DH Kiln Drying
References for DH kiln drying instruction
Question
I am considering buying a DH kiln this winter/spring. Are there any books or manuals available to train/teach/explain the processes, procedures and pitfalls? It cannot be as simple as sticker wood, turn on, take some readings, and reap profits when done? I am currently looking at Nyle and Woodmizer’s new unit.
Forum Responses
I have an Ebac 800 and I can dry 700 BF at a time, and it is just about as easy as sticker, turn on unit, and start emptying water. It takes about 20/25 days and $1 per day to get down to 6%.
Don't start without a copy of the Dry Kiln Operator's Manual, a very comprehensive book available from the USDA, many kiln associations, or kiln vendors like us.
If you are drying hardwoods, then you really need the more practical text DRYING HARDWOOD LUMBER; if you are drying mainly oak lumber, DRYING OAK LUMBER; for Southern pine, DRYING SOUTHERN PINE LUMBER.
Gene Wengert, forum technical advisor
I agree with Gene. The Dry Kiln Operators Manual (which is available free on line as a download) is outdated. Some of the basic tables are useful so it isn't a bad thing to have on the shelf. However, I also agree that it is pretty easy to dry right. I've found that the best way to go is to follow the manufacturer’s instructions as a start and then get into the books and seminars. I know that sounds backwards but otherwise you tend to get overwhelmed with information that doesn't apply to you.
All of the advice that you have received so far is good. Whatever you do, don't be afraid to step out of the "lines" and try some different things. Tricks and short cuts come from mistakes. Always check back here for advice and questions. There are a lot of good kiln operators here.
You should also consider a business plan if this is to be a business venture. You should also attend as many seminars as possible to learn how to do it right; use the experience of others. You might also get a copy of "Opportunities for DH Drying" from the Virginia Forest Products Assoc at Sandston, VA.
Gene Wengert, forum technical advisor
I'm curious as to what species and MC you are starting with in your EBAC? If it’s oak that has been air dried to under 20% I can believe your numbers. I think it would be hard to dry green oak in 20-25 days without causing some stress but then again that’s what I'm here for - to learn. My Nyle L200 can dry it faster than the recommended 34-36 day cycle but I don't like to chance it. I can dry about 3000 BF of 20% MC oak in 7 days to 6-7% MC and it is just as easy as sticker-baffle-and hit go.
From the original questioner: I air dry for at least a year before putting into kiln. I dry red oak, white oak, maple, ash, and cherry. I can also dry faster but let it idle for a week after reaching 6%. I have never tried drying green wood. From a load of about 650 BF I will get about 100 quarts of water. How does this compare with other DH Kilns?
You should get about 10 quarts of water per 1%MC from 650 BF of Oak. 100 quarts makes sense for lumber that has been air dried for a year.
As a commercial operation, it is a waste to air dry for a year--carrying cost (inventory cost) is extremely high and quality loss risk is very high. Why waste our natural resource?
In terms of drying equipment, one key is the horsepower of the DH unit. It costs money for each hp, yet it also determines how fast you can dry. There is no standard conversion of HP to BF of lumber, so when someone sells a 700 BF DH kiln, you really do not know what you are getting. Ask about the HP, and if they do not give it to you directly, move quickly to another company. (I remember one DH company that claimed that their 1 HP was twice as strong as the 1 HP from another company--WOW! I think they also sold the little device that you put on your car to double the gas mileage!)
If you are getting a DH kiln, talk to people already using them and also read the book "OPPORTUNITIES FOR DEHUMIDIFICATION DRYING" referenced above, as a start.
Gene Wengert, forum technical advisor
