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Sawmill Upgrade

A steady stream of optimization upgrades-totalling more than $20 million-have resulted in impressive increases in production at Northwood's sawmill in Houston, BC.


By Jim Stirling
Copyright 1998. Contact publisher for permission to use.

A crane gently lowers a steel beam to two waiting workers, perched atop the skeletons of new lumber sort bins. Carefully, they help manoeuvre the beam into position. Piece by painstaking piece, the structure takes shape.

That kind of activity has been happening for much of the last four years around Northwood Inc.'s Houston sawmill in west-central British Columbia. Construction workers, equipment suppliers and installers regularly rub shoulders with the mill's production, maintenance and supervisory crews, making one of the largest sawmill complexes anywhere even busier. Bit by bit, piece by piece, project by project, the mill has taken on a new look.

Sawmill Improvements

The improvements at Northwoods' Houston operation are directed at achieving greater lumber recovery from each log and a higher volume of lumber.

"In the last four years, we've had a program of optimization and it's all focused on getting more lumber recovery from each log and getting a higher value of lumber at the same time;' summarizes Dennis Hotte, plant manager at Northwood's Houston business unit. And the reason: "You can't stand still, you have to be competitive," he declares. Being competitive has never been tougher her in a working environment of ever increasing costs, stumpage rates and restrictive quotas.

All of the changes, all of the never-ending learning curves for the mill's people are paying significant dividends for the operation's bottom line. "Four years ago, we used 1.3 million cubic metres of wood annually and we were producing an average of 1.275 million board feet of lumber a day. Now, four years later and after all the improvements, we're using the same volume of wood and averaging 1.530 million board feet of lumber a day," reports Hotte. Northwood has spent more than $20 million on its sawmill, planer and dry kiln operation during that four-year period.

The log optimization project began in 1994 with the installation of an Optimil double-length infeed with auto rotation and a Porter Engineering scanning and optimization package for the mill's new north end chip In saw. The mill's other two chip'n saws and chip'n canter lines have been similarly updated. Complementing all of that is the new Porter RT 2 log scanning and processing control system on the east and west merchandising decks, which has improved the lumber recovery factor as well as the value recovery. The system's bucking solution software uses the same parameter tables as the chip'n saws and canter, allowing maximum utilization of the diversity of the four primary breakdown units.

Safety and efficiency have been enhanced with the installation of a Linden step feeder with a quadrant in front of it. The quadrant helps straighten logs and corrects cross-ups prior to the step feeder. The result is a faster and more uniform flow of logs. The Linden equipment replaces a chain unscrambler which tended to stand logs on end, requiring workers to venture on to the deck to pry logs free.

A more recent upgrade has been the installation of a Softac optimization package to the mill's three board edgers. Scanning speeds have since been increased, along with more choices for optimizing boards. Operators report the program is more user-friendly and accurate.

The accuracy factor is further boosted by the switch from a 4" scan density to a 2" density. A PLC upgrade to an Allen-Bradley PLC 5 has helped increase setting accuracies. Initial studies show the improved accuracy and speed of decision making indicates an increase in LRF and grade out-turns. A similar Softac optimization package had been installed earlier on the Newnes trimmer optimizer.

A 55-bin extension has been added to the mill's Newnes lumber-sorting system. It can now accommodate a Northern Milltech Inc. moisture-density sorting system. It provides a moisture density read-out for each board, despite changes in thicknesses, at speeds of up to 200 pieces a minute. The boards are then pre-sorted for more efficient kiln drying. The moisture system separates boards into dry (0 to 20 per cent moisture), medium (20 per cent to 40 per cent) and wet (40 per cent and above). The old system didn't have a moisture-sensing capability, meaning that all 2X8 16'lengths, for example, would end up in the same bin.

The new NMI system now allows dry, medium and wet sorts for 2X8 16' boards. Hotte says the moisture sort system prevents over- and under-drying, improves grade and reduces trim loss. "We're seeing a reduction of up to eight hours on kiln drying schedules and an improvement of two to five per cent in grade," he reports. The mill's 10 Salton steam-driven kilns have also recently been optimized.

Modifications have improved efficiencies in the planer. Progressive Mill Supply provided a new infeed to the planer and Newnes supplied the three position fences on the trimmer lines. The latter upgrade allows a 1" rather than 2" trim on either end of a board to remove defects. Lumber recovery has improved, and eliminating defects at both ends allows precision end-trimming during regular runs. The fences also permit 1' trim decisions to be made.

The drive towards maximizing lumber and grade recovery and producing the highest quality products is supported by the introduction of a new quality control program. A computerized SICAM system produces detailed information every two hours on how the mill is performing in relation to target sizes, size and quality controls. The accurate, constant monitoring from the quality control program assists early identification of potential trouble spots.

That has in turn resulted in a reduction in the mill's target lumber sizes. The tracking system reveals patterns during the lumber production process. For example, it identifies if size deviation problems occur with certain species, at certain temperatures, during specific times of day or around saw changes. The pulse of the mill, like that of a patient, indicates its health.

The mill has also traded up some of its mobile equipment in the log yard. A new Cat 66F grapple loader's primary responsibility is feeding the west merchandiser deck. A new Cat 95OF forklift has a variety of assignments, including removing lumber from the mill outfeed for stacking in the green yard, as well as stacking and feeding the kilns.

Changes will remain the norm for this operation. "We are continuing planning for 1999, 2000 and 2001 to further upgrade optimization to get more and higher-value boards from each log," says Hotte. Further anticipated improvements include real-time sawing on the chip'n saws, along with new infeeds to the board edgers and projects to improve the air flow for more uniform drying in the kilns.


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