IEC PAS 63131:2017

IEC PAS 63131 ®
Edition 1.0 2017-11
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
colour
inside
System control diagram
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IEC PAS 63131 ®
Edition 1.0 2017-11
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
colour
inside
System control diagram
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 75.200 ISBN 978-2-8322-4889-8

– 2 – IEC PAS 63131:2017 © IEC 2017
CONTENTS
FOREWORD . 11
INTRODUCTION . 13
1 Scope . 16
2 Normative references . 16
3 Terms, definitions and abbreviated terms . 16
3.1 Terms and definitions . 16
3.2 Abbreviated terms . 21
4 The system control diagram (SCD) approach . 22
4.1 Conceptual definition . 22
4.2 Framework . 23
4.3 Life cycle concept . 23
4.4 Basic design (informative) . 24
4.4.1 General . 24
4.4.2 Basic system design . 24
4.4.3 Basic function design . 25
4.4.4 Basic application design . 25
4.4.5 Application design . 26
4.5 Alarm management . 27
Annex A (normative) System control diagram (SCD) function standard . 28
A.1 Overview. 28
A.1.1 General . 28
A.1.2 Compliance . 28
A.1.3 Positive logic . 28
A.1.4 Execution sequence of logic . 28
A.1.5 Functions used in SIF . 28
A.1.6 HMI presentation . 29
A.2 Terminal codes . 29
A.2.1 General . 29
A.2.2 Signal types (1.Character) . 30
A.2.3 Explanatory code (succeeding characters) . 31
A.2.4 Terminal description for function templates . 31
A.3 SCD control function template behaviour . 35
A.4 Function templates. 35
A.4.1 General . 35
A.4.2 Function template name convention . 36
A.4.3 CA – PID controller . 40
A.4.4 CS – Step control . 47
A.4.5 HA – Analogue input command . 53
A.4.6 HB – Binary input command. 55
A.4.7 KB – Sequence logic interface template . 57
A.4.8 LB – Safeguarding shutdown level . 59
A.4.9 MA – Monitoring of analogue process variables . 62
A.4.10 MAS – Analogue measurement acquisition from subsystems . 66
A.4.11 MB – Monitoring of binary (digital) process variables . 69
A.4.12 OA – Analogue output. 71
A.4.13 QA – Totalizer . 77

A.4.14 SB – Single binary signal for shutdown . 81
A.4.15 SBB – Breaker control template . 83
A.4.16 SBC – Coordinator for SBE . 89
A.4.17 SBE – Control of electrical equipment . 94
A.4.18 SBV – Control of pneumatic/hydraulic equipment . 100
A.4.19 Sequence logic . 106
Annex B (normative) SCD drawing standard . 110
B.1 Overview. 110
B.2 Content of SCDs . 111
B.2.1 Equipment . 111
B.2.2 Measuring instruments. 112
B.2.3 Functions . 112
B.2.4 Flow paths . 112
B.2.5 Information not shown on the SCDs . 113
B.2.6 Black box representation . 113
B.2.7 Parallel equipment . 113
B.3 Layout. 114
B.3.1 Readability . 114
B.3.2 The extent of information on SCDs . 114
B.3.3 Location of information on the SCDs . 114
B.3.4 Direction of flow . 114
B.3.5 Page connectors . 114
B.3.6 From P&ID/D&ID to SCD . 114
B.4 Symbols . 115
B.4.1 General . 115
B.4.2 Function template symbol . 115
B.4.3 Symbols for logic and arithmetic functions . 117
B.4.4 Extended connection line for EFB functions . 119
B.4.5 Parameter labels . 120
B.4.6 Signal line . 120
B.4.7 Process line . 121
B.4.8 Line connections. 122
B.4.9 Process and signal line crossing/jump . 123
B.4.10 Sequential flow chart lines . 123
B.4.11 Instruments . 124
B.4.12 Mechanical equipment . 124
B.4.13 Valves . 124
B.4.14 Electrical equipment . 127
B.4.15 Sequence symbols. 128
B.4.16 Reference symbols . 132
B.5 Tagging . 134
B.6 Terminal codes . 134
B.7 Symbol and font sizes . 135
B.8 Layers and colors . 140
B.9 Legend sheets . 141
B.9.1 General . 141
B.9.2 Part 1: Symbols and codes . 141
B.9.3 Part 2: System specific function templates and terminal definition codes . 141
B.9.4 Part 3: Applications typical . 142

