Page 79 - 6634
P. 79
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.
Friction Pads - Fourteen (14) friction pad assemblies are arranged to receive
and distribute the horizontal component of the mooring force. They are disposed in
two groups - eight (8) towards the bow and six (6) aft of the turret. Each pad is
composed of a self-lubricating bearing surface which mates with nickel steel
corrosion resistant overlay counterface. The pads are arranged as individual rams.
which are supported by an hemispheric elastomeric bearing which reacts back into
the vessel keel via a box structure.
Turret Moonpool Structure
The turret moonpool structure is a cylindrical bulkhead inserted through the
hull from the FPSO main deck down to just below the keel. It is made of stiffened
plate framed back into the vessel sections by radial stiffeners. At its lower end, the
cylindrical bulkhead is equipped with inflatable seals, which can be pressurised
against a support surface attached to the chain-table below. Once temporarily
79
