dehumidification kiln drying schedules

This procedure is discussed in a following section. Soon the DH wont show much water collected in the tray. This lets the operator sort stacks by lumber species, so they will be easy to retrieve when the drying cycle is complete. 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. 0 kiln/. Go to the second letter designation (the MC Class Designation) and find the corresponding MC ranges in the table below. I prefer to empty the water tray manually and record the volume of water collected. For international returns, please click here. The dry kiln operator is fully in control, with the ability to make changes as the dry kiln schedule is executing. If severe enough, the lumber can develop honeycomb cracks throughout. Reply. Any info or advice on using dehumidification equipment to dry out chainsaw milled lumber. Built properly, a shed kiln may even increase the value of a property. With a 130 F kiln temperature, sterilization will take 10 to 12 hours ( Dry Kiln Operators Manual, 1991 ). Initially, I set the DH to 40% RH, because I dont want to remove moisture too quickly. Also, since heat rises, ceiling-mounted fans have the added benefit of circulating the warmest air over the lumber. Select a heater with an adjustable thermostat and a tip-over shutoff. 1. a furnace or oven for burning, baking, or drying, especially one for calcining lime or firing pottery. The velocity through the load is assumed to be between 275 and . A heavy-duty 1,500-watt space heater works fine. 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.. These well-known dehumidification kiln packages have been among our bestselling products for the past 30 years. HDE small kilns feature all-aluminum construction for a long, maintenance-free life span . A dehumidification kiln continuously recycles the heat throughout the chamber, rather than . Abstract. Basically the idea seems to be to maintain a constant temperature, and . Kiln drying normally involves temperatures in the range of 40-75 C (about 100-170 F). A lazy Susan with 180 detents mounts the fan box to the ceiling. Dehumidification: This kiln-drying process requires the use of a heat pump system to remove water from the wood. The last thing to do before starting the kiln is to close the gable vent with an insulated cover. This slows the end-grain drying and limits the severity of end checking. My shed kiln was stick-built from standard building material, and sized to take advantage of typical 4 x 8 sheet goods. 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. 4.4 drying schedule moisture content drying schedule . I cannot stress the importance of baffles enough. If MC readings still arent at the desired range, the heat may need to be increased for the remainder of the drying cycle. This problem is magnified if the lumber is thin or flatsawn. A higher humidity setting will run the unit sporadically to maintain that RH. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. This will allow the DH to drain automatically without you needing to enter the kiln. They are normally mounted in the gable of household attics, and they are designed to be used in high temperature environments. Our approach was to build and operate a small dehumidification dry kiln. Job Opportunities and Woodworking Services, Dust Collection, Safety and Plant Operation, Air-Drying and Kiln-Drying Methods for Wide Plank Flooring, Drying lumber - selecting the best method. I usually see a large volume of water in the DH each night when I check the kiln. 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). 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 . Determine the equalization settings and conditioning settings, as required. building the dehumidification dry kiln. If required, look-up and write down the RH (sixth column) and EMC (seventh column) for each schedule step. I selected a 36 outswing exterior door. This report contains suggested dry kiln schedules for over 500 commercial woods, both temperate and tropical. Although dehumidification kilns are slower than conventional kilns for drying, the lower drying temperature has the reported advantage of less degrade and less shrinkage. 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. Another reason I like the idea of a shed kiln is the flexibility of future use. Once the lumber is sterilized, it is ready for the conditioning phase. 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. Once all the lumber is stacked and stickered, place baffles over the lumber. 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. A free BASIC program to convert the designations into actual temperatures and humidities is available from the author. However, if you kiln dry hardwood lumber that has already been air dried, the process is much more forgiving. They are easy to use and give you precision control over your 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. 0000002827 00000 n A maximum 45 F depression often produces better lumber. 3.24 solar-dehumidification drying 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. Difficult-to-dry species might not exceed 140 degrees F. Dehumidification kilns are very . My question focuses on the initial relative humidity featured in the Safe Drying Rate table. The remaining width allows for a 36-wide door and space for your drying equipment. They are normally mounted in the gable of household attics, and they are designed to be used in high temperature environments. Always avoid conditions that add moisture back to the lumber, especially during start-up. (116 C) temperature. 1998. by Dr. Eugene Wengert. The stickers are uniform in size and usually 3/4 or 1 square. The cost associated with shed construction was similar to buying a prefabricated kit. Heat comes primarily from an integral dehumidification unit that also removes . Corrosion resistant epoxy coated aluminum cabinets and specially coated dehumidification coils for an extra long life. The kiln schedule information in the tables below has been assembled from many different sources, including drying texts and industrial contacts. Made in China, it exudes the classic style of Asian and Chinese cultures, featuring a unique shape that sets it apart from traditional jars. Temperatures inside the kiln range from 120 to 190 degrees F, depending on the stage of . Select a heater with an adjustable thermostat and a tip-over shutoff. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). Each layer of lumber is separated from the next by a series of "stickers" or spacer sticks. 