OMAE2009-79192 REFERENCE LOAD FOR A CONVENTIONAL 138K CBM LNG CARRIER IN A COMPARATIVE APPROACH

ABSTRACT Still limited to knowledge about the actual phenomena so far, the comparative method has been used to assess the design load and the strength of cargo containment system for target ship designs. In the comparative approach, the sloshing load and strength of a conventional sized LNG carrier are compared with the load and strength for target LNG vessels. A 138,000 m 3 LNG carrier with 4 cargo tanks is used as a reference vessel in the comparative approach according to the market practice. Recently, a Joint Development Project(JDP) on the formal assessment of the reference design sloshing load has been undertaken with four major Classification Societies using the sloshing test facility(21). During the JDP period, a "common" test procedure to make a reference load was developed. After a detailed investigation of the test data obtained using the developed procedure, the reference load was derived. The reference load will be used for the safety assessment of the NO96 containment system for DSME's future LNG carriers or LNG related offshore floating vessels. This paper describes the test procedure and some investigated results. INTRODUCTION In order to design the LNG cargo tank and containment system safely, the most probable maximum pressure induced by sloshing acting on the cargo containment system(CCS) needs to be estimated with appropriate technical procedures for sloshing model tests, post-processing methods to analyze the measured data and correlation methods between models and actual ships, and strength capacity of the containment systems. So far, design sloshing loads have been determined by sloshing model experiments in the design stages and the actual sloshing load acting on operating LNG carriers has not been measured with reliable measuring devices, hence there are still some uncertainties in predicting an actual value of design load in absolute manners. Recently, sloshing load measurement system in an actual LNG carrier constructed by Daewoo Shipbuilding & Marine Eng. Co. Ltd.(DSME) was developed through Joint Industrial Project(JIP) between DNV, LR, BWG, Teekay and DSME. The measurement are currently on-going and also sloshing model tests will be carried out with operational data to get a model-ship correlation of sloshing loads. A number of numerical and experimental approaches have been developed to determine extreme pressures induced b