Evolution of Plantwide Process Control

In early fluid processing plants, controlling the process frequently required many operators. To better understand the concept of distributed control, the authors look at some history of control rooms, and of computer control. They also look at some arbitrary distinctions between DCSs, programmable logic controllers (PLCs), and personal computers (PCs). The onset of distributed control was made possible by the ability of the emerging video technologies to display data and even to allow the operator to initiate control actions “through the video”. More recent PLCs have been used for distributed computing through an operation involving several PLCs on networks. PLCs are quite frequently a cost-effective alternative to DCSs where sophisticated process loop control strategies are not needed. The next generation of controllers is also being influenced significantly by Microsoft. This is equally true for factory automation and process control.