Visual Method to Assess Lumber Sorting Before Drying

Abstract

This article explores the possibility of using a simplified but intuitive method to quickly assess the potential benefits of sorting lumber before industrial kiln drying. The method consists of using scatter plots to visualize the probability of obtaining a certain drying result, such as final moisture content, as a function of a property of the green lumber that can be measured in practice. The method was first validated with four drying runs of 116 mm × 52 mm hemlock lumber: one run contained unsorted lumber and the others contained the same type of lumber but sorted into low, medium, and high groups depending on the electrical capacitance of the green wood. After validation, the scatter plots were used to assess the benefits of two typical industrial sorting strategies, namely, sorting by electric capacitance and sorting by weight. It was found that both methods have the potential to increase lumber production and reduce over dried lumber in approximately the same magnitude. For a typical industrial schedule, sorting into three groups reduced the drying time by approximately 10% and over dried lumber to practically zero.

Keywords:

• Capacitance
• Drying
• Sorting
• Weight
• Wood

Notes

^a Time difference = Actual drying time minus the time required to dry unsorted lumber to 16.5%.

^a Time difference = Actual drying time minus the time required to dry unsorted lumber to 16.7%.

^a Time difference = Actual drying time minus the time required to dry unsorted lumber to 16.7%.