(55ap) Performance of Full Containment Steel-Steel LNG Tanks Subject to Blast, Fire, and Impact Loads

A full-containment tank system consists of a secondary container, constructed of either metal or prestressed concrete, designed to contain any spilled LNG from the inner tank. However, the current regulations in the US require that if the outer wall is used as a storage tank impounding system, then it must be constructed of concrete. The objective of this study is to determine whether a metal secondary container provides an adequate level of safety and operational integrity comparable to that of an alternative concrete secondary container. The research aims to provide a better understanding of the ultimate capacity and resilience of a 9% nickel steel secondary container subjected to accidental loads including blast, fire, projectile impact, and thermal shock. The fire and blast loads considered for this study were determined from previous projects and literature using statistical methods. Detailed finite element models of both small and large capacity LNG tanks with steel secondary steel container are developed for the assessment. Response of the analyzed tanks are checked against the performance criteria developed as part of this study to evaluate structural integrity and leak tightness. Additionally, the response of steel tanks is compared with that of a concrete tank. Fragility analyses are performed to compare the degrees of safety margin for LNG tanks with steel and concrete secondary containers. This approach is expected to provide an enhanced basis of comparing the effectiveness of the two secondary containment types against accidental loads.