Oceans of knowledge

Single Point Mooring (SPM) Tower systems

The tower mooring system consists of a tower structure that is permanently fixed to the seabed by means of piles or a gravity base. The tower contains a bearing system that allows a part of it to rotate around the fixed geostatic part. When moored to this rotating part of the tower with a mooring connection, the vessel is able to freely weathervane around the geostatic part of the tower.

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

Tower mooring is specially designed to match vessel requirements and local environmental conditions. Various factors need to be included in the design, especially the water depth at the mooring site and specific environmental loads, like ice loads.

The mooring system can also be combined with a fluid transfer system that enables connection of (subsea) pipelines to the tanker. The pipeline is connected to the tower piping at the base of the tower. In the tower a swivel provides the fluid transfer path between the geostatic part and the rotating part of the tower.

Tower mooring systems are typically designed for nearshore applications with water depths of up to 40 metres. The mooring connection between the tower and the vessel depends on local environmental conditions and requirements for the permanent mooring of the vessel. The mooring connections use the following systems: hawser and soft yoke.

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