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Proper Drying Is Important At Merritt Brothers
Company's kilns utilize electronics system for comprehensive monitoring to control lumber quality.
By Jack Petree
Date Posted: 7/8/2002
ATHOL, Idaho — Value-added manufacturing in the forest products industry requires processing to precise targets if products are to meet the stringent standards for quality demanded by today’s marketplace.
In addition to maintaining a close eye on product quality issues, value-added manufacturing operations must carefully control costs, a necessary element if profitability is to be achieved over the long run. A planer that is off by a few hundredths of an inch, a saw that is not properly sharpened, or a dry kiln that is not controlled carefully all can have serious impacts on a mill’s operations and its ability to profitably produce quality lumber products.
At Merritt Brothers Lumber Company, proper drying and closely controlling moisture content are especially important to the mill’s success. First, according to plant manager Tim Denton, the company’s products ultimately wind up with customers who want higher value and quality than what is generally available in the marketplace. Second, products that do not meet Merritt Brothers standards for quality must be processed further — at additional cost and reduced profitability.
To ensure that lumber moisture content is kept within the company’s parameters, Merritt Brothers relies on technology supplied by Wagner Electronics of Rogue River, Ore. Wagner Electronics is a leading manufacturers of moisture metering systems for the forest products industry.
Merritt Brothers is owned by Buck Merritt, who founded the company in partnership with his brother, Wayne, in Priest River, Idaho in the late 1960s. A few years later, the brothers purchased a stud mill in Priest River and operated it until selling the mill in 1994.
Buck and Wayne adjusted their operations to the needs of the marketplace by constructing a lumber reman plant in Athol in 1990. The plant has been remodeled and operates as a stud planing facility in coordination with another mill — a fingerjointing plant — built by Merritt Brothers in 1995.
Both the fingerjointing plant and the stud mill are high-volume operations. The fingerjointing mill produces 2x3, 2x4 and 2x6 studs at a rate of 10,000 board feet per hour. The stud planing facility processes rough green lumber into finished 1x4, 2x4 and 2x6 and also profiles 2x8 down to 2x4. Planer capacity is 35-40,000 board feet per hour.
Three 68-foot dry kilns, two American Wood and one LSI high pressure kiln, are utilized to dry a variety of species, including Englemann spruce, larch, hemlock, white fir, Douglas fir, lodgepole pine and other softwoods.
Products manufactured at Athol are sold throughout the West, Mid-West and South. Merritt Brothers sells to contractors, retailers, and builders who want to offer their own customers unusually high value and quality.
With the variety of operations, the number of species handled, and the range of products produced at Merritt Brothers, the drying operations are an area of significant concern, according to Tim. Proper drying is important for two reasons, he noted. Precision control in drying impacts the quality of the company’s products as well as profitability.
Careful moisture control can benefit the company’s drying operations and overall profitability in a number of ways. For example, the kilns at Merritt Brothers are fired by natural gas. "Energy costs have been continually rising in recent years," Tim said. "When you’re paying for energy, you have to do everything you can to keep drying times down to the minimum required to do the job. Extra time in the kiln — beyond what is necessary to dry properly and achieve moisture content targets — adds nothing to the value of the wood. Extra drying time may even degrade the wood while it runs up energy costs unnecessarily."
On the other hand, it is equally important that lumber be dried properly. "The only thing that wastes more energy than drying a board for longer than necessary is to under-dry and then have to go through the whole process again," Tim said.
Drying also has a critical impact on quality. "The moisture content of the lumber is real critical," said Tim. "If the lumber is too wet after drying, there are too many outs. If the lumber is too dry, quality suffers due to excessive warp and twist, and, again, we end up with increased costs."
In order to control and monitor the moisture content in its lumber products, Merritt Brothers has several moisture monitoring stations so that results can be cross-checked at each stage of the drying and manufacturing process.
In the kilns, Merritt Brothers utilizes an old Wagner Electronics 778 in-kiln moisture monitoring system. Though old, the system is a tribute to the quality of Wagner’s equipment, Tim said. It is still accurate and effective after many years of use.
The model Wagner Electronics 778 monitoring system provides a true, broad field moisture measurement that accurately samples a statistically significant portion of the charge in each kiln. The 778 uses electromagnetic wave technology that Wagner pioneered. A major advantage of the system, according to Wagner, is that the technology provides truly comprehensive monitoring in the kiln environment while avoiding the pitfalls of other methods.
Merritt Brothers also utilizes a Wagner L722 stack probing sensor for support and cross-checking of the kiln sensing system. The L722 is an attachment for Wagner’s L612 hand meter, which in turn is coupled with Wagner’s Stat-Pak software system. The stack prob allows for a reach exceeding 40 inches into a stickered deck of lumber in or out of the kiln. According to Wagner, multiple readings through an entire stack can be taken in just minutes with the results being quickly available in usable form almost instantly. Newly surfaced boards are checked on succeeding shifts as part of the on-going monitoring program so that any problems that may be creeping into the drying process can be detected early and addressed.
As a last quality control check, lumber at the Merritt Brothers plant is run through a Model 683 iCE sensing system. The 683 also utilizes Wagner’s non-contact, electromagnetic RF sensing technology. As lumber passes through the sensing field, pieces that might violate pre-set moisture content limits are dropped out of the line. The 683 is not run on a continuing basis, according to Tim, but is utilized to do sampling on occasional runs. The sampling is timed to ensure that potential drying problems are caught early.
The three moisture testing regimes allow Merritt Brothers to fully control and then check the drying processes. The 778 system is utilized to control drying, an important issue since a variety of species must be addressed. The system also provides a rough check of the entire charge in the kiln as it is dried. The 722/612 combination allows for cross-checking both in and out of the kiln while the 683 provides a final check of the finished product. Their combined application provides thorough, constant quality.
The drying system, as controlled and checked by the mill’s Wagner Electronics moisture monitoring systems, is an important tool in production, value output and quality control — as important as optimization of a saw carriage in a sawmill. The Wagner moisture metering systems help to reduce operating costs by providing close control of the drying process and energy consumption. Precise, consistent control of the moisture content allows for substantial reductions in fiber loss due to degrade, a significant factor in maximizing profitability. Lastly, precise drying improves the quality of the lumber products. "Appearance is a big factor in how our product’s quality is perceived in the marketplace," Tim said. "The drying process has a good deal to do with how the wood looks when it is shipped."
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