dehumidification kiln drying schedules

The kiln operator sets the kiln controls based on the initial moisture of the lumber as it is loaded into the kiln. This fact sheet summarizes the basics of kiln drying wood, the most commonly used methods, drying schedules and some drying defects. This would allow a stack of lumber four feet wide and 10 feet long. A heavy-duty 1,500-watt space heater works fine. There might be a problem with that if the chamber overheats and has to be vented because some water will leave that way. Soon the DH won't show much water collected in the tray. 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. Our approach was to build and operate a small dehumidification dry kiln. The T-bars are made from 1/2" galvanized pipe and are attached to the rafters with threaded pipe flanges. - Model L300, L500, L1200-S Series - Medium Dehumidification Dry. Rocky Mountain . I made a simple frame from plywood strips and attached theinsulation sheets to them with screws and fender washers. Gen. Tech. In time schedules, dry- and wet . Also, today, we are often kiln drying No.2 Common lumber which requires a milder schedule than upper grades; in the 1950s, seldom was this lower grade lumber kiln dried.) Take a moisture reading in the end grain with a pin-type moisture meter or remote probe. Choosing a Kiln Schedule Apply foil tape to the edges of the main baffles to help protect the Styrofoam. A shed kiln is an attractive alternative for a couple of reasons. I often buy from sawyers or homeowners at 40% to 50% of retail price. Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 F (82 C). /BitsPerComponent 1 Academia.edu no longer supports Internet Explorer. Another common sticker size is 1 x 2, and these work fine as well. Our capacities are 4,000 board feet in a kiln . Go to the second letter designation (the MC Class Designation) and find the corresponding MC ranges in the table below. The store will not work correctly in the case when cookies are disabled. (116 C) temperature. . Abstract. This makes lightweight baffles that can be easily moved and repositioned. Over 40 years experience building kilns. Once the core readings are 6% to 8% on a fresh cut, the lumber is dry and ready for sterilization. Once the lumber is sterilized, it is ready for the conditioning phase. The baffles do not need insulating properties, and plywood would work just as well. January 27, 2007. There are many types of kilns, but the most common are dehumidification kilns and conventional kilns. Enter the email address you signed up with and we'll email you a reset link. My kiln uses four ceiling-mounted fans, each rated for 1,600 CFM. hbbd``b` $ &UD\q@u Table 1 shows a typical drying schedule for sugar maple. If it isn't overheating, it is leaking. This limits the amount of energy needed to bring lumber to the desired 6% to 8% moisture content. Wood-Mizer dehumidification and solar wood kilns range from 300 to 35,000 board feet capacity for drying lumber. Dehumidification kiln schedules 145 Sterilizing, equalizing, and conditioning treatments 145 Sterilizing treatments 145 Mold 145 Fungal stain and decay 146 . The air flow rate through your stacks should be about 350FPM. If you dry 9,500BF of slower drying Oak, youd use the 10MBF chamber with the HT8 Dehumidifier. Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 F (82 C). The KD150 Dehumidification Kiln Kit is a compact, entry-level dehumidification kiln for drying lumber between 300 and 1000 board feet. Dont even think of powering your kiln with an extension cord. As you can recycle . I modified one of the Radio Shack combo units so it could measure the RH remotely as well as the temp. (I have found that remotely monitoring the temperature and humidity with a WiFi sensor can be very helpful. JavaScript seems to be disabled in your browser. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. Add up the amp draw on all the equipment you plan to use in the kiln, including a heater, dehumidifier, fans and steam generator. USDA, 1991) . Make sure the total amp draw is well within the limit of your electrical circuit. %3.3 (Dry Kiln Operator's Manual. Please refer to Appendix A which shows the Lumber Dry Kiln Bill of Materials. I recommend a 2 x 3 sliding window with bug screen. 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. Featuring lower cost drying at speeds equal to gas & steam, these kilns are continuously exceeding industry standards and changing the game. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. Built properly, a shed kiln may even increase the value of a property. 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. For a kiln temperature of 140 F, sterilization takes three to five hours. 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 . But kiln drying may also introduce internal stresses into the woodparticularly if an improper kiln schedule is used, . I found that brackets for mounting rigid metal electrical conduit work best. Extruded polystyrene foam (blue or pink rigid foam) in this thickness has an R value of 10. Place a 16 board on the floor behind the stack, tilted to a 45 angle. Nyle. For end baffles, I use 2"-thick rigid foam insulation screwed to the main baffles. Instead of using expensive electrically reversible fans designed for commercial kilns, I came up with a simple hardware solution. Consider not only the space for the lumber stacks, but extra floor space to easily load and monitor the charge of lumber. Diy dehumidifier kiln time table. Another common sticker size is 1" x 2", and these work fine as well. After four days, I decrease the RH setting on the DH to 30% and continue to run the fans. After a short period of grumbling, they join me to lay down wood blocks for the first layer of lumber. This allows for a more gentle kiln schedule to fully dry the timber. 