Liquefied Gas Handling Principles on Ships and in Terminals (LGHP4) Fourth Edition Society of International Gas Tanker & Terminal Operators Ltd First Edition 1986 Second Edition 1996 Third Edition 2000 Fourth Edition 2016 © Copyright SIGTTO, Bermuda 1986, 1996, 2000, 2016 ISBN 13: 978-1-85609-714-7 The Society of International Gas Tanker and Terminal Operators (SIGTTO) is a non-profit making organisation dedicated to protect and promote the mutual interests of its members in matters related to the safe and reliable operation of gas tankers and terminals within a sound environment. The Society was founded in 1979 and was granted consultative status at the International Maritime Organization in November 1983. www.sigtto.org www.twitter.com/sigtto British Library Cataloguing in Publication Data The Society of International Gas Tanker and Terminal Operators Liquefied Gas Handling Principles on Ships and in Terminals Cover image: Courtesy of Singapore LNG Notice of Terms of Use The advice and information given in this publication is intended purely as guidance to be used at the user’s own risk and acceptance or otherwise of anything in this publication is entirely voluntary. The use of the terms ‘will’, ‘shall’, ‘must’ and other similar such words is for convenience only, and nothing in this publication is intended, or should be construed, as establishing standards or requirements. No warranties or representations are given nor is any duty of care or responsibility accepted by the Society of International Gas Tanker and Terminal Operators (SIGTTO) their membership, employees, or any person, firm, corporation or organisation (who or which has been in any way concerned with the furnishing of information or data, the compilation or any translation, publishing, supply of the publication) for the accuracy of any information or advice given in the publication or any omission from the publication or for any consequence whatsoever resulting directly or indirectly from compliance with, adoption of or reliance on guidance contained in the publication even if caused by a failure to exercise reasonable care on the part of any of the aforementioned parties. This publication is not a substitute for consulting the up to date applicable regulations and legislation (both national and international). For the avoidance of doubt, where such regulations and/or legislation conflict with the guidance in this publication, such regulations and/or legislation shall always be followed in preference to this publication. Printed and bound in Great Britain by Bell & Bain Ltd, Glasgow W ITHERBY Published by Witherby Publishing Group Ltd 4 Dunlop Square, Livingston, Edinburgh, EH54 8SB, Scotland, UK Tel No: +44(0)1506 463 227 Email: [email protected] Web: www.witherbys.com Witherby Seamanship International is a division of Witherby Publishing Group Ltd. Acknowledgements – Images Bernhard Schulte Shipmanagement Bob Sanguinetti Bomin Linde LNG, AGA, Karl Gabor Chevron ConocoPhillips Cryostar Dongsung FineTec Evergas Exmar Gaztransport & Technigaz Hamworthy Combustion INEOS, Duncan Bruce Liquigas MODEC, Inc. Moss Maritime National Grid Shell Singapore LNG Tangguh LNG Teekay LNG iii The term ‘Gas Carrier Codes’ includes the codes referred to in the Appendix (References 1.1 to 1.4), which since the 1983 Code have been referred to as the IGC Code. They will be referred to as the IGC Code in this publication. Blue shaded boxes – information of an operational nature, providing useful hints for planning purposes Yellow shaded boxes – cautionary information regarding operations Grey shaded boxes with red border – information that is considered to be of particular importance Preface to the Fourth Edition 'Liquefied Gas Handling Principles', after three previous editions, is firmly established as the standard reference work for the industry’s operational side. This publication deals with the safe handling of bulk liquid gases (LNG, LPG and chemical gases) on board ships and at the ship/shore interface at terminals. It is an indispensable companion for all those training for operational qualifications and an accessible work of reference for those already directly engaged in liquefied gas operations. The publication has been written primarily for serving ships’ officers and terminal staff who are responsible for cargo handling operations, but also for personnel who are about to be placed in positions of responsibility for these operations. Its appeal also extends to many others, not directly involved in the operational aspects of the industry, who require a comprehensive and ready reference for technical aspects of their businesses. Liquefied Gas Handling Principles emphasises the importance of understanding the physical properties of gases in relation to the practical operation of gas-handling equipment on ships and at terminals. The first edition of this publication had its origins in the course notes devised and drafted by Graham McGuire and Barry White of the Hazardous Cargo Handling Unit, Leith Nautical College, UK (the forerunner of The Centre for Advanced Maritime Studies, Edinburgh), to whom the Society express its sincere gratitude. In the sixteen years since this publication was last updated the liquefied gas shipping and terminal industry has undergone considerable change. This revision reflects these changes which include, but are not limited to, vessel design, propulsion systems, size of fleet, floating regasification and reliquefaction, Arctic LNG, containment systems, efficiency increases in vessel operations, vessel capacities, technology, best practice and legislation. It is recommended that a copy of this publication be kept — and used — on board every gas tanker and in every terminal to provide advice on operational procedures and the shared responsibility for safe and efficient operations. iv Prefaces to the Previous Editions Preface to Third Edition Liquefied Gas Handling Principles, after two previous editions, is firmly established as the standard text for the industry’s operational side. It is an indispensable companion for all those training for operational qualifications and an accessible work of reference for those already directly engaged in liquefied gas operations. Its appeal extends also to many others, not directly involved in the operational aspects of the industry, who require a comprehensive and ready reference for technical aspects of their businesses. It is therefore important for Liquefied Gas Handling Principles to be kept thoroughly up to date. Although there are no single major changes from previous editions, this, its Third Edition, comprises many amendments that together ensure the work is kept current with contemporary operating practices. Preface to Second Edition Since publication of the first edition, this book has become an acknowledged text for courses leading to the award of Dangerous Cargo Endorsements for seagoing certificates of competency. In this regard, the book’s contents are now recommended by IMO in the latest revision of the Standards of Training, Certification and Watchkeeping convention. In addition, the book is being used increasingly for many non-statutory courses involving the training of marine terminal personnel. These achievements are due to the efforts of many SIGTTO members who have ensured comprehensive and practical coverage of the subject. This second edition of Liquefied Gas