Cementing the Relationship Between DCS and PLC: A Review of Emerging Trends in Plant Control Systems

This paper explores the changing roles of traditional distributed control systems (DCS) and programmable logic controllers (PLC) used to automate cement manufacturing processes. The two technologies initially served two different control requirements. However, improvements in microprocessor-based controllers created conditions for two technologies to merge. The shift toward commercial, off-the-shelf automation technology, software-based control verses hard control and use of non-proprietary networks has created a new class of systems called hybrid process automation systems. In addition, the role of the plant control system has been expanded from just process visualization and control to include process optimization, plant asset management, energy management, and inventory control. Cement plants can now use the process control systems to improve operational and energy efficiency. Control system vendors have adopted unique terms to differentiate their systems from the traditional definition of a DCS or PLC. Some have expanded their process control systems to offer vertical integration with IT systems and horizontal integration with intelligent drives, motors, process instrumentation and discrete control technologies. This paper addresses a number of requirements placed on the cement automation systems as a result of these developments and identifies technologies that offer the best solution to meet the challenges faced by cement producers.