SIMULATION SUITE CHEMCAD SOFTWARE PROCESS CONTROL SYSTEMS PROCESS CONTROL SYSTEMS COURSE WITH CHEMCAD MODELS. Application > Design > Adjustment

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1 COURSE WITH CHEMCAD MODELS PROCESS CONTROL SYSTEMS Application > Design > Adjustment Based on F.G. Shinskey s 1967 Edition Presenter John Edwards P & I Design Ltd, UK Contact: jee@pidesign.co.uk

2 COURSE OBJECTIVES REVIEW Course Objectives are to study Feedback Control and Control Loop Structure Multiple Control Loops Appreciation of Basic Instrumentation Controller Equations and Control Modes Control Loop Behaviour Control Valve Types - Flow Characteristics - Actions CHEMCAD SIMULATION SOFTWARE SUITE Control Loop Dynamics - Dead Time Capacity Resistance Appreciation of Behaviour of Common Control Loops CHEMCAD Control Models Control Loop Tuning

3 FEEDBACK CONTROL PROCESS Controlled Variable (c) INCREASES IMBALANCE CONTROL RUNAWAY Manipulated Variable (m) CONTROLLER Error (e) Set Point (r) SIMULATION r c SUITE e = ± RESTORES BALANCE CONTROL STABILITY

4 CONTROL LOOP STRUCTURE FUNCTIONS & SIGNALS MEASURE Thermocouple mv Resistance bulb Ω Transmitter 4-20 ma Transmitter bar LOCATIONS & TAGGING TT 01 Field Mounted LOOP SCHEMATIC CONVERT CONTROL Characterise Measurement Linear 4-20 ma Signal 4-20 ma Signal Thermocouple Curve (mv/i) Square Root Extraction ( ) Pneumatic to Current (I/P) X Y01 c e CHEMCAD SIMULATION XI Control SOFTWARE SUITE 4-20 ma XIC 01 C01 Equipment Room Room Signal Converter Measurement Transmitter 0-100ºC TT 01 XY 01 r 4-20 ma Controller 0-100ºC Control Valve Thyristor CV 01 m 4-20 ma CONTROL DEVICE Valve Actuator 4-20 ma I/P 4-20 ma to bar Valve Actuator bar Positioner bar C V 01 Field Mounted

5 MULTIPLE CONTROL LOOPS Single Cascade Ch6, Secondary p154 Primary RatioCh6, p160 Wild Controlled Auto SelectCh6, p167 Squeaky wheel gets the grease AdaptiveCh6, p170 PID Adjust Tx Tx Tx FT FT Tx Tx Tx XIC XIC Primary Ratio RR XIC XIC XIC XIC XIC Secondary Hi Lo Select FIC < or > CHEMCAD SIMULATION SOFTWARE SUITE XIC CV CV CV CV CV CV Single Valve Split Range Valves Ratio of controlled flow to wild flow Auto selection of controlled variable Adapts - models needs of process

6 TYPICAL INSTRUMENTATION PV Process Variable Controller SV Set Point Measurement Transmitters (4 to 20 ma dc) Temperature Flow Pressure Level

7 THERMOCOUPLE DATA Industrial CHEMCAD SIMULATION SOFTWARE SUITE Surface Reference Thermo Electric Company Sanitary

8 RESISTANCE BULB DATA Industrial CHEMCAD SIMULATION SOFTWARE SUITE Surface Reference Thermo Electric Company Sanitary

9 TEMPERATURE HEAD TRANSMITTERS Reference Endress + Hauser

10 CONTROLLER MODES & EQUATIONS Proportional (P) 100 m = e + P b P = PB % b =output bias m = b for e = 0 e = r ± Gain = c 100 Proportional + Integral (PI) m = e + edt P R SIMULATION P SUITE P Gain Decreasing P Increases m R = integral time (min) dm/dt = e/r R dm/dt Never set R faster than process τ + τ d

11 CONTROLLER MODES & EQUATIONS Proportional + Derivative (PD) 100 de m = e + D + b P dt D =derivative time (min) Note D dm/dt Use D when sustained error End point control: ph target temperature Proportional + Integral + Derivative (PID) 3Mode m = e + edt + P R CHEMCAD SIMULATION SOFTWARE SUITE de D dt Low R on fast processes: Flow Liquid Pressure High R on slow processes: Batch reactor temperature Never D on noisy processes: Flow Level Liquid Pressure

12 DYNAMIC SIMULATION CHEMCAD CONTROLLER SET UP LEVEL MEASUREMENT LINEAR 0.5 to 4.5 metre SIGNAL 4.0 to 20 ma INC LEVEL INC SIGNAL CONTROLLER ACTION DIRECT INC LEVEL INC OUTPUT CHEMCAD SIMULATION SOFTWARE SUITE FAIL CLOSED VALVE ON OUTLET (OPENS) FAIL OPEN VALVE ON INLET (CLOSES)

