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Single Line VERSATILITY

With a $12-million upgrade, TimberWest's Williams Lake mill adds stream flow flexibility and improves recovery in the face of an inevitable decline in log volumes.

By Jim Stirling
Copyright 1997. Contact publisher for permission to use.

Innovation matched with a design strategy to accommodate future needs characterize a new small log sawmill at TimberWest Forest Limited's Williams Lake region in south-central British Columbia.

The single production line mill is configured to produce studs to 10' or three metres in length, 1X3 to 2X6 in size for customers in North America and Japan. The plant has a capacity of 250,000 board feet/day on two shifts. The modernization project came in on budget at slightly less than $12 million.

Fibre type and availability and existing facilities molded the planning process for the new sawmill. "We faced an existing stud mill facility with limited product flexibility and lumber sorting capability. And while it was reasonably modern with optimized edging and sorting, the log breakdown was relatively archaic with two manually set canters and a head rig," outlines Hugh Jones, TimberWest's vice-president in Williams Lake. Compounding that was the limited physical space immediately in front of the canter infeeds to make optimization improvements.

March97

But a legacy from the past was available to help chart the future. TimberWest had a retired dimension sawmill on-site. It was operated in the 1970s and 1980s when the company had access to larger-diameter timber - especially Douglas fir - and was producing up to 26' lengths. "We had the opportunity to replace existing capacity without incurring major infrastructure costs," says Jones. Renovating the existing dimension mill building had the additional attraction of reducing cost and productivity impacts during construction, equipment installation and run-in periods.

"The major objectives with the new facility were to give us a higher lumber recovery factor, a broader product stream and a sorter capability that included sorting by moisture content," he summarizes. "We also had to face the fact that the log volumes available to us will eventually decline." TimberWest has had beetle-killed timber licences renewed, helping bolster its AAC, but there's no guarantee of their continuance. Log sizes are also declining in TimberWest's harvesting areas in the lodgepole pine stands of the Chilcotin Plateau west of Williams Lake.

"We needed a facility to allow high piece counts and good recovery on small fibre with a view to expanding into processing logs that meet smaller utilization standards," continues Jones. A second line to further achieve those goals is anticipated in two or more stages during the next two to three years, he says. That will then allow the phasing out of the original stud mill operation. (The other product stream in that plant is finger-jointed material claimed from recovering side boards with 3' or more of 2'' material and from log sections 5' to 7' in length).

March97

The old dimension sawmill had received several additions during its approximately 20 years of life. Much of the floor steel had to be dismantled before installation of new equipment could begin last May. A recently installed 12'' Nicholson debarker was retained from the dimension mill set-up. It was used to process pulp wood and recover saw blocks. TimberWest plans to add a new debarker, a machine in the 17'' category. A drum debarker and whole log chipper were also part of the dimension mill.

Logs travel an infeed conveyor where they are scanned and sorted by size into two log pits. One is for 3'' to 6'' material, the other for 6'' and up. Log sections unsuitable for sawing are directed to the whole log chipper. Unscrambler feeds with sensing and scanning equipment singulate logs and provide a steady, automatic feed to the breakdown line. This involves a double-length infeed on a two-sided canter with a close-coupled 6' twin band saw. Its features include full profile scanning, auto-rotation and side shifting on the infeed.

The TimberWest team adopted an unusual approach to its equipment supplies; it purchased them in systems. Denis Comact supplied the log conveying and scanning systems, the log pits, double-length infeed and the rest of the canter/trim band line. The company also provided the lumber transport system downstream, including the sorting and stacking systems. McGeehee supplied the board and gang edger systems, including process control and optimization. Coe supplied the optimizing and process control for the bin sorter and stacker. Multimeg - a Denis Comact subsidiary - provided process control and optimization for the log sorting and canter twin primary breakdown.

"We wanted to take advantage of Denis Comact's expertise with the design and fabrication for handling and processing small logs," explains Jones of the systems approach. McGeehee was offered the edger systems control to meet TimberWest's specific performance expectations. Accordingly, the two edging systems contain interesting and unusual features. The gang edger's saw bank is divided into two clusters that can be set to different thicknesses. It's equipped with saw spacing for 1'' on the zero side so 1'' cant boards can be optimized. The edger is designed to reflect the mill's diet of small-diameter and frequently misshapen pine. The high-speed machine features an articulating translating arbor which can shift along an arc as each cant moves through it.

March97 "It's emerging technology. We made the call to accept some risk rather than go with what might essentially be out of date by the time we installed it. And we did so with full knowledge of the considerable upside potential with the maintenance and accuracy of the two edging systems," says Jones. The board edger also uses translating lineal scanning. It is more cost effective - it requires no pre-positioning table - and has fewer moving parts to maintain. "In the future design concept of the plant, in addition to log preparation and debarking facilities, we see installation of a small log line to focus on the three-inch to six-inch-diameter material and integration of a horizontal re-saw, with the board edger system to break down multiple side boards generated from the twin band," predicts Jones.

The mill makes wide use of variable frequency electric drive motors to achieve high piece counts through machine centres. The canter system can run up to 450'/min and the gang edger 480'/min. Jones says the total one-line system averages 1,000 cants/hour and he sees the potential with smaller log sizes to approach 1,500 cants/hour.

Fast, accurate materials handling is further reflected downstream with the bin sorter's performance of up to 185 lugs/min. The high feed rate is achieved with a Denis Comact rotary lug loader, followed by a high-resolution Coe scanner and optimized single saw trimming system. A blanket trimmer in front of the stacker completes the process.

imberWest's people and the chosen equipment define the new plant's synergy. "All our people, hourly and supervisory, were involved with the project right from the beginning," recalls Terry Mitchell, plant supervisor and project manager for TimberWest. Extensive training, travel to similar plant operations and co-operation from suppliers on the technical aspects of their equipment were all part of the training process. Mitchell commends the approach, despite the time and cost involved. "There's a real sense of ownership among employees," he observes.

THe cites the infeed to the canter as an example of the high degree of automation throughout the processing line. Each log is scanned, positioned, then re-scanned and centred to the canter for optimum processing. Shifting heads and anvils reduce gaps between logs.

A man-machine interface system uses software programs to provide a detailed overview of the processing line. "It shows us everything that's going on in a very visual display on multiple screens," outlines Lloyd Griffith, in charge of the electrical aspects of the project for TimberWest. For example, the system can provide instant visual information on head positions in respect to the canter's centre line and speeds of conveyors, chains and belts. "If a set work quits, we get immediate feedback of what's wrong and remedial action alternatives," says Griffith. Immediate problem identification helps production people as well as maintenance staff, he adds.

Other key members of TimberWest's team include Bill Drebit, in charge of mechanical aspects of the project; Don Fayowski, who looks after the safety aspects; and Jim Tazelaar, the production supervisor.

Stolberg Engineering was responsible for conceptual engineering on the project, with detailed engineering from the equipment supervisors. North Central Mill was responsible for the mechanical installations and Westwood Electric the electrical installations. Overall project manager was Lloyd Pederson of Pederson Management.


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