Handling Principles on Ships and in Terminals is produced to bring the first edition up to date. The main changes stem from publication by IMO of the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code). This Code was under preparation at the time of the first edition but was not fully covered as publication dates for each coincided. Also, since the IGC Code was printed, a number of amendments have been made to it. These changes are incorporated into the Safety of Life at Sea convention and, therefore, need coverage. At the time of writing, further amendments to the Gas Codes are being considered by IMO and these are also covered in this edition. One such is the new framework of rules and guidelines covering the Loading Limits for ships’ cargo tanks. This initiative has direct relevance to ship’s personnel and needs to be understood by staff involved in cargo handling operations at loading terminals. The new second edition also includes the appropriate parts from the most up to date Ship/Shore Safety Check List as printed in the latest edition of the International Safety Guide for Oil Tankers and Terminals. This check list should be used by all terminals handling gas carriers. The Ship/Shore Safety Check List is supported by IMO in its Recommendations on the Safe Transport of Dangerous Cargoes and Related Activities in Port Areas. Revision of the original text was also necessary due to the introduction of stricter environmental requirements; the decision to ban the use of halon as a fire-extinguishing medium is one example of such changes. Growing environmental awareness concerning many halogenated hydrocarbons (halons) and refrigerant gases such as CFCs (chlorofluorocarbons), resulting from an international agreement called the Montreal Protocol on Substances which Deplete the Ozone Layer (1987), will cause gradual phasing out and replacement by other products. Preface to First Edition This textbook, published by the Society of International Gas Tanker and Terminal Operators (SIGTTO), deals with the safe handling of bulk liquid gases (LNG, LPG and chemical gases) and emphasises the importance of understanding their physical properties in relation to the practical operation of gas- handling equipment on ships and at terminals. The book has been written primarily for serving ships’ officers and terminal staff who are responsible for cargo handling operations, but also for personnel who are about to be placed in positions of responsibility for these operations. The contents cover the syllabus for the IMO Dangerous Cargo Endorsement (Liquefied Gas) as outlined in the IMO Standards of Training, Certification and Watchkeeping convention. The text is complementary to the Tanker Safety Guide (Liquefied Gas) and the IMO Gas Carrier Codes. Where a point regarding ship design requires authoritative interpretation, reference should always be made to the IMO Codes. The importance of the ship/shore interface in relation to the overall safety of cargo handling operations is summarised in Chapter Six and stressed throughout the text. Names of compounds are those traditionally used by the gas industry. In general, Systeme International (Sl) units are used throughout the book although, where appropriate, alternative units are given. Definitions are provided in an introductory section and all sources of information used throughout the text are identified in Appendix 1. A comprehensive index is also provided for quick reference and topics which occur in more than one chapter are cross-referenced throughout the text. This textbook is also intended as a personal reference book for serving officers on gas carriers and for terminal operational staff. v Contents Preface to the Fourth Edition iii Prefaces to the Previous Editions iv Figures and Tables xvii Definitions xxvii Key to Symbols xxxix CHAPTER 1 Overview of the Carriage of Liquefied Gases by Sea 1 1.1 The Liquefied Gases 4 1.1.1 LNG production 4 1.1.2 LPG production 6 1.1.3 Chemical gases production 7 1.2 The Principal Products 8 1.3 Gas Carrier Fleet 10 1.4 Safety Record 12 1.5 Regulatory Framework 13 1.5.1 Safety of Life at Sea (SOLAS) 13 1.5.2 International Convention for the Prevention of Pollution From Ships, 1973, as modified by the Protocol of 1978 (MARPOL 73/78) 14 1.5.3 International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW) 14 1.5.4 Recommendations on the Safe Transport of Dangerous Cargoes and Related Activities in Port Areas 15 1.5.5 Ship certification 15 CHAPTER 2 Properties of Liquefied Gases 17 Chapter 2 Part a) The Chemistry of Liquefied Gases 19 2.1 Atoms, Molecules and Chemical Bonds 19 2.1.1 The hydrocarbon series 21 2.1.2 Chemical formulae and the IUPAC naming system 23 2.1.3 Saturated and unsaturated hydrocarbons 24 2.2 The Chemical Gases 28 2.3 Chemical Reactivity and Compatibility 31 2.3.1 Reactivity with construction materials 31 2.3.2 Reactivity with other cargoes 32 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 vi 2.4 Self-Reaction 33 2.4.1 Reactive properties 33 2.4.2 Formation of polymers or dimers 33 2.5 Reaction with Water – Hydrate Formation 37 2.6 Reaction with Air 39 2.6.1 Combustion 39 2.6.2 Flammability/flammable range 40 2.7 Suppression of Flammability 44 2.7.1 Inert gas and nitrogen 45 2.7.2 The use of inert gas 46 2.7.3 The chemical compatibility of cargoes with inert gas or nitrogen 47 Chapter 2 Part b) The Physics of Liquefied Gases 49 2.8 The Physical Properties of Liquefied Gases and their States of Matter 49 2.8.1 Temperature, heat energy and phase change 49 2.8.2 Specific heat, enthalpy and entropy 50 2.8.3 Phase change – a summary 51 2.8.4 Saturated vapour pressure (SVP) 52 2.8.5 Liquid and vapour densities 55 2.8.6 Liquid to vapour volume ratios 55 2.8.7 Spillage of cargo liquid 56 2.8.8 Viscosity of liquid cargoes 57 Chapter 2 Part c) Gas Laws, Thermodynamic Principles and Reliquefaction 59 2.9 The Gas Laws and Thermodynamic Principles 59 2.9.1 Liquefied gas mixtures, their vapour pressures and compositions 62 2.9.2 The ‘bubble point’ and ‘dew point’ of mixtures 64 2.9.3 The laws of thermodynamics 66 2.9.4 Enthalpy and Mollier charts 67 2.9.5 Thermodynamic systems – isothermal, isentropic and adiabatic processes 70 2.9.6 Heat transfer 71 2.9.7 Practical examples of heat transfer 72 2.9.8 Rollover 73 2.10 Reliquefaction 75 2.10.1 Indirect cycle 76 2.10.2 Direct cycle 77 2.10.3 Cascade cycle 84 2.10.4 LNG reliquefaction cycles 86 LGHP4 Contents vii CHAPTER 3 Liquefied Gas Carrier Types 93 Chapter 3 Part a) Gas Carrier Types 95 3.1 Design Standards and Ship Types 95 3.1.1 The IGC Code 95 3.1.2 Factors affecting gas carrier design 97 3.2 Gas Carrier Types 98 3.2.1 Fully-pressurised ships 98 3.2.2 Semi-refrigerated ships 99 3.2.3 Fully-refrigerated ships 100 3.2.4 Ethylene/ethane ships 102 3.2.5 LNG carriers 103 3.2.6 Regasification vessels (RVs) 104 3.3 Gas Carrier Layout 105 3.4 Hazardous Zones 107 3.4.1 Hazardous area classification 107 3.4.2 IEC definitions 108 3.4.3 Zone determination 109 3.4.4 Ventilation 109 3.5 Survival Capability 110 3.6 Surveys and Certification 111 3.6.1 Certificate of fitness 111 3.6.2 Carriage of noxious liquid substances (NLS) 112 Chapter 3 Part b) Cargo Containment Systems 113 3.7 Materials of Construction and Insulation 113 3.7.1 Construction materials 113 3.7.2 Tank insulation 114 3.8 Cargo Containment Systems 116 3.8.1 Type A tanks 118 3.8.2 Type B tanks 121 3.8.3 Type