The Ultimate Guide to Lumber Moisture Control – Part 4: Sawmill

Part 4 of a 4-part series – As seen in the January/February issue of Timber Processing.

Before reaching the kiln, the sawmill provides the first opportunity in lumber processing to recognize benefit from today’s advanced moisture sensing technologies. Designed to optimize lumber recovery factor, moisture systems are giving sawmills the necessary tools to quickly identify and sort boards after primary breakdown, and to improve groupings.

This data-driven sort, after primary breakdown, is critical to achieving the best grade recoveries at the end of the production process. Dunkley Lumber’s Process Control Manager, Lee Mason, agrees with this assessment.

“The most important part of our drying program is the sorting of wet and dry lumber after primary breakdown,” he said. “Sorting allows us to capture more value from the fiber due to less downgrade for being too dry, or too wet.”

Mills optimizing to achieve better grade recovery by accessing additional data parameters are also utilizing advanced moisture sensor systems connected through the Industrial Internet of Things (IIoT). This modern integration helps mills to clearly see quantifiable improvements in processing productivity and grade recovery.

Lumber Variability Controls

When mills can effectively control the natural variability of lumber, they can improve the balance of cost and time that represents their ultimate profitability measure. Sorting after primary breakdown lets mills manage the complex issues of forest biodiversity such as multiple species, varying log sizes and different conditions. Some logs or boards in the north may be frozen, and in the south, they may be subject to mold, staining or end checking.

When moisture sensing isn’t a parameter for sawmill optimization, the resulting lumber is often prone to large standard deviations in its moisture content. These deviations will typically miss the desired moisture target and decrease the mill’s productivity by consistently delivering a significantly higher volume of wet lumber and over-dried boards.

But today, the latest moisture sensors are helping mills avoid these costly drying errors and make better, more profitable products. That’s because advanced moisture sensors are going beyond simple species sorts to deliver robust data that determines critical considerations, like variations within a single species, to ensure more uniform packages for kiln drying and improved grade recovery at the planer.

“Our mills are in northern Canada and the Finna Sensors High Definition (HD) system reacts well to temperature fluctuations,” Mason said. “We also see improved kiln efficiency by reducing our drying times on the drier sorts.”

Dry-ability Index Numbers

Achieving more uniform packages for the kiln is key to improved grade recovery at the end of the process. Single species can be weight-sorted to develop bulk density output, but with moisture sensors, mills can achieve significantly better results. This is done by deploying radio frequency sensors to determine the best sort, based on a precise Dry-ability Index Number (DIN).

An accurately measured DIN allows for sorting of the total fiber basket, in up to four groups, that can create more uniform packages for the kiln and deliver better drying outcomes. Sensors controlled by advanced software can track boards as they move from the sawmill through the kiln and to the planer, allowing operators to better understand how sort decisions will affect final yield.

Moisture Sensor Advancements

Advanced moisture sensors in the sawmill are added at the end of the production line to improve production bottlenecks at the kiln and grade recovery in the planer. In the past, moisture sensors actually touched the boards using a contact system that measured both faces. However, this approach required additional and ongoing maintenance because of the system’s full contact nature.

Addressing these early concerns, sensors have been developed to be more robust and non-contact. They avoid continuous maintenance, while providing up to five sensors beneath the line, to deliver processing data for up to a nine-foot board.

But as mills required even more robust data to increase profitability and reduce waste, moisture sensors advanced even further. Today, the most modern mills are benefitting from HD moisture sensing technologies that can read data from up to 24 sensors. These sensors can be specified to fit between chain runs and can be positioned to read both the top and bottom faces of boards.

This significant increase in surface area readings delivered by HD moisture sensors can help operators to identify the boundaries of heartwood/sapwood or the areas of wet pockets to improve sorting, before kiln drying, and to help realize the double-digit productivity increases and enhanced lumber recovery.

“We currently have two of the Finna Sensors HD systems in our mills: they are built strong, easy to maintain, and don’t impede the flow of wood due to their non-contact design,” Mason said. “The payback in each mill took less than a year.”

Expanding the Best Advancements

Developers of advanced sawmill moisture systems in forestry are continuing their drive to further improve the profitability of mills. The next generation of advancements is already combining the best measurement options from previous technology wins.

Now, modern mills can opt for a hybrid sawmill system that seamlessly combines moisture measurement technologies, including bulk density, radio frequency and species inputs, to deliver even more data points. This data, when combined with advanced software and IIoT communications, is the future of data-driven sorting.

Thanks to design innovations, hybrid sawmill systems are going beyond their production benefits of higher accuracy, better yield and increased profitability. They now deliver solutions that require less maintenance and provide mills with lower costs of ownership, along with easier system startup and more streamlined operator training.

Yet, despite their importance, moisture sensing technology advancements don’t end at the sawmill. After data-driven sorting is completed on primary breakdown, the ongoing benefits of monitoring moisture across the timber processing line has just begun.

The most advanced mills are leveraging more opportunities to improve their profitability by using moisture systems that are also deployed at the kiln and in the planer. It’s this kind of enhanced process integration that lets mills achieve their biggest benefits by tracking, capturing, analyzing and responding to the real-time moisture readings developed across all areas of the lumber milling process.

<<Read Part 3: Planer