Off shore rigid steel riser termination and fixation system to Floating Production Storage Offloading (FPSO) vessel

A riser termination for connecting a steel catenary riser duct to an I-tube or J-tube connecting interface of a floating unit, said connecting interface comprising:

• a lower tubular coupling recipient installed on the floating unit at a lower riser coupling level and adapted to receive a coupling adapter of the riser termination,
• a locking mechanism provided at the lower coupling recipient for locking the coupling adapter against downward withdrawal from the lower coupling recipient,
• an upper hang off seat installed on the floating unit at an upper riser coupling level above the lower riser coupling level and adapted to receive and lock an upper hang off portion of the riser termination,
• said riser termination comprising:
• an upper hang off portion,
• a lower coupling adapter,
• a termination conduit in structural steel having an upper conduit end rigidly connected to the upper hang off portion and a lower conduit end connected to an adjacent conduit section of the steel riser duct and forming a lower end of the riser termination, said termination conduit extending through said coupling adapter and being axially slidable with respect to the coupling adapter,
• a bearing structure for supporting the termination conduit within the coupling adapter, said bearing structure comprising:
• a circular cylindrical bearing seat formed inside the coupling adapter and defining a bearing seat diameter and a bearing seat axis,
• an annular rounded bearing body having a bearing body diameter-and protruding outward from said termination conduit inside the bearing seat,
• wherein the bearing body diameter is smaller than the bearing seat diameter to provide an at least unilateral gap between the bearing body and the bearing seat and allow relative axial sliding along the bearing seat axis and relative rotation at least about the bearing seat axis between the bearing body and the bearing seat,
• wherein the termination conduit comprises at least one variable cross-section conduit portion having an external diameter and a conduit wall thickness both decreasing in a direction away from the bearing body,
• wherein the bearing body forms a bearing ball and provides together with the bearing seat a universal joint with a predetermined play due to the gap.