Spread Mooring arrangement for

Permanent tanker mooring

 

Anchor arrangement

 

 

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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.