1. CHE 185 – PROCESS CONTROL AND DYNAMICS
P&ID’S AND CONSTRAINTS FOR ROUTINE OPERATIONS

2. Model for Product Composition for CSTR with a Series Reaction

3. Model for Cell Growth in a Fed-Batch Reactor

4. Class Exercise: Dynamic Model of a Level in a Tank
Model equation is based on dynamic conservation of mass, i.e., accumulation of mass in the tank is equal to the mass flow rate into the tank minus the mass flow rate out.

5. Solution: Dynamic Model for Tank Level
Actuator on flow out of the tank.
Process model
Level sensor since the level sensor is much faster than the process and the actuator

6. PIPING AND INSTRUMENT DIAGRAMS (P&ID’s)
DESIGN DOCUMENTS
PROVIDE THE PRIMARY CONTROL LOGIC FOR A PROCESS
ALSO USED TO PROVIDE PIPING DESIGN INFORMATION
REFER TO APPENDIX b

7. P&ID SYMBOLS STANDARD LETTERS ARE USED FOR FUNCTIONS AND VARIABLES
STANDARDIZED SYMBOLS ARE USED FOR CONTROL
EQUIPMENT
STANDARD SYMBOLS ARE USED FOR CONNECTIONS

8. SIMPLIFIED P&IDS
USE THE PROCESS FLOW DIAGRAMS TO SHOW PRIMARY CONTROL LOOPS
CONSIST OF LOOPS THAT SHOW LOCATIONS OF SENSORS, A CONTROLLER OR INTERLOCK, AND THE ACTUATOR
CAN BE PRODUCED FOR A SINGLE UNIT OPERATION OR FOR AN ENTIRE FACILITY

9. EXAMPLE simplified p&id

10. EXAMPLE simplified p&id
TC AND LC REPRESENT TEMPERATURE AND LEVEL CONTROLLERS, RESPECTIVELY
THESE INDICATE THE TEMPERATURE OF THE MIXED TANK IS MAINTAINED BY THE FLOW OF STEAM TO AN EXTERNAL HEAT EXCHANGER THAT HEATS A SIDESTREAM FROM THE MIXING TANK
THE LEVEL OF THE VESSEL IS MAINTAINED BY CONTROLLING THE FLOW THROUGH A DRAIN VALVE

11. EXAMPLE simplified p&id
PT REPRESENTS A PRESSURE INDICATION LOOP
THIS INDICATOR IS NOT USED TO CONTROL PROCESS VARIABLES THROUGH A CONTROLLER
IT MAY BE USED TO PROVIDE imFORMATION DURING NON-ROUTINE OPERATIONS, SUCH AS STARTUP/SHUTDOWN OR TO FOR OPTIMIZATION
THE LOOPS ARE NOT NUMBERED

12. CONCEPTUAL DIAGRAMS
INCLUDE ALL CONTROL LOOPS AND INSTRUMENTATION FUNCTIONS
THESE SUMMARIZE THE RESULTS OF DESIGN CALCULATIONS

13. FORMAL P&IDs
INCLUDE DETAILS FOR ALL STEADY STATE CONTROL, BATCH CONTROL, INTERLOCK, SAFETY, AND STARTUP/SHUTDOWN OPERATIONS
THESE INCLUDE ALL THE DETAIL USED FOR SPECIFICATION
EACH LOOP IS NUMBERED WITH DESIGNATIONS THAT WILL BE USED FOR ALL DETAILED DESIGN
THERE MAY BE STANDARD INSTRUMENTATION DIAGRAMS THAT SUPPORT THE P&ID PRESENTATION

14. FORMAL P&IDs
LOOP IDENTIFICATION USES ISA STANDARD DESIGNATION FOR EACH COMPONENT AND FUNCTION
CONTROL VALVES ARE NORMALLY DESIGNATED ACCORDING TO THE CONTROLLED VARIABLE, PCV, TCV, LCV, FCV - THOUGH THEY ALWAYS CONTROL FLOWS
PNEUMATIC, ELECTRONIC AND COMPUTER CONNECTIONS ARE DIFFERENTIATED

15. OTHER INSTRUMENT DOCUMENTATION
LOOP DIAGRAMS ARE MADE FOR EACH SEPARATE LOOP WITH DETAILS FOR ALL COMPONENTS AND REFERENCES TO CALCULATIONS
OVERALL DCS DIAGRAMS ARE PREPARED ON THE SUPERVISORY LEVEL TO SHOW HOW THE PLANT NETWORK CONNECTS WITH THE LOCAL I/O PANELS
LADDER LOGIC DIAGRAMS ARE PROVIDED FOR PLC’s
ELECTRICAL ONE-LINE DIAGRAMS SHOW THE RELAYS THAT ARE INCLUDED IN THE CONTROL SYSTEMS

16. CONSTRAINTS FOR ROUTINE OPERATION
DYNAMIC CONTROL MODELING TENDS TO EMPHASIZECONTINUOUS AUTOMATED CONTROL - STEADY STATE OPERATION
THERE ARE OTHER NON-ROUTINE CONDITIONS WHERE OTHER CONTROL METHODS ARE APPLIED AND DYNAMICS ARE SECONDARY
NO CONTROL - SOME FUNCTIONS ARE NOT CONTROLLED DIRECTLY
RAW MATERIAL QUALITY
UTILITY QUALITIES

17. CONSTRAINTS FOR nonROUTINE OPERATION
MANUAL CONTROL - SOME SYSTEMS HAVE SUCH LARGE TIME DELAYS, THAT MANUAL CONTROL IS ADEQUATE
ON/OFF CONTROL - THIS IS INTERLOCK OPERATION WHERE THE SYSTEM MAY BE ACTIVATED OR DEACTIVATED IN RESPONSE DUE TO
OUT-OF-RANGE OPERATION
END OF A TIMER CYCLE

18. CONSTRAINTS FOR nonROUTINE OPERATION
STARTUP/SHUTDOWN OPERATION
MAY INCLUDE OPERATION UNDER A SEPARATE SET OF TUNING CONSTANTS
MAY INCLUDE SHORT-TERM INTERRUPTION AS WELL AS LONG-TERM PROCESS SHUTDOWN
NON-ROUTINE CONDITIONS WHERE OTHER CONTROL METHODS ARE APPLIED AND DYNAMICS ARE PRIMARY

19. FAIL-SAFE INTERLOCK OPERATION
THE POTENTIAL INCIDENT NEEDS TO BE DYNAMICALLY MODELED TO PREVENT SECONDARY FAILURES THAT COMPROMISE SAFETY
FOR EXAMPLE IF A RELIEF VALVE DOES NOT HAVE ADEQUATE CAPACITY, THE SYSTEM MAY OVER-PRESSURE
IF A FLARE DOES NOT PROVIDE A FLAME RAPIDLY, THERE MAY BE A RELEASE TO ATMOSPHERE.

20. CONSTRAINTS FOR ROUTINE OPERATION
Personnel protection
ENVIRONMENTAL PROTECTION
EQUIPMENT PROTECTION