For fully pressurized LPG carrier
Full pressurized LPG carrier cargo handling system is designed for loading, transporting, and unloading the liquefied petroleum gases (cargoes) at ambient temperature. They are fitted with Type 'C' tanks fabricated with carbon-manganese steel having a typical design pressure of about 18 barg. Thermal insulation and reliquefaction plant is not necessary for these ships. Cargo loading to the cargo tanks is carried out by the loading facilities of shore bases, and unloading by deep well pumps or cargo compressor.
Cargoes to be handled: Propylene、Propane、Butane、Butane-Propane mixtures、Butadiene、Vinyl chloride monomer(VCM)、Butylene、Isoprene and so on.
For semi-pressurized LPG/Ethylene carrier
Semi-pressurized gas carrier cargo handling system is similar to fully pressurized carrier in that they both have type 'C' tanks. Compared to fully pressurized ships, it is possible to reduce tank thickness due to the reduced pressure by cool cargo loaded and/or refrigeration plant and tank insulation. The tanks are usually made from low temperature steels to provide for carriage temperatures of -48°C which temperature is suitable for most LPG and chemical gas cargoes. Alternatively, they can be made from special alloyed steels or aluminum to allow for the carriage of ethylene at -104°C. The ship's cargo handling system is suitable for loading,
Cargoes to be handled: Ethylene、Ethane、NH3、LPG、Vinyl chloride and so on.
For small scale LNG carrier
Small scale LNG carriers usually have type 'C' tanks with insulation. The tanks are made from low temperature steels to provide for carriage LNG of -162°C. Small scale LNG carriers have flexible cargo handling system. There are several methods to handle boil-off gas.
● Accept a pressure increase during voyage within pressure limit (pressure build-up)
● Burning the vapour gas when emergency
● Utilize the boil-off gas as fuel
● Boil-off gas reliquefaction
Cargoes to be handled:
Ethylene, LPG, VCM and other cargoes for multipurpose gas carriers