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MEMBER Wood Products;

0.00 $ (CAD)

MEMBER Forest Operations; Pulp, Paper and Bioproducts;

N/A $ (CAD)

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Summary

A small-scale test was initiated in January 2015 to compare results from several moisture content (MC) measurement methods when applied to a range of wood materials. The purpose of the study was to identify potential MC measurement bias, and to help improve the accuracy of laboratory and field MC measurements. Wood materials tested included three species of dimension lumber (Douglas fir, lodgepole pine, and white spruce); four types of wood-based exterior sheathing (plywood, OSB, and two types of medium-density fibre board (MDF)); and one type of wood fibre insulation board. The specimens were conditioned under four environmental conditions: 25°C at relative humidity (RH) of approximately 40%, 55%, or 80%; and 30°C at an RH of 90%. Five MC measurement methods were used: two were commonly used methods / brands of hand-held moisture meters (capacitance or resistance type); and three were MC monitoring systems with data loggers based on a combination of moisture pin sensors (uninsulated screws, insulated pins, and nails). For each environmental condition, the reference MC was based on the gravimetric MC obtained by oven drying a piece cut from the centre of each specimen. After conditioning, the MC values based on oven drying of the three species of dimensional lumber were found to be in general agreement with the average equilibrium moisture contents of solid wood reported by the U.S. Forest Products Laboratory under the specified environmental conditions. Overall, the measured MCs correlated with the gravimetric MCs quite well. The MC readings from different measurement tools fell into an error range of MC from -2% to +2% for the three species of dimensional lumber, OSB, two MDF products, and wood fibre insulation. This study showed that these different measurement tools may be used for wood fibre-based products, such as MDF and insulation board, provided close contact can be maintained between the wood and the meter / moisture pins. The most important finding from this study is the need to exercise greater caution when measuring the MC of plywood. All MC readings for plywood, regardless of the measurement tool used, appeared to be higher than the gravimetric MCs, particularly at higher levels of MC. The MC was observed to be as high as 30% when the gravimetric MC was about 20%.

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