dehumidification kiln drying schedules

Omitting the sterilization phase can lead to costly losses from insect damage, so dont skip it. I find that unplugging the DH is helpful during the sterilization phase so I can add a second heater, without overwhelming my electrical circuit. The Bolivian wood products industry was surveyed to determine lumber drying capacity, technology and. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). For the sterilization phase, air temperature needs to be around 140 F, for three to five hours. The schedule designations use the popular U.S. Forest Products Laboratory designations. Changing the position of the doorway in various kiln setups helps provide the best access to the stacks of lumber. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. Both restrained and control boards were dried to approximately 9 percent moisture content, representative of final in-service condi- tions. To browse Academia.edu and the wider internet faster and more securely, please take a few seconds toupgrade your browser. Unfortunately, little information is available regarding lumber drying technology and practices used, which is essential for the formulation of improvement strategies. By. Basically, you don't want all of the air rushing out under the stack, so find a way to redirect it. 3, a simplified transverse section of a kiln chamber with an energy recovery and dehumidification system is shown. The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. Operates at a temperature range from 80F - 160F (26 - 71C). With a 130 F kiln temperature, sterilization will take 10 to 12 hours ( Dry Kiln Operators Manual, 1991 ). 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 . The DH is not needed at this time, as the lumber is already bone-dry. 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. 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. %%EOF Initially, I set the DH to 40% RH, because I dont want to remove moisture too quickly. For more capacity, consider a two stack kiln (12 x 12), or a three-stack kiln (12 x 16). In this paper, the effective schedules were further investigated for longer culm parts treated with boron. 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. Go to the second number designation (the wet-bulb depression designation) and find the corresponding depressions in the table below. 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. I'd like to know for my own curiosity, as well as to be able to generate SDR schedules for other species not given in the American Woodworker article, like the 6 foot long 24" wide slabs of 8/4 madrone I got this summer. I found that brackets for mounting rigid metal electrical conduit work best. 44. Take a moisture reading in the end grain with a pin-type moisture meter or remote probe. . It is a meaningless exercise to try to convert those schedules for the kiln you built. A free BASIC program to convert the designations into actual temperatures and humidities is available from the author. organization in the United States. Then align each subsequent layer of stickers over the last. The store will not work correctly in the case when cookies are disabled. Apply foil tape to the edges of the main baffles to help protect the Styrofoam. Detailed design and custom manufacture of dehumidification and chiller systems for food processing, lumber drying and industrial applications. . BE CAREFUL--The first temperature value must be repeated for every MC class (column #2) that is above 30% MC. I made a simple frame from plywood strips and attached the insulation sheets to them with screws and fender washers. The fact is, most of my stacks of lumber air dry to 15% moisture content before entering the kiln. 0000000710 00000 n 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 Low temperatures can be used for an extra safety margin on greener lumber. The first thing to consider when designing a shed kiln is size. This gives me a secondary method of tracking the drying process, using both water volume and moisture content (MC) readings. My four main baffles consist of sheets of 1 Styrofoam insulation. Determine the equalization settings and conditioning settings, as required. For international returns, please click here. 