Getting it Light
Richmond Plywood has successfully implemented new light-based veneer sorting technology, and while it is too early for hard numbers, accuracy has improved
By: Bill Tice
Richmond Plywood was in the spotlight in early May when the BC panel producer hosted over 70 delegates from the Second International Symposium on Veneer Processing and Products. The guests, who came from over 15 countries for the two-day event that was held in Vancouver, took in the mill as part of an optional third day that also included a tour of Forintek Canada Corp.’s office and laboratories.
In addition to seeing the entire plywood production flow from taking the logs out of the Fraser River to shipping, the tour participants had the opportunity to see Westmill Machine Automation’s new LightSORT Green Veneer Moisture LightSORT Measuring Technology in action. Richmond Plywood is the beta test sight for the technology, which is being developed by Westmill and Forintek.
“We are an active member of Forintek and our mill is very close geographically to both Forintek and Westmill,” explains Richmond Plywood’s general manager Doug Scott, when asked why they were chosen as the beta site for the new technology. “Our location was really convenient for everyone involved. If they had not been able to run their testing here, it would have meant going to the interior of the province.”
LightSORT is an alternative technology for measuring the moisture content in green veneer. Until now, the moisture content was generally measured during veneer production with industrial radio frequency (RF) sensors installed beneath the veneer ribbon, which according to Westmill’s general manager Brain Martin, is not as accurate as this newer method.
“Based on average RF moisture readings, veneer is sorted into three general groups, including sap, light sap and heartwood,” he explains. “Laboratory testing has shown us that the sensor heads within the RF technology don’t always have the positive contact with the veneer that is required for accurate readings and as little as a 1-mm gap can cause moisture readings to be off by 50%. Due to the high speeds of green end conveyors, maintaining direct contact is virtually impossible and this can lead to very inaccurate sorts.”
According to Martin, other issues with current technology can also be solved with LightSORT. This includes measuring moisture content in veneer that is above the fibre saturation point (FSP) of 34%; loss in dryer production caused by inaccurate moisture content readings; and fibre loss due to excessive veneer handling, which can result from inaccurate readings as the veneer that is graded incorrectly has to go through a resort and re-dry process.
Wet camera
LightSORT works by using current technology in both LED light transmission and CCD camera sensitivity, providing an accurate, non-contact method of green veneer moisture measuring. In a more detailed description, Martin says, “By tightly controlling the pulsed output with a high-output LED array, the green veneer is effectively ‘candled’, allowing an actual visual image of the moisture content locked within the entire sheet. By gathering this visual image through a critically aligned and highly sensitive CCD camera, and by then passing that information forward through a complex series of algorithms, the exact moisture average and peak moisture content can be instantly calculated for each sheet.”
The gathered and stored information for each sheet of veneer is assigned a specific moisture value, which becomes what Martin calls “the finger print” of the sheet. This allows for the green veneer to then be sorted by pre-determined standards that have been set by the mill for each species and thickness, or to whatever criteria the mill decides to work to. Due to the accuracy of the sorts, the sheets on the veneer line can be sorted into an unlimited number of sorts.
Dr. Chunping Dai of Forintek originally developed the LightSORT technology. “We discovered a need for the technology when we were visiting Forintek member mills to observe problems they were having so that we could work on developing solutions,” says Dai. “Accurate moisture content measurement was a recurring concern with the mills, so we came back to the lab and started to work on solutions.”
That was several years ago, and after developing prototypes, Forintek looked for an industry partner to work with them on the product development. “A number of companies had been working on technology to address moisture content as it had been a long standing problem within the industry,” adds Dai.
“There were three potential companies that we looked at working with, and we ended up going with Westmill because they are very active members of Forintek, they are specialists in veneer drying, and they have a proven track record.”
Funding for the project came from the National Research Council’s Industry Research Aid Program (IRAP), Westmill and Forintek, and in 2003, the patent process was started. In 2005, a US patent for LightSORT was approved and this year, the Canadian patent was approved. Worldwide patents are pending. Forintek also received a Canada Energy Efficiency Award for LightSORT from the Federal Ministry of Natural Resources and Time Magazine Canada because accurate moisture sorting reduces energy consumption.
For Richmond Plywood, the LightSORT technology will have to prove itself on the line, and although to date general manager Scott is seeing positive results and is optimistic that there will be improvements to the mill’s moisture sort accuracy, he says it is still too early to tell just how significant these improvements will be.
“Since Forintek and Westmill did their first set of tests, I have changed some of the programs in order to tune them up, so to be absolutely conclusive they will have to put the old programs back in and do comparisons,” explains Scott. “I have been trying to differentiate what gains have been made between the two sets of programs. Our dryers have definitely been running more efficiently as compared to last year, but it could be due to other considerations such as the outside temperature and humidity.”
Originally, Scott says the mill was running three sorts – heartwood, light sap and heavy sap. They have now gone to four sorts by adding a sort for light heartwood, which he says is reducing the mill’s re-dry. “By adding the fourth sort, we are definitely seeing some gains as we have reduced the amount of re-dry significantly and are dealing more with re-feed. My objective was to try and eliminate re-dry in the heart system and that is what we have achieved. What I can conclusively say at this point is that the increments of adjustment with the LightSORT technology are more accurate than the old system. We will just have to wait and see how much more accurate.”
Richmond Plywood produces primarily 4 ft. x 8 ft (and the metric equivalent of 1220mm x 2440mm) sheets, and a small volume of 2 ft. x 8 ft. and 3 ft. x 6 ft. product to meet certain offshore requirements. Most of the mill’s output is Douglas fir plywood, but Forintek and Westmill have tested LightSORT on other species of veneer as well, including pine, hemlock, spruce, balsam fir and aspen, In all cases, they conservatively estimate a 5 to 10% reduction in drying times due to more accurate sorting and less re-dry. Other benefits according to Westmill’s Martin, include improved veneer quality, recovery improvement through reduced dry-stacker losses, and increased ‘glue-ability’ of the more consistent veneer.
“Conservatively, we estimate annual savings to each mill that is equipped with LightSORT technology at between $750,000 and $1.8 million,” he adds.
