Direct Observation of the Tumbling of OSB Strands in an Industrial Scale Coil Blender
Keywords:Blending, strand tumbling, furnish curtain, composites, OSB
AbstractA series of experiments were carried out in an 11- by 35-ft industrial scale rotary drum blender in which a small amount of OSB furnish was placed, and the motions of strands were recorded with a video camera at various drum rotation speeds. As the blender rotated, the strands were lifted up by the flights—short fins inside and running the length of the blender—until they sloughed off and fell to the bottom of the drum. At low rotation speeds, the strands fell a short distance as they sloughed from flight to flight; at intermediate speeds, the strands fell across the diameter of the drum; and at higher speeds the freefall distance decreased again and was similar to the low speed case. The distance through which the strands fell with each revolution was shown theoretically to be inversely proportional to drum speed. The residence time of the stands in the blender set at a tilt angle of 3° was measured for five drum speeds and found to be directly proportional to drum speed. It was concluded that the speed that produces the most uniform dispersion of resin on the strands is a compromise between that which is high enough to ensure that the strands will slough from the flights many times, but low enough to provide sufficient time for the strand to twirl and flip and become coated with resin. The potential advantages of using specially shaped atomizer booms to direct strand flow to maximize the uniformity of the resin dispersion over the strand surface is also discussed.
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