New LNG Containment System

ABS has issued Approval In Principle (AIP) to a new containment system and carrier design developed by Houston-based Ocean LNG, Inc. The AIP process draws upon engineering, testing and risk assessments to determine if the concept provides acceptable levels of safety in line with current offshore and marine industry practice. This approval of the design principle is in accordance with ABS Rules and the International Gas Code (IGC). It was performed in accordance with Guidance Notes on Review and Approval of Novel Concepts, which outlines a methodology for requesting classification of a novel design that may have no precedent in the proposed environment.

As part of the AIP process, ABS evaluated the overall feasibility of the Ocean LNG design, including the containment system and structural strength; tank support system; midship section scantlings; stability analysis; hull form and speed calculations; hydrodynamic analysis and detailed sloshing analysis. A key aspect of transporting LNG is designing tank and containment systems to withstand dynamic sloshing loads of LNG cargo when a tank is partially filled. The Ocean LNG proprietary system employs IMO Type B independent tanks designed to minimize filling restrictions due to sloshing effects. The tank design calls for an elongated cylindrical tank with spherical dished ends.

The 180,000m3 carrier design features five of these large 36m diameter vertical cylinder tanks each holding a volume of 36,000m3 of LNG. The vertical arrangement of the tanks provides greater storage capacity for the footprint size.