Supplier Makes Strides in Improving Accuracy in Kiln-Drying
Companies that dry lumber add value to the lumber. It is a costly process, and it can cost more if not properly done.
Because even boards of the same dimensions and the same species vary in density, kiln-drying lumber is a tricky matter. The variables that can affect the way wood dries extend in many directions, explained Ed Wagner, president of Wagner Electronic Products, Inc. in Rogue River, Ore. For instance, the same wood from different geographic regions or elevations may dry differently. Local conditions such as position in a deck and time wood has spent in a yard also influence drying time.
Add to the variables tied to wood itself those tied to the kiln, and the complexity of drying mounts. But complexity cannot be a deal stopper because lumber that is not dried to the correct moisture content may result in wet claims and mold claims that have the potential to damage a company’s reputation.
Getting wood out of the kiln when it is optimally dried is the goal. And Wagner Electronic Products aims to help its customers do so by fully exploiting information gathered from down-line sensors. If a kiln is out of control, said Ed, the sooner the operator is alerted, the better. Analyzing trends from in-line moisture meters is one way to give a real boost to control, or correcting kiln function.
According to one study, over-drying is extremely costly. Depending on the number of board feet produced annually, over-drying can result in losses of hundreds of thousands of dollars a year. Down-graded lumber sells for less. The problem is compounded by the need to buy more green lumber, or, if the company has a sawmill, purchase more timber or logs, and so on.
Wagner Electronic Products is working to make the stark choice between under drying and over-drying a thing of the past. The company aims to develop a moisture measurement system that will compensate for variations in lumber density – which will ultimately inform the drying process even as it adds value.
In fact, Wagner already is refining its still-in-development Moisture Management Grade Recovery Program in four mills. The goal is to develop an in-line tool that can measure boards either before or after planing.
Wagner is gathering test data from the four mills, programming software and developing a new generation of software. “We’re expecting within six months” the system will be available as a tested product, said Ed Wagner, president of Wagner Electronic Products. Overseeing the implementation and test runs at the four mills is Mike Milota, who is on sabbatical leave from Oregon State University and working as a consultant to Wagner Electronic Products.
Trials demonstrate that not all moisture content data fits one particular curve or another. The key is to choose the applicable mathematical model, explained Ed. Douglas fir is more normal in drying distribution pattern while hemlock is more lognormal, he said. Data gathered at the test mill sites will help determine, among other things, drying patterns of different species.
With so many variables in the wood drying equation, the predictive value of the patented mathematical model is also dynamic, or changing. “We know from the four mills we’ve been working with that we need around 20 charges in order to establish a baseline for how the kiln is performing,” said Ed. Beyond that, the idea is to keep measuring the final moisture content and keep making adjustments to keep the kiln in control. The complacency of static charts is not an option.
The new mathematical model used to analyze the data from the in-line moisture detection system rely, as appropriate, on a lognormal modeling method for which Wagner Electronic Products is a patent co-owner with the University of British Columbia. (See accompanying article.)
Putting together state-of-the art, in-line moisture sensors and appropriate mathematical model will benefit mills significantly, said Ed. “It’s really fun to come up with a new concept that not anyone has had before and help customers make more money,” he said.
Wagner Electronic Products has a history built on innovation. Ed’s father, Delmer, founded the company after working as an electrician for a mill and inventing for the mill. “Electronics was his hobby from when he was a small child,” said Ed, and he earned many patents.
Ed joined Wagner in 1989. He holds a degree in electrical engineering (with a special emphasis in electronics) from Walla Walla University. Interest in wood products lured him back to the industry that hooked his father decades earlier.
Measuring moisture with electromagnetic (EM) waves is not destructive, like oven drying. Using EM waves takes advantage of the dielectric properties of wood to sense the amount of moisture. However, the method does not compensate for differences in wood density. So, a method for compensating for wood density must be developed. Wagner has developed a methodology for compensating for wood density and has started to introduce it.
In order to begin connecting moisture management technology to mill return over investment, Wagner has developed new software (built on newer, more flexible platform), which it calls the Kiln Analysis Trending system, or KATview for short. The software was created using a totally new database from that which had been used in the past to measure moisture. The beauty of the KATview software is that it has much more capability to analyze kiln data and provides the sort of information that allows kiln personnel to make better decisions.
When fully implemented, the Moisture Management Grade Recovery program, which uses KATview software, will offer three levels of reporting to mills. Simple reporting will offer basic reports on a regular basis. Standard reporting will enable a mill to identify any kiln where there is a problem. Finally, the diagnostic level of reporting will provide information in sufficient detail to allow a kiln’s performance to be analyzed and its functions adjusted for maximizing mill profit.
