An Edge In Scanning
The Quota Blues
With upgrading, Houston FP has gone from a three-line to a
two-line mill - with only US quota constraints standing in the way of impressive
By Jim Stirling
Completing the second phase of a staggered upgrade has positioned Houston Forest Products Co.'s sawmill in west-central British Columbia to meet the challenges of 1997 and beyond.
In the summer of 1996, two chip'n saw lines with off-line debarking were replaced by a single line with in-line twin-ring Valon Kone debarking and a Porter optimized 20'' Optimil canter line. The $6.6-million project was completed with admirable dispatch, with the loss of only nine operating days co-inciding with a long weekend.
That reflected a similar downtime period for the first phase of the mill's re-configuration in 1994. Attention then was on the large log line. Off-line debarking was retained with primary breakdown through a Porter optimized close-coupled 6' quad band Optimil line with auto rotation.
Downstream, new unscramblers were added and Newnes optimization for the edgers. The $8.5-million project involved considerable new building construction to the spruce/pine/fir dimension lumber sawmill which began production in 1978.
"We've gone from a three-line mill to two lines. We get basically the same production which averages about a million board feet a day and better recovery," reports Norm Anderson, manager of Houston Forest Products (HFP). Anderson estimates if the mill was running straight recovery the upgrades would produce an impressive 8.5 per-cent factor increase. However, the quota restrictions for softwood exports to US markets are frustrating HFP's plans and products, along with most other lumber producers in Canada. About 68 per cent of the mill's production enters the US, down from 80 per cent.
"The mill has been performing well and above our starting-up curve. But having achieved that, we know it can do better. As a company division, we're always trying to continuously improve. It's a kind of self-motivated pressure," explains Anderson. The mill was achieving production and lumber recovery records after the 1994 phase of the upgrade.
HFP is a partnership between Weldwood of Canada Limited and West Fraser Timber Co. The same two companies are also involved with a 22-year-old joint venture in Babine Forest Products Ltd., along with the Burns Lake Native Development Corporation. This sister mill had installed similar equipment before HFP's upgrades. Many of the same team members were involved with the improvements at Babine and HFP, including consulting engineer Anthony Seaman Ltd. Some of HFP's machine operators travelled the 100 km east to Babine's mill for on-hand experience and familiariztion with the equipment to be installed in their mill. Benefits from that contributed to the smoothness of the start-up, suggests Anderson. HFP also made use of SAWSIM, the HA Leach & Co. Ltd.'s computerized sawmill simulation tool. It analyzes the results of various fibre processing options with products produced.
HFP has 650,000 m3 of timber available annually under licence, providing about 75 per cent of the operation's requirements. The lumber recovery improvement-driven upgrades help reduce dependency on wood purchased from other sources. The company's wood basket contributes a wide range of diameters, from about 10 cm to more than 76 cm. About 35 per cent of it is balsam.
Full-length stems delivered to infeed decks pass through one of four staggered 183-cm cut-off saws and are separated by diameter into three new bins. The small log bin averages material about 18 cm in diameter. The large log bin has an end-to-end rather than sweep-off feed, which helps drop the logs straighter into the bin. The upgrades provide a new flexibility between logs and lines, and have improved storage capacity at both ends.
Some of the larger balsam stems have bark five cm thick and are tough to debark, especially in winter. In between the 1994 and 1996 upgrades, the mill's specifications for chip quality changed, along with halving the allowable two per cent bark content to one per cent. That's one major reason why the 35'' Valon Kone debarker is double ringed and why its speed is slowed down by about 15 per cent in winter. The reduction in speed is compensated for by an 18'' Cambio machine from the original configuration. Having the debarking off-line helps deal with the tremendous size range of stems from 23 cm to 76 cm. A 17'' Valon Kone with rotating double rings works the small log line. Porter controls help adjust tool pressure on the debarkers for maximum bark removal and minimum fibre damage.
HFP was one of the first companies to install a log ladder from New West Industries Ltd. of Winfield, BC during its 1994 upgrade. The four-step system singulates logs with never an empty lug, says Anderson. It achieves that through electronic controls and even ending rolls to provide a smooth and steady feed. "We're really happy with it," he says. An eight-step ladder was incorporated into the small log line for a regulated butt-to-butt feed through the 17'' Valon Kone. Sawmill superintendent Ken Anderson (no relation to manager Norm) explains the close-coupled 6' Optimil quad band delivers higher-valued side boards from large logs, and the auto rotation has improved recovery. HFP manufactures 12'' products from its larger balsam and spruce logs. The company estimates about 10 per cent of production is in 2x12s of varying lengths. Cants from the quad band go to a Powell 12'' double-arbor gang edger.
The new 20'' Optimil canter line with double-length infeed and auto rotation is doing a good job on the small log line, reports Anderson. Porter's new optimization system scans each log, rotates it to its optimum position, scans it again and holds it in place. "The heads can go off centre to adjust to the log profile," he says.
The rapidity of technological change is dizzying. Today's system does more than yesterday's but not as much as tomorrow's. HFP had XYZ scanning on its three chip'n saw lines but there's been a quantum leap in technology since then. "We had to upgrade the computer power and operating speeds on the 1994 line when we installed the 1996 one," outlines Anderson. Man/machine interface systems on both lines give operators and mill supervisors detailed information about each log's progress through the lumber-making process. The system translates information from PLCs to track precisely each log through each set work application through the canters, and reveals it on a console screen inside the operators' booths.
The mill's existing 10'' Ukiah edger received a major re-fit as part of the 1996 small log line upgrade. This included increasing machine horsepower, hydraulic power, air cylinder upgrades and installation of new arbors. Saw plates have been reduced, leading to finer kerfs. Linden Fabricating Ltd. was the mechanical contractor for the 1996 upgrade, with Milltron Electric Inc. responsible for the electrical contracting work.
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