LNG terminal developments are still the subject of major debate associated with potential hazards of marine accidental events. A recent U.S. Government Accountability Office (GAO) study has highlighted significant uncertainties associated with the underlying science. Prior risk studies have used estimates for potential hole size from accidental events that were based on judgment, as there have been no large accidental releases in the historical record. Hole size estimates have varied from 0.75m to 5m.A major sponsored project has undertaken a review of hole size from a detailed structural calculation methodology. This has used real collision data from the EU HARDER project to map known collision outcomes onto the actual external hull of membrane and spherical LNG vessels. Using this dimension, detailed FEM analysis was carried out to map internal damages that would result from such an external damage. This showed that LNG vessels have great strength as the structures of the hull and stringers and other structures between the outer and inner hulls take and redistribute collision loads. However, once the inner hull starts to fail, the resistance to small increments in size of failure are relatively less than before inner hull failure. Assuming conservatively a consequential LNG tank hole size would correspond to inner hull tear size, there is no specific hole size that characterizes the collision event. More energetic collisions give larger dimension holes. It is concluded that a hole-size approach to LNG carrier accidental events is not a reliable means to protect public exposures. This paper presents the results of the Finite Element Method (FEM) analysis for the two LNG vessel types and for several potential collision scenarios (size of vessel, speed, angle of collision). A suggested approach is to characterize the energy necessary to start to fail the inner hull and to plan port controls that can be shown to prevent such energetic collisions to a high and specified level of probability. In this manner, the public would be protected more effectively than nominating arbitrary hole sizes that cause events that in many cases cannot prevent public exposures in worst case scenarios. It is argued that this approach is closer in philosophy to NFPA59A than past approaches, and may therefore address some public concerns.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.