DCS (Distributed Control System) - ARCHITECHTURE - FEATURE - ADVANTANG

DCS (Distributed Control System)

• The distributed control system in the dominant form of instrumentation used for industrial process control.

• The dimensions such as distributed processing, data and control characterize the distributed control system

• DCS were originally designed to satisfy the need of continuous processes the operator

• Today DCS has evolved into a flexible and powerful integrated control system that supplies data acquisition, advanced process control, and batch control capabilities.

• In DCS, equipment is separated in a functional area and is installed in the different work areas of a process plant. The plant operator monitors and manipulates the setpoint of the process parameter from the central room.

• The operator views the process information transmitted from the processing area and displayed on the computer terminal. 

• The controlling portion of the DCS, distribution at various location, perform the following two functions at each location:

              1.   Measurement of the analog variable and discrete input

             2.  Generation of output signal to actuators that can change process condition

• The input and output signal can be both analog and discrete. The plant information is communicated between a central location and remotely located controller locations over electrical transmission media.

• The communication path is either a cable from each remote location to a central station, or a single cable data highway interfacing all the remote stations.

DCS ARCHITECTURE 

• The first priority of DCS is to provide superior operator interfacing and real-time Process control

• The system architecture provides for distribution and connectivity of control device and computing platforms throughout the plant.

• The flexibility of implementation of sequential control and integration among the various types of control is also an additional strength of DCS.

• Because of the distributed nature of the system, a single failure typically will not shut down the entire operation.

FEATURES OF DCS

The DCS architecture provides a single-window the process and control system so that it can perform the following functions:      

• Monitor and manipulate the process

• Retrieve historical data (batch history is required to facilitate display and analysis of key characteristics within a batch and between batches of similar types )

• Configure the system

• Build schematic display

• Develop control programs

• Diagnose system failures

ADVANTAGE OF DCS

• The overall cost of the installation is lower because

       1. Less wiring is required when information is transmitted serially across the two wires of a data highway, rather than in parallel over many pain of wires

       2. Panel space is reduced and so is the control room size required to house it.

• The interface with the process is improved for the benefit of the operators overview of the plant, as

     1. The group display provides a means of viewing a   combination of control loop that has meaning in terms of     process association.

    2. Configuration from the keyboard allow rearranging or adding to the display without the purchase and installation of new equipment

• They are more reliable i.e. even if the central station facilities break down, the remote control operation will continue without interruption

• It is flexible and relatively easy to expand.

• The programming required to tailor the system to the needs of the individual process to which it is applied can be done without knowing a high-level programming language.