– 4 – IEC PAS 63131:2017 © IEC 2017
B.10 Drawing frame and title block . 142
Annex C (informative) Project execution guideline . 143
C.1 Overview. 143
C.1.1 Objectives . 143
C.1.2 Quality . 143
C.1.3 Standardisation . 143
C.1.4 Safety . 144
C.1.5 Productivity. 144
C.2 Implementation . 145
C.2.1 Objectives . 145
C.2.2 Unambiguous input . 145
C.2.3 Standardisation . 145
C.2.4 Productivity. 145
C.2.5 Documentation . 146
C.2.6 Verification . 146
C.3 Commissioning . 146
C.3.1 Objectives . 146
C.3.2 Commissioning procedures . 147
C.3.3 Commissioning runs . 147
C.4 Operation . 147
C.4.1 General . 147
C.4.2 Objectives . 147
C.4.3 Production control . 148
C.5 Modifications. 148
Annex D (normative) SCD legend . 149
D.1 Overview. 149
D.2 Function template symbols . 149
D.3 Function template terminal placement . 150
D.4 Reference symbols . 150
D.5 Function identifier for safety system interface . 151
D.6 Field device symbols . 152
D.7 Instrument signals . 153
D.8 Constant values . 153
D.9 Logic and arithmetic symbols . 154
D.10 Sequential function chart symbols . 155
Annex E (informative) SCD application guidelines . 156
E.1 Purpose . 156
E.2 Tagging . 156
E.3 Application typical . 156
E.3.1 General . 156
E.3.2 Process measurements . 156
E.3.3 Action and warning alarms . 160
E.3.4 Process modulating control . 162
E.3.5 Control of on/off valves and dampers . 166
E.3.6 Failure actions for of on/off valves . 169
E.3.7 On/off valves and control valve interaction . 170
E.3.8 Electrical equipment control . 170
E.3.9 HVAC . 177
E.3.10 Shutdown . 181

E.3.11 Interface to external systems . 184
E.3.12 Condition monitoring . 186
E.3.13 Electrical distribution control . 187
E.3.14 Parallel functions . 187
E.3.15 Sequences . 188
E.3.16 Use of "black boxes" . 190
E.3.17 Use of project specific functions . 191
Annex F (normative) SCD Control function templates behaviour . 193
F.1 Purpose . 193
F.2 Method for description of behaviour (control function state charts) . 193
F.2.1 Basic idea . 193
F.2.2 State charts . 193
F.2.3 Modelling of the processing of process information . 195
F.2.4 Parallel state charts . 196
F.2.5 Symbols used for modelling control functions using state charts . 198
F.3 Description of behaviour in various modes . 199
F.3.1 General . 199
F.3.2 Auto-manual mode. 199
F.3.3 Blocked mode . 201
F.3.4 Disable transition mode . 204
F.3.5 Internal external mode . 205
F.3.6 Outside operation mode . 206
F.3.7 Safeguarding mode . 207
F.3.8 Suppress alarm mode . 208
F.3.9 Track mode . 213
F.4 Definition of templates control function behaviour . 213
F.4.1 General . 213
F.4.2 CA – PID controller template behaviour . 213
F.4.3 CS – Step control template behaviour . 216
F.4.4 HA – Analogue input command template behaviour . 218
F.4.5 HB – Binary input command template behaviour . 219
F.4.6 KB – Sequence header template behaviour . 220
F.4.7 LB – Safeguarding shutdown level template behaviour . 221
F.4.8 MA – Monitoring of analogue process variable template behaviour . 222
F.4.9 MAS – Analogue measurement acquisition from subsystem template
behaviour . 224
F.4.10 MB – Monitoring of binary (digital) process variables template behaviour . 225
F.4.11 OA – Analogue output template behaviour . 226
F.4.12 QA – Totalize template behaviour . 228
F.4.13 SB – Single binary signal for shutdown template behaviour . 229
F.4.14 SBB – Breaker control template behaviour . 229
F.4.15 SBC – Coordinator for SBE template behaviour . 231
F.4.16 SBE – Controls of electrical equipment template behaviour . 233
F.4.17 SBV – Control of pneumatic/hydraulic equipment template behaviour . 235
Annex G (informative) SCD readers manual . 237
G.1 What is a system control diagram (SCD)? . 237
G.2 Areas of use . 237
G.3 The process part of system control diagrams (SCDs) . 238
G.4 The control part of system control diagrams (SCDs) . 238

