Liquefied natural gas (LNG) carriers are designed and constructed for safe transportation of natural gas at cryogenic temperatures. Storage and transportation of LNG are very critical issues in design and safety aspects of LNG carrier. Cargo Containment System (CCS) of LNG carrier is a key component which is subjected to dynamic sloshing loads. The aim of present paper is to provide a methodology for the strength assessment of CCS subjected to the sloshing loads. Computational Fluid Dynamics (CFD) based numerical simulations for sloshing are utilized for the selected critical fill levels. A simplified method is employed to find out the critical fill levels at which severe sloshing impact pressure are induced. A detailed finite element (FE) modeling of MARK III type containment system is presented. Based on the response analysis of CCS, importance of various levels of strength assessment is discussed. Overall a comprehensive strength assessment procedure for MARK III type containment is presented.
Liquefied natural gas is touted as a clean source of energy which is gaining popularity over the traditional fossil fuels. In recent years, the consumption of the LNG fuel has seen an increase due to commitment of nations to reduce their emissions of greenhouse gases. To meet the increased demand of LNG as well to reduce the transportation cost; designers call for larger LNG carriers. The trading patterns may also require being flexible as the ship may sail to several ports. LNG carriers typically operate at fill levels higher than 95% or lower than 10% of tank capacity. The current design practices are regarded safe for sloshing load for such restricted loading conditions. However flexible trading patterns require the ship designer to conduct an assessment considering partial fill levels of LNG to mitigate the risk of higher dynamic loading in form of severe sloshing impacts which is a critical attribute in LNG CCS strength analysis (Kim et al. 2010).
