In this study, a numerical analysis was performed on hand-over between laying vessel and FPSO with truncation modeling. The installation vessel is located close to FPSO in order to hand over the flexible riser. The weight of a riser is divided into A&R (Abandonment & Recovery) winch and PIW (Pull-in Wire) according to the wire payout length. The tensions of an A&R winch wire and a PIW wire were reviewed based on the limitation criteria. A truncation modeling was considered to apply the model tests at Ocean Engineering Basin of KRISO. The anchor point and the water depth were revised considering pit diameter and basin depth. The top tensions of the wires were investigated under various wave headings, height and periods in wave conditions. The discussion is made on the effects of the load transfer condition, wave headings.
Ocean riser systems are mainly installed using the installation vessel. Three methods are widely used to install ocean risers. Deep-ocean risers are installed by J-lay installation method in deep water depths of 2,000m or more, and S-lay installation method is used at shallow water depths considering stinger capacity. Flexible riser systems are mainly installed using reel-lay method. The flexible riser is lowered to the seabed through the moonpool, and several buoyancy modules are installed to prevent the impact damage fatigue damage of the riser in the touch down point (TDP). The riser docked to FLET with buoyancy modules is paid-out in initiation stage and installation vessel arrives at the pre-determined location. The laying vessel is located close to FPSO in order to hand over the flexible riser. The flexible riser 2nd end is connected to pull-in head and pull-in head lowered using the A&R winch wire. After pull-in head lowered determined location, PIW(Pull-in wire) from the FPSO is connected to the pull-in head. The weight of the riser is transferred from the laying vessel to FPSO according to the wire payout length. Wire tension is the most important factor related to limitation criteria in hand-over operation. Fig. 1 shows the initiation and hand-over stages.