With two-stack and three stack kilns, it is better to have reversible fans to alter the direction of airflow mid-cycle. 0000000710 00000 n I found that brackets for mounting rigid metal electrical conduit work best. It uses a simple humidistat to control the dehumidifier, and a remote bulb thermostat to control the heater, which is a couple of light bulbs. Adjust the baffles or fan direction to achieve good airflow. Each layer of lumber is separated from the next by a series of "stickers" or spacer sticks. Place a sticker at each end, and every 16 along the stack for 4/4 stock. There may be more depression values than required; ignore the extra depression values in this table. Dehumidification dry kilns operate at lower drying temperatures (typically below 150F) than do conventional kilns, which results in longer drying schedules. A small "m" after the designation indicates that the wet-bulb temperatures should be adjusted to avoid temperatures below 90 F. See the above mentioned publication for details. Also check that air isnt escaping around the side baffles or under the stack of lumber. The store will not work correctly in the case when cookies are disabled. Please refer to Appendix A which shows the Lumber Dry Kiln Bill of Materials. Equalizing and Conditioning 0 \ Each layer of lumber is separated from the next by a series of stickers or spacer sticks. Kiln drying is almost always essential for wood intended for interior uses. By setting the relative humidity (RH) on the dehumidifier, you can control how often it runs. The DH is not needed at this time, as the lumber is already bone-dry. JavaScript seems to be disabled in your browser. 0000006297 00000 n Typical dehumidification kiln (FPL 1999 p. 12-10). For these items, please call the store where you purchased them or our customer service department at 1-800-376-7856 so we can assist you. Academia.edu no longer supports Internet Explorer. WOODWEB is a registered trademark of Woodweb.com. 9. I usually see a large volume of water in the DH each night when I check the kiln. Ignoring for a moment the merits of a homebrew DH kiln versus a Nyle, I was curious to see that rather than referencing the standard kiln schedules (e.g. building the dehumidification dry kiln. After seven to 10 days, I reverse the fan direction to make sure all stacks of lumber dry evenly. Contractors work on a tight schedule, and that may not allow much time for curing and drying concrete. Although I can maintain the 90 degree temperature, I could not start at the recommended humidity level unless I added humidity. Dehumidification: This kiln-drying process requires the use of a heat pump system to remove water from the wood. Size and placement of the access door are critical as well. The thinner the stock, the more critical sticker placement becomes. Total costs for the materials were $2,704 based on 2006 prices. From contributor D: 0000002827 00000 n Appendix B . /Height 2587 This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. Wood Drying/ Seasoning. 158 p. Dry kiln schedules for commercial woods : temperate and tropical. The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. Our approach was to build and operate a small dehumidification dry kiln. Secure .gov websites use HTTPS Phytosanitary heat treatments of Ceratocystis lukuohia and Ceratocystis huliohia-colonized Metrosideros polymorpha wood were evaluated using kilns. A lower RH setting will call for the DH to run more often. Reweigh and obtain the oven dry weight. My kiln uses four ceiling-mounted fans, each rated for 1,600 CFM. Kiln schedules are completely assembled and written out for easy use. The schedule designations use the popular U.S. Forest Products Laboratory designations. If your lumber stack is built on starter blocks, you will need to limit airflow there as well. A better choice might be a solar kiln, as you can dry wood from "wet" to 6-8 percent MC in 6-8 weeks. Typical . The membrane was taped and lapped to the weather so if the tape ever fails, any rain that gets behind the siding would still be shed down and away by the HomeWrap. I am removing water about 50% below the SDR. Place a 1x6 board on the floor behind the stack, tilted to a 45 angle. The Bolivian wood products industry was surveyed to determine lumber drying capacity, technology and. For end baffles, I use 2-thick rigid foam insulation screwed to the main baffles. After four days, I decrease the RH setting on the DH to 30% and continue to run the fans. I'm trying to find a timetable or drying schedule for the basic dehumidification kilns you see on youtube. Insulation for walls and ceilings should be a minimum of R13. Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. I usually see a large volume of water in the DH each night when I check the kiln. Abstract. The velocity through the load is assumed to be between 275 and 350 fpm, except for the white woods (including maple, ash, basswood, hackberry) where higher velocities (up to 600 fpm) are desired and acceptable. Without baffles, the top layers of lumber experience "potato chipping" with cupping, twisting or warping. In this paper, the effective schedules were further investigated for longer culm parts treated with boron. 