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Distributed control system

A distributed control system (DCS) is a computerized control system for a process or plant usually with many control loops, in which autonomous controllers are distributed throughout the system, but there is no central operator supervisory control. This is in contrast to systems that use centralized controllers; either discrete controllers located at a central control room or within a central computer. The DCS concept increases reliability and reduces installation costs by localizing control functions near the process plant, with remote monitoring and supervision.

Distributed control systems first emerged in large, high value, safety critical process industries, and were attractive because the DCS manufacturer would supply both the local control level and central supervisory equipment as an integrated package, thus reducing design integration risk. Today the functionality of Supervisory control and data acquisition (SCADA) and DCS systems are very similar, but DCS tends to be used on large continuous process plants where high reliability and security is important, and the control room is not geographically remote. Many machine control systems exhibit similar properties as plant and process control systems do.[1]

Level 0 contains the field devices such as flow and temperature sensors, and final control elements, such as

control valves

Level 1 contains the industrialised Input/Output (I/O) modules, and their associated distributed electronic processors.

Level 2 contains the supervisory computers, which collect information from processor nodes on the system, and provide the operator control screens.

Level 3 is the production control level, which does not directly control the process, but is concerned with monitoring production and monitoring targets

Level 4 is the production scheduling level.

Chemical plants

(oil) and refineries

Petrochemical

(see also: quality control system QCS)

Pulp and paper mills

Boiler controls and systems

power plant

Nuclear power plants

Environmental control systems

systems

Water management

plants

Water treatment

plants

Sewage treatment

Food and

food processing

and fertilizer

Agrochemical

Metal and mines

Automobile manufacturing

process plants

Metallurgical

manufacturing

Pharmaceutical

plants

Sugar refining

applications

Agriculture

Distributed control systems (DCS) are dedicated systems used in manufacturing processes that are continuous or batch-oriented.


Processes where a DCS might be used include:

Annunciator panel

Building automation

EPICS

Industrial control system

Plant process and emergency shutdown systems

Safety instrumented system (SIS)

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