The objective and scope of this development programme is to complete the pre-engineering design of an underwater motion compensated Single Point Mooring (SPM).
Two variants of the mooring system have been developed :
i) Seabed mounted buoy version (for shallow water applications)
ii) Mid-water buoy version (for deep water applications). Hydrodynamic analysis were done to analyse the quasistatic, slow frequency and wave frequency behaviour of the system with a lanker moored.
During the model tests it has been observed that the limiting seastates for operation of the system is higher than originally envisaged.
In view of the increase in the design limiting sea state further model testing is to be undertaken to investigate in more detail the performance near to the operating limit of the system.
Results obtained from the computer analysis and the model test programme confirm that the submerged piston mooring is a viable option and has potential to exceed the operating sea state threshold for other proven mooring concepts.
Project has been abandoned for organisational reasons.
The Submerged Piston Mooring System has a novel feature of a motion compensator within a spring buoy. The motion compensator is fitted within the buoy in the form or a large diameter axial piston arrangement and utilises the ambient external pressure as the motive hydraulic force. The tanker mooring is attached directly to the top of the piston thereby transmitting all mooring loads from the tanker to the buoy via the motion compensator piston.
This allows the dynamics of the mooring buoy to be altered by selecting the piston diameter, weight and buoy operating depth below the surface. The response of the overall system to dynamic motions of the moored ship are such that the dynamic peak loads are less than those encountered in a conventional mooring.
With the currently proposed system the buoy is placed well below the surface and hence away from the effects of wave action. This has the additional advantages for Arctic regions of keeping it below pack-ice and reduces the dynamic mooring forces between the buoy and the tanker.
Project consists of two phases.
Phase 1 : Preliminary design and detailed assessment of forces in all parts of the system and model testing to establish system response.
Phase 2 : Creation of a complete design package and specification of the entire system, including all components and the approval of a certifying authority.