Section 2 Structure
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 17 Pipe-laying Units - Section 2 Structure

Section 2 Structure

Parent topic: Chapter 17 Pipe-laying Units

2.1 Plans and data submission

2.1.1 In addition to the structural plans and information as required by Pt 3, Ch 1, 2 Information required and Pt 4, Ch 1, 4 Information required, additional plans are to be submitted showing structure in way of and supporting:
  1. abandonment and recovery systems and arrangements, including winches, fairleads and sheaves for abandonment and recovery wire routing;
  2. basket and reel carousels;
  3. hang-off arrangements;
  4. heavy lift cranes and other lifting appliances;
  5. mooring attachments for attending pipe-carrier vessels/tender barges and supply vessels;
  6. pipe-handling/transfer systems;
  7. pipe-lay towers and ramps;
  8. pipe storage equipment, arrangements and areas;
  9. roller boxes
  10. systems handling in-line and pipeline end termination or manifold structure;
  11. stinger and stinger handling frames;
  12. stations for pipe bevelling, welding, NDT, repair and field joint coating;
  13. winches and tensioners; and
  14. other pipe-laying equipment not listed in the above.
2.1.2 The general arrangement plan of the unit is to include the locations of the following:
  1. The structures and equipment mentioned in Pt 3, Ch 17, 2.1 Plans and data submission 2.1.1.
  2. Hatches and other openings to enclosed spaces for pipe-laying operations and adjacent cofferdams, where fitted.
  3. Doors, hatches, ventilation and other openings to crew accommodation, control stations, stations for pipe-laying operations, store rooms and workshops.
  4. Coated tanks or tanks constructed of materials other than carbon steel.

2.2 General

2.2.1 The general hull strength is to comply with the requirements of Pt 4 Steel Unit Structures, taking into account the applied weights and forces due to the accommodation, cranes, and structures and equipment mentioned in Pt 3, Ch 17, 2.1 Plans and data submission 2.1.1. The local structure is to be suitably reinforced. Attention should be paid to loads resulting from hull flexural effects at support points.

2.2.2 The design loadings for the strength of areas for pipe-laying operations, pipe-storage and hull sub-structure are to be defined by the designers/Builders, and calculations are to be submitted.

2.2.3 The primary hull strength of the unit is to be maintained in way of moonpools and other large openings, and suitable compensation is to be fitted as necessary. In general, the design should be such that the bulkheads are connected to bottom and deck girders by means of large, suitably shaped brackets arranged to give a good stress flow at their junctions with both the girders and bulkheads. The boundary bulkheads of moonpools are to be designed for the maximum forces imposed on the structure.

2.2.4 For surface type units, the continuity of longitudinal material is to be maintained, as far as is practicable, in way of moonpools and openings, and the minimum hull modulus is to satisfy the Rule requirements for longitudinal strength.

2.2.5 The structural design of integral tanks for the bulk storage of liquid chemicals, e.g. for field joint coating, is to comply with the requirements in this Part outlined for cargo tanks and other tanks designed for liquid filling. The following requirements are also to be complied with:
  1. For strength assessments, the density is to be taken as the greater of 1,025 t/m3 and the maximum for the liquid chemicals to be stored in the tank. For fatigue assessments, the density is to be taken as the mean of the liquid chemicals stored in the tank.
  2. Consideration is to be given to the nature of the chemicals being stored, including their corrosiveness, reactivity and flammability. Arrangements are in general to comply with the International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (IBC Code - International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk Amended by Resolution MEPC.225(64)), as interpreted by LR.
  3. Corrosion rates will be specially considered on the basis of the corrosiveness and reactivity of the stored chemical with the tank material.

2.3 Materials

2.3.1 Support structures for the structures and equipment mentioned in Pt 3, Ch 17, 2.1 Plans and data submission 2.1.1 are to be divided into the following categories defined in Pt 4, Ch 2, 2.1 General 2.1.2:

  • Special structure.
  • Primary structure.
  • Secondary structure.

2.4 Offshore containers

2.4.1 Offshore containers (including portable tanks for the storage of pipeline pre-commissioning chemicals) are to comply with Pt 3, Ch 4, 2.4 Offshore containers.

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