stream . Willie Sandry is a furniture maker and a lumber kiln operator in Camas, Washington. Dr. Gene Wengert provides schedules for kiln drying hardwood lumber. Dehumidification Kiln Drying. Page 30 Wood-Mizer Figure 3-4 Drying Schedules Normal Schedule Alternate Schedule Moisture Content Dry Bulb Wet Bulb Dry Bulb Wet Bulb Group 2 Above 45% 90F 85F 100F 97F . A kiln schedule is a set of temperatures and humidities that are used during kiln operation. This prevents dead spots inside the chamber that experience limited airflow. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. The company's small kilns can be configured for drying lumber, firewood, or heat-treating lumber or wood packaging. Then, write down the appropriate MC ranges (determined in #2 above) in the second column. I often buy from sawyers or homeowners at 40% to 50% of retail price. In addition, weight on top of the stack can be helpful, but nothing replaces baffles for the best lumber yield. Instead of using expensive electrically reversible fans designed for commercial kilns, I came up with a simple hardware solution. If for any reason you are not satisfied with the merchandise you ordered, just return it within 90 days to receive a refund in the manner of original payment for merchandise only. trailer << /Size 918 /Info 891 0 R /Root 907 0 R /Prev 482770 /ID[<67858f68421814977b05bc7913f6cc23><4073af979fbabe8f1c016146fd1c21ef>] >> startxref 0 %%EOF 907 0 obj << /Pages 902 0 R /Type /Catalog /DefaultGray 903 0 R /DefaultRGB 904 0 R /Metadata 905 0 R >> endobj 916 0 obj << /S 499 /Filter /FlateDecode /Length 917 0 R >> stream 3, a simplified transverse section of a kiln chamber with an energy recovery and dehumidification system is shown. Should I? Q,kjifT33P[! Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. Kiln schedules are completely assembled and written out for easy use. The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. Lock Sign In Upload. txN.a!HQ)FmCw~{B1Aq_!+zN#+j This problem is magnified if the lumber is thin or flatsawn. This shed will be essentially unheated for much of the year and very hot during the kiln-drying cycles. Wood Drying/ Seasoning. Another reason I like the idea of a shed kiln is the flexibility of future use. For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. The kiln process involves the drying of wood in a chamber where air circulation, relative humidity and temperature can be controlled so that the moisture content of wood can be reduced to a target . The four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln. Your order will come with a return form with convenient instructions, or you may send your returns directly to Returns Department, Rockler Woodworking and Hardware, 4365 Willow Drive, Medina, MN 55340. End baffles are also a good idea to prevent airflow from bypassing the stack entirely. Place some sample boards in the stack that will be easy to pull out for moisture testing later. The thinner the stock, the more critical sticker placement becomes. My question focuses on the initial relative humidity featured in the Safe Drying Rate table. I have constructed a kiln using these plans. For the sterilization phase, air temperature needs to be around 140 F, for three to five hours. Measure airflow over the stacks of lumber in various locations. Wood drying (also seasoning lumber or wood seasoning) reduces the moisture content of wood before its use. A Checklist for Operators of Small Dry Kilns A companion to A Start-up Guide for Operators of Small Dry Kilns (FOR-132) Terry Conners, Forestry and Natural Resources Most species of hardwood lumber can be safely dried this way, once the moisture content is 20% to 25% or less. My baffles hang from T-bar assemblies mounted to the ceiling. For a single-stack kiln I recommend a minimum shed size of 8 x 12. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). Basically the idea seems to be to maintain a constant temperature, and . Unlike general shop space, bigger is not always better for kiln design. The water tray can be removed and emptied manually, or a hole can be drilled through the wall of the shed to pass a drain tube. HT systems use 40-60% less energy than gas-fired or steam dry kilns. With a 130 F kiln temperature, sterilization will take 10 to 12 hours ( Dry Kiln Operators Manual, 1991 ). Warp in dimension lumber is a significant cause for loss in grade and value. Hardwood kiln drying schedules typically keep the dry bulb temperature below 80 C (176 F). MC values in the kiln schedules are based on the wettest half of the kiln samples. Omitting the sterilization phase can lead to costly losses from insect damage, so dont skip it. If MC readings still arent at the desired range, the heat may need to be increased for the remainder of the drying cycle. Taking moisture away at the rate the board will "safely" part with it . 0000001186 00000 n Exterior sheathing and siding type also factors into the heat-holding ability of the structure. Reply. I like these "starter blocks" to raise the lumber a few inches off the floor. With a well-designed dehumidification kiln, hardwood lumber can be dried for mere pennies per board foot. For example, if you dry 7,500BF of fast drying Pine, youd select the 8MBF chamber with the HT18 Dehumidifier. If the fans and dehumidifer generate enough heat to maintain a temperature of 100 to 120 F, then I wont use the auxiliary heater. Basically, you dont want all of the air rushing out under the stack, so find a way to redirect it. To browse Academia.edu and the wider internet faster and more securely, please take a few seconds toupgrade your browser. This fact sheet summarizes the basics of kiln drying wood, the most commonly used methods, drying schedules and some drying defects. Forum Responses WOODWEB is a registered trademark of Woodweb.com. Total costs for the materials were $2,704 based on 2006 prices. building the dehumidification dry kiln. The starter blocks should be as long as the stack is wide. I then manually rotate the fan boxes halfway through the drying cycle. This kicker board will help distribute the airflow more evenly through all layers of lumber. /Subtype /Image When properly loaded, this kiln can dry approximately 600 board feet of 4/4" lumber. Check out More On the Web for my complete calculations to figure savings. Difficult-to-dry species might not exceed 140 degrees F. Dehumidification kilns are very . 