CHE 185 – PROCESS CONTROL AND DYNAMICS

1. CHE 185 – PROCESS CONTROL AND DYNAMICS DCS AND PLC FUNDAMENTALS

2. Pneumatic Controller Installation

3. DISTRIBUTED CONTROL SYSTEMS • OPERATING OBJECTIVES INCLUDE PROCESS AND MANAGEMENT CONTROL • MAY BE DESCRIBED AS SUPERVISORY CONTROL AND DATA ACQUISITION (SCADA) SYSTEMS • DISTRIBUTED CONTROL MEANS LOCALIZED CONTROLLERS AND CONTROL COMPUTERS LINKED WITH SUPERVISORY COMPUTERS

4. DCS Architecture

5. HISTORY OF COMPUTER CONTROL IN PROCESSES • ANALOG COMPUTERS - ATTEMPTED TO REPLACE THE CONTROLLERS WITH ANALOG PROGRAMS • SYSTEMS WERE VERY COMPLEX • ONLY CUSTOM COMPONENTS • FAILED TO WIN ACCEPTANCE ON A LARGE SCALE http://www.computerhistory.org/semiconductor/timeline/1964-Hybrid.html

6. HISTORY OF COMPUTER CONTROL IN PROCESSES • MICROELECTRONIC ANALOG CONTROLLERS • ELECTRONIC CONTROLLERS THAT REPLACED LARGER PNEUMATIC UNITS • SOME COULD BE LINKED TOGETHER (HARDWIRED) TO PROVIDE CONTROL SYSTEMS

7. HISTORY OF COMPUTER CONTROL IN PROCESSES • DIGITAL CONTROLLERS • LOCAL CONTROL UNITS • COULD BE PROGRAMED WITH NUMEROUS FUNCTIONS • COULD RECEIVE AN EXTERNAL SETPOINT FROM ANOTHER SYSTEM • CONNECTED TO A SINGLE CENTRALIZED CONTROL ROOM COMPUTER http://www.ebay.com/itm/MICRISTAR-MODEL-828-DIGITAL-PROCESS-CONTROLLER-/400128847480

8. HISTORY OF COMPUTER CONTROL IN PROCESSES • EARLY DCS SYSTEMS • CONTROL LOOPS WERE BASED ON LOCAL CONTROLLERS • DATA HIGHWAY INTRODUCED TO PROVIDE CONNECTIVITY • DATA LOGGING BECOMES POSSIBLE • USED CUSTOM PROGRAMMING AND MOST COMPONENTS WERE SPECIALIZED

9. HISTORY OF COMPUTER CONTROL IN PROCESSES • LATER DCS SYSTEMS • PARALLEL COMPUTING DESIGN • EACH LOOP CONTROL UNIT CAN OPERATE INDEPENDENTLY • SMART COMPONENTS ALLOW FOR SELF CHECKS AND AUTOMATIC SWITCHING TO REDUNDANT CONTROLLERS

10. HISTORY OF COMPUTER CONTROL IN PROCESSES http://www.automationengineering.co.uk/categories/dcs.html

11. HISTORY OF COMPUTER CONTROL IN PROCESSES • LATER DCS SYSTEMS • INCORPORATE INTERACTIONS WITH • PROGRAMMABLE LOGIC CONTROLLERS • CAN BE USED FOR SUPERVISORY MANAGEMENT • OPERATE WITH CONVENTIONAL SYSTEMS • NETWORKING SYSTEMS (INCLUDING THE INTERNET) • OPERATING SYSTEMS EMPLOY MORE STANDARDIZED PROGRAMMING

12. HISTORY OF COMPUTER CONTROL IN PROCESSES • LATER DCS SYSTEMS • ALLOWS USE OF FIELDBUS TECHNOLOGY • SMART CONTROL COMPONENTS THAT CAN SELF CHECK FOR CORRECT OPERATION • REDUCES THE NUMBER OF DIRECT CONTROL CONNECTIONS TO THE CONTROL ROOM

13. HISTORY OF COMPUTER CONTROL IN PROCESSES • OPTIMIZATION OF FACILITY OPERATION CAN BE AUTOMATED ON EXTERNAL COMPUTERS THAT RECEIVE DATA FROM THE DCS AND RETURN IMPROVED SETPOINTS

