dehumidification kiln drying schedules

Consider not only the space for the lumber stacks, but extra floor space to easily load and monitor the charge of lumber. You could use the dehumidifier to dry wood but it would not be part of a "kiln." Just be a different process. This kicker board will help distribute the airflow more evenly through all layers of lumber. To condition the lumber, I introduce steam into the kiln for about two hours. By setting the relative humidity (RH) on the dehumidifier, you can control how often it runs. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. 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. 0000002536 00000 n Conventional kiln drying. For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. Another reason I like the idea of a shed kiln is the flexibility of future use. I find that unplugging the DH is helpful during the sterilization phase so I can add a second heater, without overwhelming my electrical circuit. This is because it needs to be dried to a lower moisture content than wood will air dry to outdoors. 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 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. It should be double-pane, well-insulated with low emissivity (low-E). Our approach was to build and operate a small dehumidification dry kiln. A bead of silicone caulking between the subfloor and sill plate will prevent air infiltration. (116 C) temperature. The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. Attic fans are a perfect way to provide airflow over the stacks of lumber. For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. /Filter /JBIG2Decode Leave an air space between the rigid foam and subfloor for additional insulating properties. 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. Omitting the sterilization phase can lead to costly losses from insect damage, so dont skip it. There are many types of kilns, but the most common are dehumidification kilns and conventional kilns. This kicker board will help distribute the airflow more evenly through all layers of lumber. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. This serves a dual purpose of supporting the rigid foam insulation as well as stiffening the floor framing. Once the lumber is sterilized, it is ready for the conditioning phase. 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.). In the majority of cases, the drying schedules are from the world literature, with emphasis on U.S., Canadian, and British publications. Basically the idea seems to be to maintain a constant temperature, and . 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. 5. With a well-designed dehumidification kiln, hardwood lumber can be dried for mere pennies per board foot. There are two ways to remove water from the DH unit, and they both work well. For end baffles, I use 2"-thick rigid foam insulation screwed to the main baffles. 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. This makes lightweight baffles that can be easily moved and repositioned. Rocky Mountain . The kiln configuration and a drying schedule can be input and the code in the Excel file will simulate . Heres a classic project that both steps up and provides overflow seating. 282 0 obj <> endobj The DH is not needed at this time, as the lumber is already bone-dry. The second most common type of drying is called dehumidification drying. Add up the amp draw on all the equipment you plan to use in the kiln, including a heater, dehumidifier, fans and steam generator. Please refer to Appendix A which shows the Lumber Dry Kiln Bill of Materials. A dehumidification kiln continuously recycles the heat throughout the chamber, rather than . Difficult-to-dry species might not exceed 60 C (140 F). Dont even think of powering your kiln with an extension cord. This makes lightweight baffles that can be easily moved and repositioned. The lumber was then measured for crook, bow, and twist. 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. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). If the fans and dehumidifer generate enough heat to maintain a temperature of 100 to 120 F, then I won't use the auxiliary heater. 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. Items shipped directly from the manufacturer cannot be returned in store. Abstract. Created and Presented by: Henco Viljoen and Elijah McCarty with Nyle Dry Kilns. 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. Each layer adds approximately .81 R value. This will allow the heater to cycle on and off automatically, according to the kiln operator's setting. The approach described in the article where you try to keep the water leaving at a steady rate is fine. 3, a simplified transverse section of a kiln chamber with an energy recovery and dehumidification system is shown. Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. I find that unplugging the DH is helpful during the sterilization phase so I can add a second heater, without overwhelming my electrical circuit. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. Select 3/4" conduit brackets for hanging baffles on 1/2" galvanized pipe. Khmer Kiln: quite similar to the Anagama kiln however, traditional Khmer Kilns had a flat roof. Commercial scale steam kilns consume large amounts of energy. If you use a lot of lumber, and youre a decent hand at carpentry, a shed kiln will quickly pay for itself. 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? However, the natural light and ventilation offered by a small window outweighs any disadvantages. Extruded polystyrene foam (blue or pink rigid foam) in this thickness has an R value of 10. My four main baffles consist of sheets of 1" Styrofoam insulation. We are proud of the quality of our products, and we stand behind them 100%. Both restrained and control boards were dried to approximately 9 percent moisture content, representative of final in-service condi- tions. 