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CHAPTER 6 THE SHIP/SHORE INTERFACE 137



6.1                     Supervision and control.......................................................................... 137

6.2                     Design considerations............................................................................. 139

6.2.1            The terminal..................................................................................... 139

6.2.2            The ship............................................................................................ 139

6.3                     Communications..................................................................................... 140

6.3.1            Prior to charter................................................................................. 140

6.3.2            Prior to arrival................................................................................... 140

6.3.3            Alongside the jetty............................................................................ 141

6.4                     Discussions prior to cargo transfer......................................................... 141


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6.5                     Ship/Shore safety check list................................................................... 142

6.6                     Operational considerations..................................................................... 143

6.6.1            Berthing and mooring....................................................................... 143

6.6.2            Connection and disconnection of cargo hoses and hard arms....... 144

6.6.3            Cargo tank atmospheres................................................................. 144

6.6.4            Cargo handling procedures.............................................................. 145

6.6.5            Cargo surveyors.............................................................................. 145

6.6.6            Gangways and ship security............................................................ 146

6.6.7            Bunkering......................................................................................... 146

6.6.8            Work permits.................................................................................... 147

6.7                     Fire-fighting and safety........................................................................... 147

6.8                     Linked Emergency shut-down systems................................................. 148

6.9                     Terminal booklet—Information and Regulation...................................... 149

6.10                   Training................................................................................................... 150


CHAPTER 7    CARGO HANDLING OPERATIONS                                               151

7.1                     Sequence of operations.......................................................................... 151

7.2                     Tank inspection, drying and inerting....................................................... 152

7.2.1            Tank inspection................................................................................ 152

7.2.2            Drying............................................................................................... 152

7.2.3            Inerting—before loading................................................................... 153

7.3                     Gassing-up.............................................................................................. 156

7.3.1            Gassing-up at sea using liquid from deck storage tanks................. 157

7.3.2            Gassing-up alongside....................................................................... 157

7.4                     Cool-down............................................................................................... 159

7.5                     Loading.................................................................................................... 161

7.5.1     Loading—preliminary procedures........................................................... 161

7.5.2     Control of vapours during loading........................................................... 163

7.5.3     Loading—early stages............................................................................ 164

7.5.4     Bulk loading............................................................................................. 166

7.5.5     Cargo tank loading limits......................................................................... 167

7.6                     The loaded voyage................................................................................. 170

7.6.1            Operation of the reliquefaction plant................................................ 172

7.6.2            LNG boil-off as fuel.......................................................................... 173

7.7                     Discharging............................................................................................. 173

7.7.1            Discharge by pressurising the vapour space................................... 174

7.7.2            Discharge by pumps........................................................................ 174

7.7.3            Discharge via booster pump and cargo heater............................... 178

7.7.4            Draining tanks and pipelines............................................................ 179

7.8                     The ballast voyage.................................................................................. 179

7.9                     Changing cargo (and preparation for drydock)...................................... 180

7.9.1            Removal of remaining liquid............................................................ 181

7.9.2            Warming-up..................................................................................... 182

7.9.3            Inerting—after discharge................................................................. 183

7.9.4            Aerating............................................................................................ 184

7.9.5            Ammonia—special procedures....................................................... 185

7.10                   Ship-to-ship transfer................................................................................ 186

7.11                   Conclusion.............................................................................................. 186

CHAPTER 8    CARGO MEASUREMENT AND CALCULATION                         187

8.1                     Principles for liquefied gases.................................................................. 187

8.1.1            Special practices for gas cargoes................................................... 187

8.1.2            General. Density in air and density in vacuum................................ 188


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8.1.3            True density (apparent density)....................................................... 189

8.1.4            Relative density (specific gravity)................................................... 189

8.1.5            Apparent relative density (apparent specific gravity)...................... 190

8.1.6            LNG quantification........................................................................... 194

8.1.7            Shore measurement versus ship measurement............................. 191

8.2                     Measurement of cargo tank volumes.................................................... 192

8.2.1            Trim correction................................................................................ 192

8.2.2            List correction.................................................................................. 193

8.2.3            Tape correction................................................................................ 193

8.2.4            Float correction................................................................................ 194

8.2.5            Tank shell contraction and expansion............................................. 194

8.3                     Measurement of density......................................................................... 194

