Section 4 Materials
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 3 Functional Unit Types and Special Features - Chapter 1 General Requirements for Offshore Units - Section 4 Materials

Section 4 Materials

Parent topic: Chapter 1 General Requirements for Offshore Units

4.1 General

4.1.1 The Rules relate in general to the construction of steel units of welded construction, although consideration will be given to the use of other materials. For concrete structures, see Pt 9 Concrete Unit Structures.

4.1.2 The materials used for the construction and repair of units and installed machinery are to be manufactured and tested in accordance with the requirements of the Rules for the Manufacture, Testing and Certification of Materials (hereinafter referred to as the Rules for Materials).

4.1.3 As an alternative, materials which comply with National or proprietary specifications may be accepted provided that these specifications give reasonable equivalence to the requirements of the Rules for Materials or are approved for a specific application. Generally, survey and certification are to be carried out in accordance with the requirements of the Rules for Materials.

4.1.4 Materials for specialised areas of the unit, related to its function or special features class notation, are to be in accordance with the relevant Chapters of this Part, see also Pt 3, Ch 1, 4.3 Structural categories.

4.2 Material selection

4.2.1 Materials are to be selected in accordance with the requirements of the design in respect of static strength, fatigue strength, fracture resistance and corrosion resistance, as appropriate.

4.2.2 The grades of steel to be used in the construction of the unit are to be related to the thickness of the material, the location on the unit and the minimum design temperature, see Pt 3, Ch 1, 4.4 Minimum design temperature.

4.2.3 The grades of steel to be used for the drilling plant and the production and process plant are to be in accordance with the requirements of Pt 3, Ch 7 Drilling Plant Facility and Pt 3, Ch 8 Process Plant Facility respectively.

4.2.4 The effects of corrosion, either from the environment or from the products handled on the unit or its associated plant and machinery, are to be taken into account in the design.

4.3 Structural categories

4.3.1 The structural categories for the hull construction and the corresponding grades of steel used in the structure are to be in accordance with Pt 4, Ch 2 Materials

4.3.2 The structural categories for supporting structures for drilling plant and production and process plant are to be in accordance with Pt 3, Ch 7 Drilling Plant Facility and Pt 3, Ch 8 Process Plant Facility respectively.

4.4 Minimum design temperature

4.4.1 The minimum design temperature is a reference temperature used as a criterion for the selection of the grade of steel to be used.

4.4.2 The minimum design air and sea temperatures for exposed structure are to be taken as the lowest daily average temperature for the unit’s proposed area of operation, based on a return period of occurrence of:
  1. 50 years for Mobile Offshore Units.
  2. 100 years for Floating Offshore Installations at a fixed location.

Where

Daily average temperature = the average temperature during one day and night.

The temperature is to be rounded down to the nearest degree Celsius. Consideration is to be given to the minimum temperature along transit routes for any voyage of the unit from one geographical location to another.

4.4.3 The minimum design temperature (MDT) for drilling plant and production and process plant is to be defined by the designers/Builders, but when appropriate the MDT should not be higher than the MDT for the exposed structure defined in Pt 3, Ch 1, 4.4 Minimum design temperature 4.4.2.

4.5 Aluminium structure, fittings and paint

4.5.1 The use of aluminium alloy is permitted for secondary structure, as defined in Pt 4, Ch 2 Materials

4.5.2 Where aluminium alloy is used for secondary structure, the material is to conform with the requirements of Ch 8 Aluminium Alloys of the Rules for Materials.

4.5.3 The use of aluminium alloy for primary structure will be specially considered.

4.5.4 Where aluminium alloy is used in the construction of fire divisions, it is to be suitably insulated in accordance with the requirements of the appropriate National Administration, see Pt 3, Ch 1, 1 Rule Application

4.5.5 Since aluminium alloys may, under certain circumstances, give rise to incendive sparking on impact with steel, the following requirements are to be complied with:
  1. Aluminium fittings in tanks used for the storage of oil, and in cofferdams and pump-rooms in oil storage units are to be avoided wherever possible.
  2. Where fitted, aluminium fittings, anodes and supports in tanks used for the storage of oil, cofferdams and pump-rooms are to satisfy the requirements specified in Pt 8, Ch 2, 5 Cathodic protection in tanks for aluminium anodes.
  3. The danger of mistaking aluminium anodes for zinc anodes must be emphasised. This gives rise to increased hazard if aluminium anodes are inadvertently fitted in unsuitable locations.
  4. The undersides of heavy portable aluminium structures such as gangways, etc., are to be protected by means of hard plastic or wood covers, in order to avoid the creation of smears when dragged or rubbed across steel, which if subsequently struck, may create an incendive spark. It is recommended that such protection be permanently and securely attached to the structures.
  5. Aluminium is not to be used in hazardous areas on drilling units and production and oil storage units unless adequately protected, and full details submitted for approval. Aluminium is not to be used for hatch covers to any openings to oil storage tanks.

4.5.6 For permissible locations of aluminium anodes, see Pt 8, Ch 2, 5 Cathodic protection in tanks.

4.5.7 The use of aluminium paint is to comply with the requirements of Pt 8, Ch 3, 1 General requirements.

Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.