There may be more depression values than required; ignore the extra depression values in this table. the hardwood kiln schedule is the equalization of the moisture content of all boards at 6-8%. A lower RH setting will call for the DH to run more often. Main thing is to not rush drying in first stages, as this will cause problems. Select a heater with an adjustable thermostat and a tip-over shutoff. Place the sample board in the lumber stack in a location where it will dry at the same rate as the rest of the lumber in the dryer (see Figure C). For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. 0000002827 00000 n With each load I did not have the initial relative humidity rate. After seven to 10 days, I reverse the fan direction to make sure all stacks of lumber dry evenly. My kiln uses four ceiling-mounted fans, each rated for 1,600 CFM. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. I modified one of the Radio Shack combo units so it could measure the RH remotely as well as the temp. Unlike general shop space, bigger is not always better for kiln design. HWn8gXA N,[mKJr2"Ec9,t After two days operating only the fans and DH, I take note of the temperature. In the third column, write down the appropriate dry-bulb temperatures. This prevents dead spots inside the chamber that experience limited airflow. They are normally mounted in the gable of household attics, and they are designed to be used in high temperature environments. H6`2}s=n:l)CR>/"\ This serves a dual purpose of supporting the rigid foam insulation as well as stiffening the floor framing. You can achieve top-quality results with incredible efficiency. Oregon-based HDE Dry Kilns has launched a new line of small kilns ranging from 2,000 to 12,000 board feet. After seven to 10 days, I reverse the fan direction to make sure all stacks of lumber dry evenly. It can be constructed in any style, with architectural features that match or complement an existing home. After a short period of grumbling, they join me to lay down wood blocks for the first layer of lumber. I am also curious why an initial temperature of 90F would have been selected. There are two main reasons for drying wood: Woodworking When wood is used as a construction material, whether as a structural support in a building . A lock ( Dr. Gene Wengert provides schedules for kiln drying hardwood lumber. It is a good idea to sterilize the lumber at the end of the kiln run. An anemometer confirms that your effort constructing baffles was worthwhile. I found that brackets for mounting rigid metal electrical conduit work best. 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. In contrast, a dehumidification kiln uses a sealed chamber, with only enough energy input to maintain the desired temperature. 0000000710 00000 n Wood Drying/ Seasoning. With advances in spray foam insulation, it may be possible to seal older, drafty structures as well. Always avoid conditions that add moisture back to the lumber, especially during start-up. Then align each subsequent layer of stickers over the last. They are based on different air flow rates, etc. Particularly, important investment has taken place in lumber drying capacity. This allows for a more gentle kiln schedule to fully dry the timber. After four days, I decrease the RH setting on the DH to 30% and continue to run the fans. Also check that air isnt escaping around the side baffles or under the stack of lumber. Another great option is to convert an existing shed or outbuilding to a lumber kiln. I found that brackets for mounting rigid metal electrical conduit work best. At the end of the cycle I have the opposite problem. Enter the email address you signed up with and we'll email you a reset link. After two days operating only the fans and DH, I take note of the temperature. For a kiln temperature of 140 F, sterilization takes three to five hours. I opted not to install a true vapor barrier between the framing and sheetrock, because of potential condensation and mold issues with sheds constructed this way. To browse Academia.edu and the wider internet faster and more securely, please take a few seconds toupgrade your browser. The last step requires a short period of high humidity to relieve the drying stresses in the boards. Among dimension lumber, the 2- by 4-inch size is typically the most susceptible to warp for a variety of reasons. Drying small amounts of lumber using a dehumidification kiln is a suitable option for woodworkers even with limited knowledge of kilns. Another reason I like the idea of a shed kiln is the flexibility of future use. Rocky Mountain . Detailed design and custom manufacture of dehumidification and chiller systems for food processing, lumber drying and industrial applications. My four main baffles consist of sheets of 1" Styrofoam insulation. In time schedules, dry- and wet . (Sawing and Drying Forum) My question focuses on the initial relative humidity featured in the Safe Drying Rate table. These are rough-saw red oak. Consider not only the space for the lumber stacks, but extra floor space to easily load and monitor the charge of lumber. How do I convert from the standard kiln schedules in the USDA's "Dry Kiln Schedules for Commercial Woods" and "Drying Hardwood Lumber" to an SDR-type schedule? Then align each subsequent layer of stickers over the last. Delete from my manuals. Each layer of lumber is separated from the next by a series of stickers or spacer sticks. Using a piece of paper with 6 columns, write down the Schedule Step numbers in the first column on the left. Sticker spacing can be increased to 24" apart for 5/4 or thicker hardwood. