Oceans of knowledge

Single Point Mooring (SPM) Buoy Mooring systems

The single point mooring buoy consists of a buoy that is permanently moored to the seabed by means of multiple mooring lines. The buoy contains a bearing system that allows a part of it to rotate around the moored geostatic part. When moored to this rotating part of the buoy with a mooring connection, the vessel is able to freely weathervane around the geostatic part of the buoy.

As the moored vessel rotates itself into the dominant environment, the system will minimise the loads on the mooring system of the buoy. This capability of the SPM system is also used during the approach of a vessel that needs to moor. The vessel will approach the buoy with its bow into the dominant environment, maximising control while minimising the need for tug assistance.

Some single point mooring buoys are off-the-shelf products with a selection of standard options, while others have been custom-designed. The mooring system (the lines and anchor points) is always specifically designed to match the vessel’s requirements and local environmental conditions.

The mooring system can also be combined with a fluid transfer system that enables connection of (subsea) pipelines to the tanker. The fluid transfer system includes submarine hoses between the pipeline end manifold (PLEM) at the seabed and the buoy, and hoses between the buoy and the tanker. In the buoy a swivel provides the fluid transfer path between the geostatic part and the rotating part of the buoy.

The type of bearing used and the split between the rotating and geostatic parts determine the concept of the buoy. The following concepts are distinguished: bogey wheel buoy, turntable buoy and turret buoy.

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