Section 2 Floating structures and subsea buoyant vessels

2.1.1 The structural design and the general hull strength of buoys and deep draught caissons are to comply with the requirements of Pt 4 Steel Unit Structures taking into account the equipment weights and forces imposed on the structure.

2.1.2 The supporting structure below swivels and other equipment is to be designed for all operating conditions and environmental loads as defined in Part 4.

2.1.3 The structure and arrangement of units with crude oil bulk storage tanks and/or production and process plant are also to comply with the requirements of Pt 3, Ch 3 Production and Storage Units and Pt 3, Ch 8 Process Plant Facility, as applicable.

2.1.4 Critical joints, depending upon transmission of tensile stresses through the thickness of the plating of one of the members (which may result in lamellar tearing), are to be avoided wherever possible. Where unavoidable, plate material with suitable through thickness properties will be required, see Ch 3 Rolled Steel Plates, Strip, Sections and Bars,Ch 8 Aluminium Alloys of the Rules for the Manufacture, Testing and Certification of Materials (hereinafter referred to as the Rules for Materials).

2.1.5 Moored floating structures supporting multi-point mooring line arrangements are to be assessed for the maximum combined forces to which they may be subjected to in service.

2.1.6 Account is to be taken of wave slamming effects, where appropriate.

2.1.7 Floating structures, including highly stressed structural elements of mooring line attachments, chain stoppers and supporting structures are to be assessed for local strength as required in Pt 10 Ship Units and for fatigue damage due to cyclic loading in accordance with Pt 4, Ch 5, 5 Fatigue design.

2.1.8 For mechanical items for bearings and swivels, see Pt 3, Ch 13, 6 Mechanical items.

2.2.1 The permissible stresses in floating structures are to comply with Pt 4, Ch 5 Primary Hull Strength, but the minimum scantlings of the local structure are to comply with Pt 4, Ch 6 Local Strength.

2.3.1 Where a classed installation is to be assigned the notation PRS in accordance with Pt 3, Ch 12 Riser Systems, riser systems incorporating subsea buoyant vessels are to comply with the requirements of this sub-Section.

2.3.2 Where subsea buoyant vessels are used in association with other systems, they will be specially considered from the classification aspects.

2.3.3 Subsea buoyant vessels are to be designed for all external operating loads and the maximum pressure head to which the structure may be subjected to in service or during installation, see Pt 4, Ch 3, 4 Structural design loads.

2.3.4 The scantlings of the shell boundaries and framing are to be determined from an internationally recognised Pressure Vessel Code.

2.3.5 All vessels are to have positive buoyancy, when subjected to their design external loads, when any one internal compartment is flooded. Special consideration will be given to vessels with compartments filled with foam, see 1.7.

2.3.6 The local structure is to be suitably reinforced in way of the loads imposed by riser systems, and other external loads and the requirements of 2.1.4 are to be complied with as applicable.

2.3.7 Internal watertight bulkheads are to withstand the flooding of any single compartment. The scantlings of watertight bulkheads are to comply with Pt 4, Ch 6 Local Strength, with determined in accordance with 2.3.3.