4. When properly loaded, this kiln can dry approximately 600 board feet of 4/4" lumber. are generally kiln dried by time scheduleswhether the wood is intended for struc-tural lumber or for appearance uses, such as furniture or millwork. My baffles hang from T-bar assemblies mounted to the ceiling. hb```[@9p(T-3jO:g)@S 4Y]g7l\V!c!$Bf J B@&xcEz8PH@ZHs1/X$qOq,x'x$0.rWg*d XAT10 );9 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. Download Table of Contents. They are easy to use and give you precision control over your drying. Should I? In-service replacement of warped 2 by 4's as wall studs or truss members is costly. After a short period of grumbling, they join me to lay down wood blocks for the first layer of lumber. Then align each subsequent layer of stickers over the last. 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. I cannot stress the importance of baffles enough. By setting the relative humidity (RH) on the dehumidifier, you can control how often it runs. Kiln schedules are completely assembled and written out for easy use. Different species should not be loaded simultaneously into the kiln due to often differing kiln schedules. Windows and doors are also sealed, as well as any holes cut for electrical service. From contributor D: Leave an air space between the rigid foam and subfloor for additional insulating properties. This publication outlines the basic construction of a small scale dehumidification dry kiln. 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. Kiln Systems. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. The thinner the stock, the more critical sticker placement becomes. I was hoping someone could point me in the right direction or share experience. A lower RH setting will call for the DH to run more often. 1998. Minus the drying equipment, a shed kiln is just an insulated storage space, with a host of possible uses. Regardless of size, allow for a 36 door that opens to a hallway of open space. Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. Each layer of lumber is separated from the next by a series of "stickers" or spacer sticks. This helps keep the lumber straight during the drying cycle; in fact, improper placement of stickers can permanently deform lumber. Official websites use .gov On this order alone, I saved over $1,300 by drying the lumber myself. 6. In Fig. Forum Responses Installing a window in a kiln may seem counterintuitive at first, because windows lose more heat than an insulated wall. After two days operating only the fans and DH, I take note of the temperature. If MC readings still arent at the desired range, the heat may need to be increased for the remainder of the drying cycle. Subtract the wet-bulb depression from the dry-bulb temperatures for each schedule step and enter the value in the fifth column. Ideally, a lumber kiln would be large enough to dry multiple stacks of lumber. The order was 540 board feet (BF) of 5/4 white oak. The starter blocks should be as long as the stack is wide. This, of course, is gross savings; we must calculate electrical costs to determine the net savings: in this case, about $62. Thus, a drying program can be adapted according to the characteristics of the kiln load, e.g., species, dimensions, and moisture content. The conversion method described in the Dry Kiln Operator's Manual is not really accurate, but it is safe. The following tables show some examples of oak schedules for steam dry kilns and dehumidification dryers. Sticker spacing can be increased to 24 apart for 5/4 or thicker hardwood. This report contains suggested dry kiln schedules for over 500 commercial woods, both temperate and tropical. These are rough-saw red oak. Once the flooring deck is constructed, think about sealing the shed framing at every opportunity. (Note: This letter designation is related to the green MC of the species. Another reason I like the idea of a shed kiln is the flexibility of future use. This will allow the DH to drain automatically without you needing to enter the 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. For example, if you dry 7,500BF of fast drying Pine, youd select the 8MBF chamber with the HT18 Dehumidifier. Drying lumber too quickly can lead to deep end checking, warping and case hardening. The kiln humidity can be expressed as an EMC, relative humidity, or wet-bulb temperature. 3, a simplified transverse section of a kiln chamber with an energy recovery and dehumidification system is shown. Many regions have increased the shed and outbuilding maximum allowable size without need for a permit. Corrosion resistant epoxy coated aluminum cabinets and specially coated dehumidification coils for an extra long life. 