1998. Once the lumber is sterilized, it is ready for the conditioning phase. I recently picked up a back issue of American Woodworker, #94 June 2002, that has a good article on constructing a simple DH kiln. On this order alone, I saved over $1,300 by drying the lumber myself. Sorry, preview is currently unavailable. I like these starter blocks to raise the lumber a few inches off the floor. For a kiln temperature of 140 F, sterilization takes three to five hours. 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. The starter blocks should be as long as the stack is wide. Share sensitive information only on official, secure websites. 3. Also, since heat rises, ceiling-mounted fans have the added benefit of circulating the warmest air over the lumber. In the fourth column, write down the wet-bulb depressions (determined in #4 above), one for each Schedule Step, starting at the top (Schedule Step 1). A 1.5-kW dehumidifier was installed in the solar dryer to determine the performance of a combined solar-dehumidification dryer. Download Table of Contents. Also, for that approach to work, the chamber needs to be air tight. Among the various sizes of southern yellow pine (SYP) dimension lumber, 2 by 4 is produced in the greatest volume. Kiln drying lumber is a simple, cost effective method recommended for anyone who wants to increase profits by selling dried lumber. Milling the stickers square is advantageous over a rectangular cross-section, because no matter how you place the stickers they will form a level stack. Excel Program for Modeling Lumber Dry Kiln Operations - a model for lumber dry kiln operation. I prefer to empty the water tray manually and record the volume of water collected. Remove samples from the stack, and cut an inch or two off one end. Would adding humidity at the start, bringing the initial relative humidity rate to 87% as suggested in the table, result in better product or faster drying? On the last load of lumber I purchased, I saved $2.50 per board foot compared to retail prices for kiln-dried lumber. Among dimension lumber, the 2- by 4-inch size is typically the most susceptible to warp for a variety of reasons. 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. Our next kiln charge is scheduled to begin around February 6, 2023. Many available kiln designs require a large, heavy door. For a kiln temperature of 140 F, sterilization takes three to five hours. When that is the case, I know Ill have usable lumber in just a few weeks. After seven to 10 days, I reverse the fan direction to make sure all stacks of lumber dry evenly. Recently, either Wood, or American Woodworker showed how to build a small version of a solar kiln. I don't remember how the air flow was arranged in the kiln in the magazine, but it sounds like that could be a problem for you. Drying small amounts of lumber using a dehumidification kiln is a suitable option for woodworkers even with limited knowledge of kilns. This makes lightweight baffles that can be easily moved and repositioned. Vacuum Kiln Drying. Kiln drying lumber is a simple, cost effective method recommended for anyone who wants to increase profits by selling dried lumber. Changing the position of the doorway in various kiln setups helps provide the best access to the stacks of lumber. The kiln operator sets the kiln controls based on the initial moisture of the lumber as it is loaded into the kiln. As a result, the kiln schedules were too severe. My aim was to develop a small dehumidification kiln for better control of the three key components of lumber drying: temperature, airflow and humidity. This lets the operator sort stacks by lumber species, so they will be easy to retrieve when the drying cycle is complete. They are based on different air flow rates, etc. Also, you can't really control well by measuring the collected water because some of the water leaks out with vented or leaking air. Dehumidification drying system. