Section 11 Mooring of ships at single point moorings

11.1.1 These requirements are applicable to conventional oil tankers which intend to utilise the fittings standardised for single point moorings. For other ship types, the applicability would be specially considered. The requirements specified include the type, strength and location of the required fittings.

11.1.2 A ship provided with mooring arrangements in accordance with the requirements of this Section will be eligible to be assigned the Class notation SPM4 where a single mooring line arrangement is provided for and DSPM4 where a dual mooring line arrangement is provided for, see Figure 13.11.1 Positioning of forward fairleads, bow chain stoppers and pedestal roller leads.

Note Pt 3, Ch 13, 11.2 Arrangements 11.2.7.(c)

Figure 13.11.1 Positioning of forward fairleads, bow chain stoppers and pedestal roller leads

11.2.1 The ship is to be fitted with bow chain stoppers and bow fairleads. In addition, pedestal roller fairleads may be required for alignment purposes but a direct straight lead from the chain stopper to the winch storage drum is the preferred arrangement. However, consideration of safety and protection from risk of injury to mooring personnel should take priority in determining whether pedestal rollers should be fitted as well as their number and positioning.

11.2.2 In order to ensure matching with terminal mooring equipment, the requirements for shipboard fittings are specified in association with ranges of ship deadweight as shown in Table 13.11.1 Deadweight group for shipboard fittings requirements.

11.2.3 Bow chain stoppers:

1. The number, chain cable size and minimum safe working load of bow chain stoppers should be as given in Table 13.11.2 Fittings requirements for deadweight group.

2. Bow chain stoppers should be located between 2,7 m and 3,7 m aft of the bow fairlead and should be positioned so as to give correct alignment with the bow fairlead and the pedestal fairlead or the storage drum of the winch, see Figure 13.11.1 Positioning of forward fairleads, bow chain stoppers and pedestal roller leads.

3. The leading edge of the stopper base plate is to be suitably faired to allow unimpeded entry of the combination chafe chain into the stopper. The chain referred to, forms part of the standardised SPM equipment.

4. The safety factor on yield of bow chain stoppers should be a minimum of 2 when the safe working load is applied.

5. The bow chain stopper(s) are to be type approved confirming that they are constructed in strict compliance with a standard recognised by LR which specifies SWL, yield strength and safety factors.

11.2.4 The deck in way of bow chain stoppers is to have a minimum thickness of 15 mm. Their foundations, welds attaching them to the ship and associated ship supporting structure are to be demonstrated adequate to resist horizontal loads equal to 2 x SWL as given in Table 13.11.2 Fittings requirements for deadweight group. This is to be accomplished by suitable engineering analysis or calculations together with an inspection of the installation.

11.2.5 Bow chain stoppers are to be permanently marked with the SWL and appropriate serial numbers so that the certificates can be easily cross-referenced to the fitted equipment.

11.2.6 Bow fairleads:

1. One centrally located bow fairlead should be provided for ships fitted with one bow chain stopper. Two bow fairleads should be provided for ships fitted with two bow chain stoppers, see Figure 13.11.1 Positioning of forward fairleads, bow chain stoppers and pedestal roller leads.

2. Bow fairlead openings should be at least 600 x 450 mm for 76 mm chafe chain size. Where more than one bow fairlead is installed, the spacing of centres should be between 2 m and 3 m.

3. The height of the centre of the bow fairlead opening above the deck should be determined by the extension, parallel to the deck, of the lead line of the chain cable to the bow chain stopper, see Figure 13.11.1 Positioning of forward fairleads, bow chain stoppers and pedestal roller leads. The fairlead should have a minimum radius equal to seven times the chain radius.

4. The scantlings of the fairlead are to be determined in association with a load of 2 x SWL with hawser angles up to 90 degrees from the ship’s centre line, both port and starboard in the horizontal plane and to 30 degrees above and below horizontal in the vertical plane.

5. The bow fairleads are to be type approved confirming that they are constructed in strict compliance with a standard recognised by LR which specifies SWL and safety factors.

6. Their foundations and associated ship supporting structure are to be demonstrated adequate by detailed engineering analysis or calculations together with an inspection of the installation.

11.2.7 Pedestal roller fairleads:

1. Pedestal roller fairleads should have a minimum radius equal to 10 times the radius of wire mooring ropes with a fibre core, seven times the radius of wire mooring ropes with a steel core or three times the radius of synthetic mooring ropes.

2. The number of pedestal roller fairleads used for each bow chain stopper should not exceed two and the angle subtended by the change of direction of the pick-up rope should be minimal.

3. The minimum distance of pedestal roller fairleads from the bow chain stopper should be 3,0 m. Any variation in the minimum distance will be specially considered.

4. Details of local strengthening of the deck in way of pedestal roller fairleads should be submitted for approval.

11.2.8 The winch drum used for handling the mooring gear should be capable of exerting a continuous duty pull of not less than 147 kN and be of sufficient size to accommodate 150 m of 80 mm diameter rope. Winch drum ends (warping ends) to handle pick-up ropes should be avoided. Remotely-operated winch storage drums are recommended.