C tanks (semi-refrigerated) 125 3.8.4 Type C tanks (fully-pressurised) 126 3.8.5 Membrane tanks 126 3.8.6 Semi-membrane containment system 134 3.8.7 Integral tanks 134 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 viii Chapter 3 Part c) Propulsion System Types 135 3.9 Propulsion System Types on LNG Carriers 135 3.9.1 Steam 137 3.9.2 Dual fuel diesel electric (DFDE) 139 3.9.3 Slow speed diesel (oil fuel) 141 3.9.4 Slow speed diesel (gas fuel) 141 CHAPTER 4 The Ship – Cargo Equipment 143 4.1 Cargo Pipelines and Valves 145 4.1.1 Cargo pipelines 145 4.1.2 Hazards of cargo line pressure testing 146 4.1.3 Cargo manifold reducers 147 4.1.4 Cargo valves 149 4.1.5 Cargo strainers 152 4.1.6 Emergency shutdown (ESD) systems 154 4.1.7 Effect of surge pressure should ESD activate 158 4.1.8 Relief valves for cargo tanks and pipelines 158 4.1.9 Types of pressure relief valves 160 4.2 Cargo Pumps 164 4.2.1 Pump performance curves 164 4.2.2 Deepwell pumps 167 4.2.3 Submerged motor pumps 168 4.2.4 Booster pumps 169 4.2.5 Ice prevention at cargo pumps 170 4.2.6 Emergency cargo pumps 170 4.3 Deck Tanks 172 4.4 Cargo Heaters 173 4.4.1 Direct cargo heaters 174 4.4.2 Indirect cargo heaters 176 4.5 Cargo Vaporisers 177 4.6 Regasification Units 179 4.6.1 Closed loop with steam heating 179 4.6.2 Combined open/closed loop with seawater and steam heating 179 4.6.3 Closed loop with steam heating and intermediate water/glycol loop 180 4.6.4 Open loop with seawater heating and intermediate propane loop 180 LGHP4 Contents ix 4.7 LPG Reliquefaction Plant and Boil-Off Control 181 4.7.1 Cargo compressors and associated equipment 181 4.7.2 Reciprocating compressors 182 4.7.3 Screw compressors 183 4.7.4 Compressor suction liquid separator 184 4.7.5 Cargo compressor suction gas cooling 184 4.7.6 Purge gas condenser 185 4.8 LNG Reliquefaction Plant and Boil-off Control Systems 186 4.8.1 LNG boil-off and vapour handling systems 186 4.8.2 LNG compressors (vapour return and fuel gas) 187 4.8.3 Gas combustion units (GCU) 188 4.8.4 LNG reliquefaction 189 4.9 Inert Gas and Nitrogen Systems 192 4.9.1 Inert gas generators 193 4.9.2 Nitrogen production on ships 196 4.9.3 Pure nitrogen from the shore 197 4.10 Electrical Equipment 198 4.11 Cargo Instrumentation 200 4.11.1 Liquid level instrumentation 200 4.11.2 Magnetic level transmitters 203 4.11.3 Level alarm and automatic shutdown systems 205 4.11.4 Pressure and temperature monitoring 205 4.11.5 Gas detection systems 206 4.11.6 LNG custody transfer measurement systems (CTMS) 208 4.11.7 Integrated systems 208 4.11.8 Calibration 208 4.12 Ship/Shore Links 209 CHAPTER 5 The Terminal 211 Chapter 5 Part a) Onshore 213 5.1 Safe Jetty Designs 213 5.2 Cargo Transfer Systems 215 5.2.1 Hoses 216 5.2.2 Marine loading arms (MLAs) 217 5.2.3 Vapour return 223 5.2.4 Insulating flanges 225 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 x 5.3 Shore Storage 226 5.3.1 Pressurised storage at ambient temperature 227 5.3.2 Storage in semi-pressurised spheres 232 5.3.3 Refrigerated storage at atmospheric pressure 233 5.3.4 Construction materials and design 239 5.4 Ancillary Equipment 240 5.4.1 Pressure relief venting 240 5.4.2 Pipelines and valves – engineering standards and surge pressure 240 5.4.3 Pumps, compressors and heat exchangers 246 5.5 Instrumentation 252 5.5.1 Product metering 252 5.5.2 Pressure, temperature and level instrumentation 254 Chapter 5 Part b) Offshore 255 5.6 Floating Terminals 256 5.7 Facility Layout 258 5.7.1 Engineering design considerations 260 5.7.2 Other considerations 261 5.8 Topsides Production Facilities 264 5.8.1 Topsides production facility (LPG specific) 264 5.8.2 Topsides production facility (LNG specific) 264 5.8.3 Topsides production facility (regas specific) 266 5.9 Product Storage and Offloading 269 5.9.1 Cargo containment systems 269 5.10 Mooring Systems 270 5.11 Cargo Transfer Systems 272 5.11.1 Side by side offloading 272 5.11.2 Tandem offloading 273 5.11.3 Hoses for ship to ship and offshore transfer systems 273 5.11.4 Surge considerations for ship to ship and offshore transfer systems 274 CHAPTER 6 The Ship/Shore Interface 275 6.1 Supervision and Control 277 6.2 Design Considerations 278 6.2.1 Jetty operations 278 6.2.2 The terminal 279 6.2.3 The ship 279 LGHP4 Contents xi 6.3 Ship/Shore Compatibility Process (LNG) 280 6.3.1 Ship and terminal particulars 280 6.3.2 Mooring arrangements 280 6.3.3 Ship manifold, shore hose and marine loading arm (MLA) characteristics 281 6.3.4 Terminal gangway characteristics and ship deck landing configuration 282 6.3.5 Ship/shore link (SSL) 283 6.3.6 Other compatibility considerations 284 6.4 Ship/Shore Compatibility Process (Other Liquefied Gases) 285 6.5 Communications 286 6.5.1 Prior to charter 286 6.5.2 Prior to arrival 286 6.5.3 Alongside the jetty 287 6.5.4 Navigation, docking, mooring, meteorological and oceanographic systems 287 6.6 Discussions Prior to Cargo Transfer 289 6.7 Ship/Shore Safety Checklist 291 6.8 Supervision and Control During Cargo Transfer 293 6.8.1 Joint agreement on readiness for cargo transfer operations 293 6.8.2 Supervision 293 6.8.3 Periodic checks during cargo transfer operations 293 6.9 Operational Considerations 294 6.9.1 Berthing and mooring 294 6.9.2 Connection and disconnection of cargo hoses and MLAs 295 6.9.3 Cargo handling procedures 296 6.9.4 Cargo surveyors 297 6.9.5 Gangways and ship security 297 6.9.6 Bunkering 298 6.9.7 Work permits 299 6.9.8 Access to cargo manifold during transfer 299 6.10 Fire-Fighting and Safety 300 6.11 Linked Emergency Shutdown (ESD) Systems 302 6.12 Terminal Booklet – Information and Regulation 304 6.13 Training 305 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 xii CHAPTER 7 Cargo Handling Operations 307 7.1 Sequence of Operations 309 7.2 Initial Preparations 311 7.2.1 Tank inspection 311 7.2.2 Drying – cargo system 311 7.2.3 Drying – hold spaces and interbarrier spaces 313 7.3 Changing Tank Atmospheres 314 7.3.1 Principles of atmosphere changing 315 7.3.2 Displacement 315 7.3.3 Dilution 317 7.4 Inerting – Before Loading 319 7.4.1 Inerting pipelines and cargo machinery 320 7.4.2 Tank preparation prior to loading ammonia 321 7.5 Gassing-Up 322 7.5.1 Gassing-up at sea using liquid from tanks 323 7.5.2 Gassing-up alongside 324 7.6 Cool-down 328 7.6.1 Refrigerated LPG cargoes 329 7.6.2 LNG 330 7.6.3 Semi-pressurised/semi-refrigerated ships 331 7.7 Loading 332 7.7.1 Preliminary procedures 332 7.7.2 Trim, stability and stress 333 7.7.3 Sloshing 333 7.7.4 Management of tank pressure during loading 334 7.7.5 Commencement of loading 338 7.7.6 Operation of the reliquefaction plant during bulk loading of LPG 340 7.7.7 Operation of the reliquefaction plant during bulk loading of LNG 341 7.7.8 Cargo tank loading limits 341 7.8 The Loaded Voyage 345 7.8.1 Cargo temperature and pressure control 345 7.8.2 Operation of the reliquefaction plant on refrigerated LPG carriers 346 7.8.3 Operation of the reliquefaction plant on LNG carriers 348 7.8.4 LNG carriers – gas combustion unit (GCU) 350 7.8.5 LNG boil-off gas (BOG) as fuel 351 7.8.6 Other boil-off gas (BOG) as fuel 352 LGHP4 Contents xiii 7.9 Discharging 353 7.9.1 Discharge by pressurising the vapour space 353 7.9.2 Discharge by cargo pump 353 7.9.3 Discharge via booster pump and cargo heater 357 7.9.4 Tank pressure management 357 7.9.5 Operation of the reliquefaction plant during discharge 361 7.9.6 Completion of