8.3.1            Density measurement methods...................................................... 194

8.3.2            Units of density................................................................................ 195

8.4                     Ship/shore calculation procedures......................................................... 195

8.4.1            Outline of weight-in-air calculation.................................................. 195

8.4.2            Procedures using standard temperature......................................... 196

8.4.3            Procedure using dynamic flow measurement................................ 197

8.5                     Example — cargo calculation................................................................ 198

8.6                     Other calculation procedures and measurement units.......................... 199

8.7                     Cargo documentation............................................................................. 199


CHAPTER 9    PERSONAL HEALTH AND SAFETY                                             202

9.1                     Cargo hazards........................................................................................ 202

9.2                     Flammability........................................................................................... 205

9.2.1            Operational aspects......................................................................... 205

9.2.2            Emergency aspects......................................................................... 205

9.3                     Air deficiency.......................................................................................... 205

9.3.1            Toxicity............................................................................................ 205

9.3.2            Asphyxia (suffocation)..................................................................... 207

9.3.3            Medical treatment............................................................................ 208

9.3.4            Oxygen therapy............................................................................... 209

9.4                     Frostbite.................................................................................................. 210

9.5                     Chemical burns....................................................................................... 211

9.6                     Transport to hospital............................................................................... 212

9.7                     Hazardous atmospheres......................................................................... 212

9.7.1     The need for gas testing......................................................................... 212

9.7.2     Oxygen analysers................................................................................... 213

9.7.3     Combustible gas indicators..................................................................... 215

9.7.4     Toxicity detectors................................................................................... 217

9.8                     Entry into enclosed spaces..................................................................... 218

9.8.1            Precautions for tank entry............................................................... 218

9.8.2            Procedures...................................................................................... 219

9.8.3            Rescue from enclosed spaces........................................................ 220

9.9                     Personal protection................................................................................. 220

9.9.1     Breathing apparatus................................................................................ 220

9.9.2     Protective clothing.................................................................................. 222

CHAPTER10   EMERGENCY PROCEDURES                                                        223

10.1                   The principal hazards.............................................................................. 223

10.1.1          Flammability.................................................................................... 223

10.1.2          Vaporisation of spilled liquid............................................................. 224

10.1.3          Toxicity and toxic products of combustion...................................... 230

10.1.4          Frostbite........................................................................................... 224

10.1.5          Brittle fracture.................................................................................. 224


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10.2                   Liquefied gas fires................................................................................... 224

10.2.1          Fire detection................................................................................... 225

10.2.2          Jet fires............................................................................................ 225

10.2.3          Liquid (pool) fires.............................................................................. 225

10.2.4          Fires in compressor rooms.............................................................. 226

10.3                   Liquefied gas fire-fighting........................................................................ 227

10.3.1          Alarm procedures............................................................................ 227

10.3.2          Extinguishing mediums.................................................................... 227

10.3.3          Training............................................................................................ 229

10.4                   Emergency procedures.......................................................................... 229

10.4.1          The emergency plan........................................................................ 229

10.4.2          Ship emergency procedures........................................................... 230

10.4.3          Terminal emergency procedures.................................................... 231

10.5                   Emergency release and emergency shut-down.................................... 232

10.5.1          Emergency shut-down (ESD) —ship/shore links............................ 232

10.5.2          Emergency release systems (ERS)................................................ 232

10.6                   Removal of ship from berth.................................................................... 233

10.7                   Ship-to-ship cargo transfer..................................................................... 233

APPENDIX 1    References............................................................................................. 234

APPENDIX 2    Liquefied and Chemical Gases Covered by the IGC Code .................. 237

APPENDIX 3    Ship/Shore Safety Check List................................................................ 239

INDEX              ................................................................................................................ 260




Figures and Tables

Inside front and back covers — LPG and LNG carriers (to scale)

