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metres above the vessel’s main deck, where it is supported by the
main weathervaning bearing.
An annulus between the turret cylinder and the moonpool
shell provides a flooded passage for the anchor chain connection
lines. The chains pass to individual mooring line gypsy winches.
The turret cylinder houses the riser and umbilical ‘I-tubes’, which
provide protection to the flexible risers over their transit height
inside the turret cylinder.
The turret cylinder extends from the chain-table up to the
vessel’s main deck and also supports the turret main deck, the
manifold structure. the swivel stack and all earth bound parts of
the fluid transfer system.
Bearing Support Stvuctures
Weathervaning Bearing Support Structure - In order to
effectively transit the vertical and the horizontal mooring loads
from the turret chain-table and the turret cylinder into the FPSO
vessel’s structure, and to keep deformations at the main
weathervaning bearing support within very tight tolerances, a
conical piece of welded structure is fitted. The continuation of this
cone forms the outside shell of the turret moonpool and interfaces
with the vessel’s structure. On the one hand, this conical structure
must be flexible enough to decouple the bearing from the vessel’s
deformations, but on the other hand, the top surface of the insert
piece must be formed of thick plate to rigidly support the rotating
part of the weathervaning bearing.
Friction Pad Assembly Support Structure - The horizontal
component of the mooring load is taken by an arrangement of
friction pads. The support structure of the pads is integrated into
the vessel keel and reinforced locally. The pads react on a heavy
steel ring, which is an integral part of the turret cylinder.
Bearing Systems
Main Bearing - The link between the weathervaning vessel
and the fixed turret column is a large diameter heavy duty three (3)
race slewing bearing. The bearing is mounted to its support
structure by high strength, hydraulically pre-tensioned bolts.
The slewing bearing provides the revolving connection of
the mooring structure about the fixed (earth bound) structure of the
TMIT. It therefore transmits forces and moments applied by the
moored vessel under the combined action of wind, wave and
current in either weathervaning or oscillatory rolling mode.

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