discharge 361 7.9.7 Draining of tanks and pipelines 362 7.10 The Ballast Voyage 364 7.10.1 LPG carriers 364 7.10.2 LNG carriers 364 7.11 LNG Carrier – Ballast Voyage on Ships Fitted with a Combination of a Reliquefaction Plant/GCU 365 7.11.1 Warm ballast voyage (use of GCU) 365 7.11.2 Cold ballast voyage (use of reliquefaction plant) 365 7.12 Gas-Freeing 366 7.12.1 LPG/NH3 carriers 366 7.12.2 LNG carriers 372 7.13 Ship to Ship Transfer (STS) 377 CHAPTER 8 Cargo Measurement and Calculation 379 8.1 Principles for Liquefied Gases 381 8.1.1 Special practices for gas cargoes 381 8.1.2 General – density in air and density in a vacuum 382 8.1.3 Gas-up and cool-down quantity calculation 386 8.1.4 Shore terminal considerations 387 8.2 Taking Samples of Liquefied Gas Cargoes 389 8.2.1 Why cargo samples are taken 389 8.2.2 Sampling systems – ‘open loop’ or ‘closed loop’ systems 390 8.2.3 The procedures involved in taking samples 393 8.3 Measurement of Cargo Tank Volumes 396 8.3.1 Trim correction 397 8.3.2 List correction 398 8.3.3 Tape correction 398 8.3.4 Float correction 398 8.3.5 Tank shell contraction and expansion 398 8.4 Measurement of Density 399 8.4.1 Density measurement methods 399 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 xiv 8.5 Ship/Shore Calculation Procedures 401 8.5.1 Outline of weight in air calculation 401 8.5.2 Procedures using standard temperature 401 8.6 Example – LPG Cargo Calculation 403 8.7 Other Calculation Procedures and Measurement Units 404 8.8 LNG Quantification 405 8.8.1 Example of contractual requirements for the measurement of the energy transferred at an LNG unloading terminal 410 8.9 Cargo Documentation 415 CHAPTER 9 Health, Environment and Safety Management 417 Chapter 9 Part a) Safety Management 419 9.1 Safety Management Systems (SMS) 419 9.2 Security 421 9.3 Safety Organisation 422 9.3.1 Terminal organisational structure 422 9.3.2 Shipboard safety organisation 422 9.3.3 Training, competency and experience 424 Chapter 9 Part b) Hazards and Emergency Procedures 425 9.4 Principal Hazards 425 9.4.1 Flammability 426 9.4.2 Jet fires 427 9.4.3 Liquid (pool) fires 427 9.4.4 Vapour cloud explosion 429 9.4.5 BLEVE 429 9.4.6 Vaporisation of spilled liquid 430 9.4.7 Rapid phase transitions (RPT) 430 9.4.8 Uncontrolled release of vapour 431 9.4.9 Vapour exposure 431 9.4.10 Asphyxia (suffocation) 434 9.4.11 Medical treatment for asphyxia or the effects of toxic materials 436 9.4.12 Giving oxygen to a casualty 438 9.4.13 Frostbite 440 9.4.14 Chemical burns 442 9.4.15 Other hazards of liquefied gases 442 LGHP4 Contents xv 9.5 Emergency Planning 443 9.5.1 The emergency plan 443 9.5.2 Ship emergency procedures 443 9.5.3 Terminal emergency procedures 444 9.6 Removal of Ship from Berth 446 9.7 Ship to Ship Cargo Transfer 447 9.8 Hazards with the Use of Hoses and Marine Loading Arms (MLAs) 448 9.9 Sources of Ignition 450 9.10 Fire and Fire-Fighting Management 451 9.11 Extinguishing Mediums 452 9.11.1 Water 452 9.11.2 Foam 453 9.11.3 Dry chemical powders 453 9.11.4 Carbon dioxide (CO2) systems 454 9.11.5 Alarm procedures 455 9.11.6 Training 456 Chapter 9 Part c) Process Safety 457 9.12 Risk Assessment 460 9.12.1 Principles of risk assessment 460 9.12.2 Qualitative versus quantitative 461 9.12.3 Inherent risk versus residual risk 461 9.12.4 Risk assessments in practice 462 9.13 Procedures 463 9.14 Standards 464 9.15 Management of Change (MoC) 465 9.16 Inspection and Maintenance 467 9.17 Permit to Work Systems (PTW) 469 9.17.1 Types of permit to work 472 9.17.2 Lock-out and tag-out 476 9.18 Incident Investigation and Reporting 478 9.18.1 Incident reporting 478 9.18.2 Root cause analysis (RCA) and risk assessments 479 9.19 Process Safety Information 480 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 xvi Chapter 9 Part d) Personal Health & Safety 481 9.20 Hazardous Atmospheres 481 9.21 Personal Protection 482 9.21.1 Induction 482 9.22 Entry into Enclosed Spaces 484 9.22.1 Precautions for tank entry 484 9.22.2 Procedures for tank entry 485 9.22.3 Rescue from enclosed spaces 485 9.22.4 Mandatory enclosed space entry and rescue drills 486 9.23 Personal Protective Equipment (PPE) 487 9.24 General Safety Precautions 488 9.24.1 Breathing apparatus 490 9.24.2 Protective clothing 492 9.25 Safety Data Sheets (SDS) 493 Chapter 9 Part e) Environmental Stewardship 495 9.26 Air Emissions 496 9.27 Energy Efficiency Design Index (EEDI) 497 9.28 Effect of Non-Core Ship/Shore Services 498 Appendix 499 Index 505 Other SIGTTO Publications You May be Interested in 521 Reference Tables and Diagrams xvii Figures and Tables Inside front and back covers — LPG, LEC and LNG carriers (to scale) Figure No. Title Figure 1.1 Constituents of natural gas 4 Figure 1.2 Flow diagram for a typical gas liquefaction plant (known as a ‘train’) 5 Figure 1.3 The production, transport and use of LPGs 6 Figure 1.4 Production of chemical gases (simplified) 7 Figure 2.1 Atoms consist of electrons, protons and neutrons 19 Figure 2.2 Methane CH4 21 Figure 2.3 Ethane C2H6 21 Figure 2.4 Propane C3H8 22 Figure 2.5 Normal butane C4H10 22 Figure 2.6 Iso-butane 22 Figure 2.7 Saturated hydrocarbon (ethane (C2H6)) 24 Figure 2.8 Unsaturated hydrocarbons (ethylene (C2H4) and acetylene (C2H2)) 25 Figure 2.9 Butadiene structures 25 Figure 2.10 Vinyl chloride (C2H3CI) 29 Figure 2.11 Ethylene oxide (C2H4O) and propylene oxide (C3H6O) 30 Figure 2.12 The dimerisation and polymerisation of VCM (C2H3Cl) 34 Figure 2.13 Cargo pump, spool piece and strainer showing polymerisation 34 Figure 2.14 Inhibitor information form 35 Figure 2.15 Dimerisation of butadiene 36 Figure 2.16 Hydrate plug in the pump sump of a semi-refrigerated LPG carrier after a cargo of ‘wet’ butane 37 Figure 2.17 Hydrate at the cargo manifold after the discharge of a ‘wet’ butane cargo 37 Figure 2.18 Solubility of water in butadiene 38 Figure 2.19 Flammable ranges of butane, ethylene and methane (percent in air) 40 Figure 2.20 Likely flammable vapour zones in the event of a liquefied gas spill 43 Figure 2.21 Flammable range diagram 44 Figure 2.22 Changes of state 51 Figure 2.23 Barometric method for measuring saturated vapour pressure 52 Figure 2.24 Pressure vs temperature – liquefied gases 53 Figure 2.25 Properties of propane liquid and vapour 55 Figure 2.26a Boyle’s Law for gas at constant temperature 59 Figure 2.26b Charles’ Law for gas at constant pressure 59 Figure 2.26c The Pressure Law for gas at constant volume 59 Figure 2.27 Illustration of ‘absolute temperature’ 60 Figure 2.28 Equilibrium diagram for propane/butane mixtures at atmospheric pressure 65 Figure 2.29 Natural boil-off, weathering or flash vaporisation 66 Figure 2.30 Schematic Mollier diagram 68 Figure 2.31 Relationship between adiabatic and isothermal compression 70 Figure 2.32 Comparative heat transfer rates for various materials 72 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 xviii Figure 2.33 Heat transfer within a cargo tank 72 Figure 2.34 LNG tank with normal non-stratified convection heat transfer 73 Figure 2.35 Conditions in an LNG tank where stable stratification has been caused by filling with liquids of different densities 73 Figure 2.36 Rollover 74 Figure 2.37 Indirect cooling cycles 76 Figure 2.38 Single stage, direct cargo reliquefaction cycle 78 Figure 2.39 Mollier chart: Single stage direct reliquefaction cycle 80 Figure 2.40 Propane – ethane equilibrium diagram 81 Figure 2.41 Schematic