Forced-Air Drying of Lumber–Research and Experimental

A special lumber drying test in a commercial forced-air dryer was carried out and the data compared with the research data obtained in Forest Service test studies at Athens, Ga. Air velocities, of about 500 to 600 feet per minute are optimum from the standpoint of drying rate balanced against fan operation costs. Without intermittent reversal of fans, air travel across lumber should be limited to 10 feet to maintain fast and uniform drying in all parts of the lumber pile. Temperature is extremely important in forced-air drying and should be maintained above 70?F. When equilibrium moisture content exceeds 12 to 14 percent in the dryer, additional heat is necessary to maintain the drying rate and to avoid staining of green lumber. This usually requires an inside temperature of 10?F to 20?F above outside temperature during humid periods and at night if round-the-clock drying is desired. The above facts were established in research studies by the Forest Service and have been tested and found applicable in a commercial forced-air dryer at Jacksonville, where operation conditions favor daytime drying only and where various thicknesses of magnolia lumber up to 10/4 are included in the same charge. Drying degrade has been almost eliminated, and drying costs have been reduced

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