External Mooring Systems

The concept of an External Turret Mooring System became a reality when the stern of the 140,000 DWT Floating Storage and Offloading (FSO) vessel, the Alba Marina, was fitted with an external turret in 1985.

An External Turret Mooring system comprises of a steel box-type structure that can be either close to or extended some distance from the bow or stern of the vessel, providing a foundation for a rotating bearing arrangement and a turret located above water. The bearing accommodates a fixed chaintable to which mooring chains and fluid transfer hoses are attached. The chain legs are fastened to the seabed either by anchors or piles.

Product and utility connections are made between the facilities on the vessel and the seabed via a swivel stack in the turret, allowing the vessel to weather vane around the fixed part whilst continuing production. An alternative design is the clamped bow turret where the rotating bearing arrangement is split between an above and below water section.