Mollier chart: 2-stage direct compression cycle 81 Figure 2.42 2-stage direct reliquefaction cycle 82 Figure 2.43 Refrigerant type reliquefaction plant (cascade cycle) 84 Figure 2.44 Schematic Mollier chart – cascade cycle 86 Figure 2.45 Simplified cascade refrigeration cycle for LNG 87 Figure 2.46 Cooling curve for multi-stage cascade refrigeration cycle for LNG 88 Figure 2.47 Simplified precooled MR reliquefaction process 89 Figure 2.48 Comparative cooling curves for the cascade, precooled MR and dual MR liquefaction processes 90 Figure 2.49 Brayton refrigeration cycle and temperature-entropy diagram 91 Figure 2.50a Nitrogen expander cycle 91 Figure 2.50b 3-stage nitrogen expander cycle 91 Figure 3.1 Selection of containment system 97 Figure 3.2 Fully-pressurised gas carrier 98 Figure 3.3 Semi-refrigerated gas carrier 99 Figure 3.4 Fully-refrigerated LPG carrier (85,000 m3) 101 Figure 3.5 Ethylene carrier 102 Figure 3.6 Ethane carrier 102 Figure 3.7a Membrane type LNG carrier 103 Figure 3.7b Moss type LNG carrier 103 Figure 3.8 The LNG fuelling vessel Seagas refuels the ferry Viking Grace 103 Figure 3.9 Regasification vessel connected to a submerged turret loading system (STL) 104 Figure 3.10 Typical compressor room/electric motor room on a fully-refrigerated LPG carrier 105 Figure 3.11 Cargo compressor room on a 37,000 m3 LPG carrier 105 Figure 3.12 Fixed dry powder monitor on semi-refrigerated LPG carrier 106 Figure 3.13 Fixed water protection for the front of the accommodation block 106 Figure 3.14 Diagram showing hazardous area on an LPG carrier 107 Figure 3.15 Diagram showing hazardous area on an LNG storage tank 107 Figure 3.16 View of a Type A tank as found on a fully-refrigerated LPG carrier 118 Figure 3.17 Prismatic Type A tank 120 Figure 3.18 Self-supporting spherical Type B – LNG carrier 121 Figure 3.19 Self-supporting prismatic Type B tank 122 Figure 3.20 Self-supporting spherical Type B – LNG carrier 122 Figure 3.21 Moss (Type B) tank under construction, showing the equatorial ring (To increase the volume without increasing hull dimensions, the Moss tank can be constructed in a ‘stretched version’ where a cylindrical section is inserted in the equatorial area) 123 LGHP4 Figures and Tables xix Figure 3.22 Moss (Type B) tank under construction and showing the central pipe tower arrangement 124 Figure 3.23 Type C tank (semi-refrigerated) 125 Figure 3.24 Type C tanks – fully-pressurised gas carrier 126 Figure 3.25 Type C tanks mounted in a barge to be used in a floating LNG project 126 Figure 3.26 Principles of membrane containment system 127 Figure 3.27 Membrane containment system 127 Figure 3.28 GTT NO 96 containment system 128 Figure 3.29 Construction of the Gaztransport membrane system (NO 96) 130 Figure 3.30 GTT NO 96 containment system 130 Figure 3.31 GTT NO 96 containment system 131 Figure 3.32 Technigaz MK III containment system 131 Figure 3.33 Technigaz waffle 132 Figure 3.34 Technigaz reinforcement 132 Figure 3.35 Construction of the Technigaz membrane – MK lll 133 Figure 3.36 BOG, BOR and their relationship to vessel speed 136 Figure 3.37 Simplified steam turbine propulsion plant overview 137 Figure 3.38 Simplified schematic of steam turbine propulsion system with reheat 138 Figure 3.39 Simplified dual fuel propulsion plant overview 139 Figure 3.40 Otto cycle 139 Figure 3.41 Major components of a diesel-electric propulsion plant 140 Figure 3.42 Typical diesel-electric drive train efficiency 140 Figure 3.43 Simplified slow speed diesel propulsion plant 141 Figure 3.44 Simplified representative ME-GI propulsion plant (with high pressure pump/vaporiser) and DF auxiliary diesel generators 142 Figure 3.45 Combustion process in gas injection diesel engine 142 Figure 4.1 Liquid and vapour manifold arrangement on a fully-pressurised gas carrier 145 Figure 4.2 Piping arrangement on the tank dome adjacent to a deck tank on a fully-refrigerated LPG carrier 145 Figure 4.3 Cargo manifold reducers 147 Figure 4.4 Cargo manifold with reducer fitted 147 Figure 4.5 Orientation of presentation flange bolt holes 148 Figure 4.6 Pneumatic and manually operated valves on a fully-refrigerated LPG carrier 149 Figure 4.7 Piping system on a Type C cargo tank dome, including the valve arrangement. This particular drawing is typical for a semi-pressurised ship 150 Figure 4.8 Example placement of manifold strainer 152 Figure 4.9 Hydrates in a manifold strainer from a cargo of butane 153 Figure 4.10 Cargo manifold strainer on an LNG carrier 153 Figure 4.11 ESDs on semi-refrigerated LPG carriers 154 Figure 4.12 Initiation of ESD2 156 Figure 4.13 ESD2 closes ERS valves and uncouples MLAs 156 Figure 4.14 MLAs disconnect and retract with minimum spillage 156 Figure 4.15 ESD systems 157 Figure 4.16 Pilot operated relief valve, diaphragm type (interbarrier space) 158 Figure 4.17 Maximum allowable relief valve setting (MARVS) of 18 kg/cm2 on a Type C tank 159 Figure 4.18a Pilot operated pressure relief valve (piston type) 160 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 xx Figure 4.18b Pilot operated pressure relief valve (diaphragm type) 161 Figure 4.18c Working principles of a pilot operated pressure relief valve (piston type) 161 Figure 4.19 Conventional spring loaded pressure relief valve 162 Figure 4.20 Characteristics of main types of pressure relief valves 163 Figure 4.21 Cargo pump dome on an LPG carrier 164 Figure 4.22 Pump performance curves – a deepwell pump 165 Figure 4.23 Centrifugal pumps in parallel – combined characteristics 166 Figure 4.24 Centrifugal pumps in series – combined characteristics 166 Figure 4.25 Typical deepwell pump 167 Figure 4.26 Deepwell pump assembly being removed during refit 167 Figure 4.27 Typical LNG submerged motor pump assembly 168 Figure 4.28 Submerged motor pump being removed during refit of an ammonia carrier 169 Figure 4.29 Horizontal booster pump 169 Figure 4.30 Horizontal booster pump 169 Figure 4.31 Fitting of an emergency cargo pump on an LNG carrier 171 Figure 4.32 Type C deck tank on a fully-refrigerated LPG carrier 172 Figure 4.33 Cargo heater on a fully-pressurised LPG carrier 173 Figure 4.34 Cargo heater on a fully-refrigerated LPG carrier 173 Figure 4.35 Direct cargo heater 175 Figure 4.36 An indirect cargo heater using an intermediate fluid 176 Figure 4.37 Steam heated cargo vaporiser 177 Figure 4.38 Typical LNG vaporiser 178 Figure 4.39 LNG regasification system – closed loop with steam heating 179 Figure 4.40 LNG regasification system – combined open/closed loop with seawater and steam heating 179 Figure 4.41 LNG regasification system – closed loop with steam heating and intermediate water/glycol loop 180 Figure 4.42 LNG regasification system – open loop with seawater heating and intermediate propane loop 180 Figure 4.43 LPG cargo compressor and motor arrangement 181 Figure 4.44 LPG cargo compressor 181 Figure 4.45 Burckhardt oil-free compressor 182 Figure 4.46 Typical rotor for an oil-free screw compressor 184 Figure 4.47 Typical purge gas condenser system 185 Figure 4.48 Gas heater (with steam as heating medium) 186 Figure 4.49 2-stage LD compressor: equipped with precoolers to achieve full pressure under conditions of warm BOG 186 Figure 4.50 4-stage LD compressor: typical DFDE propulsion plant 187 Figure 4.51 HD compressor 188 Figure 4.52 LD compressors 188 Figure 4.53 LNG gas combustion unit 188 Figure 4.54 Process flow diagram for the Hamworthy