Impact failure characteristics of LNG carrier cargo containment system

Abstract

The most critical issue related to the maritime transportation of liquefied natural gas (LNG) is the structural safety of the cargo containment system (CCS), because LNG is stored at temperatures below –163 °C. During the unloading of LNG, several types of structural components can fall into CCSs from significant heights. Thus, the structural safety of LNG CCSs against dropped objects should be verified; however, the actual failure characteristics of the primary barrier are not well understood. In this study, the failure mechanism of the primary barrier of an LNG CCS was investigated by conducting falling-object-induced structural failure tests. To clarify the effect of the failure response of the primary barrier, impact tests were performed using various membrane types and impactor types. In addition, to ensure the wide applicability of the results, a finite element analysis-based design-aid numerical method was developed by comparison with experimental observations. Excellent numerical verification results were obtained using the Johnson–Cook material model, which can be applied to the dynamic failure problem for the corrugated plates used in LNG CCSs. Finally, guidelines that could set safety standards for the primary barrier were identified, considering the shape, weight, and height of potential falling objects.