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. This problem is magnified if the lumber is thin or flatsawn. Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. These well-known dehumidification kiln packages have been among our bestselling products for the past 30 years. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. In Fig. This helps keep the lumber straight during the drying cycle; in fact, improper placement of stickers can permanently deform lumber. A dehumidification kiln continuously recycles the heat throughout the chamber, rather than . Table 1 shows a typical drying schedule for sugar maple. Featuring lower cost drying at speeds equal to gas & steam, these kilns are continuously exceeding industry standards and changing the game. The last thing to do before starting the kiln is to close the gable vent with an insulated cover. A lazy Susan with 180 detents mounts the fan box to the ceiling. Just walk out to the shed kiln and grab what you need from your custom-dried supply. The second most common type of drying is called dehumidification drying. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). 4.4 drying schedule moisture content drying schedule . I also wrapped the shed with Tyvek HomeWrap. The schedule designations use the popular U.S. Forest Products Laboratory designations. 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. Dehumidification kilns are similar to other kilns in basic construction and drying times are usually comparable. You can download the paper by clicking the button above. The air flow rate through your stacks should be about 350FPM. The lumber was then measured for crook, bow, and twist. Kiln dried wood typically sells for a third more than green lumber and eliminates the need for . For the best experience on our site, be sure to turn on Javascript in your browser. /Name /ImagePart_0 I decided on a dehumidification kiln after reading an article in Fine Woodworking (1991). Also, you can't really control well by measuring the collected water because some of the water leaks out with vented or leaking air. On the last load of lumber I purchased, I saved $2.50 per board foot compared to retail prices for kiln-dried lumber. 293 0 obj <>/Filter/FlateDecode/ID[<87A322ACC143C740A97F712BC6C2FBCD>]/Index[282 20]/Info 281 0 R/Length 68/Prev 378162/Root 283 0 R/Size 302/Type/XRef/W[1 2 1]>>stream There are two ways to remove water from the DH unit, and they both work well. In this paper, the effective schedules were further investigated for longer culm parts treated with boron. A typical home center sheds floors are underbuilt for the weight of a load of lumber. Solar kiln drying was most effective in the summer and early fall, when kiln efficiencies were 90% to 67%, respectively, and drying times were 2 to 3/one-half/ times faster than air drying. . The baffles do not need insulating properties, and plywood would work just as well. A.gov website belongs to an official government The four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln. From contributor D: The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. Dehumidification drying system. Measure airflow over the stacks of lumber in various locations. 10. Formulating a Kiln Schedule Then, write down the appropriate MC ranges (determined in #2 above) in the second column. There are many types of kilns, but the most common are dehumidification kilns and conventional kilns. My baffles hang from T-bar assemblies mounted to the ceiling. txN.a!HQ)FmCw~{B1Aq_!+zN#+j 0000000591 00000 n For example, if you dry 7,500BF of fast drying Pine, you'd select the 8MBF chamber with the HT18 . The MC ranges are chosen so that the loss of the first one-third of moisture, and the highest risk of checking and staining, will occur in the first step listed.). Windows and doors are also sealed, as well as any holes cut for electrical service. 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 major source was Dry Kiln Schedules for Commercial Woods which is available from the Forest Products Society in Madison, WI.) Use the gridded drawings provided on the PDF, Woodworking | Blog | Videos | Plans | How To. 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. Many regions have increased the shed and outbuilding maximum allowable size without need for a permit. A lower RH setting will call for the DH to run more often. The T-bars are made from 1/2 galvanized pipe and are attached to the rafters with threaded pipe flanges. For DH kilns, use the same RH, but lower the temperature to the typical operating temperature for the compressor; raise temperature to steam values when convenient and possible. The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. Initially, I set the DH to 40% RH, because I dont want to remove moisture too quickly. T8-C3 or similar for hard maple), the article instead provided a table showing the "safe drying rates" (SDR) for a number of species. If you use a lot of lumber, and youre a decent hand at carpentry, a shed kiln will quickly pay for itself. Subtract the wet-bulb depression from the dry-bulb temperatures for each schedule step and enter the value in the fifth column. End baffles are also a good idea