0000001417 00000 n Sears Canada 70 Pint Dehumidifier. Chinese, Korean or Japanese kilns have an arch roof. The kiln operator sets the kiln controls based on the initial moisture of the lumber as it is loaded into the kiln. Particularly, important investment has taken place in lumber drying capacity. 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. Determine the correct designation, such as T3-D2 for 4/4 red oak. My kiln uses four ceiling-mounted fans, each rated for 1,600 CFM. Using a piece of paper with 6 columns, write down the Schedule Step numbers in the first column on the left. 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. 7. 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. Sticker spacing can be increased to 24 apart for 5/4 or thicker hardwood. Nyle Systems dehumidification kiln packages are our best known product with nearly unlimited drying capabilities. 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. Also, for that approach to work, the chamber needs to be air tight. Each layer of lumber is separated from the next by a series of "stickers" or spacer sticks. This can create internal stress in the lumber that is released when sawing. A discussion of how to apply "safe drying rate" calibrations with a home-built dehumidifying kiln. (See the following sections for a discussion of how to develop a schedule from these designations.) Low Temperature Kiln Drying Systems (120F), High Temperature Kiln Drying Systems (160F), Very High Temperature Kiln Drying Systems (220F), Website Content Copyright 2023 Nyle Systems |, Affordable and easy method to accomplish top quality lumber drying, Designed specifically for any sized operation, Modular based systems for unlimited capacity, No boiler or steam required with gas furnace, Can be installed along side existing kilns, Chambers are sized with our DH systems to meet your lumber drying requirements. Willie Sandry is a furniture maker and a lumber kiln operator in Camas, Washington. Dr. Gene Wengert provides schedules for kiln drying hardwood lumber. Detailed design and custom manufacture of dehumidification and chiller systems for food processing, lumber drying and industrial applications. My question focuses on the initial relative humidity featured in the Safe Drying Rate table. Kiln drying lumber is a simple, cost effective method recommended for anyone who wants to increase profits by selling dried lumber. (A major source was Dry Kiln Schedules for Commercial Woods which is available from the Forest Products Society in Madison, WI.) 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. This will allow the DH to drain automatically without you needing to enter the kiln. Vote. the hardwood kiln schedule is the equalization of the moisture content of all boards at 6-8%. The schedule designations use the popular U.S. Forest Products Laboratory designations. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. A heavy-duty 1,500-watt space heater works fine. I was hoping someone could point me in the right direction or share experience. A household dehumidifier (DH) removes moisture from the kiln chamber. In this system, moist air is not vented out of the kiln but is dehumidified, then recirculated . A variety of wood drying kiln technologies exist today: conventional, dehumidification, solar, vacuum and radio frequency. Wood Shrink/Swell estimator - A web-based program to estimate shrink/ swell in wood. (Dry Kiln Operator's Manual. (I have found that remotely monitoring the temperature and humidity with a WiFi sensor can be very helpful. High Temperature Kiln Drying Systems (160F) Loads up to 350,000 BF; Pull up to 20,000 pounds of water daily; Use standard drying schedule; Precision temperature and RH . From contributor D: I found that brackets for mounting rigid metal electrical conduit work best. For a kiln temperature of 140 F, sterilization takes three to five hours. Measure airflow over the stacks of lumber in various locations. WOODWEB is a registered trademark of Woodweb.com. Air speed of 350 feet per minute is appropriate for common hardwoods such as oak and maple. To browse Academia.edu and the wider internet faster and more securely, please take a few seconds toupgrade your browser. If required, look-up and write down the RH (sixth column) and EMC (seventh column) for each schedule step. The starter blocks should be as long as the stack is wide. The cost associated with shed construction was similar to buying a prefabricated kit. Should a Moulding Mill Bring Sawmill Operations In-House? Use the gridded drawings provided on the PDF, Woodworking | Blog | Videos | Plans | How To. The air flow rate through your stacks should be about 350FPM. Also, since heat rises, ceiling-mounted fans have the added benefit of circulating the warmest air over the lumber. A kiln schedule is a set of temperatures and humidities that are used during kiln operation. A higher humidity setting will run the unit sporadically to maintain that RH. I made a simple frame from plywood strips and attached theinsulation sheets to them with screws and fender washers. Total costs for the materials were $2,704 based on 2006 prices. Thicker lumber like 5/4 or quartersawn lumber is naturally more stable. You can download the paper by clicking the button above. 4.4 drying schedule moisture content drying schedule . Dehumidification Kiln Drying. The dry kiln operator is fully in control, with the ability to make changes as the dry kiln schedule is executing. Unfortunately, little information is available regarding lumber drying technology and practices used, which is essential for the formulation of improvement strategies. In larger kilns, the heater may be needed in the latter part of the drying cycle. This problem is magnified if the lumber is thin or flatsawn. November 1, 2020. In Fig. Do not know just how the end point of moisture would compare. Job Opportunities and Woodworking Services, Dust Collection, Safety and Plant Operation. 