dehumidification kiln drying schedules

Ideally, a lumber kiln would be large enough to dry multiple stacks of lumber. An official website of the United States government. That purchase was an average deal, and one I dont consider a particular bargain. The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. For example, if you dry 7,500BF of fast drying Pine, you'd select the 8MBF chamber with the HT18 . 8. 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. HT systems use 40-60% less energy than gas-fired or steam dry kilns. . Dehumidification Opportunities for Dehumidification Drying Of Hardwood Lumber Dimension Kiln Drying Hardwood Dimension Parts Discoloration Preventing Discolorations in Hardwood and Softwood Logs . However, because wood from Omitting the sterilization phase can lead to costly losses from insect damage, so dont skip it. 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? 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. When properly loaded, this kiln can dry approximately 600 board feet of 4/4" lumber. 7. Drying lumber too quickly can lead to deep end checking, warping and case hardening. noun. 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 . Regardless of size, allow for a 36 door that opens to a hallway of open space. A better choice might be a solar kiln, as you can dry wood from "wet" to 6-8 percent MC in 6-8 weeks. Measure airflow over the stacks of lumber in various locations. Items shipped directly from the manufacturer cannot be returned in store. This, of course, is gross savings; we must calculate electrical costs to determine the net savings: in this case, about $62. Minus the drying equipment, a shed kiln is just an insulated storage space, with a host of possible uses. Subtract the wet-bulb depression from the dry-bulb temperatures for each schedule step and enter the value in the fifth column. If you use a lot of lumber, and youre a decent hand at carpentry, a shed kiln will quickly pay for itself. The stickers are uniform in size and usually 3/4 or 1 square. In addition, weight on top of the stack can be helpful, but nothing replaces baffles for the best lumber yield. 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 Unlike general shop space, bigger is not always better for kiln design. They are based on different air flow rates, etc. Secure .gov websites use HTTPS This shed will be essentially unheated for much of the year and very hot during the kiln-drying cycles. Temps are in Celsius (20C = 70F, 40C = 105F). A bead of silicone caulking between the subfloor and sill plate will prevent air infiltration. Place some sample boards in the stack that will be easy to pull out for moisture testing later. Job Opportunities and Woodworking Services, Dust Collection, Safety and Plant Operation. Kiln schedules are completely assembled and written out for easy use. We are proud of the quality of our products, and we stand behind them 100%. Share. 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). I use a Rockler steam generator, item #42826 (www.rockler.com). In exchange for building the shed myself, I wound up with a shed of higher quality, with more features. 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. Basically, you dont want all of the air rushing out under the stack, so find a way to redirect it. To condition the lumber, I introduce steam into the kiln for about two hours. Dont even think of powering your kiln with an extension cord. The schedule designations use the popular U.S. Forest Products Laboratory designations. My baffles hang from T-bar assemblies mounted to the ceiling. (Note: This letter designation is related to the green MC of the species. For single-stack kilns, stationary fans are adequate. I have constructed a kiln using these plans. In the third column, write down the appropriate dry-bulb temperatures. This gives me a secondary method of tracking the drying process, using both water volume and moisture content (MC) readings. In vacuum kiln trials, logs were heated to 56C at 70 percent log radius depth and the temperature maintained for . 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. Without baffles, the top layers of lumber experience potato chipping with cupping, twisting or warping. The last thing to do before starting the kiln is to close the gable vent with an insulated cover. %PDF-1.6 % If your lumber stack is built on starter blocks, you will need to limit airflow there as well. Remove samples from the stack, and cut an inch or two off one end. Just walk out to the shed kiln and grab what you need from your custom-dried supply. Temperatures inside the kiln range from 120 to 190 degrees F, depending on the stage of . I like these starter blocks to raise the lumber a few inches off the floor. 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 The four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln. USDA, 1991) . Made in China, it exudes the classic style of Asian and Chinese cultures, featuring a unique shape that sets it apart from traditional jars. Delete from my manuals. Equalizing and conditioning are required for almost all hardwood lumber. Dehumidification kilns from Nyle Systems in Brewer, Maine. A kiln schedule is a set of temperatures and humidities that are used during kiln operation. (I use the Mini-Ligno MD/C from Lignomat, www.lignomatusa.com.) Kiln drying is almost always essential for wood intended for interior uses. 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 . Vacuum Kiln Drying. Once the core readings are 6% to 8% on a fresh cut, the lumber is dry and ready for sterilization. For a kiln temperature of 140 F, sterilization takes three to five hours. My baffles hang from T-bar assemblies mounted to the ceiling. organization in the United States. 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. Go to the first number designation (the temperature designation) and find the corresponding temperatures in the table below. Reply. For single-stack kilns, stationary fans are adequate. In this paper, the effective schedules were further investigated for longer culm parts treated with boron. (See the following sections for a discussion of how to develop a schedule from these designations.) Dehumidification dry kilns operate at lower drying temperatures (typically below 150F) than do conventional kilns, which results in longer drying schedules. I made a simple frame from plywood strips and attached the insulation sheets to them with screws and fender washers. Thus, a drying program can be adapted according to the characteristics of the kiln load, e.g., species, dimensions, and moisture content. 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? The T-bars are made from 1/2 galvanized pipe and are attached to the rafters with threaded pipe flanges. Nyle. Vote. After a short period of grumbling, they join me to lay down wood blocks for the first layer of lumber. the hardwood kiln schedule is the equalization of the moisture content of all boards at 6-8%. Apply foil tape to the edges of the main baffles to help protect the Styrofoam. Consider not only the space for the lumber stacks, but extra floor space to easily load and monitor the charge of lumber. 