Figure No. Title

1.1                Constituents of natural gas

1.2                Typical flow diagram for LNG liquefaction

1.3                Typical oil/gas flow diagram

1.4                Typical flow diagram — production of chemical gas

2.1                Molecular structure of some saturated hydrocarbons

2.2                Molecular structure of some unsaturated hydrocarbons

2.3                Molecular structure of some chemical gases

2.4                Solubility of water in butadiene

2.5                The polymerisation of vinyl chloride
2.5(a)            Inhibitor information form

2.6                Temperature/heat diagram for varying states of matter

2.7                Characteristics of methane

2.8                Simple refrigeration — evaporation/condensation cycle
2.9(a)            Boyle's Law for gases (constant temperature)
2.9(b)            Charles' Law for gases (constant pressure)
2.9(c)            Pressure Law for gases (constant volume)

2.10              Relationship between adiabatic and isothermal compression

2.11              Barometric method for measuring saturated vapour pressure

2.12              Characteristics of propane

2.13              Pressure/temperature relationship for hydrocarbon gases

2.14              Pressure/temperature relationship for chemical gases

2.15              Equilibrium diagram for propane/butane mixtures

2.16              Mollier diagram for propane

2.17              Flammable range for propane

2.18              Flammable vapour zones — a liquefied gas spill

2.19              Flammable limits of gas mixtures in air and nitrogen

3.1                Prismatic self-supporting Type 'A' tank — fully refrigerated LPG carrier

3.2(a)            Self-supporting spherical Type 'B' tank

3.2(b)            Self-supporting prismatic Type 'B' tank

3.3                Type 'C' tanks — fully pressurised gas carrier

3.4                Type 'C' tanks — semi-pressurised gas carrier with bi-lobe tanks

3.5(a)            Gaz Transport membrane containment system — larger LNG carriers