to prevent airflow from bypassing the stack entirely. Apply foil tape to the edges of the main baffles to help protect the Styrofoam. The common lumber name is used throughout. After four days, I decrease the RH setting on the DH to 30% and continue to run the fans. 906 0 obj << /Linearized 1 /O 908 /H [ 710 498 ] /L 501020 /E 6532 /N 45 /T 482781 >> endobj xref 906 12 0000000016 00000 n After a short period of grumbling, they join me to lay down wood blocks for the first layer of lumber. Remote operation and networking is optional. I have sensors in the kiln for moisture levels & probes in the center of the wood attached to a lignomat moisture meter. The KD150 Dehumidification Kiln Kit is a compact, entry-level dehumidification kiln for drying lumber between 300 and 1000 board feet. 4. When the operating conditions of this option are followed the material will meet the requirements of being kiln dried (KD) and heat treated . Dehumidification dry kilns operate at lower drying temperatures (typically below 150F) than do conventional kilns, which results in longer drying schedules. Low Temperature Kiln Drying Systems (120F) 300BF - 4000BF Capacity . Adjust the baffles or fan direction to achieve good airflow. They are normally mounted in the gable of household attics, and they are designed to be used in high temperature environments. Dont even think of powering your kiln with an extension cord. All of these products were purchased at a local home center, except the remote hygrometer/thermometer which was purchased at a local electronics store. I selected a 36 outswing exterior door. The T-bars are made from 1/2" galvanized pipe and are attached to the rafters with threaded pipe flanges. Dehumidification: This kiln-drying process requires the use of a heat pump system to remove water from the wood. hbbd``b` $ &UD\q@u This will allow the DH to drain automatically without you needing to enter the kiln. There might be a problem with that if the chamber overheats and has to be vented because some water will leave that way. 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. /Width 1628 Contractors work on a tight schedule, and that may not allow much time for curing and drying concrete. To accommodate the floor insulation, blocking between joists is oriented horizontally instead of the normal vertical position. Align the stickers over the starter blocks on the first course. Air drying to 6 - 8% MC is a very long term proposition and I'm not a patient man so I wanted a means to finish dry lumber after air drying outside to the EMC of my area of around 12 - 14%. The cost associated with shed construction was similar to buying a prefabricated kit. Check out More On the Web for my complete calculations to figure savings. My kiln schedule starts with running all fans and the dehumidifier for two days, measuring and removing water as it accumulates. Usually, you need anywhere between five to eight kiln schedules to complete the process. But kiln drying may also introduce internal stresses into the woodparticularly if an improper kiln schedule is used, . Place some sample boards in the stack that will be easy to pull out for moisture testing later. Instead of using expensive electrically reversible fans designed for commercial kilns, I came up with a simple hardware solution. Initially, I set the DH to 40% RH, because I dont want to remove moisture too quickly. Typical dehumidification kiln (FPL 1999 p. 12-10). (I have found that remotely monitoring the temperature and humidity with a WiFi sensor can be very helpful. Difficult-to-dry species might not exceed 140 degrees F. Dehumidification kilns are very . For a kiln temperature of 140 F, sterilization takes three to five hours. Heres a classic project that both steps up and provides overflow seating. I then manually rotate the fan boxes halfway through the drying cycle. Size and placement of the access door are critical as well. Once the core readings are 6% to 8% on a fresh cut, the lumber is dry and ready for sterilization. 6. This helps keep the lumber straight during the drying cycle; in fact, improper placement of stickers can permanently deform lumber. My kiln schedule starts with running all fans and the dehumidifier for two days, measuring and removing water as it accumulates. /ColorSpace /DeviceGray I usually see a large volume of water in the DH each night when I check the kiln. 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 . The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. Willie Sandry is a furniture maker and a lumber kiln operator in Camas, Washington. temperature. Dehumidifier suggestion: http://amzn.to/2iYZqVZThis is the first in a series of videos showing how I built a kiln for drying lumber. A shed kiln is an attractive alternative for a couple of reasons. Our approach was to build and operate a small dehumidification dry kiln. The column on the right I added part way through is the kiln's internal RH. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). An official website of the United States government. Do not know just how the end point of moisture would compare. Inexpensive Dehumidification KilnIn this video we'll build and load a 14' long 4' by 4' wood kiln that dries wood by heat and dehumidification.We had quite a. are generally kiln dried by time scheduleswhether the wood is intended for struc-tural lumber or for appearance uses, such as furniture or millwork. A kiln schedule is a set of temperatures and humidities that are used during kiln operation. The first charge of mixed air-dried 4/4 hardwoods and softwoods was kiln-dried from 18.4% to 7.3% moisture content (MC) in 15 days with no . The schedules can also be formulated manually as follows. 