LNG CUSTODY TRANSFER HANDBOOK - giignl.org

1 _____ GIIGNL _____ LNG CUSTODY TRANSFER HANDBOOK FOURTH EDITION version GIIGNL 2015 GIIGNL LNG CUSTODY TRANSFER HANDBOOK Fourth edition version Uncontrolled when printed DOCUMENT STATUS AND PURPOSE This fourth (2015) edition of the GIIGNL LNG CUSTODY TRANSFER HANDBOOK reflects GIIGNL s understanding of best current practice at the time of publication. The purpose of this HANDBOOK is to serve as a reference manual to assist readers to understand the procedures and equipment available to and used by the members of GIIGNL* to determine the energy quantity of LNG transferred between LNG ships and LNG terminals. It is neither a standard nor a specification. This HANDBOOK is not intended to provide the reader with a detailed LNG ship shore CUSTODY TRANSFER procedure as such, but sets out the practical issues and requirements to guide and facilitate a skilled operator team to work out a suitable procedure for a specific LNG ship shore CUSTODY TRANSFER application.

2 Due to the rapidly changing market conditions, new (commercial) opportunities arise leading to new technical solutions and different operations (such as partial unloading, reloading at an LNG import terminal, ship to ship LNG TRANSFER operations, development of the small scale LNG market not only with much smaller LNG ships and in much smaller quantities, but also with a different ship design and other cargo containment systems), the GIIGNL General Assembly requested the GIIGNL Technical Study Group to review and update the third edition (version March 2011) of the GIIGNL LNG CUSTODY TRANSFER HANDBOOK . Therefore, this fourth edition must be seen as an extensive revision of the previous version including not only CUSTODY TRANSFER from a large scale LNG ship to an onshore terminal (or vice versa), but also containing a lot more useful information with regard to ship to ship LNG TRANSFER and CUSTODY TRANSFER from an onshore terminal to small LNG carriers.

3 However it is not specifically intended to work out procedures for overland LNG CUSTODY TRANSFER operations involving LNG trucks, containers or trains, or for small scale LNG TRANSFER such as bunkering or refuelling of ships and trucks. For these, kind reference is made to the GIIGNL Retail LNG / LNG as a fuel HANDBOOK . No proprietary procedure, nor particular manufacture of equipment, is recommended or implied suitable for any specific purpose in this HANDBOOK . Readers should ensure that they are in possession of the latest information, standards and specifications for any procedures and equipment they intend to employ. GIIGNL, and any of its members, disclaims any direct or indirect liability as to information contained in this document for any industrial, commercial or other use whatsoever.

4 This latest version replaces all previous editions of the CUSTODY TRANSFER HANDBOOK . Please always consult the GIIGNL website to check for the latest version of this HANDBOOK , esp. when referring to a pdf download or a printout of this HANDBOOK . * GIIGNL Groupe International des Importateurs de Gaz Naturel Liqu fi Paris (International Group of Liquefied Natural Gas Importers Paris, France) GIIGNL LNG CUSTODY TRANSFER HANDBOOK Fourth edition version Uncontrolled when printed 1 CONTENTS 1. INTRODUCTION 5 2. GENERAL DESCRIPTION OF THE MEASUREMENT 6 GENERAL FORMULA FOR CALCULATING THE LNG ENERGY TRANSFERRED 7 GENERAL SCHEME OF THE MEASUREMENT OPERATIONS 7 LNG Volume 7 LNG Density 8 LNG Gross calorific value 8 Energy of the gas displaced by the TRANSFER of LNG 8 Flowchart for determining the energy transferred 9 INSTRUMENTS USED 9 For the determination of the LNG volume 9 For the determination of LNG density and gross calorific value 9 For the determination of the energy of displaced gas 10 For the determination of the energy of Gas to engine room 10 Periodic instruments recalibration 10 STANDARDIZATION 10 PARTIAL LOADING OR UNLOADING OF LNG CARRIERS 10 Gassing up and cooling down operations 11

5 Gassing up operations 11 Cooling down operations 11 3. VOLUME MEASUREMENT 12 GAUGE TABLES 12 Use of gauge tables 12 Correction tables 13 Correction according to the condition of the LNG carrier 13 Corrections according to the temperatures in the liquid and gaseous phases 13 Approval by authorities 13 INSTRUMENTS AND METHODS FOR MEASURING THE LEVEL OF LIQUID IN THE LNG CARRIER'S TANKS 15 Main liquid level gauging devices 15 Electrical capacitance type level gauge 15 Float type level gauge 15 Radar (microwave) type level gauge 15 Laser type level gauge 16 Timing of the level measurement 16 Readings 16 Reading of the level with float gauges 16 Reading of the level with capacitance and radar gauges 17 Correction of readings 17 Float gauge 17 Capacitance, radar and laser gauges 17 Use of spare level gauge 21 Complete unloading (tank stripping) 21 Automated systems 21 CALCULATION OF THE VOLUME OF LNG TRANSFERRED 22 4.

6 TEMPERATURE MEASUREMENT 23 LIQUID TEMPERATURE 23 Device 23 Testing and accuracy 24 VAPOUR TEMPERATURE 24 5. VAPOUR PRESSURE MEASUREMENT 24 6. SAMPLING OF LNG 26 LNG SAMPLING PRINCIPLES 26 SAMPLING POINT 27 SAMPLING PROBES 28 PIPING ARRANGEMENT BETWEEN SAMPLING PROBE AND VAPORIZER 29 LNG VAPORIZER AND CONTROL DEVICES 29 Main devices 29 Electrical vaporizer 29 Water or steam vaporizer 31 Auxiliary vaporization control devices 31 On regasified LNG outlet 31 On LNG inlet 32 On heating fluid (water, steam or electricity) 32 Safety devices 32 Operating parameters 32 Gas sample collection systems 32 GAS SAMPLE CONDITIONING 33 Gas sample containers 33 Direct piping to a gas analyzer 33 Examples 33 PERFORMANCE OF THE DEVICES 36 GIIGNL LNG CUSTODY TRANSFER HANDBOOK Fourth edition version Uncontrolled when printed 2 SAMPLING PROCEDURE 37 Sampling period 37 Sampling frequency 37 Purging 37 Sampling parameters 37 Utilisation of gas sample containers 37 SPOT SAMPLING DEVICE 37 7.