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 four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln. stream Remove samples from the stack, and cut an inch or two off one end. The dry kiln operator is fully in control, with the ability to make changes as the dry kiln schedule is executing. For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. Its a nice use of technology and adds a measure of safety as well.) 9. This prevents dead spots inside the chamber that experience limited airflow. endstream endobj 283 0 obj <>/Metadata 40 0 R/OCProperties<>/OCGs[294 0 R]>>/Outlines 53 0 R/PageLayout/SinglePage/Pages 280 0 R/StructTreeRoot 72 0 R/Type/Catalog>> endobj 284 0 obj <>/Font<>/Properties<>/XObject<>>>/Rotate 0/StructParents 0/Tabs/S/Type/Page>> endobj 285 0 obj <>stream The last step requires a short period of high humidity to relieve the drying stresses in the boards. 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. After seven to 10 days, I reverse the fan direction to make sure all stacks of lumber dry evenly. /Type /XObject Know how to choose and apply the correct schedule for the lumber. squares, handle stock, gunstock blanks) are given for many species. Q,kjifT33P[! When the drying is done in a kiln, the product is known as kiln-dried timber or lumber, whereas air drying is the more traditional method.. Dehumidification Kilns An outswing door can always be opened, regardless of shed contents. Temperatures inside the kiln range from 120 to 190 degrees F, depending on the stage of . If you use a lot of lumber, and youre a decent hand at carpentry, a shed kiln will quickly pay for itself. I either use some cedar 3 x 5, or 4 x 4 stock. Dehumidification drying equipment is available, but an enclosure must be built to house the equipment and dry the lumber. My number one priority was to build a kiln that was easy to load and easy to monitor. Once all the lumber is stacked and stickered, place baffles over the lumber. In addition, weight on top of the stack can be helpful, but nothing replaces baffles for the best lumber yield. (In the original Dry Kiln Operators Manual written in the early 1950s, some species were not used in high quality products. Nyle. Another great option is to convert an existing shed or outbuilding to a lumber kiln. Dehumidifier suggestion: http://amzn.to/2iYZqVZThis is the first in a series of videos showing how I built a kiln for drying lumber. The T-bars are made from 1/2 galvanized pipe and are attached to the rafters with threaded pipe flanges. endstream endobj startxref In addition, wood can be dried by special methods that include solar drying (use of greenhouse-type dryers or those equipped with solar collectors . This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. Many available kiln designs require a large, heavy door. HT systems use 40-60% less energy than gas-fired or steam dry kilns. For a single-stack kiln I recommend a minimum shed size of 8 x 12. They are based on different air flow rates, etc. Extruded polystyrene foam (blue or pink rigid foam) in this thickness has an R value of 10. Soon the DH wont show much water collected in the tray. Total costs for the materials were $2,704 based on 2006 prices. A dehumidification kiln makes sense particularly when the lumber is air-dried first. Rep. FPL-GTR-57. 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. . Contractors work on a tight schedule, and that may not allow much time for curing and drying concrete. 73. Air speed of 350 feet per minute is appropriate for common hardwoods such as oak and maple. I found that brackets for mounting rigid metal electrical conduit work best. You can achieve top-quality results with incredible efficiency. 6. 0 The schedules can also be formulated manually as follows. . The kiln climate is controlled by venting the hot air and replacing it with ambient air. 