Effect of geometry characteristic of oil tanker’s t stiffener profile towards ultimate strength under axial compressive load

Future LNG field development project in Indonesia will be dominated by local buyer of the country, so that additional LNG tankers are needed for the domestic market in the future. Theoretically Dual Fuel Steam Mechanical (DFSM) or steam propulsion system has a low thermal efficiency, but more reliable than the DFDE propulsion system. On the other hand Dual Fuel Diesel Electric (DFDE) propulsion system has shortcomings in the technology that is the presence of methane slip potential for global warming with a Global Warming Potential (GWP) of 20-25 times greater than CO2 over a period of 100 years or 20 times at intervals of 20 years, thus actually reducing the achievement of the energy efficiency of the propulsion system. In this paper, two LNG ship propulsion system that is DFSM and DFDE which is currently the most widely used by operators in Indonesia were compared technically and economically. Technically, the IMO guidelines on Energy Efficiency Design Index (EEDI) and the Energy Efficiency Operational Index (EEOI) were used as a means of comparison, while from the economical side life cycle cost (LCC) CAPEX and OPEX cost-based of the ships were analysed. Based on the technical evaluation using the guidelines EEDI and EEOI of LNG tankers by considering the slip of methane in the DFDE propulsion system, showed that the value of the achievement of EEDI and EEOI the DFSM propulsion system lower (more efficient) than the value of the achievement of the DFDE propulsion system and economics evaluation based on the LNG tankers cost life cycle (LCC) for 20 years by considering the risks of loss and penalty carriage of LNG that may occur due to the failure of the propulsion system and the BOG system, shows the DFSM propulsion system more efficient than DFDE system.