A Hierarchical Programmable Controller System for Batch Material Handling

From 1977 to 1979 PPG Industries, Inc. reworked the batch material handling systems in both of its fiber glass manufacturing plants in North Carolina. In Pecember, 1976, PPG decided to use programmable controllers to handle the control system logic. The original control systems were handled by a GE-PAC Model 4020 process computer. The resulting control system is a multilevel hierarchical system using the process computer, a master programmable controller, 17 discrete-function programmable controllers, and analog scale control logic. The batch handling system, the programmable controllers, and the control hierarchy are described. Some of the decisions made in system design, controller selection, and problems encountered are discussed.