Section 5 Mooring hawsers and load monitoring
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 13 Buoys, Deep Draught Caissons, Turrets and Special Structures - Section 5 Mooring hawsers and load monitoring

Section 5 Mooring hawsers and load monitoring

Parent topic: Chapter 13 Buoys, Deep Draught Caissons, Turrets and Special Structures

5.1 Mooring hawsers

5.1.1 Mooring hawsers permanently attached to a classed installation and used to moor a shuttle tanker, or other ship/unit are included in the classification.

5.1.2 Mooring hawsers are to be of suitable material and construction for the intended service and are to be fitted with:
  1. a chafe chain assembly in accordance with Oil Companies International Marine Forum (OCIMF) Recommendations for Equipment Employed in the Mooring of Ships at Single Point Moorings, or equivalent; and
  2. a pick-up line to facilitate the picking up of the hawser by the ship/unit.
5.1.3 Testing and manufacturing inspections of ropes for mooring hawsers are to be in accordance with the following OCIMF Standards, or suitable alternative recognised National or International Standards:
  • Prototype Rope Testing.
  • Procedures for Quality Control and Inspection during the Production of Hawsers.

5.1.4 A single-point mooring hawser is to have a minimum rated strength of twice the maximum mooring load, see 5.1.5. In the case of a double mooring hawser comprising two individual ropes running to well separated fairleads, each hawser is to have a minimum rated strength of 1,5 times the total maximum mooring load. For classification purposes, the rated strength of a single-point mooring hawser is to be taken as the ‘New Wet Break Strength’ (NWBS) of the particular hawser assembly, as defined in OCIMF Standards referenced in 5.1.3.

5.1.5 The maximum mooring load used to determine the required strength of a mooring hawser will also be regarded as the maximum allowable peak mooring load in service. This allowable load will be included in the limiting design criteria on which classification is based.

5.2 Load monitoring

5.2.1 Single-point mooring (SPM) installations are to be provided with an approved means of monitoring the load occurring in the mooring hawser connecting the SPM to the ship/unit (alternatively such equipment can be provided on the attending vessel, see Pt 7, Ch 6, 3 Positioning, monitoring and control arrangements of the Rules for Ships). This equipment is to be designed so that automatic warning is given to the ship/unit in the event that tension in the mooring hawser exceeds designated limits, see 5.1.5. Warning is to be given by both visual indication and audible alarm. Consideration will be given to alternative proposals such as provision of a ‘weak link’. Full details of such proposals are to be submitted for LR approval.

5.2.2 The load level designated to initiate automatic warning is to be below the maximum allowable hawser load level by a sufficient margin to allow such steps to be taken as may be necessary, to prevent excessive loads, or to prepare for ship/unit disconnection from the SPM. It is recommended that two warning levels be incorporated, the first level at 60 per cent of allowable load and the second level at 80 per cent of allowable load. Where only one warning level is provided it should be set at no more than 70 per cent of allowable load.

5.2.3 The load level designated to initiate the automatic warning should be set giving due consideration to the safe working load of the chain stoppers fitted to the attending vessel.

5.3 Spare parts and maintenance

5.3.1 An adequate number of spare parts for the hawser system is to be provided on board a classed unit.

5.3.2 A planned maintenance and replacement scheme for mooring hawsers are to be submitted to LR and suitable instructions are to be included in the Operations Manual.

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