked and worthless. The folks at USDA were cooperative, but they're bound by rules that don't necessarily make any sense. Why, for example, did I have to heat treat kiln dried wood?



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