Main thing is to not rush drying in first stages, as this will cause problems. For a single-stack kiln I recommend a minimum shed size of 8 x 12. In Fig. Size and placement of the access door are critical as well. Our capacities are 4,000 board feet in a kiln . 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. Job Opportunities and Woodworking Services, Dust Collection, Safety and Plant Operation. With a 130 F kiln temperature, sterilization will take 10 to 12 hours ( Dry Kiln Operators Manual, 1991 ). Among the various sizes of southern yellow pine (SYP) dimension lumber, 2 by 4 is produced in the greatest volume. I either use some cedar 3 x 5, or 4 x 4 stock. After two days operating only the fans and DH, I take note of the temperature. This will allow the DH to drain automatically without you needing to enter the kiln. As the MC drops and I crank the DH on more and more, the temp tends to rise up too high just from the heat the DH throws off, even though the light bulb heaters are not on at that point. My shed kiln was stick-built from standard building material, and sized to take advantage of typical 4 x 8 sheet goods. /ColorSpace /DeviceGray Q,kjifT33P[! Difficult-to-dry species might not exceed 60 C (140 F). If you use a lot of lumber, and youre a decent hand at carpentry, a shed kiln will quickly pay for itself. Also check that air isnt escaping around the side baffles or under the stack of lumber. Basically the idea seems to be to maintain a constant temperature, and . %%EOF Always use adequate samples representing both the wettest and driest lumber in the dryer. The approach described in the article where you try to keep the water leaving at a steady rate is fine. Also, you can't really control well by measuring the collected water because some of the water leaks out with vented or leaking air. This report contains suggested dry kiln schedules for over 500 commercial woods, both temperate and tropical. Anyway, I included my log of a load I did in Nov '06 for everyone's amusement. Kiln drying is the process of drying wood in a controlled environment, where temperature, air circulation and humidity are monitored and stabilized. Although I can maintain the 90 degree temperature, I could not start at the recommended humidity level unless I added humidity. Wood-Mizer dehumidification and solar wood kilns range from 300 to 35,000 board feet capacity for drying lumber. To hang the baffles, simply attach hooks to the plywood frame. I have sensors in the kiln for moisture levels & probes in the center of the wood attached to a lignomat moisture meter. They are easy to use and give you precision control over your drying. This slows the end-grain drying and limits the severity of end checking. In the third column, write down the appropriate dry-bulb temperatures. If MC readings still arent at the desired range, the heat may need to be increased for the remainder of the drying cycle. hb```[@9p(T-3jO:g)@S 4Y]g7l\V!c!$Bf J B@&xcEz8PH@ZHs1/X$qOq,x'x$0.rWg*d XAT10 );9 My kiln uses four ceiling-mounted fans, each rated for 1,600 CFM. H6`2}s=n:l)CR>/"\ Make sure the total amp draw is well within the limit of your electrical circuit. The common lumber name is used throughout. The moisture loss, drying time and drying defects were determined. Table 1 shows a typical drying schedule for sugar maple. Without baffles, the top layers of lumber experience potato chipping with cupping, twisting or warping. Most species of hardwood lumber can be safely dried this way, once the moisture content is 20% to 25% or less. 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 A kiln schedule is a set of temperatures and humidities that are used during kiln operation. I like these starter blocks to raise the lumber a few inches off the floor. They are easy to use and give you precision control over your drying. This makes lightweight baffles that can be easily moved and repositioned. A lazy Susan with 180 detents mounts the fan box to the ceiling. Small, complete dehumidification dry kilns under 5,000 board-foot capacity are not available for sale. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). Sticker spacing can be increased to 24" apart for 5/4 or thicker hardwood. Its a nice use of technology and adds a measure of safety as well.) Reweigh and obtain the oven dry weight. Kiln Drying . are generally kiln dried by time scheduleswhether the wood is intended for struc-tural lumber or for appearance uses, such as furniture or millwork. kiln/. A lower RH setting will call for the DH to run more often. In this research, a drying restraint system was evaluated as a means of warp reduction in 8- and 16-foot-long SYP lumber. 0000000710 00000 n A free BASIC program to convert the designations into actual temperatures and humidities is available from the author. Thicker lumber like 5/4 or quartersawn lumber is naturally more stable. Kiln drying lumber is a simple, cost effective method recommended for anyone who wants to increase profits by selling dried lumber. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. (In the original Dry Kiln Operators Manual written in the early 1950s, some species were not used in high quality products. Exterior sheathing and siding type also factors into the heat-holding ability of the structure. My four main baffles consist of sheets of 1 Styrofoam insulation. Do not know just how the end point of moisture would compare. A household dehumidifier (DH) removes moisture from the kiln chamber. The lumber was then measured for crook, bow, and twist. So, with that lengthy introduction, here is my question. The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. Warp in dimension lumber is a significant cause for loss in grade and value. This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. 0000006297 00000 n Air speed of 350 feet per minute is appropriate for common hardwoods such as oak and maple. These figures hold true for lumber up to 2 thick. This publication outlines the basic construction of a small scale dehumidification dry kiln. A bead of silicone caulking between the subfloor and sill plate will prevent air infiltration. My baffles hang from T-bar assemblies mounted to the ceiling. Using a piece of paper with 6 columns, write down the Schedule Step numbers in the first column on the left. Check your local building codes for regionally specific requirements and electrical permits. To accommodate the floor insulation, blocking between joists is oriented horizontally instead of the normal vertical position. After seven to 10 days, I reverse the fan direction to make sure all stacks of lumber dry evenly. 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). Many articles have been dedicated to solar lumber kilns: everything from a simple sheet of Visqueen over a stack of lumber in the sunshine to elaborate enclosures designed for solar gain. This procedure is discussed in a following section. Wood Shrink/Swell estimator - A web-based program to estimate shrink/ swell in wood. Measure airflow over the stacks of lumber in various locations. 0000001417 00000 n Dehumidification drying system. /Length 7 0 R Staggering the seams between the sheathing and siding layers helps avoid air infiltration. 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 Be sure that all of the kiln equipment is working prop-erly before lumber is loaded into the kiln. On the last load of lumber I purchased, I saved $2.50 per board foot compared to retail prices for kiln-dried lumber. We proudly stand behind all of our products. 0 \ The last step requires a short period of high humidity to relieve the drying stresses in the boards. This Blue&White Ginger Jar is a stunning piece of porcelain and pottery, expertly handcrafted with natural variations in each piece. Different species should not be loaded simultaneously into the kiln due to often differing kiln schedules. The second temperature value is written for the 25 to 30% MC class; the third for the 20 to 25% MC class; and so on. When that is the case, I know Ill have usable lumber in just a few weeks. I know your kiln is absolutely tight and perfectly sealed, but it has to vent some or it would overheat. If the interior volume of a kiln becomes too large, basic heaters and home dehumidifiers may be inadequate to control the kiln environment. You may also return purchases to a Rockler store near you for store credit. By. An anemometer confirms that your effort constructing baffles was worthwhile. Always avoid conditions that add moisture back to the lumber, especially during start-up. Basically, you dont want all of the air rushing out under the stack, so find a way to redirect it. If the fans and dehumidifer generate enough heat to maintain a temperature of 100 to 120 F, then I wont use the auxiliary heater. 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. building the dehumidification dry kiln. For end baffles, I use 2-thick rigid foam insulation screwed to the main baffles. The baffles do not need insulating properties, and plywood would work just as well. Without baffles, the top layers of lumber experience "potato chipping" with cupping, twisting or warping. This serves a dual purpose of supporting the rigid foam insulation as well as stiffening the floor framing. Place a 16 board on the floor behind the stack, tilted to a 45 angle. Basically the idea seems to be to maintain a constant temperature, and to keep lowering the humidistat to maintain the SDR until the moisture content gets to the desired level. of this publication is to make available to dry kiln operators and others interested in kiln-drying wood, kiln schedules that are completely assembled and written out for ready reference and easy use. Gen. Tech. In vacuum kiln trials, logs were heated to 56C at 70 percent log radius depth and the temperature maintained for . But kiln drying may also introduce internal stresses into the woodparticularly if an improper kiln schedule is used, . Each layer of lumber is separated from the next by a series of stickers or spacer sticks. Leave an air space between the rigid foam and subfloor for additional insulating properties. The DH is not needed at this time, as the lumber is already bone-dry. Ideally, a lumber kiln would be large enough to dry multiple stacks of lumber. Hardwood kiln drying