7 GAS ANALYSIS 37 TYPE OF GAS CHROMATOGRAPH 38 CALIBRATION 38 Calibration gas/working standard 38 ENVIRONMENT FOR A GAS CHROMATOGRAPHIC SYSTEM 38 ANALYSIS OF REGASIFIED LNG AND RETAINED SAMPLES 39 UNCERTAINTY OF GAS ANALYSIS 39 RAMAN SPECTROSCOPY 39 IMPURITIES 40 General 40 Specifications and measurement of trace impurities in LNG 40 Carbon dioxide 40 Sulphur 40 Total sulphur 41 Sulphur components 41 Mercury 41 8. DATA PROCESSING & TREATMENT 41 GENERAL 41 DATA HANDLING: QUALITY 41 Data processing 42 Data treatment 42 9. DENSITY 42 GENERAL 42 DENSITY CALCULATION METHODS 42 REVISED KLOSEK Mc KINLEY METHOD 43 Limits of the method 43 Formula 43 Example of LNG density calculation 43 10.

8 GROSS CALORIFIC VALUE 43 GENERAL 43 METHOD OF DETERMINATION OF THE GROSS CALORIFIC VALUE 43 Determination with the help of calorimeters 44 Determination of GCV by calculation 44 Examples of formula 44 Examples of charts of basic physical constants 45 Example of calculation 45 11. ANALYSIS REPORT 46 IDENTIFICATION 46 BASIC DATA 46 RESULTS 46 12. ENERGY OF GAS DISPLACED OR CONSUMED 46 ENERGY OF GAS DISPLACED FROM THE LNG TANKS 46 ENERGY OF GAS CONSUMED AS FUEL BY THE LNG CARRIER 47 13. ENERGY TRANSFER DETERMINATION 47 14. ENERGY TRANSFER MEASUREMENT 47 15. UNCERTAINTY OF THE ENERGY TRANSFER DETERMINATION 48 VOLUME 48 Cargo Liquid Lines 48 DENSITY 49 GROSS CALORIFIC VALUE 49 SAMPLING AND VAPORIZATION 49 GAS DISPLACED 49 GAS CONSUMED IN ENGINE ROOM 49 COMBINED STANDARD UNCERTAINTY AND EXPANDED UNCERTAINTY OF THE ENERGY TRANSFER DETERMINATION 49 ROUNDING OF NUMBERS AND COMMERCIAL IMPACT 50 16.

9 SHIP TO SHIP LNG TRANSFER OPERATIONS 50 17. SMALL SHIP TO SHORE LNG OPERATIONS 51 18. RELOADING OPERATIONS IN REGASIFICATION TERMINALS 51 19. LNG SALES CONTRACT CUSTODY TRANSFER CHECKLIST 52 ENCLOSURE 1: CONVERSION FACTOR TABLE FOR ENERGY UNITS 55 ENCLOSURE 2: LNG AND NATURAL GAS CUSTODY TRANSFER METHODS 56 ENCLOSURE 3: OTHER RELEVANT STANDARDS AND REFERENCES 59 ENCLOSURE 4: NOTES ON TERMINOLOGY 60 LIST OF FIGURES 61 LIST OF TABLES 62 REFERENCES 63 APPENDIX 1: USE OF IN LINE MEASUREMENT OF LNG FLOW 64 GIIGNL LNG CUSTODY TRANSFER HANDBOOK Fourth edition version Uncontrolled when printed 3 APPENDIX 2: LASER TYPE CARGO TANK LEVEL GAUGE 65 APPENDIX 3: SOME RECOMMENDATIONS FOR PARTIAL RELOADING OF CARGO TANKS OF LNG CARRIERS, WITH REGARD TO BOTH SAFETY AND CUSTODY TRANSFER ISSUE 66 APPENDIX 4: EXAMPLE OF GAUGE TABLES 68 APPENDIX 5.

10 EXAMPLE OF VOLUME CALCULATION 72 APPENDIX 6: EXAMPLES OF DISCONTINUOUS AND CONTINUOUS SAMPLING AND VAPORIZATION SYSTEMS 77 APPENDIX 7: DIRECT IN LINE ANALYSIS WITH RAMAN SPECTROSCOPY 80 APPENDIX 8: GRUBB s TEST 82 APPENDIX 9: TABLES FOR LNG DENSITY CALCULATION ACCORDING TO NBS 86 APPENDIX 10: EXAMPLE OF LNG DENSITY CALCULATION 88 APPENDIX 11: EXAMPLE OF GCV CALCULATION 91 APPENDIX 12:UNCERTAINTY CALCULATIONS 93 APPENDIX 13: EXAMPLE OF COMMERCIAL IMPACT OF ROUNDING OF NUMBERS 96 APPENDIX 14: TWO CASE STUDIES ILLUSTRATING POTENTIAL RISKS OF STRATIFICATION AND ROLLOVER IN LNG SHIP s CARGO TANKS 97 APPENDIX 15: EXAMPLE OF CUSTODY TRANSFER DATA LOGS ON BOARD A LNG VESSEL 101 GIIGNL LNG CUSTODY TRANSFER HANDBOOK Fourth edition version Uncontrolled when printed 5 1.