Methodology to analyse LNG spill on steel structure in congested marine offshore facility

The cryogenic temperature of LNG induces unexpected thermal stress on a metallic structure when LNG comes in contact with it. The induced thermal stress may combine with other operational stress causing the system to face abnormally high stress rates. Furthermore, small cracks, imperfections or design flaws can propagate at high rate under the new increased stress condition. This may lead to catastrophic failure of the structure. In this study, a methodology is proposed for the assessment of the impact of a fugitive LNG spill on a typical steel structure. The study outlines an insight into the structural integrity assessment of the structure during an LNG spill. The focus of the study is to model an LNG pool formation in a complex offshore structure using Flame Acceleration Simulator (FLACS), and to analyse the temperature profile of the pool using thermal analysis. The thermal stress obtained from the transient analysis is considered as a load for LNG spill impact assessment. Ten different semi-elliptical crack sizes are considered to analyse the impact of thermal stress on crack propagation. The outcome of this study reveals that the fugitive release of LNG does not cause immediate crack propagation, however, it has a significant impact on the operational life of the structure. This study confirms that the fugitive release of LNG is a serious hazard for structural integrity and demands effective preventive and/or control measures.