Technology Roadmap: Lumber and Value-Added Wood Products
4.14.3 Dry Moisture Content Monitoring and Quality Control

Existing Technology

The most critical aspect of dry lumber quality, from the customer's standpoint, is conformance with the final moisture content requirement. The majority of softwood construction lumber is dried to 19 percent or less, with smaller amounts being dried to 15 percent, or even tighter specifications, for specialty and value-added products. Final moisture content variability, due to within- and betweenspecies drying differences, has always been an issue for softwood producers. In-line moisture meters have become quite popular over the past 10 years as they are the only way of monitoring all production. It is estimated that 75 percent of large softwood mills in Western Canada have such meters. In Eastern Canada, it is estimated that 60 percent of the larger mills have them in place.

Most mills are using them strictly as a watchdog to ensure that the percentage of "wets" does not exceed acceptable levels. Only a few mills have "closed the loop" by setting up a system that ensures that all information makes it back to the kiln operator and that the kiln operator uses it as a diagnostic tool to evaluate his equipment and practices. Another potential use of in-line meters is to sort out material for re-drying.

Some confusion exists within the industry on the accuracy and reliability of in-line and hand-held meters. Some mills have also experienced problems with frozen lumber. The confusion stems from each meter being affected by different environmental and wood-related factors. Some laboratory work to confirm or develop new correction factors for both meters, and to identify proper operating practices would go a long way toward clearing up the confusion.

With most softwood producers, quality control in lumber drying is limited to final moisture content monitoring. More detailed and accurate moisture content information would be helpful in developing and refining drying schedules and ensuring maximum recovery of high-value grades or products from the available resource. An automated way of collecting information on lumber moisture contents and conditions prevailing in the kiln would also facilitate equipment evaluation and process improvement.

Incremental Technological Innovation

• Develop technology to establish consistency between on-line moisture meters, hand-held resistance meters and hand-held RF-power meters so that all moisture content measurements in the mill may be comparable and usable in common databases.
• Develop and implement methods to remotely monitor moisture content and temperatures inside the kiln (see Section 4.14.2).
• Develop and implement methods to monitor kiln-dried lumber for drying defects (checking, warp, etc.) in real time and to analyse this information for kiln control.

Breakthrough Technological Innovation

• Develop and implement an integrated method to analyse all data pertaining to kiln-dried lumber production and relate it back to information collected at the dryers and at the sorting station in order to optimise sorting and drying strategies.