6. Windows and doors are also sealed, as well as any holes cut for electrical service. Many regions have increased the shed and outbuilding maximum allowable size without need for a permit. The conversion method described in the Dry Kiln Operator's Manual is not really accurate, but it is safe. There are two ways to remove water from the DH unit, and they both work well. This will allow the DH to drain automatically without you needing to enter the kiln. Once the lumber is sterilized, it is ready for the conditioning phase. temperature. Regardless of size, allow for a 36 door that opens to a hallway of open space. You can achieve top-quality results with incredible efficiency. . We are proud of the quality of our products, and we stand behind them 100%. I selected a 36 outswing exterior door. My shed kiln was stick-built from standard building material, and sized to take advantage of typical 4 x 8 sheet goods. The last step requires a short period of high humidity to relieve the drying stresses in the boards. They are based on different air flow rates, etc. In a professional DH kiln, the final climate for oak is 120F and <40>t over-dry it at that rate. If we revisit the example of a $1,300 gross savings from a load of 540 BF of white oak lumber, and we subtract the estimated cost of $62 to kiln dry the lumber, we arrive at a net savings of $1,238 less than retail. A dehumidification kiln continuously recycles the heat throughout the chamber, rather than . Kiln drying is usually preceded by air drying to bring the moisture content of the wood down below 30%. This can be done by heating above 133F for 4 hours (measured at the core of the wood), or at 120F for about 7 - 10 days. 1998. by Dr. Eugene Wengert. The baffles do not need insulating properties, and plywood would work just as well. Be sure that all of the kiln equipment is working prop-erly before lumber is loaded into the kiln. With two-stack and three stack kilns, it is better to have reversible fans to alter the direction of airflow mid-cycle. The lumber was then measured for crook, bow, and twist. The schedules can also be formulated manually as follows. Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. The delicate blue and white color scheme c Job Opportunities and Woodworking Services, Dust Collection, Safety and Plant Operation. Changes in kiln temperatures and humidities are based on the MC of the lumber being dried, which in turn is determined from properly prepared kiln samples. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). I have sensors in the kiln for moisture levels & probes in the center of the wood attached to a lignomat moisture meter. The problems with solar kilns include limited control over temperature and limited solar exposure, depending on your region and site location. This air space is absolutely critical for even airflow, so count on the extra floor space right from the design phase. My baffles hang from T-bar assemblies mounted to the ceiling. I made a simple frame from plywood strips and attached the insulation sheets to them with screws and fender washers. The schedule designations use the popular U.S. Forest Products Laboratory designations. For end baffles, I use 2"-thick rigid foam insulation screwed to the main baffles. I hope that the sawyer coated the ends of the lumber with Anchor-Seal or oil-based paint when it was green. 4. 8. Choosing a Kiln Schedule This gives me a secondary method of tracking the drying process, using both water volume and moisture content (MC) readings. This, of course, is gross savings; we must calculate electrical costs to determine the net savings: in this case, about $62. A dry kiln needs to be operated when it is filled with lumber and forces airflow through the tiers of lumber instead of around the ends or over the top of the stack(s). For 4/4 hard maple, with an initial temperature of 90F and an initial relative humidity of 81%, the SDR was given as .0061 pints per hour per board foot. I modified one of the Radio Shack combo units so it could measure the RH remotely as well as the temp. https://www.fs.usda.gov/research/treesearch/9635, International Institute of Tropical Forestry, Eastern Forest Environmental Threat Assessment Center, Northern Institute of Applied Climate Science, Western Wildland Environmental Threat Assessment Center, conventional-temperature (< 180 F) schedules, elevated-temperature (180-212 F) schedules, R. Sidney Boone, Charles J. Kozlik, Paul J. Bois, Eugene M. Wengert. Additionally, I have been underwhelmed by the performance of solar-operated fans. Always avoid conditions that add moisture back to the lumber, especially during start-up. Another great option is to convert an existing shed or outbuilding to a lumber kiln. For the best experience on our site, be sure to turn on Javascript in your browser. Oregon-based HDE Dry Kilns has launched a new line of small kilns ranging from 2,000 to 12,000 board feet. Leave an air space between the rigid foam and subfloor for additional insulating properties. My four main baffles consist of sheets of 1 Styrofoam insulation. Official websites use .gov Reweigh and obtain the oven dry weight. A small electric heater supplies auxiliary heat to maintain adequate kiln temperature. It is a meaningless exercise to try to convert those schedules for the kiln you built. 301 0 obj <>stream 73. Once all the lumber is stacked and stickered, place baffles over the lumber. If you intend to kiln dry lumber from a green state, right off the sawmill, you will need to be well-versed in airflow rates and follow a detailed drying schedule. Place the one inch sections in an oven 215F to 218F (102C to 103C) and dry - usually 18 to 36 hours depending on the oven. Insulate the floor with 2 rigid foam for convenience and durability. 0000003109 00000 n Phytosanitary heat treatments of Ceratocystis lukuohia and Ceratocystis huliohia-colonized Metrosideros polymorpha wood were evaluated using kilns. Schedules Dry Kiln Schedules for Commercial Woods You won't ever have the fastest kiln in town, but it can still work. A.gov website belongs to an official government I either use some cedar 3" x 5", or 4" x 4" stock. . The kiln operator sets the kiln controls based on the initial moisture of the lumber as it is loaded into the kiln. 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