UNDER CONSTRUCTION
Trieste-based naval architecture firm Marine Engineering Company (MES) is continuing to build on its portfolio of gas carrier designs. Reflecting the current growing interest in extending the LNG supply chain at the small-scale downstream end, the new concepts include an LNG distribution tanker and an LNG bunkering vessel.
MES has designated the LNG distribution tanker as its Super Green Ship design. This refers to a 40,000 m³ semi-pressurised fully refrigerated (semi-ref) gas carrier with four twin-lobe IMO Type C cargo tanks manufactured from stainless steel. The tanks are insulated with polyurethane foam, are designed for a pressure of 6 barg and will provide a carriage temperature of -163°C.
“In our Super Green Ship design the Type C cargo tank dimensions have been optimised in relation to the hull form through the bilobe configuration in order to maximise cargo-carrying capacity within a given set of hull dimensions,” says Marco La Valle, MES General Manager.
“A particular characteristic we want to emphasise with this design is the ship’s shallow draft. This enables the Super Green Ship to navigate locations where the water depth is restricted, such as rivers, with the maximum possible amount of cargo. At the same time we have had to ensure that the chosen hull form offers the optimum in terms of the vessel’s hydrodynamic performance.”
MES has also used its gas carrier design expertise to ensure that the tank insulation and support system in the cargo hold space is configured to minimise heat inflow from the external environment to the LNG cargo. This helps ensure that boil-off gas (BOG) levels are kept as low as possible.
MES has verified the structural integrity of the Super Green Ship using finite element method (FEM) calculations. The verification work considered the vessel in all loading scenarios and encompassed the cargo tanks, the tank support and the surrounding hull structures. FEM calculations have also been utilised to carry out ship motion and structural analyses for the Super Green Ship under way states. Similar checks were made for fatigue issues around the girders and other reinforcements in the hull.
MES completed the design verification phase with ship fatigue analyses for all operating conditions, i.e., loading, discharge, laden voyage, ballast voyage, etc.