Operation And Cost Of A Small Dehumidification Dry Kiln

Obtaining small quantities of custom kiln-dried lumber can be an expensive process for an individual woodworker. Building and operating a small kiln capable of drying custom cuts of lumber (such as slabs, bowl blanks) gives woodworkers another option. Our approach was to build and operate a small dehumidification dry kiln. The four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln. The first charge of mixed air-dried 4/4 hardwoods and softwoods was kiln-dried from 18.4% to 7.3% moisture content (MC) in 15 days with no casehardening. The second charge of 5/4 black cherry lumber was kiln-dried from 47.5% to 6.8% MC in 27 days with no casehardening, and the third charge of 4/4 northern red oak lumber was kiln-dried from 82.9% to 6.1% MC in 45 days and to 5.2% MC in 50 days with severe casehardening relieved by conditioning. A fourth charge of 300 bf 4/4 northern red oak, 200 bf of 4/4 shagbark hickory, and 100 bf of mixed 4/4 box elder and 4/4 black cherry was kiln-dried from 69.7% to 8.5% MC in 29 days with casehardening only in the northern red oak, and that was relieved by conditioning. We found that greater control of the dehumidifier operation earlier in the kiln schedule to maintain the safe drying rate would decrease the severity of casehardening when drying green northern red oak. New building materials, which are most of the initial cost, could be replaced by reused lumber. Drying small amounts of lumber using a dehumidification kiln is a suitable option for woodworkers even with limited knowledge of kilns.

Executive summary: A summary of the construction and operation of Manitoba's first commercial small-scale dehumidification lumber kiln is given. The test unit was an EBAC LD 3000 kiln purchased in January 1994. Details are provided as to kiln chamber construction, load preparation, monitoring, and performance with four loads of woods native to Manitoba. The report is presented within the context of developing a rural micro-sawing industry built around portable bandsaw mills. Lumber drying is shown as the first and most important value-added operation available to the small-scale sawyer. An overview of drying options is given. An outline of current offerings from 3 major manufacturers is included, as well as a bibliography for further reading.

Drying Hardwood Lumber focuses on common methods for drying lumber of different thickness, with minimal drying defects, for high quality applications. This manual also includes predrying treatments that, when part of an overall quality-oriented drying system, reduce defects and improve drying quality, especially of oak lumber. Special attention is given to drying white wood, such as hard maple and ash, without sticker shadow or other discoloration. Several special drying methods, such as solar drying, are described, and proper techniques for storing dried lumber are discussed. Suggestions are provided for ways to economize on drying costs by reducing drying time and energy demands when feasible. Each chapter is accompanied by a list of references. Some references are cited in the chapter; others are listed as additional sources of information.