schedules typically keep the dry bulb temperature below 80 C (176 F). This makes lightweight baffles that can be easily moved and repositioned. (I have found that remotely monitoring the temperature and humidity with a WiFi sensor can be very helpful. In larger kilns, the heater may be needed in the latter part of the drying cycle. Dehumidification: This kiln-drying process requires the use of a heat pump system to remove water from the wood. With advances in spray foam insulation, it may be possible to seal older, drafty structures as well. By setting the relative humidity (RH) on the dehumidifier, you can control how often it runs. I hope that the sawyer coated the ends of the lumber with Anchor-Seal or oil-based paint when it was green. John Baines Reply to Dann Barry 1 year ago 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. txN.a!HQ)FmCw~{B1Aq_!+zN#+j Typical . Whether to Wax Walnut Ends Before Steaming, Frequently Asked Questions about Widebelt Sanders. We are proud of the quality of our products, and we stand behind them 100%. , , o* j=d Schedules for several thicknesses and specialty products (e.g. The last thing to do before starting the kiln is to close the gable vent with an insulated cover. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. A discussion of how to apply "safe drying rate" calibrations with a home-built dehumidifying kiln. This would allow a stack of lumber four feet wide and 10 feet long. In addition, weight on top of the stack can be helpful, but nothing replaces baffles for the best lumber yield. The thinner the stock, the more critical sticker placement becomes. This problem is magnified if the lumber is thin or flatsawn. 0000000591 00000 n Joining end grain to long grain forms the king of joints. Determine the correct designation, such as T3-D2 for 4/4 red oak. I prefer to empty the water tray manually and record the volume of water collected. Soon the DH won't show much water collected in the tray. Remove samples from the stack, and cut an inch or two off one end. 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. Kiln dried wood typically sells for a third more than green lumber and eliminates the need for customers to incur costs associated with drying lumber . KD150 Series dehumidifier pdf manual download. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. For a kiln temperature of 140 F, sterilization takes three to five hours. Dehumidification Kilns Dr. Gene Wengert provides schedules for kiln drying hardwood lumber. They are normally mounted in the gable of household attics, and they are designed to be used in high temperature environments. Attic fans are a perfect way to provide airflow over the stacks of lumber. The kiln humidity can be expressed as an EMC, relative humidity, or wet-bulb temperature. This air space is absolutely critical for even airflow, so count on the extra floor space right from the design phase. The stickers are uniform in size and usually 3/4" or 1" square. %3.3 You can achieve top-quality results with incredible efficiency. However, if you kiln dry hardwood lumber that has already been air dried, the process is much more forgiving. 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. . For the best experience on our site, be sure to turn on Javascript in your browser. 6. . Attic fans are a perfect way to provide airflow over the stacks of lumber. Every Nyle Dehumidification Dry Kiln System Example: If the WBT falls below the set parameter measures and regulates internal kiln conditions the system will turn on the spray system. My kiln uses four ceiling-mounted fans, each rated for 1,600 CFM. Frequently, the lumber has already air-dried for several years in a barn or outbuilding. Construction of a kiln chamber is very similar to building a small house. For single-stack kilns, stationary fans are adequate. Also, since heat rises, ceiling-mounted fans have the added benefit of circulating the warmest air over the lumber. . %PDF-1.5 Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 F (82 C). Once all the lumber is stacked and stickered, place baffles over the lumber. (116 C) temperature. Rep. FPL-GTR-57. Nyle Systems dehumidification kiln packages are our best known product with nearly unlimited drying capabilities. 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. This is because it needs to be dried to a lower moisture content than wood will air dry to outdoors. (Note: This letter designation is related to the green MC of the species. Ciencia y Tecnologia, Duygu Kocaefe, Ayhan Aytin, The Bolivian secondary forest products industry has experienced substantial growth during the last 10 years. Items shipped directly from the manufacturer cannot be returned in store. If severe enough, the lumber can develop honeycomb cracks throughout. temperature. The first thing to consider when designing a shed kiln is size. This can create internal stress in the lumber that is released when sawing. Apply foil tape to the edges of the main baffles to help protect the Styrofoam. 1998. Abstract. Corrosion resistant epoxy coated aluminum cabinets and specially coated dehumidification coils for an extra long life.