A tension leg consists usually of several tethers. The number of tethers varies, depending on the design.
The system can be divided into three parts
- an interface at the platform
- an interface at the seabed
- the link between seabed and the subsea interface.
Platform Interface
The components at the platform provide the following functions:
- Apply and adjust the prescribed tension in the tethers
- React side loads and control the bending stress
- Connect a tensioned tendon to the platform
Seafloor Interface
The seafloor interface must perform the following functions:
- Provide a structural connection between the tendon and foundation
- React to the loads and control the bending stresses
Link Platform – Subsea Interface
This is the main body of the tendon. There are many various forms, like tubulars, solid rods or bar shapes, stranded constructions. Like parallel or helical wire rope.
Material
Steel is the most used material for the tethers. Synthetic materials are proposed, but not used until today. The advantage of using synthetic materials is the strength-weight ratio is larger. In deep water the weight of steel tethers may become a problem; synthetic material could be a solution.
There can be special components in the design:
- Corrosion protection units, which includes coatings, sacrificial anodes, elements of impressed current system
- Buoyancy devices, to reduce the submerged weight of the tether
- Devices to reduce hydraulic resistance or vibrations
- Sensors or other instruments to measure the condition or performance of the tethers
- Elastic elements
Back to components
|