Trials of a Prototype Roll-Feed, High Temperature Dryer for 8/4 Southern-Pine

Previous research has shown that 8-foot southern pine studs 4 inches wide and 1.9 inches thick can be dried from the green condition to 9 percent moisture content in 21 hours in a kiln providing a cross-circulation velocity of 1,000 fpm at dry- and wet-bulb temperatures of 240? F and 160? F. Casehardening can be relieved by 3 hours at 195? F dry-bulb and 185? F wet-bulb temperatures. Moreover, this research showed that very straight dry studs can be obtained if effective mechanical restraint is applied during the drying process. A prototype continuous roll-feed, high-temperature kiln to hold 8/4 lumber under complete mechanical restraint during the high-temperature drying process was built and tested. The prototype had powered roll pairs spaced 1 foot on centers. Continuous 3/4-inch-wide by 1-1/2-inch-high, cold-rolled, fixed steel guides (spaced 3.85 inches apart) restrained the studs against crook as they were power driven, flat sides down, between the roll pairs. In each kiln charge, six studs were placed between the roll pairs of the 9-foot-long apparatus; after charging into a compartment kiln, the rolls were made to rotate 18 inches first in one direction and then in the other; this oscillating motion was maintained throughout each 24-hour cycle. The 1.75 by 3.84 inch studs, cut from veneer cores had an 87.9 percent moisture content when green; they were dried without casehardening to 8.3 percent during the 24- hour cycle. warp was significantly less (0.01 level) in the studs roll-dried-than in those conventionally stickered.

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