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 Perhaps the best part: you wont need to calculate your lumber needs down to the board foot. By setting the relative humidity (RH) on the dehumidifier, you can control how often it runs. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. I found that brackets for mounting rigid metal electrical conduit work best. A small electric heater supplies auxiliary heat to maintain adequate kiln temperature. Main thing is to not rush drying in first stages, as this will cause problems. Sticker spacing can be increased to 24" apart for 5/4 or thicker hardwood. Using a piece of paper with 6 columns, write down the Schedule Step numbers in the first column on the left. Wood poles subjected to a 22- to 34-day dehumidification kiln schedule with a heat treatment to 60C to the poles' core. To condition the lumber, I introduce steam into the kiln for about two hours. To browse Academia.edu and the wider internet faster and more securely, please take a few seconds toupgrade your browser. In time schedules, dry- and wet . The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. For end baffles, I use 2-thick rigid foam insulation screwed to the main baffles. Take a moisture reading in the end grain with a pin-type moisture meter or remote probe.) Insulate the floor with 2 rigid foam for convenience and durability. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. txN.a!HQ)FmCw~{B1Aq_!+zN#+j Select a heater with an adjustable thermostat and a tip-over shutoff. This can create internal stress in the lumber that is released when sawing. . temperature. 0000002536 00000 n There may be more depression values than required; ignore the extra depression values in this table. The following tables show some examples of oak schedules for steam dry kilns and dehumidification dryers. Then align each subsequent layer of stickers over the last. Schedules Dry Kiln Schedules for Commercial Woods Over 40 years experience building kilns. Kiln Drying . Size and placement of the access door are critical as well. Air speed of 350 feet per minute is appropriate for common hardwoods such as oak and maple. Low temperatures can be used for an extra safety margin on greener lumber. Instead of using expensive electrically reversible fans designed for commercial kilns, I came up with a simple hardware solution. The starter blocks should be as long as the stack is wide. In this research, a drying restraint system was evaluated as a means of warp reduction in 8- and 16-foot-long SYP lumber. 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. On this order alone, I saved over $1,300 by drying the lumber myself. I like these "starter blocks" to raise the lumber a few inches off the floor. Projects included design, construction, installation and commissioning of heat-pump based dehumidification equipment for seafood and fish gelatin products, hardwood lumber kilns and laboratory testing. However, if you kiln dry hardwood lumber that has already been air dried, the process is much more forgiving. Difficult-to-dry species might not exceed 140 degrees F. Dehumidification kilns are very . The cost associated with shed construction was similar to buying a prefabricated kit. If the temperature is below this range, I start the heater and adjust the thermostat accordingly. I prefer to empty the water tray manually and record the volume of water collected. Each layer of lumber is separated from the next by a series of "stickers" or spacer sticks. This will allow the heater to cycle on and off automatically, according to the kiln operators setting. /Filter /JBIG2Decode There are many types of kilns, but the most common are dehumidification kilns and conventional kilns. The problems with solar kilns include limited control over temperature and limited solar exposure, depending on your region and site location. I have been reading & studying kiln schedules for years too. Question Unfortunately, little information is available regarding lumber drying technology and practices used, which is essential for the formulation of improvement strategies. 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. This fact sheet summarizes the basics of kiln drying wood, the most commonly used methods, drying schedules and some drying defects. Particularly, important investment has taken place in lumber drying capacity. For the sterilization phase, air temperature needs to be around 140 F, for three to five hours. I recommend a 2 x 3 sliding window with bug screen. In addition, wood can be dried by special methods that include solar drying (use of greenhouse-type dryers or those equipped with solar collectors . If required, look-up and write down the RH (sixth column) and EMC (seventh column) for each schedule step. Heat comes primarily from an integral dehumidification unit that also removes . Khmer Kiln: quite similar to the Anagama kiln however, traditional Khmer Kilns had a flat roof. 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. . If MC readings still arent at the desired range, the heat may need to be increased for the remainder of the drying cycle. This will allow the heater to cycle on and off automatically, according to the kiln operator's setting. 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. The baffles do not need insulating properties, and plywood would work just as well. /ColorSpace /DeviceGray (116 C) temperature. Heres a classic project that both steps up and provides overflow seating. Kiln Systems. (Sawing and Drying Forum) Select 3/4" conduit brackets for hanging baffles on 1/2" galvanized pipe. Built properly, a shed kiln may even increase the value of a property. 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. Dehumidification: This kiln-drying process requires the use of a heat pump system to remove water from the wood. 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 . /BitsPerComponent 1 (In the original Dry Kiln Operators Manual written in the early 1950s, some species were not used in high quality products. H6`2}s=n:l)CR>/"\ Kiln drying is the process of drying wood in a controlled environment, where temperature, air circulation and humidity are monitored and stabilized. Download Table of Contents. Academia.edu no longer supports Internet Explorer. So, with that lengthy introduction, here is my question. Willie Sandry is a furniture maker and a lumber kiln operator in Camas, Washington. But kiln drying may also introduce internal stresses into the woodparticularly if an improper kiln schedule is used, . Determine the equalization settings and conditioning settings, as required. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. In-service replacement of warped 2 by 4's as wall studs or truss members is costly. A shed kiln is an attractive alternative for a couple of reasons.