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%. My number one priority was to build a kiln that was easy to load and easy to monitor. are generally kiln dried by time scheduleswhether the wood is intended for struc-tural lumber or for appearance uses, such as furniture or millwork. , , o* j=d Soon the DH wont show much water collected in the tray. Align the stickers over the starter blocks on the first course. . After seven to 10 days, I reverse the fan direction to make sure all stacks of lumber dry evenly. This report contains suggested dry kiln schedules for over 500 commercial woods, both temperate and tropical. Main thing is to not rush drying in first stages, as this will cause problems. Attic fans are a perfect way to provide airflow over the stacks of lumber. Kiln Structure . Reweigh and obtain the oven dry weight. Ciencia y Tecnologia, Duygu Kocaefe, Ayhan Aytin, The Bolivian secondary forest products industry has experienced substantial growth during the last 10 years. 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. Diy dehumidifier kiln time table. %PDF-1.6 % Consider the weight of the lumber that will be placed in the structure and fortify the building accordingly. Dehumidification drying equipment is available, but an enclosure must be built to house the equipment and dry the lumber. 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.) This plan allows . Construction of a kiln chamber is very similar to building a small house. This problem is magnified if the lumber is thin or flatsawn. However, you may need more cycles depending on the species, moisture content, and size of the timber. The delicate blue and white color scheme c Hardwood kiln drying schedules typically keep the dry bulb temperature below 80 C (176 F). 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. However, if you kiln dry hardwood lumber that has already been air dried, the process is much more forgiving. I recommend a 2 x 3 sliding window with bug screen. That purchase was an average deal, and one I dont consider a particular bargain. Kiln drying lumber is a simple, cost effective method recommended for anyone who wants to increase profits by selling dried lumber. Difficult-to-dry species might not exceed 140 degrees F. Dehumidification kilns are very . %PDF-1.4 % The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. Be sure that all of the kiln equipment is working prop-erly before lumber is loaded into the kiln. H6`2}s=n:l)CR>/"\ I selected a 36 outswing exterior door. The thinner the stock, the more critical sticker placement becomes. At the planer mill, warped 2 by 4's represent a significant loss in value. Staff. Another common sticker size is 1 x 2, and these work fine as well. Also check that air isnt escaping around the side baffles or under the stack of lumber. Installing sheetrock and fire taping is a good idea for a heated room. Keenan Slab Works has a vacuum kiln located at 4917 Elizabethtown Road, Manheim, Lancaster County, Pennsylvania, 17545 and is expanding services for the general public to have their slabs and lumber vacuum dried. I dont think the same could be said for an old reefer truck converted into a kiln (no matter how well it dries lumber). 6. 3.24 solar-dehumidification drying kiln . This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. The kiln climate is controlled by venting the hot air and replacing it with ambient air. The schedules can also be formulated manually as follows. This will allow the DH to drain automatically without you needing to enter the kiln. Standard kiln drying temperatures are low - around 120 degrees Fahrenheit or so, and drying times vary by wood size and moisture level. Dehumidification kiln schedules 145 Sterilizing, equalizing, and conditioning treatments 145 Sterilizing treatments 145 Mold 145 Fungal stain and decay 146 . . 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 I have been reading & studying kiln schedules for years too. 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. Kiln Drying . A higher humidity setting will run the unit sporadically to maintain that RH. The T-bars are made from 1/2" galvanized pipe and are attached to the rafters with threaded pipe flanges. 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. The problems with solar kilns include limited control over temperature and limited solar exposure, depending on your region and site location. JavaScript seems to be disabled in your browser. Remove samples from the stack, and cut an inch or two off one end. In vacuum kiln trials, logs were heated to 56C at 70 percent log radius depth and the temperature maintained for . However, because wood from Share. Kiln dried wood typically sells for a third more than green lumber and eliminates the need for . A lazy Susan with 180 detents mounts the fan box to the ceiling. noun. Lay down the bead of caulking before raising the walls. For end baffles, I use 2-thick rigid foam insulation screwed to the main baffles. Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 F (82 C). Place the one inch sections in an oven 215F to 218F (102C to 103C) and dry - usually 18 to 36 hours depending on the oven. 44. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. The following tables show some examples of oak schedules for steam dry kilns and dehumidification dryers. For example, if you dry 7,500BF of fast drying Pine, youd select the 8MBF chamber with the HT18 Dehumidifier. I either use some cedar 3 x 5, or 4 x 4 stock. Equalizing and conditioning are required for almost all hardwood lumber. 