Section 1 General

1.1.2 The Rules also cover mooring yokes, loading arm arrangements, hinged joints and support structures on floating units.

1.1.3 These Rules assume that floating moored units will be tethered with catenary-type mooring cables attached to the sea bed by anchors, gravity blocks or piles. Proposals for the use of pivot arms or other methods of tethering will be specially considered, see Pt 3, Ch 13, 4 Mooring arms and towers and Pt 3, Ch 13, 6 Mechanical items.

1.1.4 Requirements for positional mooring systems are given in Pt 3, Ch 10 Positional Mooring Systems.

1.1.5 Foundations for mooring systems are to comply with Pt 3, Ch 14 Foundations, see also Pt 3, Ch 13, 4 Mooring arms and towers.

1.1.6 Buoys and other floating units may be fitted with pipelines or risers for loading and unloading linked ship/unit and additionally be fitted with crude oil bulk storage tanks, process plant facility, power generating capability, accommodation modules and similar facilities.

1.1.7 Units with crude oil or liquefied gas bulk storage tanks and/or production and process plant are to comply with the applicable requirements of Pt 3, Ch 3 Production and Storage Units and Pt 3, Ch 8 Process Plant Facility.

1.2.1 The definitions in this Chapter are stated for Rule application only and may not necessarily be valid in any other context.

1.2.2  Buoy. A floating mooring facility secured by a flexible tether or tethers to the sea bed, but excluding the other unit types defined in Pt 1, Ch 2, 2 Definitions, character of classification and class notations.

1.2.3  Deep draught caisson units are single column floating units which operate at a deep draught in relation to their overall depth.

1.2.4  Subsea buoyant vessel. A submerged structure with positive buoyancy secured by a flexible tether or tethers to the sea bed and used to support flexible risers.

1.2.5  Mooring tower. A structure for single point mooring which is attached directly to the sea bed. The tower may be a single or multiple member structure and can be fixed to the sea bed, or articulated by means of a universal joint attached to the sea bed.

1.2.7  Multi-point mooring. A mooring facility embodying a number of separate buoys or mooring points. A multi-point mooring terminal is used to hold a ship/unit on a general constant heading and can incorporate facilities for the transfer of oil, gas and other fluids.

1.2.8  Turret mooring. A single-point mooring variant where the slewing function, allowing complete or partial weathervaning, forms an integral part of the unit. Turret mooring is mainly applicable to permanently moored surface type units.

1.2.9  Spread mooring. A multi-line mooring system designed to maintain an offshore unit on an approximately fixed heading.

1.2.10  Mooring hawser. A mooring rope connecting a ship/unit to a single-point mooring or buoy. Only a hawser permanently attached to a single-point mooring or buoy will be included in the classification of the installation.

1.2.11  Mooring yoke. A structural arm connecting a ship/unit to a single-point mooring or buoy. A yoke is normally used for permanently moored units.

1.3.1 Where pipelines, power cables, etc., are incorporated into or trail from single-point mooring installations, details of their number, position, size and method of attachment are to be submitted in order that their effect on wave forces, etc., acting on the structure, and of any restraining forces that they may impose, can be assessed.

1.3.2 For units with production and process plant, the boundaries for classification are to be as defined in Pt 3, Ch 8, 1.3 Scope.

1.3.3 Pipelines carrying high pressure fluids, cables carrying high energy electricity supplies and cable carrying control signals critical to the safety of the unit, or to its operational reliability, are to be located in suitable positions on the unit in order to avoid accidental damage by moored ships/units, maintenance craft, or other sources which may cause large impact loads. Where this is impracticable, they are to be adequately protected and the arrangements submitted for approval.

NOTE

This information is required whether the pipework and cables are permanent or temporary and whether they are situated above water or subsea.

1.3.6 Where power cables are attached to the structure for the purpose of supplying electricity to a moored ship/unit, etc., the extent, if any, of cable included in the class of the structure will be specially considered by LR.

1.4.1 The Regulations for classification, and the assignment of class notations, are given in List of abbreviations, to which reference should be made.

1.4.3 Deep draught caisson units will be eligible for the assignment of a type class notation in accordance with the unit’s function, see Pt 3, Ch 3 Production and Storage Units. In addition a descriptive note will be added in the Class Direct website, e.g., ‘Deep draught caisson unit’.

1.4.4 Associated integral mooring equipment, including anchors, mooring lines and their connections to the sea bed, will generally be included in the class of an installation, see Pt 1, Ch 2, 2 Definitions, character of classification and class notations. For mooring hawsers, see Pt 3, Ch 13, 5 Mooring hawsers and load monitoring.

1.4.6 Units with oil or liquefied gas bulk storage tanks or production/process plant may be assigned type class notations in accordance with Pt 3, Ch 3 Production and Storage Units.

1.4.7 Product riser systems which comply with the requirements of Pt 3, Ch 12 Riser Systems will be eligible for the special features notation PRS.

1.4.8 When a unit is to be verified in accordance with the Regulations of a Coastal State Authority, an additional class notation may be assigned in accordance with List of abbreviations.

1.4.9 Vessels designed for offshore loading should have the arrangements for offshore loading designed and constructed in accordance with suitable standards. For vessels classed LR, the requirements are outlined in Pt 7, Ch 6 Arrangements for Offshore Loading of the Rules for Ships.

1.6.1 In principle units engaged in production and/or crude oil storage are to be divided into main functional areas in accordance with the requirements of Chapter 3.

1.6.2 The requirements for fire safety are to be in accordance with the requirements of a National Administration. Additional requirements for the fire safety on units with production and process plant are given in Pt 7, Ch 3 Fire Safety, see also Pt 1, Ch 2, 1 Conditions for classification.

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

1.6.4 Living quarters, lifeboats and other evacuation equipment are to be located in non-hazardous areas and be protected and separated from production and wellhead areas.

1.6.5 Suitable arrangements are to be incorporated in the design to enable supply and maintenance craft to come along side as necessary and to moor safely while maintenance staff and equipment are being transferred to, or from, the installation.

1.6.6 Protection against damage which might otherwise be caused by impacts from moored ships/units over-riding the mooring installations or by supply and maintenance craft coming along side is to be provided. This protection is to include suitable fendering, adequately reinforced landing platforms or their equivalent, see also Pt 4, Ch 3, 1 General.

1.6.7 Proper means of access are to be provided for maintenance and survey. Arrangements are to include a suitable platform or other landing area. It is the Owner’s responsibility to provide suitable ladders, where the height of the deck is too great to facilitate direct access of personnel from maintenance craft.

1.7.1 The general requirements for watertight and weathertight integrity are to be in accordance with Pt 4, Ch 7 Watertight and Weathertight Integrity and Load Lines .

1.7.2 Floating units and subsea buoyant vessels are to have adequate buoyancy and stability in both intact and damage conditions, see Pt 4, Ch 7 Watertight and Weathertight Integrity and Load Lines. They are to be sub-divided by watertight divisions, especially in zones where there is a risk of collision.

1.7.3 When requested, LR will give special consideration to the incorporation of equivalent approved means of protection against accidental sinking on buoys and subsea buoyant vessels. Where compartments are to be filled with foam, full details are to be submitted for approval.

1.7.4 The integrity of the weather deck of buoys and other floating structures is to be maintained. Where items of plant equipment penetrate the weather deck and are intended to constitute the structural barrier to prevent the ingress of water to spaces below the deck, their structural strength is to be equivalent to the Rule requirements for this purpose. Otherwise, such items are to be enclosed in deckhouses fully complying with the Rules. Full details are to be submitted for approval.