Comparing On-line Gauging Statistics from Different Paper Machines, 1993 Process Control, Electrical & Information Conference Proceedings

Robert J. Pfeifer

Robert G. Wilhelm

The caliber of paper machine gauging equipment available today has heightened process visibility to the point where papermakers are seeing sheet variations they never knew existed. With laboratory accuracy and proven reliability, these high- resolution measurements have alerted papermakers to problems in comparing on-line gauging statistics across different paper machines. These machines typically have different operating parameters (such as machine speed), and may have gauging equipment set up with different parameters as well (such as profile resolution and scan speed). With IS0 9000 compelling paper companies to establish common methodologies and product quality standards, it becomes necessary to address the feasibility of making direct comparisons of gauging statistics from different machines.

Inherent in making such comparisons are many ramifications and difficulties. However, a pragmatic approach is available to make valid comparisons. It requires knowledge concerning the nature of the variations in a particular machine, recommends the establishment of a common "data box width" for gauging statistics calculations, and includes mathematical normalization to account for differences in particular paper machine and gauging system set-up parameters.