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 starter blocks should be as long as the stack is wide. 0000001208 00000 n Our capacities are 4,000 board feet in a kiln . I have sensors in the kiln for moisture levels & probes in the center of the wood attached to a lignomat moisture meter. Dehumidification Opportunities for Dehumidification Drying Of Hardwood Lumber Dimension Kiln Drying Hardwood Dimension Parts Discoloration Preventing Discolorations in Hardwood and Softwood Logs . On the last load of lumber I purchased, I saved $2.50 per board foot compared to retail prices for kiln-dried lumber. Take a moisture reading in the end grain with a pin-type moisture meter or remote probe.) A heavy-duty 1,500-watt space heater works fine. 1998. Table 1 shows a typical drying schedule for sugar maple. Select 3/4" conduit brackets for hanging baffles on 1/2" galvanized pipe. This shed will be essentially unheated for much of the year and very hot during the kiln-drying cycles. Remove samples from the stack, and cut an inch or two off one end. Schedules for several thicknesses and specialty products (e.g. Choosing a Kiln Schedule 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. - Model L300, L500, L1200-S Series - Medium Dehumidification Dry. A lower RH setting will call for the DH to run more often. 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 . 0000002827 00000 n If severe enough, the lumber can develop honeycomb cracks throughout. Warp in dimension lumber is a significant cause for loss in grade and value. Dehumidification kilns are similar to other kilns in basic construction and drying times are usually comparable. 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. Wood Shrink/Swell estimator - A web-based program to estimate shrink/ swell in wood. Select a heater with an adjustable thermostat and a tip-over shutoff. This will allow the DH to drain automatically without you needing to enter the kiln. This slows the end-grain drying and limits the severity of end checking. /Length 7 0 R The problems with solar kilns include limited control over temperature and limited solar exposure, depending on your region and site location. If it isn't overheating, it is leaking. I modified one of the Radio Shack combo units so it could measure the RH remotely as well as the temp. Ciencia y Tecnologia, Duygu Kocaefe, Ayhan Aytin, The Bolivian secondary forest products industry has experienced substantial growth during the last 10 years. 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. I have constructed a kiln using these plans. Particularly, important investment has taken place in lumber drying capacity. Leave an air space between the rigid foam and subfloor for additional insulating properties. Also, you can't really control well by measuring the collected water because some of the water leaks out with vented or leaking air. 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. Any small building could work, as long as it has a minimum of 2 x 4 framing, and will seal out unwanted air. The kiln operator sets the kiln controls based on the initial moisture of the lumber as it is loaded into the kiln. 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. A household dehumidifier (DH) removes moisture from the kiln chamber. This will allow the DH to drain automatically without you needing to enter the kiln. You may also return purchases to a Rockler store near you for store credit. Abstract. Dehumidification kilns from Nyle Systems in Brewer, Maine. The delicate blue and white color scheme c When that is the case, I know Ill have usable lumber in just a few weeks. Gen. Tech. A low temperature heat treatment chamber and/or dehumidification kiln is identified as operating between approximately 43C (110F) and 56C (133F) for an extended period during the kiln drying cycle. The lumber was then measured for crook, bow, and twist. Built properly, a shed kiln may even increase the value of a property. Also, since heat rises, ceiling-mounted fans have the added benefit of circulating the warmest air over the lumber. Standard kiln drying temperatures are low - around 120 degrees Fahrenheit or so, and drying times vary by wood size and moisture level. There are two ways to remove water from the DH unit, and they both work well. 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. Once all the lumber is stacked and stickered, place baffles over the 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. Hb```f``:A2,@!p"4|QP(y;ysc6f{f+&FfKi-L4+i`Vlf nwj2MM/E)rQ,^wm{'_B&%F`dbt JB*UWTmdIb& z P"f#*E4% @BHA!4I( I0 !