Anchor
Arrangement.
The anchor arrangement is designed to keep the FPSO in
position. In the design process it will be taken into account the constant
changing motions and forces of the ships due to current, wind and waves. Depending
on the environmental conditions, like soil type of the location an anchor
arrangement is chosen.
Types
Internal Turrets
In this design the turret is build inside the hull in
what is called a moon pool. The chain table, connecting the mooring lines to the turret, can be
either above or below the waterline. Usually the system is located in the front
end of a vessel. In very exceptional cases it can be found at mid-length of
the ship. This type of turrets can accommodate over 100 risers which gives
this system a high fluid transfer capability. Because the turret is
directly attached to the hull, the forces on the mooring cables are better
transferred in the hull than in the case of an external turret.
However for construction or if damaged, an internal
turret requires dry-docking, which is a great disadvantage. An internal
turret is also more expensive than external turret designs and requires a
longer construction time. The system described is an permanent turret but
there are disconnectable internal systems as well. The operations depth of
a FPSO with an internal permanent turret range is between 30 and 3000
meters