Every current deep water disconnectable mooring system involves a semi-taut mooring line configuration combined with spring buoys. These mooring systems predominantly consist of polyester fiber rope combined with a long ground chain connected to the anchor. The spring buoys are in-line buoyancy elements that induce geometric stiffness.
Recently, two novel mooring system concepts have been developed that may show better behavior in both connected and disconnected condition. This paper addresses both design and performance of these two concepts.
The first novel concept is the weighted taut mooring system. It involves a taut configuration of predominantly polyester fiber rope, connected to a short anchor chain, which is never laid down on the sea bed. In addition, there is a middle chain section which provides for added weight. This weight causes a shape change of the mooring line between the connected and disconnected condition and hence introduces geometric stiffness.
The second novel configuration involves a taut mooring system as well, but combined with spring buoys.
Two applications are considered for case studies, for which mooring systems are designed according to each of the three available concepts. The first application entails arctic conditions, where the system must submerge sufficiently deep to avoid iceberg keels. The second application covers the Gulf of Mexico, which is prone to hurricanes and strong currents.
It is concluded that any configuration can be made to work for any application. The weighted mooring system is most economic, but introduces additional requirements on other elements. Between the two concepts that involve spring buoys, the taut system is found to be more advantageous than the semi-taut system.