The objective of this paper is to examine the characteristics of leaked-gas dispersion in ship to ship LNG bunkering, thereby providing an insight towards determining the appropriate level of safety zones in which the potential hazards pertinent to LNG bunkering are required to be minimized. For this purpose, parametric studies are undertaken in various operational and environmental conditions, with varying geometry of the bunkering ship, gas leak rate, wind speed and wind direction. The study applies computational fluid dynamics (CFD) simulations for case-specific scenarios where a hypothetical LNG bunkering ship with a capacity of 5,100 m 3 in tank space is considered to refuel two typical types of large-ocean going vessels: an 18,000 TEU containership and a 319,000 DWT very large crude oil carrier. Research findings reveal that the gas leak rate and leak duration would be the parameters with the most influence in determining the extent of safety zones. It is pointed out that other parameters such as ship geometry, wind speed, and wind direction are also influential parameters. Details of the computations and discussions are presented.

This paper is to evaluate the LNG bunkering safety for a 50,000 dead weight tonnage bulk carrier renowned as the world first LNG fuelled bulk carrier. To establish a proper level of the safety zone against the potential risk of gas release from the LNG bunkering systems encompassing from truck to ship, it introduces an enhanced quantitative risk assessment process with two key ideas: firstly, the integration of the population-independent analysis with the population-dependent analysis, and secondly, the combination between the probabilistic analysis and CFD simulation for gas dispersion.Research results reveal that the appropriate levels of the safe zone can be set at 28.8 m in 1E-4 /year criterion that concerns the individual risk of a fatality at the given distance to the risk source of 1 in 10,000 years, whereas at 46.6 m (in 1E-5 /year criterion) and at 213.3 m (in 1E-6 / year criterion) when the area within 5 % and higher gas concentration in air is regarded the critical zone. On the other hand, in case of the critical area considered to be within 2.5 % and higher gas concentration in air, the safety zone will much expand to 34.9 m (in 1E-4 /year criterion), 80.4 m (in 1E-5 /year criterion) and 541.8 m (in 1E-6 /year criterion). These dissimilarities suggest that LNG bunkering ports pay attention to selecting appropriate safety criteria which would considerably change the range of safety zones. The case study also demonstrates the effectiveness of the proposed approach that can remedy the shortcomings/shortfalls of existing technical and regulatory guidance on establishing the zones. It is, therefore, believed that the risk assessment approach proposed in this paper can contribute to determining the appropriate level of safety zones whereas providing practical insight into port authorities and flag states.

This version is available at https://strathprints.strath.ac.uk/61716/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. still evolving and their safety has yet to be fully and objectively evaluated. This paper explores the probability of occurrence of accidents leading to vapour cloud explosion at one of the topside liquefaction modules of an FLNG. The worst possible scenario with the maximum tolerable probability is identified and the impact of the corresponding vapour cloud explosion is estimated. The strength of the structures supporting the neighbouring modules was examined using finite element analysis to determine if the accident has a potential of escalating to neighbouring modules. Potential Risk of Vapour Cloud Explosion in FLNG Liquefaction ModulesIt is found that the current levels of safety gaps between the liquefaction modules may be insufficient for the structural arrangement in place. It is thought that a new structural design using circular pipes as the structural elements instead of the I-beams may enhance the integrity of the top-side supporting structures against the impact of potential vapour cloud explosion. The effectiveness of the new structure is demonstrated by comparing it to the conventional supporting structure using I-beam members. This also implies that, by using pipe elements, the safety gaps can be reduced, thus making it possible to optimise the topside arrangement more easily.

No abstract