– 6 – IEC PAS 63131:2017 © IEC 2017
G.4.1 General . 238
G.4.2 Function blocks . 238
G.4.3 Simple logic elements . 239
G.4.4 Logic connections . 239
G.5 Examples . 239
G.5.1 Level control . 239
G.5.2 Temperature control . 240
Bibliography . 241

Figure 1 – SCD framework . 23
Figure 2 – Basic design . 24
Figure 3 – Basic system design . 25
Figure 4 – Basic function design . 25
Figure 5 – Basic application design, application typical . 26
Figure 6 – Object typical . 26
Figure 7 – Object typical . 27
Figure A.1 – Typical function template schematic . 39
Figure A.2 – CA function template schematic . 40
Figure A.3 – CS function template schematic . 48
Figure A.4 – HA function template schematic . 53
Figure A.5 – HB function template schematic l . 55
Figure A.6 – KB function template schematic . 57
Figure A.7 – LB function template schematic . 60
Figure A.8 – MA function template schematic . 62
Figure A.9 – MAS function template schematic . 67
Figure A.10 – MB function template schematic . 69
Figure A.11 – OA function template schematic . 72
Figure A.12 – A function template schematic . 78
Figure A.13 – SB function template schematic . 81
Figure A.14 – SBB function template schematic . 84
Figure A.15 – SBC function template schematic . 90
Figure A.16 – SBE function template schematic . 95
Figure A.17 – SBV function template schematic . 101
Figure A.18 – Sequential control functions . 107
Figure B.1 – The function template symbol . 115
Figure B.2 – The additional information field . 115
Figure B.3 – Integration level I symbol . 117
Figure B.4 – Integration level II symbol . 117
Figure B.5 – Integration level III symbol . 117
Figure B.6 – Object typical . 117
Figure B.7 – Analogue selector . 118
Figure B.8 – Use of the "optional" notation "#" . 119
Figure B.9 – Multiple split by extended connection line . 119
Figure B.10 – Multiple or/and by extended connection line . 120

Figure B.11 – Multiple function terminals by extended connection line . 120
Figure B.12 – Fixed parameter label . 120
Figure B.13 – Signal line . 120
Figure B.14 – Digital communication link. 121
Figure B.15 – Electrical power line . 121
Figure B.16 – Node split symbol for signal lines . 121
Figure B.17 – Major process line . 121
Figure B.18 – Minor process line . 121
Figure B.19 – Line connections . 122
Figure B.20 – Simplified line connections . 122
Figure B.21 – Process line connections . 122
Figure B.22 – Line crossing . 123
Figure B.23 – SFC lines . 123
Figure B.24 – SFC alternative branch line . 123
Figure B.25 – SFC parallel branch line . 123
Figure B.26 – Instrument . 124
Figure B.27 – Instrument tag location. 124
Figure B.28 – On/off valve . 125
Figure B.29 – Modulating control valve . 125
Figure B.30 – Actuators variations . 125
Figure B.31 – HVAC damper variations . 125
Figure B.32 – Limit switches . 126
Figure B.33 – Signal failure valve action . 126
Figure B.34 – Normally energised input and output signals . 126
Figure B.35 – Valve normal position . 126
Figure B.36 – Electrical reference symbol . 127
Figure B.37 – Electrical reference symbol use for variable drive . 128
Figure B.38 – SFC sequence start and reference symbol . 128
Figure B.39 – SFC step symbol . 129
Figure B.40 – SFC transition symbol . 129
Figure B.41 – SFC transition condition symbol . 129
Figure B.42 – SFC step action symbol . 129
Figure B.43 – SFC sequence end symbol . 130
Figure B.44 – Single branch sequence path . 130
Figure B.45– Alternate sequence path . 131
Figure B.46 – Parallel branch sequence path . 132
Figure B.47 – Process line page connectors . 132
Figure B.48 – Signal line page connectors . 132
Figure B.49 – SIS reference triangle . 133
Figure B.50 – Multiple SIS levels reference triangle . 133
Figure B.51 – Sequence reference flags . 133
Figure B.52 – Arrangement of terminals on function symbol . 134
Figure B.53 – Colours . 141