MK I reliquefaction system 190 Figure 4.55 Process flow diagram for the Cryostar EcoRel reliquefaction system 191 Figure 4.56 Inert gas generator 192 Figure 4.57 Flow diagram of an inert gas generator 194 LGHP4 Figures and Tables xxi Figure 4.58 Saturated water content of inert gas 195 Figure 4.59 Drying inert gas (adsorption drier) 195 Figure 4.60 The membrane system for producing nitrogen (N2) 196 Figure 4.61 Nitrogen system, filling air compressors and storage tank 196 Figure 4.62 The pressure swing adsorption process for producing nitrogen (N2) 197 Figure 4.63a Float level gauge 200 Figure 4.63b Float level gauge 201 Figure 4.64 Diagram of a float gauge installed in a tubular well 201 Figure 4.65 Float gauge on an LNG carrier with MK III containment system 201 Figure 4.66a Radar tank level gauge 201 Figure 4.66b Radar tank level gauge 202 Figure 4.67 Slip-tube 203 Figure 4.68 Direct insertion magnetic gauge 204 Figure 4.69 Externally mounted 204 Figure 4.70 High level alarms on a fully-pressurised LPG carrier 205 Figure 5.1 Cargo transfer piping arrangement from jetty to LNGC 215 Figure 5.2 Marine loading arms 217 Figure 5.3 LPG marine loading arm 218 Figure 5.4 LNG marine loading arms 218 Figure 5.5 Representative marine loading arm operating envelopes 219 Figure 5.6 Typical gas carrier marine loading arm 219 Figure 5.7 MLA presentation flange 220 Figure 5.8a Quick connect/disconnect coupling (QC/DC) – Hydraulic 221 Figure 5.8b QC/DC plan view diagram 221 Figure 5.9 Powered emergency release coupling (ERC) 222 Figure 5.10 Emergency release coupling (dry-break coupling) 222 Figure 5.11 BOG compressor station at an LNG loading terminal 223 Figure 5.12 A typical shore-based blower, used for removing LPG vapours from a ship's tanks and returning them to shore 224 Figure 5.13 LPG loading terminal arrangement. This is a typical arrangement, with vapour return capability using a shore based in-line blower 224 Figure 5.14 Insulation flange arrangement and components 225 Figure 5.15 LNG storage tanks 226 Figure 5.16 Fully-pressurised storage in a horizontal cylindrical tank above ground 228 Figure 5.17 Fully-pressurised storage in a mounded horizontal cylindrical tank 229 Figure 5.18 Mined rock cavern suitable for LPG storage 230 Figure 5.19 Salt cavern LPG storage 231 Figure 5.20 Semi-pressurised storage in spheres 232 Figure 5.21 Semi-pressurised storage tank 232 Figure 5.22 Typical single wall tank – LPG storage 234 Figure 5.23 Double wall LNG tank – concrete bund 235 Figure 5.24 LNG tank – double wall 236 Figure 5.25 Double wall tank for LNG 236 Figure 5.26 Double containment steel tank for LPG 237 Figure 5.27 LPG tank with earth berm 238 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 xxii Figure 5.28 In-ground tank for LNG 238 Figure 5.29 In-ground tank for LNG 239 Figure 5.30 Pneumatically controlled valves in shore line 241 Figure 5.31 Shore pipeline to semi-pressurised sphere tanks 242 Figure 5.32 Aerial view showing expansion loops on the jetty 244 Figure 5.33 Bursting disk and surge drum arrangement for surge pressure relief 245 Figure 5.34 Simplified pipeline arrangement within an LPG terminal 248 Figure 5.35 Simplified arrangement of an LNG receiving terminal 250 Figure 5.36 A positive displacement meter 252 Figure 5.37 A turbine meter 253 Figure 5.38 A prover loop 254 Figure 5.39 Escravos LPG FSO with export LPG carrier Berge Spirit in tandem 256 Figure 5.40 Sanha LPG FPSO 256 Figure 5.41 LNG FPSO concept diagram 257 Figure 5.42 Large scale FLNG facility 258 Figure 5.43 The Shell Prelude FLNG facility 259 Figure 5.44 Typical system boundaries for FLNG 264 Figure 5.45 LNG carrier discharging to an RV 266 Figure 5.46 LNG regasification process for an open-loop/closed-loop solution with propane as the intermediary heat transfer medium 266 Figure 5.47 The internal turret mooring system 270 Figure 5.48 An external turret mooring system 271 Figure 5.49 Spread mooring systems 271 Figure 5.50 Tower mooring systems 271 Figure 5.51 Articulated tandem offloading 273 Figure 6.1 Cargo manifold on an LNG carrier 281 Figure 6.2 Telescopic shore gangway landed on an LNGC's deck 282 Figure 6.3 Ship/shore link (SSL) storage bins on jetty (Left: fibre optic, middle: pneumatic and right: electric) 283 Figure 6.4 Ship/shore compatibility process should consider all items directly relevant to the gas carrier berthed alongside, such as whether the ship’s refrigeration plant seawater cooling outlet would be obstructed by the terminal fenders 285 Figure 6.5 Mooring tension monitoring display 287 Figure 6.6 When a ship is alongside, no cargo operations or inerting should commence until the ISGOTT (Reference 2.4) ship/shore safety checklist has been completed by the ship and the terminal and it has been confirmed that operations can be safely carried out. It is normal practice that this checklist is presented to the ship by the terminal 291 Figure 6.7 OOW communicating with the deck watch 293 Figure 6.8 LNG carrier forward mooring area 294 Figure 6.9 Example connection and disconnection of cargo hoses and MLAs 295 Figure 6.10 Smaller gas carriers will often have to use their own gangway in port. It will usually be positioned as close to the accommodation as possible, with a strong safety net beneath, and be properly illuminated at night 297 Figure 6.11 Telescopic gangway on LNGC, viewed from the jetty 298 Figure 6.12 Dry powder monitors positioned and ready for immediate use 300 LGHP4 Figures and Tables xxiii Figure 6.13 Deck water spray system on an LNG carrier 301 Figure 7.1 LNG sequence of operations 309 Figure 7.2 LPG sequence of operations 310 Figure 7.3 Air drying – operational cycle 312 Figure 7.4 Access to hold spaces on a fully-refrigerated LPG carrier (Note: The hold spaces on LPG carriers fitted with independent Type A tanks must be inerted when carrying flammable cargoes, as is required by the IGC Code) 313 Figure 7.5 Inerting cargo tanks by the displacement method 314 Figure 7.6 Air/inert gas interface 315 Figure 7.7 All tanks being inerted in parallel 316 Figure 7.8 Displacement in series (‘cascading’), used in conjunction with cargo scavenging 316 Figure 7.9 Inerting by continuous dilution under vacuum 317 Figure 7.10 Forward vent mast on a fully-refrigerated LPG carrier 319 Figure 7.11 Gassing-up LPG cargo tanks using liquid from shore 322 Figure 7.12 Gassing-up LPG cargo tanks using vapour from shore 326 Figure 7.13 LPG cargo tank cool-down using liquid from shore: vapour returned to shore 328 Figure 7.14a Spray piping connections on a Moss tank dome 330 Figure 7.14b Spray piping in tower in a Moss tank dome 330 Figure 7.15 Spray rails on a membrane vessel 330 Figure 7.16 Gas carriers should calculate the trim and stability (SF, BM & GM) for each stage of the cargo operation 333 Figure 7.17 Sloshing action within a membrane tank 333 Figure 7.18 Loading with vapour return 336 Figure 7.19 Loading without vapour return 337 Figure 7.20 Type C tank that is operated between 0°C and 45°C 342 Figure 7.21 LNG carrier on loaded voyage 345 Figure 7.22 Cargo refrigeration at sea 347 Figure 7.23 BOG compressor 349 Figure 7.24 Precooler and cold box 349 Figure 7.25 BOG compressor 349 Figure 7.26 Cold box 350 Figure 7.27 Compander unit (with electric motor drives) 350 Figure 7.28 LNG cargo BOG vapour header 351 Figure 7.29 Forcing vaporiser 352 Figure 7.30 Centrifugal cargo pumps should always be started