13 CONTROL VALVE CHARACTERISTICS 100 ANY CHARACTERISTIC QUICK OPENING CHARACTERISTIC VALVE STROKE (%) VALVE 0 POSITIONER FLOW % VALVE COEFFICIENT (C v ) BUTTERFLY VALVE LINEAR EQUAL PERCENTAGE QUICK OPENING

14 CONTROL VALVE CHARACTERISTICS FISHER EASY E GLOBE VALVE SIZING COEFFICIENTS SIZE Cv Quick Opening Cv Equal %

15 CONTROL VALVE CHARACTERISTICS Flow-Tek Vee Ball

16 CONTROL VALVE CALIBRATION-ACTION SINGLE CONTROL VALVE OPERATIONS CONTROL OUTPUT COEFFICIENTS ACTION FAIL CLOSED POSITION STATE LOGIC EQUATION ma % A v B v 4 0 Closed 0 0 = 4A v +B v Open 1 1 = 20A v +B v FAIL OPEN Open V a l v e Fail Open Signal to Close 4 0 Open 1 1 = 4A v +B v Closed 0 0 = 20A v +B v Cooling Valve A v = B v = 1.25 CHEMCAD SIMULATION SOFTWARE SUITE Heating Valve A v = B v = Fail Closed Signal to Open Open V a l v e Closed 4 20 Controller Output (ma) 4 Controller Output (ma) Closed 20 A v and B v are CHEMCAD scaling constants

17 CONTROL VALVE CALIBRATION-ACTION DUAL CONTROL VALVE OPERATIONS IN SPLIT RANGE ACTION CONTROL OUTPUT POSITION STATE LOGIC EQUATION COEFFICIENTS ma % A v B v FAIL CLOSED Closed 0 0 = 12A v +B v Open 1 1 = 20A v +B v FAIL OPEN 4 0 Open 1 1 = 4A v +B v Closed 0 0 = 12A v +B v Open V a l v e Closed 4 A v = B v = 1.5 Split Range Valves A CHEMCAD SIMULATION v = A A v = SOFTWARE SUITE v = B = -1.5 Open B = 1.25 B = v v v 3 Way Valve Controller Output (ma) V a l v e Closed 4 A v and B v are CHEMCAD scaling constants Controller Output (ma)

18 DYNAMIC SIMULATION CHEMCAD CONTROL VALVE SETTINGS CHEMCAD SIMULATION SOFTWARE SUITE Fail Closed Signal to Open

19 PROPERTIES OF COMMON LOOPS COMMON LOOP CHARACTERISTICS & TUNING PARAMETER RANGES Ch3, Table 3.3 PARAMETER CHARACTERISTIC P (%) I (min) D (min) FLOW FAST - NOISY NO PRESSURE (LIQUID) FAST - NOISY NO COMPOSITION (GAS) FAST - NOISY NO LEVEL SLOW FAST - NOISY SOMETIMES NO TEMPERATURE SLOW - STEADY I/4 < D > I/2 COMPOSITION (LIQUID) SLOW - STEADY I/4 < D > I/2 PRESSURE (GAS) SLOW - STEADY 1-5 UNNECCESSARY UNNECCESSARY CHEMCAD SIMULATION SOFTWARE SUITE VAPOR PRESSURE SLOW - STEADY I/4 < D > I/2 CONTROL MODES P (%) T i (min) T d (min) P 2 Pu P + I 2.2 Pu T u / 1.2 P + I + D 1.6 Pu T u / 2.0 T u / 8.0 = T i /4 P u measurement starts to oscillate at constant amplitude T u for small SP changes

20 DYNAMIC SIMULATION CHEMCAD DYNAMIC VESSEL SETTINGS

21 CONTROL OF DEAD TIME Ch1-p6

22 CAPACITY TANK LEVEL Ch1-p18 Tank Level m SIMULATION Run Time min SUITE

23 CAPACITY TANK LEVEL SELF REGULATE Ch1-p18 τ 1 = V Fk Tank Level m Flow Change 15 to 20 m 3 /h τ 1 Run Time min CHEMCAD SIMULATION SOFTWARE SUITE Fixed Position 47.5% Off

24 DYNAMIC SIMULATION TANK BALANCING HYDRAULICS Ch3-p71 Period is function of wetted surface length only τ = 2π 0 L1+ L 2g Throttling displacer valves reduces amplitude allowing narrower PB 2 0.5

25 DISPLACER TANK LEVEL CONTROL

26 TANK LEVEL CONTROLLER TUNING

27 GAS PRESSURE CONTROL Ch3-p68

28 FLOW CONTROLLER TUNING

29 TEMPERATURE CONTROL

30 BYPASS TEMPERATURE CONTROL Ch9-p234

31 DYNAMIC SIMULATION TRAINING SIMULATOR CHEMCAD MODEL

32 DYNAMIC SIMULATION TRAINING SIMULATOR OTS SETTINGS CHEMCAD SIMULATION SOFTWARE SUITE Real Time Step 1.0m Simulation Time 0.1m

33 DYNAMIC SIMULATION TRAINING SIMULATOR GUI