– 8 – IEC PAS 63131:2017 © IEC 2017
Figure C.1 – SAS supplier interface . 146
Figure E.1 – MA terminals . 157
Figure E.2 – Totalization . 157
Figure E.3 – Compensation of flow via a formula . 158
Figure E.4 – Use of optional symbol for voting . 158
Figure E.5 – Use of project specific function . 158
Figure E.6 – Differential pressure measurement . 159
Figure E.7 – MB with action . 159
Figure E.8 – MB with alarm only . 159
Figure E.9 – Valve feedback presentation . 160
Figure E.10 – Action alarms . 160
Figure E.11 – Warnings . 160
Figure E.12 – Force blocking action alarm high . 161
Figure E.13 – Action alarm suppression . 161
Figure E.14 – PID control . 162
Figure E.15 – PID control and action alarm . 162
Figure E.16 – Cascade control . 163
Figure E.17 – Split range control . 163
Figure E.18 – Choke valve control . 164
Figure E.19 – Binary control. 164
Figure E.20 – Binary control with modulating control valve . 164
Figure E.21 – Start/Stop control of pump . 165
Figure E.22 – Tracking of control valve . 165
Figure E.23 – On/Off valve. 166
Figure E.24 – Safeguarding of On/Off valve . 166
Figure E.25 – Safeguarding of PSD valve . 167
Figure E.26 – Safeguarding of ESD valve . 167
Figure E.27 – Safeguarding blowdown valve with only ESD solenoid . 168
Figure E.28 – Safeguarding blowdown valve with both ESD and PSD solenoid . 168
Figure E.29 – Fail close . 169
Figure E.30 – Fail open . 169
Figure E.31 – Normally energised output signal . 169
Figure E.32 – Fail maintain . 170
Figure E.33 – On/Off and control valve interaction . 170
Figure E.34 – Communication interface to motor control center . 171
Figure E.35 – Safeguarding of motor . 172
Figure E.36 – Unit shutdown level stop of pump . 172
Figure E.37 – Process shutdown level safeguarding of pump . 173
Figure E.38 – Pump with automatic on/off control and PSD interlock. 174
Figure E.39 – Heater with automatic on/off control and PSD interlock . 174
Figure E.40 – Low voltage motors with modulating control via data communication . 175
Figure E.41 – Low voltage motors with modulating control via hardwired signals . 176
Figure E.42 – Duty/standby or lead/lag . 176

Figure E.43 – Three pumps in duty/standby . 177
Figure E.44 – Control of HVAC dampers . 178
Figure E.45 – HVAC fan and fire damper control on BCL and BCH . 179
Figure E.46 – Control of multiple fans . 179
Figure E.47 – HVAC heating and fan control . 180
Figure E.48 – Control of thyristor controlled heater . 181
Figure E.49 – Process shutdown group / level . 181
Figure E.50 – Single process shutdown . 182
Figure E.51 – Process shutdown level . 183
Figure E.52 – Unit shutdown in PCS . 183
Figure E.53 – Metering interface with flow computer shown . 184
Figure E.54 – Metering interface without showing the flow computer on the SCD . 185
Figure E.55 – Anti-surge interface. 185
Figure E.56 – Vibration interface . 186
Figure E.57 – Control of breakers . 187
Figure E.58 – Sequence references . 188
Figure E.59 – Sequence header . 188
Figure E.60 – Sequence flow chart . 189
Figure E.61 – Setpoint of flow for 3 pumps . 190
Figure E.62 – Black box representation . 190
Figure E.63 – Terminal representation for supplier F . 192
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