Section 9 Fibre ropes

9.1.1 This Section gives requirements for fibre ropes part of loose or semi-taut catenary mooring lines of positional mooring systems of offshore units.

The use of fibre rope is confined to the suspended immersed part of the catenary system.

Generally chain or wire rope or special connectors shall be fitted in parts of the anchor leg subject to contact with sea bed or in the vicinity of the attachment point of the mooring line to the offshore unit.

Note that the requirements Pt 3, Ch 13, 5 Mooring hawsers and load monitoring, only apply to hawsers used in temporary berthing of shuttle tankers or ship to CALM buoys operated, inspected and maintained in accordance with OCIMF recommendations. Fibre ropes used as hawsers in the long term mooring of Offshore Units to CALM buoy or SALM system shall generally comply with the requirements of this Pt 3, Ch 10 Positional Mooring Systems and specific requirements on fibre ropes from this section. They shall be designed for the site specific loading (strength and fatigue) with sufficient redundancy (i.e. considering one line failed case).

9.1.2 Acceptance of fibre ropes will be based on:

• submission of complete design, manufacturing and installation documentations for design appraisal by LR.
• compliance with API RP 2SM Design, Manufacture, Installation, and Maintenance of Synthetic Fibre Ropes for Offshore Mooring as applicable to the specific rope design, field deployment and service.
• compliance with the requirements of this section and the requirement of LR Rules for Materials (especially Ch 10 Equipment for Mooring and Anchoring) where this is more specific or onerous as applicable to the specific rope design, field deployment and service.
• qualification testing as agreed with LR (and generally in line with API RP 2SM).
• manufacturing and production testing under LR Survey and certification by LR.

9.2.2 Factors of safety for fibre rope are to be a minimum of 20 per cent higher than the levels given in Pt 3, Ch 10, 6 Anchor lines for chain and wire rope materials.

Factor of safety =

A reduction factor will require to be applied to the standard designated Minimum Breaking Strength, where the test database for the rope type is statistically small.

This does not generally apply to polyester fibre ropes for which sufficient test data, manufacturing and service experience can be documented.

9.2.3 Fibre ropes shall remain within the water column under all service conditions and not touch the sea bed in any intact or damaged condition.

9.2.4 Fibre ropes shall be kept sufficiently far below the waterline, and below the connection point on the unit, to avoid any possibility of contact damage, degradation by UV exposure, excessive marine growth developing on the sheathing, detrimental intermittent soaking/drying etc.

9.3.1 Fibre ropes are to be manufactured at a works approved by LR.

9.3.2 Ropes and fittings will be subject to LR survey during manufacture and testing.

9.3.3 A certified ISO 9001/9002 Quality System is to be in place and a quality plan is to be produced and agreed with LR Surveyors.

9.3.4 The ropes and fittings are to be manufactured in accordance with the approved design, standards and procedures.

9.3.5  See also requirement of Ch 10, 7 Fibre ropes of the Rules for Materials.

9.4.1 The purchaser is to specify the project specific material, manufacturing and testing requirements where these complement, exceed or are more onerous than those of this Pt 3, Ch 10, 9 Fibre ropes , Ch 10 Equipment for Mooring and Anchoring of the Rules for Materials (e.g. chain length and tolerances, maximum yield strength, coating, reference link identification etc.) or API RP 2SM. These shall be reported and agreed with LR.

9.4.2 A datasheet is to summarise all characteristics of each fibre rope segment as necessary to ensure satisfactory deployment of the rope within the Positional Mooring System and to support the in service inspection, repair and maintenance plan.