Creativity Was Paramount in Finding a Solution - A new polyurethane roll cover helped Green Bay Packaging gain a 10% production increase
June 2008
Pulp & Paper Special Report
When Green Bay Packaging in Morrilton, AR, set its sites on increasing the production of its No. 1 paper machine, it solicited input from the industry’s leaders in pressing technologies. Metso Paper was selected as a key supplier to the mill and entered into an agreement with the mill to provide resources and products to aid the mill in reaching its goals. The obvious choice would be to rebuild the machine and upgrade it to the latest technology and equipment. In the end, a decision was made to use creativity over major capital and employ a strategy that focused on reduced scale upgrades of existing equipment.
It began with the pressing optimization study presented to mill personnel. The target was machine speed with an understanding that there are always compromises in the process. Metso conducted a press optimization study to determine the best possible covers for machine speed.
The initial studies revealed some opportunities based on Metso’s press modeling tools “PressSim” and “FlowSim”. These programs are based on years of experience developing new machines and the trials and experiments used in developing these machines. Initial reports were reviewed with key personnel and discussions about the results indicated the direction to proceed regarding hardness and surface textures. The mill was willing to take even a bit more risk than Metso initially proposed in regards to cover run times and regrind frequencies.
PressFox™ was selected as the cover that could provide the highest load and run times, which would be required with the necessary changes to hardness and surface properties. PressFox is a specially engineered polyurethane roll cover that allows reliable, consistent performance with the highest load and abrasion properties in the industry. The mill was very willing to sacrifice some increase in change-out frequencies if it really meant substantial increases to machine speeds.
The initial hardness was selected to provide optimum pressing impulse to the sheet and drilling patterns were selected. The mill was even willing to go a step further than the initial recommendation to maximize the ability of the water to be removed from the sheet. The drilling and grooving patterns were calculated to maximize the water removal and increase the Lateral Flow Index (LFI) of the roll cover. This is the number that predicts how well the water may be removed from the paper.
Results from the initial startup of the covers were extremely positive. So positive in fact that the decision was made to go ahead and recover the spare rolls also. Green Bay Packaging initially reported an increase of 10% in production on the heavy weight grades. Later, the mill confirmed that there was also an increase on lightweight grades, which has assisted the mill in setting record machine speeds on all grades.
A recent Lockwood-Post Directory of Pulp & Paper Mills shows the No. 1 machine with a capacity (before the upgrade) of 250,000 tons/yr and a maximum machine speed of 2,000 ft/min. Grades produced were listed as kraft linerboard (29-69 lb) and white top/mottled linerboard (31-69 lb).
Green Bay Packaging, Morrilton has entered into an After Market Partnership “AMP” program with Metso and together continue to find additional ways and tools to increase the production of Green Bay Packaging’s paper machines.
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