LPG & Ammonia cargo handling -Precautions on cargo operation
Carrying and handling liquefied gas cargo onboard poses significant potential hazards including risk of injury or death,threats to environment and each person working on a gas carrier and terminal ashore needs to understand the risks involved, obtain the necessary training and take all the needed precautions.
Prevention of Cargo Leaks
(1) The most important thing on board LPG & Ammonia carriers is to prevent leaks of cargo in the form of liquid or gas.
(2) Although the leak of cargo does not cause sea pollution like petroleum, it generates the danger of fire and explosion as it spreads to a large area as cargo evaporates producing a large amount of gas (260 times in the case of propane; and 230 times in the case of butane, 900 times in the case of ammonia).
(3) If a large amount of cargo is involved in the leak, it may cause such serious secondary accidents which are not confined to the vessel only but which may affect the environment as the brittle fracture by excessive cooling of the vessel hull, outflow of cargo, dispersion of gas, ignition and explosion.
Prevention of Damage to the Hull owing to Brittle Fracture
If the liquid cargo happens to leak, the vessel should prevent fire and damage to the vessel due to its low temperature. In order to protect the vessel hull from being damaged, it is necessary to evaporate the leaked liquid as soon as possible and also disperse such gas for the prevention of fire.
Fig: LPG carrier at sea
Cargo Transfer
Cargo transfer is performed not only in the form of liquid but also in the form of gas, and when vapors are transferred by opening a manifold gas valve where the vessel line and shore line are connected, crew members should be aware that this is also a form of cargo transfer.
Disposal of Boil-off Gas
Crew members should perform cargo handling operations taking into consideration the disposing method of BOG (boil-off gas) which is generated at all times in cargo tanks with liquid left over.
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