Section 1 General

1.1.1 The requirements of this Chapter apply to mobile offshore units, intended for pipe-laying operations, fitted with pipe-laying equipment and are additional to those applicable in other Parts of the Rules. For the purpose of these Rules, pipe-laying operations include pipe storage, handling and transfer, bevelling, welding and cutting, NDT, repair, field joint coating, laying, abandonment, recovery and pipeline pre-commissioning.

1.1.2 The requirements may also be applied to units intended for laying cables and installing risers and umbilicals, as applicable.

1.1.3 Pipe-laying column-stabilised semi-submersible units and pipe-laying twin-hull surface-type units are to be classed as mobile offshore units and are to comply with the relevant Parts of these Rules.

1.1.4 Pipe-laying barges and ships may be optionally classed as mobile offshore units, in which case they are to comply with the relevant Parts of these Rules. Alternatively, pipe-laying barges and ships may be classed entirely with the Rules and Regulations for the Classification of Ships, July 2022, in which case they are not eligible for the OU and OIWS class notations. The Rules and Regulations for the Classification of Ships, July 2022 provide a higher basis of design for the hull (50-year return period loads and 25-year minimum fatigue life, see Pt 4, Ch 3, 4.1 General 4.1.4.(a) and Pt 4, Ch 4, 5.2 Environmental considerations 5.2.3) compared to the Rules and Regulations for the Classification of Ships, July 2022 (20-year return period loads and no required fatigue assessment).

1.1.5 Pipe-laying units which have a diving complex on board are to have the diving installation approved in accordance with LR’s Rules and Regulations for the Construction & Classification of Submersibles & Diving Systems, July 2022 or a recognised Standard acceptable to LR.

1.1.6 Classification of the unit will cease to be valid if a significant alteration is made to the pipe-laying equipment or the arrangements on board without the written approval of LR. Where it is intended at times to operate the unit with the pipe-laying equipment removed, all modes of operation with and without the pipe-laying equipment fitted are to be approved.

1.1.7 Requirements additional to those of this Chapter may be imposed by the National Authority in the country in which the unit is registered and/or Coastal State Authority under which jurisdiction the unit is to operate e.g. pipe-laying units may require compliance with ISPS Code - International Code for the Security of Ships and of Port Facilities and 2008 SPS Code – Code of Safety for Special Purpose Ships, 2008 – Resolution MSC.266(84) supplemented by the stability requirements of the 2009 MODU Code - Code for the Construction and Equipment of Mobile Offshore Drilling Units, 2009 – Resolution A.1023(26).

1.2.1 Mobile offshore units complying with the requirements of this Chapter and the relevant Parts of these Rules will be eligible for the assignment of the Pipe-laying unit class type notation.

1.2.2 Support units may be assigned additional class type notations when appropriate, see Pt 3, Ch 4, 1.2 Class notations.

1.2.3 LR classed pipe-laying systems that have been constructed, installed and tested under LR’s Special Survey and in accordance with LR’s Code for Lifting Appliances in a Marine Environment, July 2022 (as applicable) will be eligible for the special features pipe-laying system class notation PLS. When a PLS notation is not assigned to a unit fitted with a pipe-laying system, classification of the unit will be subject to the pipe-laying system being certified by LR.

1.2.4 Pipe-laying units are to have preventive measures to protect personnel from the hazards of dropped objects in accordance with Pt 3, Ch 1, 8 Risks to personnel from dropped objects and are eligible for the special features class notation DROPS.

1.2.5 Dynamic positioning systems for pipe-laying units are to comply with the requirements of Pt 3, Ch 9 Dynamic Positioning Systems and will be eligible for the DP(AA) or DP(AAA) class notation.

1.2.6 LR classed oxy-acetylene welding and cutting plants that have been constructed, installed and tested under LR’s Special Survey in accordance with Pt 3, Ch 17, 6 Oxy-acetylene plants for welding and cutting and Pt 1, Ch 3, 23 Notations and Descriptive Notes will be eligible for the special features class notation OXY. When an OXY notation is not assigned to a unit fitted with an oxy-acetylene welding and cutting plant, classification of the unit will be subject to the plant being certified by LR.

1.3.1 The following additional topics applicable to the class type notation are covered by this Chapter:

• Structural arrangements of the unit related to pipe-laying operations.
• Supporting structures for pipe-laying equipment, associated structures and offshore containers.
• Areas for pipe-laying operations and pipe-storage.
• Structural arrangements in way of moon pools.
• Integral tanks for the bulk storage of liquid chemicals.
• Hazardous areas and ventilation.
• Pollution prevention.
• Oxy-acetylene plants for welding and cutting.

1.4.2 Attention is to be given to the relevant Statutory Regulations for fire safety of the National Administration in the country of registration and the areas of operation as applicable, see Pt 1, Ch 2, 1 Conditions for classification and Pt 7, Ch 3 Fire Safety.

1.4.3 Additional requirements for safety systems and hazardous areas are given in Pt 7 Safety Systems, Hazardous Areas and Fire.

1.4.4 Living quarters, lifeboats and other evacuation equipment are to be located in non-hazardous areas and be protected and separated from the areas for pipe-laying operations and pipe-storage.

1.5.1 Plans, calculations and data are to be submitted as required by the relevant Parts of the Rules together with the additional plans and information listed in this Chapter.