Speed optimization control for fibrous sheet making machines such as

Abstract

Specifically disclosed is the combination of a paper making machine and a control system including an automatic arrangement which, on demand of the machine operator, performs a coordinated machine speed increase, maintaining the paper sheet characteristics substantially constant until the dryer steam pressure or the steam valve opening reaches a limit. During the speed increase, a number of other machine variables are compared with set limit values and the speed increase is discontinued when a limit is exceeded for a predetermined time period. When the steam pressure has been at a limit, or the steam valve has been wide open, for a predetermined time period the control system, upon sensing the limit being reached, switches to a dryer limited mode of operation wherein the steam pressure is maintained at the limit or the steam valve is locked open. The sheet moisture content is then controlled by a combination of automatic stock valve and machine speed adjustments, while basis weight is controlled by coordinated machine speed adjustments. The control system is adapted for universal use with many machine arrangements which may have separated and/or split dryer sections for rewet or coating operations and the like and/or curl control. To this end, the controller includes a system of logic which determines the optimum control procedure in each case.