against a closed or partially open valve 353 Figure 7.31 Combined ship and shore cargo pumping characteristics – single pump 354 Figure 7.32 Illustrations of static head and friction head 355 Figure 7.33 Combined ship and shore cargo pumping characteristics – parallel pumps 355 Figure 7.34 Pipeline diagram of a cargo booster pump and heater 358 Figure 7.35 Discharge without vapour return (Vapour returned to the cargo tank during discharge from the cargo vaporiser) 359 Figure 7.36 Discharge with vapour return (Vapour returned to the cargo tank during discharge from the shore via the ship’s vapour return line) 360 Figure 7.37 Excess cargo vapour from a cargo tank, passing via the tank’s vapour line to the ship’s cargo compressor, while discharging cargo on a semi-refrigerated LPG carrier 361 Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 xxiv Figure 7.38 Q-Flex LNG carrier fitted with LNG reliquefaction plant and GCU 365 Figure 7.39 Removal of cargo liquid residue by pressurisation in a Type C tank 367 Figure 7.40 Inerting of cargo tanks to remove cargo vapour 369 Figure 7.41 Aeration of cargo tanks 370 Figure 7.42 Removal of residual liquid in an LNG carrier’s tank prior to gas-freeing 374 Figure 7.43 Aerating of cargo tanks with dry air, venting inert gas 376 Figure 7.44 LNG ship to ship transfer 377 Figure 8.1 Weight in air conversion 382 Figure 8.2 Loading terminal general arrangement 387 Figure 8.3 Sampling presentation connection arrangement showing top/middle/bottom sampling connections (Note that the second valve is not shown) 390 Figure 8.4 Release of a small amount of cargo vapour while creating an ullage in a liquid sample container 390 Figure 8.5 Semi-refrigerated LPG carrier closed loop sampling connection 391 Figure 8.6 Fully-refrigerated LPG carrier closed loop sampling connection 391 Figure 8.7 Semi-refrigerated cargo system showing alternative sampling connections 392 Figure 8.8 Cargo sampling point 393 Figure 8.9 Cargo calculations – correction for trim 397 Figure 8.10 Effect of vessel trim on tank levels 397 Figure 8.11 Cargo calculations – correction for list (As viewed from astern. Note the centreline bulkhead valve is closed) 398 Figure 8.12 Custody transfer measurement system (CTMS) 405 Figure 8.13 Flow diagram for calculating the energy of LNG transferred 409 Figure 8.14 Example of a certificate of discharge from custody transfer measurement system (CTMS) 412 Figure 8.15 Example of a certificate of analysis 413 Figure 8.16 Example of the energy calculation of LNG transferred at a discharge port on the basis of the certificate of discharge 414 Figure 9.1 On LNG ships, a water curtain is fitted to provide a warming flow of water down the ship’s side adjacent to the cargo manifold. This is to limit the possibility of any brittle fracture in the event of any spillage of LNG 427 Figure 9.2 Pool fire configurations 428 Figure 9.3a Open the airway with a head tilt-chin lift manoeuvre 436 Figure 9.3b Look, listen and feel for signs of breathing. Where there are no signs of meaningful breathing – chest compressions will normally need to be started 436 Figure 9.4 Placing a casualty in the recovery position 437 Figure 9.5 High sitting up position for a casualty 438 Figure 9.6 Emergency decontamination shower 442 Figure 9.7 LNG STS 447 Figure 9.8 Deck spray line 452 Figure 9.9 Deck and accommodation deluge systems 452 Figure 9.10 Dry powder hose and gun 454 Figure 9.11 The Swiss Cheese Model, including progression of a process safety incident 458 Figure 9.12 The ALARP triangle 461 Figure 9.13 A toolbox talk briefs everyone on the work before the work is commenced 471 Figure 9.14 Example of an Enclosed Space Entry Permit (IMO) 475 LGHP4 Figures and Tables xxv Figure 9.15 The effectiveness of any isolation will usually need be confirmed prior to issuing the permit 476 Figure 9.16 A safety induction, including details of muster stations and roles in the event of an emergency, will be conducted as soon as possible after joining 482 Figure 9.17 Representative air flow over an accommodation block 489 Figure 9.18 EEBD set that will provide an air supply for 15 minutes 490 Figure 9.19 Self-contained breathing apparatus (SCBA) 490 Figure 9.20 Crew member wearing a splash suit and SCBA 491 Figure 9.21 Respirator mask (gas mask) fitted with an NH3 cartridge. These cartridges are colour coded to help you select the right one. Green is the cartridge colour code for ammonia/NH3 492 Figure 9.22 General environmental challenges for ships 495 Table No. Title Table 1.1 Atmospheric boiling point of certain liquefied gases 3 Table 2.1 Common elements 20 Table 2.2 IUPAC names and synonyms 27 Table 2.3 Reactive properties of liquefied gas cargoes with construction materials 31 Table 2.4 Chemical incompatibilities of liquefied gases 32 Table 2.5 Reactive properties of liquefied gas cargoes 33 Table 2.6 Ignition properties for liquefied gases 41 Table 2.7 Flammability range in air and oxygen for some liquefied gases 44 Table 2.8 Typical compositions of inert gas produced on board gas carriers 45 Table 2.9 Conversion factors for units of pressure 54 Table 2.10 Physical properties of gases 56 Table 2.11 Viscosity comparison of liquid cargoes 57 Table 2.12 Raoult’s Law 63 Table 2.13 Calculation for molecular mass of a natural gas mixture 64 Table 3.1 Typical insulation material conductivities at 20°C 114 Table 3.2 Main cargo containment systems comparison 117 Table 3.3 IGC Code requirements for secondary barriers in relation to cargo containment tank types 117 Table 3.4 General propulsion plant thermal efficiencies 136 Table 4.1 Classification of explosion proof equipment 199 Table 6.1 Emergencies that may initiate the ESD 303 Table 6.2 Actions that are usually initiated by the ESD 303 Table 8.1 Extract based on ASTM D1250-08 Density/ Weight/ Volume Intraconversion Part 3 ‘Conversions for Absolute Density at 15 degrees C’ (This is similar to the old ASTM Table 56 1980) 385 Table 9.1 Toxicity classifications 431 Table 9.2 Main liquefied gases, including their flammable and toxic hazards 433 Table 9.3 Health data – cargo inhibitors 434 Table 9.4 Health data – liquids 440 Table 9.5 Enclosed spaces on gas carriers 484 LGHP4 CHAPTER 3 – Liquefied Gas Carrier Types 117 Containment System Type A PrismaticType B Prismatic (SPB) Type B Spherical (Moss) Type CMembrane see Figure 3.16see Figure 3.19see Figure 3.20see Figure 3.24see Figure 3.27 Characterstics Benefits• Very robust • centreline bulkhead prevents sloshing • Very robust • centreline bulkhead prevents sloshing • Very robust • design prevents sloshing • partial secondary barrier • no partial filling limitations • no free surface effect • Single hull construction acceptable • very robust • centreline bulkhead prevents sloshing • no secondary barrier required • Extensive experience for LNG carriers • typically low boil-off rate (BOR) Limitations• Requires an independent secondary barrier • Limited number of shipyards licensed to fabricate • Less cargo capacity for same physical size of ship • height of tanks affects forward visibility from wheelhouse • Less attractive for very large capacities (cost/weight) • less space efficient • Limited impact resistance • full width tanks prone to sloshing • partial filling restrictions unless reinforcements applied Table 3.2 Main cargo containment systems comparison Cargo Temperature at Atmospheric Pressure -10°C and Above Below -10°C Down to -55°C Below -55°C Basic tank typeNo secondary barrier required Hull may act as secondary barrier Separate secondary barrier where required Integral Membrane Semi-membrane Independent: • Type A • Type B • Type C Tank type not normally allowed Complete secondary barrier Complete secondary barrier Complete secondary barrier Partial secondary barrier No secondary barrier required The full requirements are set out in the IGC Code, which should always be consulted in preference to this publication. For additional information, please refer to Chapter 4 of the IGC Code – Cargo Containment. Table 3.3 IGC Code requirements for secondary barriers in relation to cargo containment tank types Liquefied Gas Handling Principles on Ships and in Terminals LGHP4LGHP4 CHAPTER 3 – Liquefied Gas Carrier Types 118119 the whole tank volume at a defined angle of list. It may form part of the ship’s hull, which is the most commonly adopted design approach for this type of vessel, and it means that certain areas of the ship’s hull will be constructed of special steel capable of withstanding low temperatures. The alternative is to build a separate secondary barrier around each cargo tank. A secondary barrier, separate from the hull, is required by the IGC Code for Type A tanks designed to carry cargoes below minus 55°C (-55°C), such as ethane or LNG. The IGC Code stipulates that a secondary barrier must be able to contain tank leakage for a period of 15 days. The space between the cargo tank (sometimes referred to as the primary barrier) and the secondary barrier, ie the outer hull, is known as the hold space. When flammable cargoes are being carried these spaces are required by the IGC Code to be filled with inert gas. This is to prevent a flammable atmosphere being created in the event of primary barrier leakage. 3.8.1 Type A tanks Figure 3.16 View of a Type A tank as found on a fully-refrigerated LPG carrier Type A tanks are primarily constructed of flat surfaces. Under the IGC Code, the maximum allowable tank design pressure in the vapour space for this type of system is 0.7 bar. This means that cargoes will be carried in a fully-refrigerated condition, at or near atmospheric pressure (normally below 0.25 bar). A Type A tank is a self-supporting prismatic tank that requires conventional internal stiffening. In Figure 3.16 the tank is surrounded by a skin of foam insulation. The typical arrangement is shown in Figure 3.16, with the tank covered by a skin of foam insulation. In some simpler, less efficient arrangements, perlite insulation is used, filling the hold space completely. The material used for Type A and Type B tanks is the same. Type A tanks are not designed on the ‘leak before failure’ concept used for Type B tanks. Therefore, to ensure safety in the unlikely event of cargo tank leakage, a secondary containment system is required under the IGC Code. This secondary containment system is known as a secondary barrier and is a feature of all ships with Type A tanks that are capable of carrying cargoes below minus 10°C (-10°C). For a fully-refrigerated LPG carrier (which will not carry cargoes below minus 55°C (-55°C)) the secondary barrier is required by the IGC Code to be a complete barrier capable of containing Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 120 Figure 3.17 Prismatic Type A tank Courtesy of Dongsung FineTec Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 124 Figure 3.22 Moss (Type B) tank under construction and showing the central pipe tower arrangement A Type B tank does not need to be spherical. There are Type B tanks of a prismatic shape in LNG service (known as ‘SPB’ – self-supporting prismatic Type B). The prismatic Type B tank has the benefit of maximising ship hull volumetric efficiency and has the entire cargo tank placed beneath the main deck. Where the prismatic shape is used, the maximum design vapour space pressure is, as for Type A tanks, limited, under the IGC Code, to 0.7 bar. LGHP4 CHAPTER 3 – Liquefied Gas Carrier Types 125 3.8.3 Type C tanks (semi-refrigerated) Type C tanks are normally spherical or cylindrical pressure vessels with design pressures higher than 2 bar. The cylindrical vessels may be vertically or horizontally mounted. This type of containment system is always used for semi-refrigerated gas carriers. In the case of the semi-refrigerated ships, it can also be used for fully- refrigerated carriage provided appropriate low temperature steels are used in tank construction. Type C tanks are designed and built to conventional pressure vessel codes and, as a result, can be subjected to accurate stress analysis. Design stresses are kept low. No secondary barrier is required by the IGC Code for Type C tanks and the hold space can be filled with either inert gas or dry air. For a semi-refrigerated ship, the cargo tanks and associated equipment are designed for a working pressure of approximately 5 to 7 bar and a vacuum of 0.5 bar. Typically, the tank steels for the semi-refrigerated ships are capable of withstanding carriage temperatures as low as minus 104°C (-104°C), which is adequate for the range of LPG cargoes and is also suitable for ethylene and ethane. Figure 3.23 Type C tank (semi-refrigerated) Liquefied Gas Handling Principles on Ships and in Terminals LGHP4 126 3.8.4 Type C tanks (fully-pressurised) WBTWBT Figure 3.24 Type C tanks – fully-pressurised gas carrier In the case of a typical fully-pressurised ship (where the cargo is carried at ambient temperature), the tanks may be designed for a maximum working pressure of about 18 bar. Type C tanks, when fitted in a typical fully- pressurised gas carrier, make a comparatively poor utilisation of the hull volume. However, this can be improved by using intersecting pressure vessels or bi-lobe type tanks, which may be designed with a taper at the forward end of the ship. This is also a common arrangement in semi-pressurised ships, as shown in Section 3.8.3. Figure 3.25 Type C tanks mounted in a barge to be used in a floating LNG project 3.8.5 Membrane tanks Unlike self-supporting independent tanks, membrane tanks utilise the inner hull of the ship as the primary load bearing structure. The main safety features incorporated into the design of a membrane LNG carrier, to prevent the low-temperature cargo coming into contact with and damaging the ship’s steel structure, are the double barriers of the containment system itself. Each barrier consists of a thin membrane that is made of material able to withstand and absorb thermal contraction and is backed by a layer of insulation. The membrane is designed in such a way that thermal expansion or contraction is compensated for without over-stressing the membrane itself. The primary barrier (membrane of 0.7 to 1.5 mm thick) is the inner element that comes into contact with the cargo and is designed to contain that cargo. The distributions of the steel grades that are to form the inner hull are selected at the design stage by considering the worst possible environmental conditions and a full liquid cargo flooding of the primary space. The secondary barrier is designed to contain any envisaged leak of liquid cargo through the primary barrier for a period of 15 days, as prescribed by the IGC Code. During this time the temperature on the double hull must not drop to or below a level that could cause brittle fracture of the steels used in the hull construction.