Paper machine dry line position control during grade changes

The detection and control of the dry line machine direction position on a fourdrinier paper machine are considered. The dry line position is detected using a digital image processing system consisting of a CCD camera, a frame grabber and a standard PC. The system was installed on a kraft liner machine and both open loop and closed loop experiments were performed with encouraging results. The introduction of automatic control of the dry line position reduces the time for grade changes and it also reduces the machine operators work load. The reduced time leads to smaller production losses and hence to economical benefits