3.5(b)            Construction of the Gaz Transport membrane system

3.6(a)            Technigaz membrane containment system — larger LNG carriers

3.6(b)            Construction of the Technigaz membrane — Mark III

3.7                Compressor room/electric motor room on a gas carrier

4.1                Cargo tank dome piping arrangement — Type 'C' tank

4.2                Pilot-operated relief valve

4.3                Pump performance curves — a deepwell pump

4.4                Centrifugal pumps in parallel — combined characteristics


Figure No. Title

4.5                Centrifugal pumps in series — combined characteristics

4.6                Typical deepwell pump

4.7(a)           Submerged motor pump for LPG

4.7(b)           Typical LNG submerged motor pump assembly

4.8                Vertical booster pump

4.9                Horizontal booster pump

4.10              Cargo heater

4.10(a)         Examples of indirect cooling cycles

4.11 (a)        Single-stage direct reliquefaction cycle

4.11(b)         Mollier diagram — single-stage direct reliquefaction cycle

4.12(a)         Two-stage direct reliquefaction cycle with inter-stage cooling

4.12(b)         Mollier diagram — two-stage direct reliquefaction cycle

4.13              Simplified cascade reliquefaction cycle

4.14              Sulzer oil-free compressor

4.15              Linde oil-free compressor

4.16              Typical rotor for an oil-free screw compressor

4.17              Typical purge gas condenser system

4.18              Flow diagram of an inert gas generator

4.19              Saturated water content of inert gas

4.20              Drying of inert gas

4.21              The membrane system for producing nitrogen

4.22              Intrinsic safety using Zener barriers

4.23              Float level gauge

4.24              Nitrogen bubbler level gauge

4.25              Differential pressure level gauge

4.26              Electrical capacitance level gauge

5.1                Typical gas carrier loading arm

5.2                Loading arm operating envelope

5.3                Quick connect/disconnect coupling

5.4                Powered emergency release coupling (PERC)

5.5                Roots blower typically used for vapour return

5.6                LPG loading terminal — vapour return using a shore based blower

5.7                Fully pressurised storage in horizontal cylindrical tanks

5.8                Rock cavern LPG storage

5.9                Salt cavern LPG storage

5.10              Semi-pressurised storage in spheres

5.11              Typical single-wall tank — LPG storage

5.12              LNG tank — concrete bund

5.13              LNG tank — double-wall

5.14              Double containment steel tank for LPG

5.15              LPG tank — earth berm

5.16              In-ground tank for LNG

5.17              Bursting disc for surge pressure relief

5.18              Flow diagram for reliquefaction within an LPG terminal

5.19              LNG receiving terminal — vaporiser/sendout

5.20              A positive displacement meter

5.21              A turbine meter

5.22              A prover loop

7.1                Air drying — operational cycle

7.2                Inerting cargo tanks by the displacement method

7.3(a)           Gassing-up cargo tanks using liquid from shore

7.3(b)           Gassing-up cargo tanks using vapour from shore

7.4                Cargo tank cool-down using liquid from shore

7.5                Loading with vapour return

7.6                Loading without vapour return

7.7                Cargo refrigeration at sea


Figure No. Title

7.8                Combined ship and shore pumping characteristics — single pump

7.9                Illustration of static head and friction head

7.10              Combined ship and shore pumping characteristics — parallel pumps

7.11              Discharge without vapour return

7.12              Discharge with vapour return

7.13              Pipeline diagram of a cargo booster pump and heater

7.14              Removal of cargo liquid residue by pressurisation

7.15              Inerting of cargo tanks

7.16              Aeration of cargo tanks

8.1                Cargo calculations — correction for trim

8.2                Cargo calculations — correction for list

9.1                Patient label

9.2(a)           Oxygen indicator — circuit diagram

9.2(b)           Oxygen indicator — plan view

9.2(c)           A polarographic cell

9.3(a)           Combustible gas indicator — circuit diagram

9.3(b)           Combustible gas indicator — calibration graph

9.4                Infrared gas analyser

9.5                Toxic gas indicator

9.6                Maritime safety card with safety check list

10.1              Pool fire configurations

Table No. Title

1.1                Physical properties of some liquefied gases

2.1                Synonyms for the main liquefied gases

2.2                Chemical properties of liquefied gases

2.3(a)           Chemical compatibilities of liquefied gases

2.3(b)           Previous cargo compatibilities of liquefied gases

2.4                Inert gas compositions

2.4(a)           Factors affecting lubrication

2.5                Physical properties of gases

2.6                Conversion factors for units of pressure

2.7                Calculation for molecular mass of a gas mixture

2.8                Ignition properties for liquefied gases

2.9                Flammability range in air and oxygen for some liquefied gases

3.1                Typical insulation materials

8.1                ASTM 56 (short table)

9.1                Health data — cargo vapour

9.1 (a)          Health data — cargo inhibitors

9.2                Additional health data — cargo liquid

9.3                Liquefied gas groups — for medical first aid purposes

9.4                Enclosed spaces on gas carriers









Definitions

The definitions listed in this section relate to their usage within this book. Other publications may use similar terms with different interpretations.

Absolute Pressure

The absolute pressure is the total of the gauge pressure plus the pressure of the surrounding atmosphere .

Absolute Temperature

The fundamental temperature scale with its zero at absolute zero and expressed in degrees Kelvin. One degree Kelvin is equal to one degree Celsius or one degree Centigrade. For the purpose of practical calculations in order to convert Celsius to Kelvin add 273. It is normal for the degree Kelvin to be abbreviated in mathematical formulae to 'K' with the degree symbol being omitted.

Absolute Zero

The temperature at which the volume of a gas theoretically becomes zero and all thermal motion ceases. It is generally accepted as being -273.16°C.

Activated Alumina

A desiccant (or drying) medium which operates by adsorption of water molecules (see 4.7.1).

Adiabatic

Describes an ideal process undergone by a gas in which no gain or loss of heat occurs (see 2.1).

Aerating

Aerating means the introduction of fresh air into a tank with the object of removing toxic, flammable and inert gases and increasing the oxygen content to 21 per cent by volume (see 7.9.4).

Airlock

A separation area used to maintain adjacent areas at a pressure differential. For example, the airlock to an electric motor room on a gas carrier is used to maintain pressure segregation between a gas-dangerous zone on the open deck and the gas-safe motor room which is pressurised.

Approved Equipment

Equipment of a design that has been type-tested and approved by an appropriate authority such as a governmental agency or classification society. Such an authority will have certified the particular equipment as safe for use in a specified hazardous atmosphere.


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