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1.2: Introduction to DCS- Control system hardware

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  • 2.1 Introduction

    Digital Control Systems(DCS) also known as Distributed Control System is the brain of the control system. It is used mainly for the automation of a manufacturing process and manages the logic that exist for major unit operations. A DCS in the past was tailor made for the process, plant or company that intended to use the structure to control and model it’s process. Before the beginning of the DCS era there were pneumatic devices that controlled process and engineers manually turned valves on the site. Modeling of the systems was made possible by DCS as it allowed the ability to record and manage process from comfort of a computer screen. Because of DCS we are able to control processes remotely and gain a better understanding of how the process operate and how they can be improved to both increase safety and increase profit possibilities.

    Control Systems are collectively named as "ICSS" Integrated Control and Safety System. Distinctly identified as "BPCS" Basic Process Control System. "SIS" Safety Instrumentation System. "F&G" Fire and Gas System.

    DCS is employed in BPCS as well as used and prevalent control system. How does a DCS work?

    In the field you have sensors and gauges that give and recieve information. They convert this information into a electric signal that is sent to a control room somewhere in the field. This control room has programmed logic that is able to converts the signal into a pressure, flow rate, concentration, temperature, or level. This logic also contains the information that controls the process and takes the signal compares it with the set point sent from the operator may or may not be in the field and sends a signal to the manipulated variables in the field. The DCS covers all of the computer logic from the operator screen to the field box that contain the logic.

    Shutdown systems

    Shutdown systems are the emergency setting of the logic to make sure the process can be contained and is environmentally safe. These setting are important for emergency response of the system. It is the job of the DCS to contain the logic for the shutdown system and be able to operate when a process exceed a certain limit.