Section 12 Emergency towing arrangements

12.1.1 This Section applies to ships equipped with emergency towing arrangements in accordance with IMO Resolution MSC.35(63) - Adoption of Guidelines for Emergency Towing Arrangements on Tankers - (adopted on 20 May 1994)Amended by Resolution MSC.132(75).

12.1.2 Where a ship is provided with an emergency towing arrangement and the supporting structure complies with the requirements of this Section, the ship will be eligible to be assigned the descriptive note ETA which will be entered in column 6 of the Register Book.

12.1.3 The design load for strong points and associated fairleads shall be at least the specified breaking strength of the weakest component of the emergency towing arrangement, for angles of tow as specified in IMO Resolution MSC.35(63) - Adoption of Guidelines for Emergency Towing Arrangements on Tankers - (adopted on 20 May 1994)Amended by Resolution MSC.132(75).

12.1.4 The deck and its supporting structure in way of strongpoints and fairleads are to be suitably reinforced to resist design loads of at least 1,3 times the specified breaking strength of the weakest component of the emergency towing arrangement, for angles of tow as specified in IMO Resolution MSC.35(63) - Adoption of Guidelines for Emergency Towing Arrangements on Tankers - (adopted on 20 May 1994)Amended by Resolution MSC.132(75). The deck in way of strongpoints and fairleads is to have a minimum thickness of 15 mm.

12.1.5  Stresses induced in the strongpoints, fairleads and associated ship supporting structure, determined using the design loads from Pt 3, Ch 13, 12.1 Structural requirements 12.1.3 and Pt 3, Ch 13, 12.1 Structural requirements 12.1.4 as appropriate, are not to exceed the permissible values given in Table 13.12.1 Permissible stress values. The capability of the structure to withstand buckling is also to be assessed.

Table 13.12.1 Permissible stress values

	Permissible stress N/mm2
Direct stress	σo
Shear stress
Combined stress	σo
Symbols
σo = specified minimum yield stress, in N/mm2

12.1.6 The weld between the fittings and the deck shall be capable of resisting the design load specified in Pt 3, Ch 13, 12.1 Structural requirements 12.1.3.

12.1.7 The structural arrangement is to be such that continuity will be ensured. Abrupt changes of shape or section, sharp corners and other points of stress concentration are to be avoided.

12.1.8 Designs of emergency towing arrangements shall be prototype-tested as required by the IMO Resolution MSC.35(63) - Adoption of Guidelines for Emergency Towing Arrangements on Tankers - (adopted on 20 May 1994)Amended by Resolution MSC.132(75)

12.2.1 Chafing chains are to be manufactured, tested and certified in accordance with Ch 10, 2 Stud link chain cables for ships of the Rules for Materials Grades U2 and U3.

12.2.2 The outboard end of the chafing chain is to include a pear-shaped link allowing connection to a shackle corresponding to the type of ETA and chain grade. A typical arrangement is shown in Figure 13.12.1 Typical outboard chafing chain end.

Figure 13.12.1 Typical outboard chafing chain end

12.2.3 The chafing chain is to be able to withstand a breaking load not less than twice the safe working load (SWL). The nominal diameter of common link for chafing chains is to comply with the value indicated in Table 13.12.2 Nominal diameter of common link for chafing chains for ETA.

12.2.4 Steel wire ropes are to be manufactured, tested and certified in accordance with Ch 10, 6 Steel wire ropes of the Rules for Materials.

12.2.5 Fibre ropes are to be manufactured, tested and certified in accordance with Ch 10, 7 Fibre ropes of the Rules for Materials.