Paper machine controllability: effect of disturbances on basis weight and first-pass retention

A controllability analysis of a paper machine Forming zone in a newsprint m ill was performed to determine the maximum allowable variability of the pul p furnished to the process. The goal was to keep the output variables, basi s weight and first-pass retention between certain limits in spite of distur bances and paper grade changes. The results indicate that the process is mo re disturbed at high frequencies, and that the two output variables may be maintained within the interval +/-1% of their nominal values if the maximum variability in the consistency and fines content of the thick-stock is kep t lower than +/-1 and +/-2%, respectively. (C) 2001 Elsevier Science Ltd. A ll rights reserved.