Does anyone have any printed material on this subject? I mean really scientific evidence of test. I ask cause I am a little confused on the exact temp to use. On this forum and that other one the temp range will varie from 130 to 160 degrees. It seems to change with the individual. I have always thought it was 160 but why the heck am I wasting that much electricity if I don't need to?
I guess I could put a bug in a oven and increase the temp till he is dead. :D
I don't have many printed materials at hand but temperatures in the 130 range should do it. That's hot. It would kill me. :D
The trick is to remember that the wood at the point where the insect or its eggs are located must reach 130 degrees. Wood is a great insulator. If you bring the outside temperature up and don't leave it there long enough, the inside of the timber may never reach 90 degrees much less the 130 it would take to kill the insect.
I've talked a lot about the Wood Handbook and all the good information in it. It has a link on our knowledge base under "Wood and Lumber". I generally go there first when I have a question.
http://www.fpl.fs.fed.us/documnts/FPLGTR/fplgtr113/fplgtr113.htm
Some of the info you are looking for is located on page 13-10 of this copy of the manual. :)
Tom,
I moitor the wood temp just like I do MC. With a sensor inserted into the center of the wood. So are you saying if I (hypothetically speaking) could bring the center temp to 130 in 1 hour all is dead?
I would guess there are bugs like people and we are all differant. 130 doesn't seem that hot to me. I have worked in 125 degree attics all afternoon when the guys with me had to come down every 15 minutes. It gets so hot that you can't lay a tool on a metal unit it will almost blister your hand to pick it up. I have had to pick up a pair of pliers with a rag till they cooled off a moment.
I guess my problem here is does 130 kill all bugs or just the ones that die at 130?
The "Good Doctor" on the other side of the fence used to say 160°. Then, he dropped it to 130°. Several folks questioned his difference in temps and he got miffed. Now, he says 160°, or so, and hold it for 6 hours ??? ::) ;D ;D
Woodhaven,
It is my understanding that one brings the kiln to 130 degrees for 48 hours straight and that will insure that the load is completely sterilized.
See what I mean guys!!
Out of 3 post 2 are differant.
Mabe I am more aware of bugs than most because I live in a log home and I am always spraying something for those things. I would hate to use wood that already had bugs in it for a inside project. Mabe I am asking to much but it seems ficticious to say the wood has been at __degrees for__hours Yep they are dead.
woodhaven,
I too have wondered why there is so much variance in the numbers given to sterilize wood. It certainly is confusing when the experts can't agree!
I asked a friend of mine who is the enviromental officer for a large cereal company how they handle insect infestations. His reply was, "We close off the entire building and heat it to 140* F. overnite. If there were any insects in there, they're dead in the morning!" He also said, "The pesticide boys will argue till they're blue in the face that this method isn't effective, you need to spray for insects." Not so He said, "We've found that the heat treatment is very effective".
I heat all my lumber to 135* F. in the kiln for 24 hrs.and haven't had a bit of trouble with PPB.
This is done at the end of the drying cycle so the lumber is at 120* when I raise the temp to 135*.
If you are starting with lumber at room temperature, I'd allow extra time to make sure that the lumber core does actually reach the higher temp.
I believe the 160* comes from the use of standard kiln schedules that use these higher temps.
Just some thoughts from a part time kiln operator :).
It's a time and temperature thing, and not the kind you call on the telephone. :D
Notice:
Now, he says 160°, or so, and hold it for 6 hours
It is my understanding that one brings the kiln to 130 degrees for 48 hours straight and that will insure that the load is completely sterilized.
Not so different as it seems. 160 does it quick, 130 takes longer. Both get the job done.
The Dry Kiln Operator's Manual lists in table 7-31, Schedule for killing Lyctus (powder post) beetles and their eggs.
3 hours @ 140* F. for 1" lumber
Here's a link, check out Chapter 7, table 7-31
http://www.fpl.fs.fed.us/documnts/usda/ah188/ah188.htm
In response to the request for documents, here are some more links.
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr130.pdf
http://www.ces.ncsu.edu/nreos/wood/wpn/pallets.html
http://www.epa.gov/spdpublc/mbr/casestudies/volume2/heatlog2.html
"Core temperatures can be monitored by using thermocouples. Heat treatment techniques may include the use of steam, hot water, kilns (lumber only), microwave energy, or any other method that raises the temperature at the center of the log to at a minimum of 71° C (167° F) for at least 60 minutes."
I can't answer why there are different temperatures and times other than to say that there are different organizations with different rules. There are accepted guidelines proposed by organizations like the USDA to prohibit alien insect invasion. That indicates that studies have been performed.
There has been quite a bit of work done and published information regarding sterilization because of the new requirements that all pallet and crate wood crossing an international border be heat treated or fumigated to kill any bugs or larvae. The international standard that has been accepted by almost every country is 56C (about 133F) for 30 minutes. There is a lot of published material backing this up and comparing heat treating to fumigation. In fact heat treating is generally preferred and some countries were phasing out fumigation. But there seems to be no argument about the 56/30 rule. Hundreds of mills have already installed systems to do this. Usually three probes are placed in the center of the wood but some agaencies are accepting time schedules. It takes 1-24 hours, depending on the amount of heat available and the air temperature, to get the center of the wood 56C for 30 minutes. We normally set the air temperature at 160F(72C) to avoid excessive damage to the wood. That is not the temperature we want the wood to be but the temperature of the air that assured the center of the wood gets to be 133F in a reasonable time.
Don, I believe you hit upon the right issue, getting the air temp up to 160* and the wood up to at least 133*. In my case I run the last 4 days of drying with an air temp of 160* on a 30 day cycle. I have had 4" thick wood in there at that temp for only 4 days and got rid of powderpost issues in that time. 8) The wood had, had the critters prior to being put in the kiln. :-/
OK,
Now it is makeing sense. Thanks to all.
That brings me to one more question. Are there limits on how fast you can bring the temp up? Can I bring the temp up in a few hours or should it be increased slowly untill the holding point?
WH, I have had better succes in taking my time in increaasing the temp. I tried with some of our Oregon Oak and found that the only success I had was with creating a load of honeycomb Oak. :'( I got smart real quick after that experience about 5 years ago. I take 3 weeks plust to get to 135-145 degrees. I found that if you push wood it will talk back to you in ways you never thought possible. :P
Don,
If it gets the job done, 30 mins @ 133F certainly is better than 135F for 24hrs. I hate paying the electric co. anymore than I have to.
As a furniture maker I avoid using lumber that has seen higher temps.in my products. That is one of the reasons I purchased your low temp kiln many years ago.
There is no need to take it slow if the wood is all below 20%. However, if you have no control of humidity, when you raise the temperature quickly, and the wood is dry and giving up little of no water, you will end up with a low EMC and that is why you may see some additional check. It isn't possible to cause honeycomb when wood is below 20% but if you did something when it was above 30% to cause honeycomb, you see the result at the end. Wengert uses the example of jumping out a ten story window. The result is damage at the end but the cause if much sooner.
oops,
I kinda left you in the dark for a moment. I am only talking about dried wood at 20% or less.
So in general once it is less than 20%. I can turn up the heat real fast until I get to the holding point?