Spread Mooring system for
permanent mooring
A spread mooring system allows a tanker to moor at a
fixed location at a fixed heading using its own anchors. The heading of the
system is independent from the direction of wind and waves. Therefore, no
swiveling components are required and subsea hoses can be directly
connected from the seabed to the ship’s manifold.
These systems are only recommended for ships on locations with mild
environmental conditions having the same prevailing wind and wave direction
all year through. It typically consists of the following main components:
·
Anchor Arrangement
Anchor
sizes for spread mooring systems are usually larger than for rotating
mooring systems such as buoy-, turret- or tower mooring systems. This is
caused by the inability of the system to position itself in a direction
where wind and wave forces are minimized. This inability causes heavy
rolling motions on the ship when wind and or waves are coming in from the
side.
·
Subsea Hose String
The
subsea hose string(s) provides the interface between the offloading manifold
on the berthed tanker and the Pipeline End Manifold (PLEM) riser base or
wellhead which is fixed to the seabed or any other source. Its total length
depends on the water depth and the environmental conditions expected during
(off)loading activities.