CLASSIFICATION AND IMPLEMENTATION OF INSTRUMENTED PROTECTIVE FUNCTIONS

he objective is to set the recommended standard for good design and engineering practice applied by Group
companies operating an oil refinery, gas handling installation, chemical plant, oil and gas production facility, or any other
such facility, and thereby to achieve maximum technical and economic benefit from standardization.
TABLE OF CONTENTS
1. INTRODUCTION ........................................................................................................4
1.1 SCOPE.......................................................................................................................4
1.2 DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS .........4
1.3 DEFINITIONS ...........................................................................................................4
1.4 ABBREVIATIONS ......................................................................................................7
1.5 CROSS-REFERENCES ............................................................................................8
1.6 SUMMARY OF CHANGES SINCE PREVIOUS EDITION .......................................8
2. GENERAL.................................................................................................................10
3. IPF CLASSIFICATION METHODOLOGY (SIL ASSESSMENT
METHODOLOGY)...11
3.1 BACKGROUND .................................................11
3.2 THE CLASSIFICATION PROCESS .........................................................................12
4. IMPLEMENTION OF IPFs........................................................................................27
4.1 INTRODUCTION .....................................................................................................27
4.2 ASSIGNING A SIL TO THE INITIATOR, LOGIC SOLVER AND FINAL
ELEMENT .................................................................................................................28
4.3 GENERAL IMPLEMENTATION REQUIREMENTS..................................................29
4.4 ROBUSTNESS ......................................................................................................32
4.5 IMPLEMENTATION OF PROCESS RELATED IPFs ...............................................36
4.6 IMPLEMENTATION OF FIRE, GAS AND SMOKE DETECTION IPFs....................50
5. TESTING...................................................................................................................52
5.1 CLASSIFICATION RESULTS AND TEST PHILOSOPHY .......................................52
5.2 TEST COVERAGE FACTOR....................................................................................53
5.3 INITIATOR TESTING................................................................................................53
5.4 LOGIC SOLVER TESTING.......................................................................................53
5.5 FINAL ELEMENT TESTING .....................................................................................53
5.6 AUTOMATIC TESTING ...........................................................................................54
6. PFD CALCULATIONS .............................................................................................56
6.1 GENERAL.................................................................................................................56
6.2 ASSUMPTIONS........................................................................................................56
6.3 INPUTS INTO THE PFD CALCULATIONS ............................................................56
6.4 OUTPUTS OF THE CALCULATION METHODOLOGY...........................................59
6.5 CALCULATION OF TEST INTERVAL - SPECIAL CASES ......................................60
7. REFERENCES .........................................................................................................62
APPENDICES
APPENDIX 1 TYPICAL TEST INTERVALS .........................................................64
APPENDIX 2 SETTING UP A CLASSIFICATION EXERCISE...................................67
APPENDIX 3 IPF CLASSIFICATION RESULTS: DATABASE PRINT-OUT EXAMPLE....68