Bringing headboxes up to their potential

摘要

Many Valmet and Beloit single layer headboxes around the world are operating without any vanes installed. The reasons can be various. Some were supplied with flexible sheets, which have been removed by the mill and others never had any vanes installed from the beginning, due to old design standards. In many of these headboxes the flow is not as stable as it potentially could be. A typical sign of this can be formation defects, such as lower weight areas "moving" uncontrolled over the paper width.