Types of Anchors are:
- Ordinary anchors of “stockless” type are to be generally adopted and they are to be of appropriate design in compliance with the rules or practice of each individual Society.
- The mass of the heads of stockless anchors including pins and fittings are not to be less than 60% of the total mass of the anchor.
- The mass, per anchor, of bower anchor given in Table 1 is required for anchors of equal mass.
The mass of individual anchor may vary to 7% of the Table mass provided that the total mass of anchors is not less than that required for anchors of equal mass.
High holding power (HHP) anchors
- A “high holding power” anchor is to be suitable for ship’s use and is not to require prior adjustment or special placement on the sea bottom.
- When special type of anchors designated “high holding power anchor” of proven superior holding ability are used as bower anchors, the mass of each anchor may be 75% of the mass required for ordinary stockless bower anchors in the Table 1.
- For approval and/or acceptance as a HHP anchor satisfactory tests are to be made on various types of bottom, and the anchor is to have a holding power at least twice than of an ordinary stockless anchor of the same weight. Full scale tests are to be carried out at sea on various types of bottom and to be applied to anchors the weights of which are, as far as possible, representative of the full range of sizes proposed; for a definite group of the range the two anchors selected for testing (ordinary stockless anchors and HHP anchors) should be of approximately the same weight, and should be tested in association with the size of chain cable appropriate to this weight.
The length of cable with each anchor should be such that the pull on the shank remains practically horizontal, for this purpose a scope of 10 is considered normal but a scope of not less than 6 may be accepted. Scope is defined as the ratio of length of cable to depth of water.
Three tests shall be taken for each anchor and nature of bed. The pull shall be measured by dynamometer. The stability of the anchor and ease of breaking out should be noted where possible. Tests are normally to be carried out from a tug but alternatively shore based tests may be accepted.
Measurements of pull based on RPM/bollard pull curve of tug may be accepted instead of dynamometer readings. Tests in comparison with a previously approved HHP anchor may be accepted as a basis for approval. For approval and/or acceptance of high holding power anchors of the whole range of weight, tests should be carried out on at least two – sizes of anchors and the weight of the maximum size to be approved could be accepted up to 10 times the weight of large size tested.