To realize LNG offshore units (LNG FPSO, LNG FSRU and etc.), one of the critical design issues is a selection of cargo containment system such as membrane-type containment systems or independent tank type B. Each containment system has pros and cons regarding the structural safety of tank against sloshing loads under partially-filled conditions, hull strength against topside module weight, onboard maintenance availability, accumulated experiences with proven technologies and construction costs. This paper describes recent study results on sloshing load assessment for FLNG. To assess sloshing loads for any filling level in a LNG tank, sloshing model tests and numerical simulations have been being carried out for some DSME's FLNG projects. The evaluated sloshing loads for FLNGs with two-row tank arrangement will be described as intermediate results.

INTRODUCTION

As offshore floating LNG storage platforms require unlimited filling operations and practically the vessel cannot be moved to a dry dock for repair, more stringent design criteria are applied. The cargo containment systems for FLNGs should be verified in advance for all scenarios of operation and environmental conditions. The large breadth of cargo tanks and some leak incidents at the secondary barrier in other membrane system have caused worries about all kinds of membrane type cargo containment systems. Until so far, not enough operation reference data are available for FLNGs. DSME (Daewoo Shipbuilding and Marine Engineering Co. Ltd.) has operation data for a partial filling condition during hurricane "Katrina" in August 28, 2005 at Excelerate Energy Gulf Gateway offshore terminal in Gulf of Mexico. It was observed at that time that the significant wave height was approximately 6-7 meters and LNG tanks were in approximately 25% to 30% of tank height levels. During the hurricane, the regasification operation was continued, and no specific symptom was observed in the tank sloshing.

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