Section 4 Anchors

4.1.1 The Rules are based on the use of high holding power (HHP) type anchors.

4.1.2 When ordinary holding power anchors are used as bower anchors, the mass given in Table 5.4.1 Equipment - HHP Bower anchors and chain cables is to be increased by 33 per cent.

4.1.3 Where it is proposed to fit other types of anchor, the mass will be specially considered.

4.1.4 Ships are to be provided with the number of anchors as specified in Table 5.4.1 Equipment - HHP Bower anchors and chain cables on board which must be ready for immediate use. Where this is impractical, see Vol 1, Pt 3, Ch 5, 9.2 Hawse pipes and anchor recesses 9.2.4, special consideration may be given to only having one anchor ready for immediate use.

4.1.5 Where there is a high degree of redundancy in propulsion and steering and where the engine can be brought to readiness quickly, consideration may be given to the fitting of a single anchor where Table 5.4.1 Equipment - HHP Bower anchors and chain cables requires the fitting of two anchors.

4.1.6 Anchors are to be of an approved design. The design of all anchor heads is to be such as to minimise stress concentrations, and in particular, the radii on all parts of cast anchor heads are to be as large as possible, especially where there is considerable change of section.

4.1.7 Anchors which must be specially laid the right way up, or which require the fluke angle or profile to be adjusted for varying types of sea bed, will not generally be approved for normal ship use, but may be accepted for offshore units, floating cranes, etc. In such cases suitable tests may be required.

4.1.8 Where kedge anchors are specified, they are to be in accordance with Table 5.6.1 Equipment - Kedge anchors and wires, towlines and mooring lines.

4.2.1 The requirements for the manufacture, testing and certification of anchors are contained in Ch 10 Equipment for Mooring and Anchoring of the Rules for the Manufacture, Testing and Certification of Materials (hereinafter referred to as the Rules for Materials).

4.3.1 Anchors are generally to be housed in suitable hawse pipes, or stowed in dedicated chocks on deck.

4.3.2 Hawse pipes and anchor pockets are to be in accordance with Vol 1, Pt 3, Ch 5, 8.11 On-board testing. Alternatively, roller fairleads of suitable design may be fitted. Where hawse pipes are not fitted, alternative arrangements will be specially considered.

4.3.3 It is recommended that anchor lashings, e.g. a ‘devil’s claw’, be fitted to hold the anchor tight against the hull or the anchor pocket. Anchor lashings are to be designed to resist at least a load corresponding to twice the anchor mass plus 10 m of cable without exceeding 40 per cent of the yield strength of the material.

4.4.1 Anchors of designs for which approval is sought as high holding power anchors are to be tested in accordance with Ch 10, 1.3 Anchor holding power tests for HHP and SHHP anchors of the Rules for the Manufacture, Testing and Certification of Materials, July 2022. It needs to be suitable for ship’s use and shall not require prior adjustment or special placement on the sea bottom.

4.5.1 Proposals to use anchors of the SHHP type will be subject to special consideration.

4.5.2 Final acceptance will be dependent upon satisfactory strength and performance tests.

4.5.3 Anchors of designs for which approval is sought as SHHP anchors are to be tested in accordance with Ch 10, 1.3 Anchor holding power tests for HHP and SHHP anchors of the Rules for the Manufacture, Testing and Certification of Materials, July 2022. They are to have holding powers of at least four times those of approved standard stockless anchors of the same mass.

4.6.1 The mass of each bower anchor given in Table 5.4.1 Equipment - HHP Bower anchors and chain cables is for anchors of equal mass. The masses of individual anchors may vary by ±7 per cent of the masses given in the Table, provided that the total mass of the anchors is not less than would have been required for anchors of equal mass.

4.6.2 The mass of the head, including pins and fittings, of an ordinary stockless anchor is to be not less than 60 per cent of the total mass of the anchor.

4.6.3 When stocked bower or kedge anchors are to be used, the mass excluding the stock is to be not less than 80 per cent of the mass given in Table 5.4.1 Equipment - HHP Bower anchors and chain cables for ordinary stockless bower anchors and Table 5.6.1 Equipment - Kedge anchors and wires, towlines and mooring lines for kedge anchors. The mass of the stock is to be 25 per cent of the total mass of the anchor, including the shackle, etc. but excluding the stock.

4.7.1 Identification of anchors which have been tested is to be in accordance with Ch 10 Equipment for Mooring and Anchoring of the Rules for Materials.