Dynamic load acting on side-by-side mooring system is one of key factors to estimate the offloading operability of the LNG FPSO. In this paper, a numerical mooring analysis for the side-by-side moored LNG FPSO is carried out. As input data for mooring analysis, two-body motion responses are computed using a three-dimensional diffraction/radiation program. Wind and current loads including shielding effects are also applied to the mooring analysis. Results of the mooring analysis are validated by a comparison with another numerical program. In order to estimate the STS(ship to ship) offloading operability, dynamic loads acting on the side-by-side mooring system are calculated for two different mooring system configurations. Through the present study, it is found that the calculation results of two numerical programs are almost similar.
As the demand of natural gas is increasing, a LNG-related offshore plant such as LNG FPSO(Floating Production Storage and offloading) and LNG FSRU(Floating Storage and Re-Gasification Unit) is receiving much attention these days. In case of the LNG-related offshore plant, a side-by-side offloading system is applied instead of a typical tandem offloading system. The side-by-side moored vessels show different characteristics from the tandem moored vessels. Hydrodynamic interaction between the vessels is highly increased and it gives an effect on relative motion and drift forces due to their close proximity (Kim and Ha, 2002, 2003, Ha and Kim, 2004). The shielding effect on current and wind load is another important consideration (Yuck et al. 2007). This paper presents a numerical investigation on the STS (ship-to-ship) offloading operability for the side-by-side moored LNG FPSO and LNG carrier. A two-body motion analysis is carried out by a threedimensional hydrodynamic analysis program. In order to estimate the accurate offloading operability, dynamic load acting on the mooring system is computed considering motion responses of vessels and environmental load.