A finite element analysis-based approach for blast-resistant design of LNG containment tanks

Abstract

Inside Liquid Natural Gas (LNG) facilities, ignition of large vapor clouds in a congested region might result in Vapor Cloud Explosions (VCE) leading to high speed blast waves and compromising the structural integrity of equipment and structures. The escalation of an initial blast is referred to as ‘Cascading Effect’. In performing risk assessment of a facility, structural damage of LNG containment tanks due to blast scenarios needs to be considered. This article presents a numerical approach-based methodology to analyze containment structures using Finite Element Analysis (FEA). The objective of this study is to elucidate the critical parameters in blast resistant design of containment tanks. Four major types of containment tanks are studied under representative scenarios of deflagration and detonation. Containment tank geometries were created almost in its entirety and the structural response is modeled with appropriate constitutive relations for steel and concrete. Additionally, pertinent hard contact with friction interaction between the tank inner to outer shell surfaces are assigned. The results indicate that a single containment tank model experienced severe damage in its outer shell under deflagration compared to other types of containment tanks. In the case of double, full and membrane containment tanks cracking in the prestressed concrete wall was observed due tensile damage which is pronounced for detonation than for deflagration cases. It is concluded that single containment tanks are most vulnerable to Cascading Effect. Based on the results of FEA, recommendations are provided for safe practice of designing the structures and maintaining the structural integrity of tanks.