ABSTRACT:

The motion dynamics and mooring loads of a turret moored FSRU are studied by experiments. The FSRU is moored by turret and catenary mooring lines. It can weathervane to minimize the environmental loads exerted on the body. Therefore the heading changes according to wind, wave and current. The FSRU can reach an equilibrium yaw angle and oscillate in range of large amplitude of 10 to 40 degrees in regular waves. The yaw instability is also investigated in the present study as well. The horizontal motions and mooring loads are analyzed and compared for various environmental conditions. It was confirmed that the mooring loads are strongly affected by yaw angle

INTRODUCTION

Recently a concept of FSRU (Floating Storage and Regasification Unit) is paid attention to by LNG industries due to its advantages in environment and safety terms compared with on-land LNG terminals such as no money for land, NYMBY, short construction time, etc. One of key issues for using FSRU is assurance of safe and reliable LNG offloading operation from LNGC to FSRU. The LNG offloading and loading operation are affected by many factors; sea state under operation, mooring system, loading arm and hydrodynamic interaction between FSRU and LNGC. FSRU should be moored at operation site to conduct its functions. The possible mooring systems are STL (Submerged Turret Loading; Kaalstad and Hovde, 2004; Yang, Chezhian and Hovde, 2009), Internal/External Turret, YMS (Yoke Mooring System), SPM (Single Point Mooring) and spread mooring. The water depth in this study is about 50 m ~ 200 m and sites are GoM, East Asia, east and west coast of US etc. Since the water depth and environmental conditions of these regions are different, an adequate mooring system should be considered according to site and operation consideration.

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