14. OPTIMIZATION OF FACILITY • POWER PLANT EXAMPLE • NOx CONTROL • OVERALL EFFICIENCY • WATER CONSUMPTION • ISA HAS DEVELOPED A RANGE OF STANDARDS TO FACILITATE DEVELOPMENT OF DCS

15. THE FUTURE OF DCS • WIRELESS SEEMS TO BE THE NEXT MAJOR STEP • COULD ELIMINATE MOST WIRED CONNECTIONS • SYSTEM IS MORE PHYSICALLY SECURE THAN ONE WHICH RELIES ON HARDWIRING • HACKERS ARE A MAJOR HAZARD

16. PROGRAMMABLE LOGIC CONTROLLERS • USES FOR PLC’s • BATCH OPERATIONS • RELAY PANEL OPERATIONS • UNITS ARE PROGRAMMED TO PROVIDE FUNCTIONS • PROGRAMS ARE TYPICALLY WRITTEN IN A FORM THAT STATES IF CONDITION “X” OCCURS, THEN • PROCEED TO CONDITION “Y” • THE SUBSEQUENT CONDITION MAY INVOLVE TRANSFER OF SIGNALS OR STARTING A TIMER.

17. PROGRAMMABLE LOGIC CONTROLLERS • TYPICAL PLC PROGRAM SEQUENCE

18. COMPONENTS IN PLC’s • CONNECTIONS TO THE OUTSIDE • INPUTS • OUTPUTS • PROGRAMMED COMPONENTS • TIMERS • COUNTERS • DATA STORAGE • CIRCUITS

19. PROGRAMMABLE LOGIC CONTROLLERS • PROGRAMS • FOLLOW THE FORM USED FOR CIRCUIT LOGIC • CALLED LADDER DIAGRAMS

20. PROGRAMMABLE LOGIC CONTROLLERS • EXAMPLE OF A PLC LADDER DIAGRAM FOR FILLING A PROCESS TANK

21. PROGRAMMABLE LOGIC CONTROLLERS • PROCESS CRITERIA • START TRANSFER PUMP WHEN LOW LEVEL IS REACHED • STOP TRANSFER PUMP WHEN HIGH LEVEL IS REACHED

22. PROGRAMMABLE LOGIC CONTROLLERS • LADDER DIAGRAM FOR THIS SYSTEM • LOW AND HIGH LEVEL INPUTS ARE LABELED 01 AND 02, RESPECTIVELY • OUTPUT 500 IS TO THE MOTOR RELAY • 1001 IS THE PROGRAMMED CIRCUIT - CLOSES WHEN 01 AND 02 ARE CLOSED.

23. PROGRAMMABLE LOGIC CONTROLLERS • OPERATION SEQUENCE • WHEN TANK IS EMPTY, 01 AND 02 ARE BOTH CLOSED, SO THE PUMP IS ON. THE LOGIC PATH IS THROUGH 01-02-1001, AS 1001 IS CLOSED • WHEN THE LOW LEVEL IS ACHIEVED, INPUT 01 OPENS, BUT THE PUMP STILL RUNS BECAUSE THE LOGIC PATH IS THROUGH 1001-02-1001

24. PROGRAMMABLE LOGIC CONTROLLERS • OPERATION SEQUENCE • WHEN THE HIGH LEVEL IS ACHIEVED, INPUT 02 OPENS AND THE LOGIC PATH IS BROKEN, SO 1001 OPENS AND THE PUMP SHUTS OFF. • WHEN THE LEVEL DROPS BELOW HIGH, 02 CLOSES, BUT THE PUMP DOES NOT RESTART BECAUSE 1001 IS STILL OPEN. • WHEN THE PUMP DROPS BELOW LOW, 02 CLOSES, SO 1001 CLOSES AND THE PUMP RESTARTS

25. PROGRAMMABLE LOGIC CONTROLLERS • OTHER COMPONENTS • COUNTERS - ALLOW SUMMATION OF STEPS TO DETERMINE WHEN A TOTAL HAS BEEN REACHED • TIMERS - CHECK ON THE DURATION OF A STEP

26. Fieldbus Technology • Based upon smart valves, smart sensors and controllers installed in the field. • Uses data highway to replace wires from sensor to DCS and to the control valves. • Less expensive installations and better reliability. • Can mix different sources (vendors) of sensors, transmitters, and control valves. • Now commercially available and should begin to replace DCSs.

27. Fieldbus Architecture