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. Determine the correct designation, such as T3-D2 for 4/4 red oak. USDA, 1991) . I have sensors in the kiln for moisture levels & probes in the center of the wood attached to a lignomat moisture meter. , , o* j=d This shed will be essentially unheated for much of the year and very hot during the kiln-drying cycles. My kiln schedule starts with running all fans and the dehumidifier for two days, measuring and removing water as it accumulates. Be sure that all of the kiln equipment is working prop-erly before lumber is loaded into the kiln. Different species should not be loaded simultaneously into the kiln due to often differing kiln schedules. Drying lumber too quickly can lead to deep end checking, warping and case hardening. Also, since heat rises, ceiling-mounted fans have the added benefit of circulating the warmest air over the lumber. The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. With a 130 F kiln temperature, sterilization will take 10 to 12 hours ( Dry Kiln Operators Manual, 1991 ). Windows and doors are also sealed, as well as any holes cut for electrical service. Most species of hardwood lumber can be safely dried this way, once the moisture content is 20% to 25% or less. This will allow the heater to cycle on and off automatically, according to the kiln operator's setting. Commercial scale steam kilns consume large amounts of energy. BE CAREFUL--The first temperature value must be repeated for every MC class (column #2) that is above 30% MC. Basically, you don't want all of the air rushing out under the stack, so find a way to redirect it. Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 F (82 C). Small, complete dehumidification dry kilns under 5,000 board-foot capacity are not available for sale. This kicker board will help distribute the airflow more evenly through all layers of lumber. A lower RH setting will call for the DH to run more often. HDE small kilns feature all-aluminum construction for a long, maintenance-free life span . Usually, you need anywhere between five to eight kiln schedules to complete the process. Culm parts with 2.0 and 2.2 m length after pressure treatment were dried in industrial kilns using three schedules with mild, severe and highly severe drying intensity. Measure airflow over the stacks of lumber in various locations. In the majority of cases, the drying schedules are from the world literature, with emphasis on U.S., Canadian, and British publications. 6. (Dry Kiln Operator's Manual. A variety of wood drying kiln technologies exist today: conventional, dehumidification, solar, vacuum and radio frequency. If required, look-up and write down the RH (sixth column) and EMC (seventh column) for each schedule step. . More than 75 percent of the existing hardwood dry kilns in the United States are steam heated, are humidity controlled and have reversible fans inside the kiln. Corrosion resistant epoxy coated aluminum cabinets and specially coated dehumidification coils for an extra long life. /Length 7 0 R 0000004213 00000 n 0000006274 00000 n A typical home center sheds floors are underbuilt for the weight of a load of lumber. However, if you kiln dry hardwood lumber that has already been air dried, the process is much more forgiving. Saving money by drying your lumber may not be the answer for every woodworker, but the basics shown here demonstrate that it is within the reach and skills of the average person. The dry kiln operator is fully in control, with the ability to make changes as the dry kiln schedule is executing. 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. Extruded polystyrene foam (blue or pink rigid foam) in this thickness has an R value of 10. Corners where walls meet should be sealed with expanding foam sealant. Only the fans need electricity. Moisture Content Dry Bulb Wet Bulb Depression percent degree F degree F degree F Above 50 110 106 4 50 to 40 110 105 5 40 to 35 110 102 8 35 to 30 110 96 14 30 to 25 120 90 30 Vote. The moisture loss, drying time and drying defects were determined. noun. Question Share. These figures hold true for lumber up to 2 thick. I find that unplugging the DH is helpful during the sterilization phase so I can add a second heater, without overwhelming my electrical circuit. /Name /ImagePart_0 Seems like a pretty simple way to run the kiln - once or twice a day just measure the amount of water extracted, and turn down the humidity a bit as needed. are generally kiln dried by time scheduleswhether the wood is intended for struc-tural lumber or for appearance uses, such as furniture or millwork. Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 F (82 C). Dehumidification kiln schedules 145 Sterilizing, equalizing, and conditioning treatments 145 Sterilizing treatments 145 Mold 145 Fungal stain and decay 146 . For a small scale shed kiln, I recommend a maximum footprint of 200 square feet. . This prevents dead spots inside the chamber that experience limited airflow. I have been reading & studying kiln schedules for years too. I am also curious why an initial temperature of 90F would have been selected. Another great option is to convert an existing shed or outbuilding to a lumber kiln. Detailed design and custom manufacture of dehumidification and chiller systems for food processing, lumber drying and industrial applications. Basically, you dont want all of the air rushing out under the stack, so find a way to redirect it. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. This problem is magnified if the lumber is thin or flatsawn. Built properly, a shed kiln may even increase the value of a property. %PDF-1.4 % The stickers are uniform in size and usually 3/4 or 1 square. The approach described in the article where you try to keep the water leaving at a steady rate is fine. I've been drying hardwood lumber in this Sauno dehumidification kiln for 4 years with excellent results. This slows the end-grain drying and limits the severity of end checking. If the temperature is below this range, I start the heater and adjust the thermostat accordingly. For equalizing, use an EMC 2% below the target MC at a dry-bulb of 170 F. For conditioning, use an EMC 4% above the target MC at a dry-bulb of 180 F. Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison. End baffles are also a good idea to prevent airflow from bypassing the stack entirely. Construction of a kiln chamber is very similar to building a small house. Once the core readings are 6% to 8% on a fresh cut, the lumber is dry and ready for sterilization. Remote operation and networking is optional. Schedule for drying 4/4 and 5/4 upland red oak in a steam dry kiln. A lazy Susan with 180 detents mounts the fan box to the ceiling. Moisture content step schedules can be converted to schedules based on time once a kiln operator develops a data record from at least 6 different kiln runs with lumber of the same thickness and species. This slows the end-grain drying and limits the severity of end checking. Add up the amp draw on all the equipment you plan to use in the kiln, including a heater, dehumidifier, fans and steam generator. You can achieve top-quality results with incredible efficiency. Staff. A kiln schedule is a set of temperatures and humidities that are used during kiln operation. Another common sticker size is 1" x 2", and these work fine as well. Matched to one of our L-Series and HT Dehumidifiers they can handle whichever species you are drying, fast drying softwoods to slow drying hardwoods. The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. Looking at the cost-benefit analysis of a shed kiln can be enlightening. Over 40 years experience building kilns. If MC readings still arent at the desired range, the heat may need to be increased for the remainder of the drying cycle. Thicker lumber like 5/4 or quartersawn lumber is naturally more stable. Electrical requirements for a DIY kiln are pretty straightforward, but hiring an electrician is still a good idea. Job Opportunities and Woodworking Services, Dust Collection, Safety and Plant Operation. Subtract the wet-bulb depression from the dry-bulb temperatures for each schedule step and enter the value in the fifth column. In addition, weight on top of the stack can be helpful, but nothing replaces baffles for the best lumber yield. Lay down the bead of caulking before raising the walls. To condition the lumber, I introduce steam into the kiln for about two hours. There is a way to do the conversions and there is a chart published by Nyle to do it, if you want to do some academic exercise. For a kiln temperature of 140 F, sterilization takes three to five hours. Q,kjifT33P[! With a 130 F kiln temperature, sterilization will take 10 to 12 hours ( Dry Kiln Operators Manual, 1991 ). For single-stack kilns, stationary fans are adequate. 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. organization in the United States. 3, a simplified transverse section of a kiln chamber with an energy recovery and dehumidification system is shown. Wood-Mizer dehumidification and solar wood kilns range from 300 to 35,000 board feet capacity for drying lumber. Insulate the floor with 2 rigid foam for convenience and durability. I made a simple frame from plywood strips and attached theinsulation sheets to them with screws and fender washers. Then align each subsequent layer of stickers over the last. The four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln. I have constructed a kiln using these plans. You may also return purchases to a Rockler store near you for store credit. /Width 1628 . Attic fans are a perfect way to provide airflow over the stacks of lumber. Main thing is to not rush drying in first stages, as this will cause problems. You can achieve top-quality results with incredible efficiency. The second most common type of drying is called dehumidification drying. A heavy-duty 1,500-watt space heater works fine. 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. The schedules can also be formulated manually as follows. txN.a!HQ)FmCw~{B1Aq_!+zN#+j Two-by-four material sawn from young trees, thinnings, and stem tops contains a significant proportion of juvenile wood and is particularly notorious for warp. Air speed of 350 feet per minute is appropriate for common hardwoods such as oak and maple. There might be a problem with that if the chamber overheats and has to be vented because some water will leave that way. A typical kiln schedule is a series of temperatures and relative humidities, which are applied at various stages of drying as can be seen in Table 1. .