The development of computer control in the continuous process industries

Among the many spectacular aspects of the growth of the digital computer field has been its application to industrial process control. From very modest beginnings in 1959 and 1960, the field has now progressed until it is an indispensable part of many new industrial plants, particularly in the steel industry, petrochemical plant operations, refineries, and several others. Due to small memory sizes, relatively slow machine speeds, and poor reliability, early applications were in a data-logging or operator's guide configuration. Increased knowledge of process requirements led to the closed loop supervisory or steady-state, economic optimization phase of computer control. However, because of limitations in plant excursion ranges, results here were small, although positive. Dynamic control by digital computer has come only recently with direct digital control. This was made possible by the emergence of a third-generation group of small, fast, highly-reliable, and relatively inexpensive machines. These machines have shown themselves to be economically attractive media for plant control, with a resulting major increase in applications in the digital computer control field. Overall plant or hierarchy control, where several levels of computers operate together to control a large plant complex or a whole company, is now under active study by many groups and preliminary installations of this type are already on order or being installed. This area promises to grow rapidly in the next few years, along with the other phases of computer control. This paper reviews the areas of digital plant control, pointing out areas of difficulty and of successes in each. It lists some requirements for future progress in terms of both equipment and software requirements. It also attempts to predict some probable future areas and rates of development.