`Hke0 PQI ([@R R`0 &xgTh( *p1 ~L{ endstream endobj 917 0 obj 389 endobj 908 0 obj << /Type /Page /Parent 892 0 R /Resources << /Font << /F0 909 0 R /F1 912 0 R >> /ProcSet 915 0 R >> /Contents 913 0 R /MediaBox [ 0 0 607 792 ] /CropBox [ 0 0 607 792 ] /Rotate 0 >> endobj 909 0 obj << /Type /Font /Subtype /TrueType /Name /F0 /BaseFont /CenturySchoolbook,Bold /FirstChar 31 /LastChar 255 /Widths [ 750 287 296 333 574 574 833 852 241 389 389 500 606 278 333 278 278 574 574 574 574 574 574 574 574 574 574 278 278 606 606 606 500 747 759 778 778 833 759 722 833 870 444 648 815 722 981 833 833 759 833 815 667 722 833 759 981 722 722 667 389 606 389 606 500 333 611 648 556 667 574 389 611 685 370 352 667 352 963 685 611 667 648 519 500 426 685 611 889 611 611 537 389 606 389 606 750 750 750 241 574 481 1000 500 500 333 1000 667 333 1000 750 750 750 750 241 241 481 481 606 500 1000 333 1000 500 333 907 750 750 722 287 296 574 574 606 722 606 500 333 747 367 500 606 333 747 500 400 549 344 344 333 576 747 278 333 344 367 500 861 861 861 500 759 759 759 759 759 759 981 778 759 759 759 759 444 444 444 444 833 833 833 833 833 833 833 650 833 833 833 833 833 722 759 611 611 611 611 611 611 611 870 556 574 574 574 574 370 370 370 370 611 685 611 611 611 611 611 549 611 685 685 685 685 611 667 611 ] /Encoding /WinAnsiEncoding /FontDescriptor 910 0 R >> endobj 910 0 obj << /Type /FontDescriptor /FontName /CenturySchoolbook,Bold /Flags 16418 /FontBBox [ -250 -215 1079 962 ] /MissingWidth 671 /StemV 149 /StemH 149 /ItalicAngle 0 /CapHeight 962 /XHeight 673 /Ascent 962 /Descent 215 /Leading 202 /MaxWidth 899 /AvgWidth 468 >> endobj 911 0 obj << /Type /FontDescriptor /FontName /CenturySchoolbook /Flags 34 /FontBBox [ -250 -220 1200 951 ] /MissingWidth 756 /StemV 84 /StemH 84 /ItalicAngle 0 /CapHeight 951 /XHeight 665 /Ascent 951 /Descent 220 /Leading 171 /MaxWidth 1000 /AvgWidth 463 >> endobj 912 0 obj << /Type /Font /Subtype /TrueType /FontDescriptor 911 0 R /BaseFont /CenturySchoolbook /FirstChar 31 /LastChar 255 /Widths [ 750 278 296 389 556 556 833 815 204 333 333 500 606 278 333 278 278 556 556 556 556 556 556 556 556 556 556 278 278 606 606 606 444 737 722 722 722 778 722 667 778 833 407 556 778 667 944 815 778 667 778 722 630 667 815 722 981 704 704 611 333 606 333 606 500 333 556 556 444 574 500 333 537 611 315 296 593 315 889 611 500 574 556 444 463 389 611 537 778 537 537 481 333 606 333 606 750 750 750 204 556 389 1000 500 500 333 1000 630 259 1000 750 750 750 750 204 204 389 389 606 556 1000 333 1000 463 259 833 750 750 704 287 296 556 556 606 704 606 500 333 737 334 426 606 333 737 500 400 549 333 333 333 576 606 278 333 333 300 426 833 833 833 444 722 722 722 722 722 722 1000 722 722 722 722 722 407 407 407 407 778 815 778 778 778 778 778 606 778 815 815 815 815 704 667 574 556 556 556 556 556 556 796 444 500 500 500 500 315 315 315 315 500 611 500 500 500 500 500 549 500 611 611 611 611 537 574 537 ] /Encoding /WinAnsiEncoding >> endobj 913 0 obj << /Filter /FlateDecode /Length 914 0 R >> stream In contrast, a dehumidification kiln uses a sealed chamber, with only enough energy input to maintain the desired temperature. You could use the dehumidifier to dry wood but it would not be part of a "kiln." Just be a different process. _0e`bd\ p@ As a result, the kiln schedules were too severe. 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. I cannot stress the importance of baffles enough. Select 3/4 conduit brackets for hanging baffles on 1/2 galvanized pipe. For end baffles, I use 2"-thick rigid foam insulation screwed to the main baffles. There is a way to do the conversions and there is a chart published by Nyle to do it, if you want to do some academic exercise. Adjust the baffles or fan direction to achieve good airflow. An official website of the United States government. I'm trying to find a timetable or drying schedule for the basic dehumidification kilns you see on youtube. The last thing to do before starting the kiln is to close the gable vent with an insulated cover. The baffles do not need insulating properties, and plywood would work just as well. Using a Kiln Schedule Please refer to Appendix A which shows the Lumber Dry Kiln Bill of Materials. Recently, either Wood, or American Woodworker showed how to build a small version of a solar kiln. MC values in the kiln schedules are based on the wettest half of the kiln samples. 0000001186 00000 n 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. Size and placement of the access door are critical as well. Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 F (82 C). Without baffles, the top layers of lumber experience "potato chipping" with cupping, twisting or warping. Kiln drying lumber is a simple, cost effective method recommended for anyone who wants to increase profits by selling dried lumber. To hang the baffles, simply attach hooks to the plywood frame. If your lumber stack is built on starter blocks, you will need to limit airflow there as well. