A study on availability and safety of new propulsion systems for LNG carriers

This study investigated the availability and safety concerns of the conventional and prospective propulsion systems for LNG carriers:
• dual-fuel steam turbine mechanical (DFSM) propulsion,
• dual-fuel diesel electric (DFDE) propulsion,
• dual-fuel gas turbine electric (DFGE) propulsion,
• dual-fuel diesel mechanical (DFDM) propulsion, and
• diesel mechanical propulsion with reliquefaction (SFDM+R).The two prospective candidates, the DFDM and DFGE, exhibited the availabilities of design and emergency propulsion loads as high as the newly adopted DFDE and SFDM+R, while the DFSM demonstrated the highest. All the propulsion systems achieved a satisfactory level of the availability for the BOG utilization. The newly introduced dual-fuel systems of DFDE, DFDM, and DFGE accompanied new hazards due to their need for pressurized fuel gas supply. The failure modes caused by these hazards were identified, and feasible safe guards were suggested. The hazards of fire and explosion stemming from flammable gas leak were considered to be acceptably mitigated by the safety requirements from the current industrial standards and classification society.