PURPOSE: To prevent the damage of a flexible riser by connecting a connecting pipe on the upper end of the flexible riser for transporting a crude oil from a submarine oil field to a crude oil processing and storing ship, and attaching a buoy and a collar whose diameters are smaller than the bore of the through hole of a turret to the connecting pipe.

CONSTITUTION: A flexible riser 8 provided in a crude oil processing and storing ship has a steel connecting pipe 10 connected through a vent stiffener 9 to its upper end, and a buoy 11 and a collar 12 whose outer diameters are smaller than the bore of plural through holes 5B formed around the moon pool (not shown in a figure) of a turret 5 are fixed to the connecting pipe 10. The upper end of the connecting pipe 10 is connected with a separating device 6 fixed to the turret 5. Thus, even when the crude oil processing and storing ship 4 is rolled by a wind or a tide, or the flexible riser 8 is flowed by the tide, the coller 12 functions to prevent the flexible riser 8 from coming into direct contact with the wall surface of the through hole 5B for preventing the flexible riser 8 and the through hole 5B from suffering damage.