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. A shed kiln is an attractive alternative for a couple of reasons. Made in China, it exudes the classic style of Asian and Chinese cultures, featuring a unique shape that sets it apart from traditional jars. This makes lightweight baffles that can be easily moved and repositioned. Nyle Systems dehumidification kiln packages are our best known product with nearly unlimited drying capabilities. My baffles hang from T-bar assemblies mounted to the ceiling. Dont even think of powering your kiln with an extension cord. 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%. Thicker lumber like 5/4 or quartersawn lumber is naturally more stable. 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? This makes lightweight baffles that can be easily moved and repositioned. Then align each subsequent layer of stickers over the last. For a kiln temperature of 140 F, sterilization takes three to five hours. Bring your moisture meter to confirm. 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 . Place a sticker at each end, and every 16" along the stack for 4/4 stock. Add to my manuals. Frequently, the lumber has already air-dried for several years in a barn or outbuilding. This fact sheet summarizes the basics of kiln drying wood, the most commonly used methods, drying schedules and some drying defects. Should I? The T-bars are made from 1/2" galvanized pipe and are attached to the rafters with threaded pipe flanges. Not bragging or anything! A heavy-duty 1,500-watt space heater works fine. Kiln schedules are completely assembled and written out for easy use. However, you may need more cycles depending on the species, moisture content, and size of the timber. The remaining width allows for a 36-wide door and space for your drying equipment. I usually see a large volume of water in the DH each night when I check the kiln. My question focuses on the initial relative humidity featured in the Safe Drying Rate table. >> 301 0 obj <>stream This serves a dual purpose of supporting the rigid foam insulation as well as stiffening the floor framing. 0000002536 00000 n The schedules are all moisture content based, using the moisture content of the wettest half of the kiln samples. In larger kilns, the heater may be needed in the latter part of the drying cycle. HWn8gXA N,[mKJr2"Ec9,t However, because wood from Construction of a kiln chamber is very similar to building a small house. . I prefer to empty the water tray manually and record the volume of water collected. There are two ways to remove water from the DH unit, and they both work well. Align the stickers over the starter blocks on the first course. A shed kiln has minimal venting (usually one or two gable vents) and sealed soffits. For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. /Width 1628 Reply. temperature. Loading the kiln begins by rousing my sons and letting them know Ive planned a day of work. Dr. Gene Wengert provides schedules for kiln drying hardwood lumber. https://www.fs.usda.gov/research/treesearch/9635, International Institute of Tropical Forestry, Eastern Forest Environmental Threat Assessment Center, Northern Institute of Applied Climate Science, Western Wildland Environmental Threat Assessment Center, conventional-temperature (< 180 F) schedules, elevated-temperature (180-212 F) schedules, R. Sidney Boone, Charles J. Kozlik, Paul J. Bois, Eugene M. Wengert. Insulate the floor with 2 rigid foam for convenience and durability. Perhaps the best part: you wont need to calculate your lumber needs down to the board foot. I hope that the sawyer coated the ends of the lumber with Anchor-Seal or oil-based paint when it was green. Subtract the wet-bulb depression from the dry-bulb temperatures for each schedule step and enter the value in the fifth column. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. Hardwood kiln drying schedules typically keep the dry bulb temperature below 80 C (176 F). Created and Presented by: Henco Viljoen and Elijah McCarty with Nyle Dry Kilns. Reweigh and obtain the oven dry weight.

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