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. Among the various sizes of southern yellow pine (SYP) dimension lumber, 2 by 4 is produced in the greatest volume. I like these "starter blocks" to raise the lumber a few inches off the floor. Wood Drying/ Seasoning. Should I? . A small electric heater supplies auxiliary heat to maintain adequate kiln temperature. Y}-m+'@DQ4\h8GP]y@ yL. After four days, I decrease the RH setting on the DH to 30% and continue to run the fans. 0000002827 00000 n This slows the end-grain drying and limits the severity of end checking. Also, since heat rises, ceiling-mounted fans have the added benefit of circulating the warmest air over the lumber. 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. This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. Drying lumber too quickly can lead to deep end checking, warping and case hardening. The four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln. T8-C3 or similar for hard maple), the article instead provided a table showing the "safe drying rates" (SDR) for a number of species. 0000000591 00000 n After two days operating only the fans and DH, I take note of the temperature. I then manually rotate the fan boxes halfway through the drying cycle. 8. Reply. In-service replacement of warped 2 by 4's as wall studs or truss members is costly. To hang the baffles, simply attach hooks to the plywood frame. Phytosanitary heat treatments of Ceratocystis lukuohia and Ceratocystis huliohia-colonized Metrosideros polymorpha wood were evaluated using kilns. Thus, a drying program can be adapted according to the characteristics of the kiln load, e.g., species, dimensions, and moisture content. End baffles are also a good idea to prevent airflow from bypassing the stack entirely. I cannot stress the importance of baffles enough. Size and placement of the access door are critical as well. These well-known dehumidification kiln packages have been among our bestselling products for the past 30 years. 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. For a kiln temperature of 140 F, sterilization takes three to five hours. Instead of using expensive electrically reversible fans designed for commercial kilns, I came up with a simple hardware solution. Soon the DH won't show much water collected in the tray. Unlike general shop space, bigger is not always better for kiln design. Built properly, a shed kiln may even increase the value of a property. The first thing to consider when designing a shed kiln is size. Remove samples from the stack, and cut an inch or two off one end. When properly loaded, this kiln can dry approximately 600 board feet of 4/4" lumber. /Subtype /Image I know your kiln is absolutely tight and perfectly sealed, but it has to vent some or it would overheat. 6. 1998. by Dr. Eugene Wengert. For single-stack kilns, stationary fans are adequate. If your lumber stack is built on starter blocks, you will need to limit airflow there as well. 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. This gives me a secondary method of tracking the drying process, using both water volume and moisture content (MC) readings. 301 0 obj <>stream This lets the operator sort stacks by lumber species, so they will be easy to retrieve when the drying cycle is complete. What can you do to speed up drying time? In this paper, the effective schedules were further investigated for longer culm parts treated with boron. _0e`bd\ p@ Once all the lumber is stacked and stickered, place baffles over the lumber. I've been drying hardwood lumber in this Sauno dehumidification kiln for 4 years with excellent results. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. Only the fans need electricity. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. I either use some cedar 3" x 5", or 4" x 4" stock. Align the stickers over the starter blocks on the first course. If severe enough, the lumber can develop honeycomb cracks throughout. The DH is not needed at this time, as the lumber is already bone-dry. Any small building could work, as long as it has a minimum of 2 x 4 framing, and will seal out unwanted air. A heavy-duty 1,500-watt space heater works fine. Many available kiln designs require a large, heavy door. An anemometer confirms that your effort constructing baffles was worthwhile. I prefer to empty the water tray manually and record the volume of water collected. A lazy Susan with 180 detents mounts the fan box to the ceiling. The kiln schedule information in the tables below has been assembled from many different sources, including drying texts and industrial contacts. I hope that the sawyer coated the ends of the lumber with Anchor-Seal or oil-based paint when it was green. When the operating conditions of this option are followed the material will meet the requirements of being kiln dried (KD) and heat treated . After four days, I decrease the RH setting on the DH to 30% and continue to run the fans. I made a simple frame from plywood strips and attached the insulation sheets to them with screws and fender washers. Place some sample boards in the stack that will be easy to pull out for moisture testing later. Go to the first number designation (the temperature designation) and find the corresponding temperatures in the table below. Loading the kiln begins by rousing my sons and letting them know Ive planned a day of work. Any info or advice on using dehumidification equipment to dry out chainsaw milled lumber. 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. With two-stack and three stack kilns, it is better to have reversible fans to alter the direction of airflow mid-cycle. Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. The stickers are uniform in size and usually 3/4" or 1" square. A.gov website belongs to an official government With two-stack and three stack kilns, it is better to have reversible fans to alter the direction of airflow mid-cycle. 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 .