158 p. Dry kiln schedules for commercial woods : temperate and tropical. 0000001186 00000 n Evaluation of kiln-drying schedules for wild cherry wood (Cerasus avium), Model to assess energy consumption in industrial lumber kilns, Mathematical modelling and experimental investigation of dehumidifier drying of radiata pine timber, A survey of Bolivian lumber drying operations, Warp reduction of SYP lumber by restrained drying, Western Juniper Drying Project Summaries, 1993-96, Vacuum contact drying kinetics of Jack pine wood and its influence on mechanical properties: industrial applications, Kiln drying behavior of lumber from ten fast-growth plantation species in Costa Rica, Effect of fire-retardant treatment and redrying on the mechanical properties of Douglas-fir and aspen plywood, Properties of Douglas-Fir and Aspen Plywood, A numerical study on the influence of the bond-line diffusivity on moisture-related stresses and deformations of three-layered spruce cross-laminates, Error in Estimates of the Moisture Content of White Oak Kiln Sample Boards, Green Kerfing Treatment for Improving Softwood Lumber Drying: A Review, A comparison of kiln-drying schedules and quality outcomes for 4/4-thickness black cherry lumber sawn from small-diameter logs, A comparison of kiln-drying schedules and quality outcomes in 4/4-thickness black cherry lumber sawn from small-diameter logs, Data bank for short-length red oak lumber, Hardwood lumber widths and grades used by the furniture and cabinet industries: Results of a 14-mill survey, Lumber and veneer recovery from intensively managed young-growth Douglas-fir, WOOD-FRAME HOUSE CONSTRUCTION U.S. DEPARTMENT OF AGRICULTURE FOREST SERVICBAGRICULTURE HANDBOOK NO. Most species of hardwood lumber can be safely dried this way, once the moisture content is 20% to 25% or less. This is because it needs to be dried to a lower moisture content than wood will air dry to outdoors. I know mixed loads are taboo, but this one worked well, other than the horse chestnut. 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. These kilns will typically hold several thousand board foot of lumber. Kiln drying lumber is a simple, cost effective method recommended for anyone who wants to increase profits by selling dried lumber. This will allow the heater to cycle on and off automatically, according to the kiln operator's setting. Job Opportunities and Woodworking Services, Dust Collection, Safety and Plant Operation, Air-Drying and Kiln-Drying Methods for Wide Plank Flooring, Drying lumber - selecting the best method. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. I recommend a 2 x 3 sliding window with bug screen. )f7haRoMRhib5Sd|-=RBkBBN r-hzf+1\IFgk;v]3_, KxL$9oL "Qw#"BFGfk}>cT2g yP K|7@N*v9!Wy9jB. op(y"X)Fz"q]fQC/ha>7=k_p}}^VXQmj e'2fyXQ{~23X^H1,d>Hq|^KQ*cN=yF%z. Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 F (82 C). Created and Presented by: Henco Viljoen and Elijah McCarty with Nyle Dry Kilns. To hang the baffles, simply attach hooks to the plywood frame. I cannot stress the importance of baffles enough. This makes lightweight baffles that can be easily moved and repositioned. 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. . Air speed of 350 feet per minute is appropriate for common hardwoods such as oak and maple. If the temperature is below this range, I start the heater and adjust the thermostat accordingly. Place a 1x6 board on the floor behind the stack, tilted to a 45 angle. << 2. Once the core readings are 6% to 8% on a fresh cut, the lumber is dry and ready for sterilization. Staggering the seams between the sheathing and siding layers helps avoid air infiltration. The Bolivian wood products industry was surveyed to determine lumber drying capacity, technology and. Sign In Upload. I hope that the sawyer coated the ends of the lumber with Anchor-Seal or oil-based paint when it was green. This can create internal stress in the lumber that is released when sawing. I either use some cedar 3" x 5", or 4" x 4" stock. Once all the lumber is stacked and stickered, place baffles over the lumber. Secure .gov websites use HTTPS Built properly, a shed kiln may even increase the value of a property. in the kiln to dry specific wood products at a satisfactory rate without causing objectionable drying defects. 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. 