Northern Milltech's moisture density sort system for green lumber reduces kiln cycle times and trim loss, and increases grade recovery, say mill users.

By Jim Stirling
Copyright 1996. Contact publisher for permission to use.

Quality control people are an integral part of sawmill management teams and are always searching for an edge. They examine the lumber production process for ways to cut costs and improve quality. A newly developed system to sort green lumber based on moisture content and board density is making happier campers out of quality control types in parts of central BC and northern Alberta.

The Northern Milltech Inc., moisture density sorting system uses on-line sensors and a computerized software package. The Prince George based company has designed the system to accurately measure and allocate each board frozen or otherwise at line speeds of about 160 pieces per minute. The system's sort determination results in reduced kiln drying cycle times, less trim loss and an increased grade recovery.

Sensor heads use an on-board microprocessor and electromagnetic energy to help produce moisture density readings from along the top and bottom of each piece. Information from the sensor heads is directed to a control station where a computer ascertains the moisture and density of each piece and instructs the sorter appropriately. The denser the piece, the more time required to kiln dry it. The combination moisture density of each piece is reflected in a digital scale readout.

The NMI system found quick acceptance at area mills. ``We know for sure our drying times have improved immensely since we installed the NMI system,''vouches Bruce Wood, quality control supervisor at Chetwynd Forest Industries, a division of West Fraser Mills Ltd., in northeastern BC. The mill operates mid and wet sorts. The NMI system separates out the wet sorts for five or six weeks of air drying after which they can be kiln dried like a normal charge, adds Wood.

The system's payback potential becomes apparent. ``With taking out the wet sorts and air drying them, we can save 12 hours drying time right there. That's big time savings.'' The moisture density system also contributes to less trim loss, improved quality through higher grade recovery and allows us to experiment on different charges with different heating, continues Wood. Mill staff have conducted many studies with wood frozen to 40 below. ``The difference between green lumber and our mid sort can be 5 to 5.5 pounds per piece in 16 foot 2x6s and up to 4 pounds in 2x4s. The system picks them out beautiful.'' There's more. ``The system has been virtually maintenance free. It's been just a gem for us.''

The verdict is similar at Pacific Inland Resources in Smithers, another West Fraser division. An eight month before and after study of trim loss in the mill is revealing. Between September, 1994 and May, 1995, the trim loss on 2x4s with a species mix of 40% balsam and 60% spruce averaged 17.9%. From July to January, 1996 and after the installation of NMI's system, the trim loss dropped to 12.8% although the wetter balsam component had risen to 57% with 43% spruce.

It's been a heady couple of years for the three owners of Northern Milltech Inc., and their blend of practical sawmill experience and electronic know-how. It began innocently enough. ``We had no idea at the beginning it would evolve into a business,''says Peter Robin. He and Tyler Graham workedfor Apollo Forest Products in Fort St.James, BC. They were disatisfied with the moisture sensor system used in the mill. It lacked consistent accuracy and was manually adjusted. ``We started looking at sensors that were commercially available but couldn't find what we wanted,''continues Robin. The pair was convinced there was a more efficient way and developed a prototype sensor. But they realized they needed specialized help for it to reach its potential.

They approached the Northern BC Technology Centre. The Tech Centre is a joint program of the College of New Caldeonia and the University of Northern British Columbia in Prince George designed to apply academic expertise to solve practical business problems. As luck would have it, the first person Robin and Graham spoke to about their aspirations turned out to be their future partner. Todd Walker was a sessional electronics instructor at the college.

``My background is in electronic design and integrated circuits and though I'd never been in a sawmill before,this sounded really interesting,'' recalls Walker. Visits to Apollo's mill confirmed that.

``We started from the ground up using different technology. We used the on-board microprocessor that can adjust automatically to tempertaure, humidity or dust present in the mill environment. It also provides some self-diagnostics. We insisted right from the start that the system be easily usable and maintained by mill personnel. And we use off-the-shelf partsfor most things that can wear out,'' adds Walker. The system can be installed in a day, followed by configuration to each mill's sorting capacity and kilns.

The trio commend Dean Shaw, then the owner of Apollo for allowing the moisture density sorting system to be built and tested in his mill. Kudos, too, to the Tech Centre's Pat Oliver who assisted with funding through the National Research Council's Industrial Research Assisstance Program. And to 2C Welding & Machine Ltd., of Fort St. James for developing ``robust and fixable hardware.''

West Fraser Mills was quick off the mark with the first installation of the NMI system in its Smithers operation followed by Chetwynd and other divisions.``They realized we were still in the development stage but they liked the product and were very patient with us,'' adds Graham. Along the way, the trio had to decide whether to take the bull by the horns and devote all their energies to their emerging business. It wasn't that tough.

``As a team, we felt we really had something. We are all a little entrepreneurial and at one time or another have run small companies on the side,''explains Robin.