Distributed control system PPT 1 2 3 4 5
- 1. DCS Vs PLC The most basic difference between a PLC and a DCS is that PLCs were designed to replace relay-based controls and analog equipment, controlling one machine. DCS, on the other hand, are used to control entire plants, buildings, or processes that are vast and interconnected.
- 2. Distributed control system A distributed control system (DCS) is a platform for automated control and operation of a plant or industrial process. A DCS combines the following into a single automated system: human machine interface (HMI), logic solvers, historian, common database, alarm management, and a common engineering suite.
- 3. DCS
- 5. DCS Operator Control Panel Main Control Computer Operator Control Panel Archival Data Storage Supervisory (host) Computer PROCESS Local Computer Local Computer Local Computer Local Display Local Display Data highway To other Processes To other Processes Local data acquisition and control computers
- 6. DCS Elements-1 • Local Control Unit: This unit can handle 8 to 16 individual PID loops. • Data Acquisition Unit: Digital (discrete) and analog I/O can be handle. • Batch Sequencing Unit: This unit controls a timing counters, arbitrary function generators, and internal logic. • Local Display: This device provides analog display stations, and video display for readout. • Bulk Memory Unit: This unit is used to store and recall process data.
- 7. DCS Elements-2 • General Purpose Computer : This unit is programmed by a customer or third party to perform optimization, advance control, expert system, etc • Central Operator Display: This unit typically contain several consoles for operator communication with the system, and multiple video color graphics display units • Data Highway : A serial digital data transmission link connecting all other components in the system. It allow for redundant data highway to reduce the risk of data loss • Local area Network (LAN)
- 13. Need for DCS • DCS is a system of sensors, controllers, and associated computers that are distributed throughout a plant. • Each of these elements serves a unique purpose such as data acquisition, process control, as well as data storage and graphical display. • These individual elements communicate with a centralized computer through the plant’s local area network – often referred to as a control network.
- 14. Example • DCS at a power plant might automatically increase generation capacity in order to keep up with changing demand for electricity during hot Summer days and then decrease it as outdoor temperatures cool overnight and demand subsides. • Whereas a PLC could adjust a single unit operation, the DCS can make adjustments to each of a plant’s many interacting unit operations.
- 16. How is a DCS Used? • As the ‘central brain’ of the plant the DCS makes automated decisions based on production trends it sees them in real-time throughout a plant. • While DCSs are used across the process control industries to supervise complex production processes, they are more widely deployed at large, continuous manufacturing plants such as those in the petrochemical industry.
- 17. • With the help of a DCS these and other manufactures can efficiently coordinate adjustments in a top-down fashion using a centralized network of computers. • Instructions from the DCS are deployed throughout a plant and fed to individual controllers. • When configured appropriately the DCS can improve safety while also enhancing production efficiency.
- 18. What Makes the DCS so Important? • A comparison of two plants may help to illustrate the importance of the DCS. • First, imagine a small municipal waste water treatment facility that employs a dozen control loops. • The plant’s engineering staff can easily keep a mindful eye on the performance of such a limited number of controllers. • Next, imagine a large refinery that operates 10,000 highly dynamic and interacting control loops.
- 19. • While coordinating control at the treatment facility is relatively easy, the task of orchestrating control at the refinery can be overwhelming without the use of a DCS. • Over the years, the line between DCS and PLC has blurred. While the DCS has traditionally been the only solution for achieving safe and efficient plant- wide control, advancement in processing capabilities has allowed the PLC to rapidly take on greater responsibility.
- 20. Advantages of DCS • Access a large amount of real time information from the data highway. • Monitoring trends of past process conditions. • Readily install new on-line measurements together with local computers. • Alternate quickly among standard control strategies and read controller parameters in software. • A sight full engineer can use the flexibility of the framework to implement his latest controller design ideas on the host computer.
- 21. DCS Vendors • Honeywell • Fisher-Rosemont • Baily • Foxboro • Yokogawa • Siemens
- 22. DCS Applications