As the size of LNG carrier ship has been expanded, it is expected that the sloshing impact on the LNG CCS (cargo containment system) is getting higher at the low filling condition. The sloshing pressure and structural capacity of the LNG CCS is carefully investigated during the CCS design since the sloshing impact has many technical issues such as extremely low temperature, high impact pressure, non-linearity of the fluid motion and so on. At first, the strength assessment procedure suggested by shipping registers, shipyards and several research groups are compared and discussed. This study also suggests a strength assessment procedure of LNG CCS including the sloshing pressure of large scaled model test and numerical analysis, static and dynamic structural response of cargo containment. Numerical analysis and experimental approaches of sloshing motion and pressures are commonly discussed to assess the sloshing pressure. Three different levels of strength assessment procedures are discussed based.
LNG cargo containment should maintain the extremely low temperature and also should withstand the impact pressure induced by the sloshing motion that may lead the structural failure on the insulation structures. Over the past four decades, LNG industry has experienced the changes that have leaded the significant cost-savings in delivering LNG cargo by virtue of efficient cargo containment systems. Larger LNG carriers, whose capacity exceeds 180,000 m3, have been constructed from the beginning of 2000s in order to get the more efficient transportation and huge LNG-FPSO and LNG-FSRU has been also introduced along with the partial filling transportation (Kim et al., 2010). This drastic growth of LNG carriers and offshore structures brings again the problem of the sloshing impact. Therefore, the existing technical approaches require being re-investigated and the practical methods are necessary to assess the sloshing load of the larger containment system.
