Liquefied natural gas (LNG) exhibits significant environmental advantages. However, the hazards of LNG-fuelled ships need to be investigated in their early design stages, particularly with regard to accidental fuel leakage. In this study, a hypothetical oil tanker model was used with a fuel gas supply system installed on the main deck; the objective was to establish a critical zone for natural gas dispersion. A probabilistic approach was applied to determine credible scenarios, and leak size, location, and direction were considered as parameters along with environmental parameters such as wind direction and speed. Computational fluid dynamics was used to present the critical zone in terms of the contours of the natural gas concentration. The simulation results indicated that the leak size and wind speed significantly influence the size of the critical zone.

The growing demand for liquefied natural gas (LNG)-fueled ships necessitates the establishment of an LNG bunkering facility. Ship-to-ship (STS) is one of the most practical forms of LNG bunkering systems. Although there are benefits to the LNG bunkering of ships, risk and safety issues are a concern due to the volatile cargo. Ship collision could result in accidental LNG release. The purpose of this study was to build LNG leakage scenarios, establish critical zones based on gas concentrations, and estimate the temperature reduction in a bunkering ship’s structure resulting from the use of cryogenic fluid. The condition of a target ship’s structure, both intact and when damaged due to collision, was considered. Leak size, leak direction, leak position, release rate, and reservoir pressure were included as leak parameters, and environmental parameters, such as the wind direction, wind speed, and ambient temperature, were also included. The release duration was set based on the shutdown duration of the emergency shutdown valve (ESD). A total of 72 leakage scenarios were generated for the main CFD analysis. Convergence tests were conducted to determine the appropriate grid and iteration numbers for a computational fluid dynamics (CFD) simulation. The gas dispersion characteristics and the cryogenic flow impact on the LNG bunkering ship’s structure are discussed through a parametric study.

Liquefied natural gas (LNG)-fuelled ships provide a good option for the air pollution problem. However, safety and reliability have to investigate in the design process. A hypothetical LNG-fuelled ship model is used as the target ship. The gas explosion parameters include the gas cloud volume for determining the gas cloud size and the gas cloud centre of gravity for specifying the gas cloud position and ignition point. Previously reported gas dispersion results are utilised to establish these parameters regarding both frequency and physical data. The Latin hypercube sampling is used to generate 50 gas explosion scenarios. The blast overpressure of vapour cloud explosion (VCE) is simulated by the ExSim computational fluid dynamics (CFD) code, and software validation is provided. Finally, the gas explosion frequency can be compiled with blast overpressure to produce the exceedance frequency diagram. Subsequently, this diagram can be used to determine the design accidental loads under VCE.