Section 4 Surface type units
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 4 Steel Unit Structures - Chapter 4 Structural Unit Types - Section 4 Surface type units

Section 4 Surface type units

Parent topic: Chapter 4 Structural Unit Types

4.1 General

4.1.1 The hull structural design requirements of permanently moored/disconnectable ship units with hull construction in steel engaged in hydrocarbon production and/or storage/offloading at offshore locations are given in Pt 10 Ship Units.

4.1.2 Units which operate as shuttle oil tankers will be assigned class in accordance with the Rules for Ships.

4.1.3 The hull structural design requirements of surface type units engaged in drilling and support activities are given in Pt 4, Ch 4, 4.2 Surface type units for drilling, pipe-laying and support activities.

4.2 Surface type units for drilling, pipe-laying and support activities

4.2.1 In general, hull strength, scantlings and arrangements for surface type units are to comply with the relevant requirements of the Rules for Ships as applicable to the service of the unit. For drilling units, the local design heads to be used for the derivation of scantlings for walkways and access areas, work areas and storage areas are not to be less than as shown in Table 6.2.1 Design heads and permissible deck loadings (SI units) in Pt 4, Ch 6 Local Strength.

4.2.2 All aspects which relate to the specialised offshore function of the unit are to be considered on the basis of these Rules, see also Pt 3, Ch 1 General Requirements for Offshore Units. Additional requirements related to the design arrangements and function of drilling and production units given in Pt 3, Ch 13 Buoys, Deep Draught Caissons, Turrets and Special Structures and Pt 4, Ch 3 Structural Design are to be complied with.

4.2.3  Drilling well/Moonpool. The hull structure in way of the drilling well/moonpool is to be suitably strengthened so as to ensure continuity of the required longitudinal strength.

4.2.4  Structural analysis. For surface type units, the strength of primary structures of hull compartments and of deck supporting structures, including longitudinal and transverse bulkheads, is to be assessed in accordance with relevant LR ShipRight SDA Procedures.

4.2.5  Fatigue design. Fatigue damage due to cyclic loading is to be considered. The nature and extent of the fatigue analysis will depend on the mode and area of operation. For details of the fatigue required analyses, see Pt 4, Ch 5, 5 Fatigue design.

4.2.6 The scantlings and arrangements of units with a limited number of tanks for bulk storage of flammable liquids having a flash point not exceeding 60°C (closed-cup test) will be specially considered. Double hull construction in bulk oil tank storage regions will normally be required, see also Pt 3, Ch 3 Production and Storage Units.

4.2.7 Additional requirements related to the design function of the unit are given in Pt 3 Functional Unit Types and Special Features.

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