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 schedules are all moisture content based, using the moisture content of the wettest half of the kiln samples. Initially, I set the DH to 40% RH, because I dont want to remove moisture too quickly. , , o* j=d For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. You can achieve top-quality results with incredible efficiency. Y}-m+'@DQ4\h8GP]y@ yL. Vacuum Kiln Drying. I have been reading & studying kiln schedules for years too. Items shipped directly from the manufacturer cannot be returned in store. Always avoid conditions that add moisture back to the lumber, especially during start-up. 5. Low Temperature Kiln Drying Systems (120F) 300BF - 4000BF Capacity . (A major source was Dry Kiln Schedules for Commercial Woods which is available from the Forest Products Society in Madison, WI.) By setting the relative humidity (RH) on the dehumidifier, you can control how often it runs. . My four main baffles consist of sheets of 1 Styrofoam insulation. Our next kiln charge is scheduled to begin around February 6, 2023. /Subtype /Image Additionally, a 12 air plenum is required between the walls and stacks of lumber. Adjust the baffles or fan direction to achieve good airflow. Among the various sizes of southern yellow pine (SYP) dimension lumber, 2 by 4 is produced in the greatest volume. /ColorSpace /DeviceGray 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. noun: kiln; plural noun: kilns. I usually see a large volume of water in the DH each night when I check the kiln. This will allow the heater to cycle on and off automatically, according to the kiln operator's setting. I made a simple frame from plywood strips and attached the insulation sheets to them with screws and fender washers. A dehumidification kiln makes sense particularly when the lumber is air-dried first. However, if you kiln dry hardwood lumber that has already been air dried, the process is much more forgiving. This makes lightweight baffles that can be easily moved and repositioned. Heat comes primarily from an integral dehumidification unit that also removes . 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. _0e`bd\ p@ Schedules. Temperatures inside the kiln range from 120 to 190 degrees F, depending on the stage of . Drying small amounts of lumber using a dehumidification kiln is a suitable option for woodworkers even with limited knowledge of kilns. A kiln schedule is a set of temperatures and humidities that are used during kiln operation. In vacuum kiln trials, logs were heated to 56C at 70 percent log radius depth and the temperature maintained for . I guess I am thinking that while I am seeing the wood's MC and the kiln's RH drop smoothly, the fact that the temperature jumps around a bit may mean that the drying rates are hard to control, hence my loss of horse chestnut. I found that brackets for mounting rigid metal electrical conduit work best. Wood Drying/ Seasoning. 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 A free BASIC program to convert the designations into actual temperatures and humidities is available from the author. I then manually rotate the fan boxes halfway through the drying cycle. Each layer adds approximately .81 R value. Check your local building codes for regionally specific requirements and electrical permits. The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. My number one priority was to build a kiln that was easy to load and easy to monitor. Standard kiln drying temperatures are low - around 120 degrees Fahrenheit or so, and drying times vary by wood size and moisture level. hTn8>_l7h.&E:Bem=C9n\8]lMPc. KD150 Series dehumidifier pdf manual download. You could use the dehumidifier to dry wood but it would not be part of a "kiln." Just be a different process. 6. Custom Doors, Drawers & Glass Accessories, Using a Small Scale Dehumidification Kiln, Learn Woodworking Tips & Tricks with Rockler, High-quality brands and products you can trust, Expert advice and free post-purchase support, Exclusive, innovative products that help you Create with Confidence, Detailed instructions, technical specs and guides to make the most of your purchases. The schedule designations use the popular U.S. Forest Products Laboratory designations. For a kiln temperature of 140 F, sterilization takes three to five hours. Rep. FPL-GTR-57. Remove samples from the stack, and cut an inch or two off one end. When that is the case, I know Ill have usable lumber in just a few weeks. Any small building could work, as long as it has a minimum of 2 x 4 framing, and will seal out unwanted air. I find that unplugging the DH is helpful during the sterilization phase so I can add a second heater, without overwhelming my electrical circuit. End baffles are also a good idea to prevent airflow from bypassing the stack entirely. The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. Remote operation and networking is optional. Loading the kiln begins by rousing my sons and letting them know Ive planned a day of work. Nyle Systems dehumidification kiln packages are our best known product with nearly unlimited drying capabilities. For a kiln temperature of 140 F, sterilization takes three to five hours. This kicker board will help distribute the airflow more evenly through all layers of lumber. WOODWEB is a registered trademark of Woodweb.com. The second most common type of drying is called dehumidification drying. 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. Low temperatures can be used for an extra safety margin on greener lumber. Air speed of 350 feet per minute is appropriate for common hardwoods such as oak and maple. If required, look-up and write down the RH (sixth column) and EMC (seventh column) for each schedule step. The last step requires a short period of high humidity to relieve the drying stresses in the boards. BE CAREFUL--The first temperature value must be repeated for every MC class (column #2) that is above 30% MC. This is because it needs to be dried to a lower moisture content than wood will air dry to outdoors. Remove samples from the stack, and cut an inch or two off one end. End baffles are also a good idea to prevent airflow from bypassing the stack entirely. 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. . Commercial scale steam kilns consume large amounts of energy. Operates at a temperature range from 80F - 160F (26 - 71C). 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. 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