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 starter blocks should be as long as the stack is wide. I had these custom cut and I air dried them outside under a tarp for 6 to 18 months (depending on which load they came in on) and then I kiln dried them in a Nyle dehumidification kiln for 3 months. To hang the baffles, simply attach hooks to the plywood frame. Download Table of Contents. I find that unplugging the DH is helpful during the sterilization phase so I can add a second heater, without overwhelming my electrical circuit. You could use the dehumidifier to dry wood but it would not be part of a "kiln." Just be a different process. If required, look-up and write down the RH (sixth column) and EMC (seventh column) for each schedule step. Installing a window in a kiln may seem counterintuitive at first, because windows lose more heat than an insulated wall. Warp in dimension lumber is a significant cause for loss in grade and value. I often buy from sawyers or homeowners at 40% to 50% of retail price. A shed kiln has minimal venting (usually one or two gable vents) and sealed soffits. For the sterilization phase, air temperature needs to be around 140 F, for three to five hours. (I use the Mini-Ligno MD/C from Lignomat, www.lignomatusa.com.) Not bragging or anything! The delicate blue and white color scheme c 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). I made a simple frame from plywood strips and attached the insulation sheets to them with screws and fender washers. Leave an air space between the rigid foam and subfloor for additional insulating properties. 9. This will allow the heater to cycle on and off automatically, according to the kiln operators setting. However, if you kiln dry hardwood lumber that has already been air dried, the process is much more forgiving. 0 This problem is magnified if the lumber is thin or flatsawn. Total costs for the materials were $2,704 based on 2006 prices. 1. a furnace or oven for burning, baking, or drying, especially one for calcining lime or firing pottery. Choosing a Kiln Schedule Add up the amp draw on all the equipment you plan to use in the kiln, including a heater, dehumidifier, fans and steam generator. Basically the idea seems to be to maintain a constant temperature, and . Dehumidification Kilns The thinner the stock, the more critical sticker placement becomes. (Dry Kiln Operator's Manual. Consider the weight of the lumber that will be placed in the structure and fortify the building accordingly. The DH is not needed at this time, as the lumber is already bone-dry. Forum Responses Items shipped directly from the manufacturer cannot be returned in store. Our next kiln charge is scheduled to begin around February 6, 2023. JavaScript seems to be disabled in your browser. Understand how kiln performance must be modified to permit the use of custom schedules for specific product applications; Be able to modify existing conventional kiln schedules to dry products in dehumidifier kilns; Recognize degrades common to various species, including hardwoods, and modify handling practices to minimize these The starter blocks should be as long as the stack is wide. Align the stickers over the starter blocks on the first course. I hope that the sawyer coated the ends of the lumber with Anchor-Seal or oil-based paint when it was green. This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. Adjust the baffles or fan direction to achieve good airflow. Rep. FPL-GTR-57. This, of course, is gross savings; we must calculate electrical costs to determine the net savings: in this case, about $62. This makes lightweight baffles that can be easily moved and repositioned. To condition the lumber, I introduce steam into the kiln for about two hours. _0e`bd\ p@ With two-stack and three stack kilns, it is better to have reversible fans to alter the direction of airflow mid-cycle. Regardless of size, allow for a 36 door that opens to a hallway of open space. Once the lumber is sterilized, it is ready for the conditioning phase. I like these starter blocks to raise the lumber a few inches off the floor. Place some sample boards in the stack that will be easy to pull out for moisture testing later. 1. A heavy-duty 1,500-watt space heater works fine. Small, complete dehumidification dry kilns under 5,000 board-foot capacity are not available for sale. 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. This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. I made a simple frame from plywood strips and attached theinsulation sheets to them with screws and fender washers. The stickers are uniform in size and usually 3/4 or 1 square. When properly loaded, this kiln can dry approximately 600 board feet of 4/4" lumber. This listing incorporates current market requirements for the various species, as well as the current quality of the lumber resource itself. For the best experience on our site, be sure to turn on Javascript in your browser. It should be double-pane, well-insulated with low emissivity (low-E). My shed kiln was stick-built from standard building material, and sized to take advantage of typical 4 x 8 sheet goods. This gives me a secondary method of tracking the drying process, using both water volume and moisture content (MC) readings. This kicker board will help distribute the airflow more evenly through all layers of lumber. Vacuum Kiln Drying. An Overview. The first charge of mixed air-dried 4/4 hardwoods and softwoods was kiln-dried from 18.4% to 7.3% moisture content (MC) in 15 days with no . Each layer adds approximately .81 R value. So, if you have 100 bf in the kiln, every 12 hours you would extract (12 hours *100bf * .0061 SDR) = 7.3 pints of water. 6. Low temperatures can be used for an extra safety margin on greener lumber. So, if you have 100 bf in the kiln, every 12 hours you would extract (12 hours *100bf * .0061 SDR) = 7.3 pints of water. Kiln drying normally involves temperatures in the range of 40-75 C (about 100-170 F). Instead of using expensive electrically reversible fans designed for commercial kilns, I came up with a simple hardware solution.

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