Multivariable Testing: Getting the Measurements Right

May 13, 2013
Before You Begin to Implement MVT, Make Sure You're Measuring What Can Be Quantified
About the Author
Nancy Bartels is Control's managing editor. You can her at [email protected] or check out her Google+ profile.Keith Van Scotter, CEO of Lincoln Paper and Tissue, who has used multivariable testing to turn around his paper company, says that even before you begin to implement (MVT) you have to make sure what you're measuring can be quantified, and that your measurement system is correct.

For example, at Lincoln, one of the processes that needed improvement was the brown stock washing process. Brown stock starts with a collection of wood products—hemlock, spruce, fir, pine, cedar, sawdust, shavings, pin chips, waste from the local sawmills. This material is cooked to dissolve the lignin and separate the fibers to prepare them to be turned into paper and tissue.

Part of the process turns this black, soupy mess into a much more solid, concentrated material and removes as much of the black liquor as possible to reduce the amount of bleach required to get it light enough to be turned into paper. Every bit of water in the material requires steam to dry it out, and bleach is expensive. The process becomes a balancing act between using large amounts of steam in washing to get more of the black liquor out of the pulp and having a more solid material that is less white and requires more bleaching.

In the course of the brainstorming sessions about improving the brown stock process at Lincoln, it became clear that no one had a baseline for what the process settings should be. The process had never been run exactly the same way on any two shifts.

Scott Jipsen, an assistant digester cook at Lincoln, explains: "Basically, there was no set way to run brown stock. If the guy on the next shift didn't like the way you were running it, he would go out and tweak a valve a little bit—open it or close it—they would change stuff so much, you didn't know where you were. Everyone was saying, 'That's the way we've always run it.'"

Out of the brainstorming and MVT process firm baselines were developed, among other process improvements. "Brown stock is run three times better now because everybody runs it the same way," says Jipsen.