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 These figures hold true for lumber up to 2" thick. If you use a lot of lumber, and youre a decent hand at carpentry, a shed kiln will quickly pay for itself. My kiln uses four ceiling-mounted fans, each rated for 1,600 CFM. 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. _0e`bd\ p@ Wood Drying/ Seasoning. The T-bars are made from 1/2" galvanized pipe and are attached to the rafters with threaded pipe flanges. The first thing to consider when designing a shed kiln is size. Apply foil tape to the edges of the main baffles to help protect the Styrofoam. %PDF-1.4 % Difficult-to-dry species might not exceed 140 degrees F. Dehumidification kilns are very . 8. A kiln schedule is a set of temperatures and humidities that are used during kiln operation. Nyle Systems dehumidification kiln packages are our best known product with nearly unlimited drying capabilities. Nyle. Kiln Systems. My kiln schedule starts with running all fans and the dehumidifier for two days, measuring and removing water as it accumulates. Once the core readings are 6% to 8% on a fresh cut, the lumber is dry and ready for sterilization. I am also curious why an initial temperature of 90F would have been selected. 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. There are many types of kilns, but the most common are dehumidification kilns and conventional kilns. I modified one of the Radio Shack combo units so it could measure the RH remotely as well as the temp. /BitsPerComponent 1 Gen. Tech. Size and placement of the access door are critical as well. Manufacturer guarantees/warranties for power tools, CNC and laser products will supersede the Rockler Guarantee if these items are damaged or defective. Another common sticker size is 1 x 2, and these work fine as well. Among dimension lumber, the 2- by 4-inch size is typically the most susceptible to warp for a variety of reasons. . On the last load of lumber I purchased, I saved $2.50 per board foot compared to retail prices for kiln-dried lumber. Soon the DH won't show much water collected in the tray. 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. The DH is not needed at this time, as the lumber is already bone-dry. Y}-m+'@DQ4\h8GP]y@ yL. There may be more depression values than required; ignore the extra depression values in this table. Its a nice use of technology and adds a measure of safety as well.) With a 130 F kiln temperature, sterilization will take 10 to 12 hours ( Dry Kiln Operators Manual, 1991 ). Its a nice use of technology and adds a measure of safety as well.) The sheetrock also helps to protect the fiberglass insulation. Hardwood kiln drying schedules typically keep the dry bulb temperature below 80 C (176 F). When that is the case, I know Ill have usable lumber in just a few weeks. This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. A 1.5-kW dehumidifier was installed in the solar dryer to determine the performance of a combined solar-dehumidification dryer. -. A better choice might be a solar kiln, as you can dry wood from "wet" to 6-8 percent MC in 6-8 weeks. Milling the stickers square is advantageous over a rectangular cross-section, because no matter how you place the stickers they will form a level stack. In Fig. I'm thinking I could vent it manually, but with the RH so high externally I am not sure if that is the right thing to do. 158 p. Dry kiln schedules for commercial woods : temperate and tropical. 0000006274 00000 n 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. This would allow a stack of lumber four feet wide and 10 feet long. 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. To condition the lumber, I introduce steam into the kiln for about two hours. This is because it needs to be dried to a lower moisture content than wood will air dry to outdoors. Enter the email address you signed up with and we'll email you a reset link. For the best experience on our site, be sure to turn on Javascript in your browser. In larger kilns, the heater may be needed in the latter part of the drying cycle. A heavy-duty 1,500-watt space heater works fine. For these reasons, I feel it is best to let the shed breathe, and forgo a plastic vapor barrier. Different species should not be loaded simultaneously into the kiln due to often differing kiln schedules. Select 3/4 conduit brackets for hanging baffles on 1/2 galvanized pipe. Select 3/4" conduit brackets for hanging baffles on 1/2" galvanized pipe. 301 0 obj <>stream This helps keep the lumber straight during the drying cycle; in fact, improper placement of stickers can permanently deform lumber. 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. Kiln drying is usually preceded by air drying to bring the moisture content of the wood down below 30%. Then align each subsequent layer of stickers over the last. We are proud of the quality of our products, and we stand behind them 100%. 2. Once the core readings are 6% to 8% on a fresh cut, the lumber is dry and ready for sterilization. The starter blocks should be as long as the stack is wide. In-service replacement of warped 2 by 4's as wall studs or truss members is costly. (See the following sections for a discussion of how to develop a schedule from these designations.) To hang the baffles, simply attach hooks to the plywood frame. I usually see a large volume of water in the DH each night when I check the kiln. . Place some sample boards in the stack that will be easy to pull out for moisture testing later. In time schedules, dry- and wet . 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. I can show you the kiln schedules and data. I either use some cedar 3" x 5", or 4" x 4" stock. Forum Responses BE CAREFUL--The first temperature value must be repeated for every MC class (column #2) that is above 30% MC. With a well-designed dehumidification kiln, hardwood lumber can be dried for mere pennies per board foot. You may also return purchases to a Rockler store near you for store credit. For these items, please call the store where you purchased them or our customer service department at 1-800-376-7856 so we can assist you. I hope that the sawyer coated the ends of the lumber with Anchor-Seal or oil-based paint when it was green. Delete from my manuals. Most species of hardwood lumber can be safely dried this way, once the moisture content is 20% to 25% or less. It should be double-pane, well-insulated with low emissivity (low-E). The starter blocks should be as long as the stack is wide. The four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln.

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