The subsurface buoy should support the weight of the vertical riser, the subsea swivel and part of the weight of the catenary riser.
It should be placed at 160 ft (49 m) or more below the still water level, in order to be beneath the region of wave action.
The buoy should also provide the necessary tension for the vertical riser to prevent failure from compressive stresses.
If constructed of steel, the buoy should be compartmentalized for integrity.
The buoy should fulfill the following requirements:
- Support the weight of the vertical riser
- Support the weight of the swivel gooseneck
- Support the partial weight of the catenary riser
- Maintain adequate tension in the vertical riser
- Maintain the desired configuration under design load conditions