20.1 General
20.1.1 The requirements given in Tables 20.1 and 20.2 are for a vessel of normal form
which may be expected to ride-out storms whilst at anchor. The anchors and cables are
not designed to hold a vessel off exposed coasts in rough weather nor stop a vessel that
is moving.
20.1.2 Provision is to be made for the secure storage of the anchor and its cable.
20.2 Anchors
20.2.1 The tabulated values for anchor masses refer to ‘High Holding Power’ anchors.
Anchors of other designs may be accepted based on the stated holding power.
20.2.2 When a fisherman type of anchor is provided, the mass given in Table 20.1 or 20.2
should be increased by 33% but the diameter of the anchor cable need not be
increased.
20.2.3 For vessels with an unusually high windage, due to high freeboard, a large rig,
large deckhouses or superstructures, the mass of the anchor and the anchor cable
diameter should be increased above that required in Table 20.1 or 20.2 to correspond to
the increased wind loading. The increase in anchor mass and corresponding cable strength
is to be to the satisfaction of the Certifying Authority.
20.2.4 For vessels of unusual or non-conventional ship form (including pontoon barges)
or working under specified restricted coastal or inshore operations, the anchor and
cable size and material should be to the satisfaction of the Certifying Authority in
accordance with the appropriate certification standards for the vessel type recognised
by one of the Load Line Assigning Authorities (4.2.2.4 refers). Any service restriction
placed by the certification standards’ reduction should be noted on the Small Workboat
Certificate and the owner / managing agent should ensure that this equipment carried is
commensurate with any voyage undertaken and with any specific local environmental
conditions e.g. tidal strength.
20.2.5 Anchors are to be rigged ready for use. Only where the particular operating
patterns dictate may the anchor be left unready, e.g. Pilot boat duties.
20.2.6 The design of the anchor is to be acceptable to the Certifying Authority.
20.2.7 Stainless steel and aluminium anchors will be separately considered dependent
upon the test loads for which the anchor has been designed.
20.2.8 Where vessels are to be engaged in coastal towing Owners should give
consideration to uplifting the size of the anchors and cables.
20.3 Cablesfootnote
20.3.1 The length of anchor cable attached to an anchor should be appropriate to the
area of operation but generally should be not less than 4 x the vessel’s mean length or
30 metres, whichever is the longer, for each of the main and spare anchors. (For a
definition of mean length see Note 4 of Tables 20.1 or 2).
20.3.2 The cable for main anchors and for spare anchors may be of chain, wire or rope,
subject to section 20.3.3.
20.3.3 When the anchor cable is of fibre rope or wire, there should be not less than 10
metres or 20% of the minimum required cable length, whichever is the greater, of chain
between the rope and the anchor. Where the anchor cable is wire then proposals to
substitute the chain tail by an anchor and/or chain of enhanced mass will be considered
to the satisfaction of the Certifying Authority, with special attention paid to the
anchor performance, i.e. catenary.
20.3.4 The strength and form of the anchor cable and its attachments to the anchor and
the vessel should be approved by the Certifying Authority. The material should be to the
satisfaction of the Certifying Authority in accordance with the appropriate
certification standards for the vessel type recognised by one of the Load Line Assigning
Authorities (4.2.2.4 refers).
20.3.5 Anchoring systems incorporating a windlass should have the bitter end of the
cable secured to the vessel’s structure and capable of being released in an emergency.
20.3.6 Anchor steel wire rope is to be fitted with thimbles at both ends.
20.4 Tow Line
20.4.1 A vessel should be provided with a towline of not less than the length and
diameter of the spare anchor cable. The towline may be the warp for the second anchor
and in the case of Pilot Boats, the tow line may be the spare anchor rope. Where
practicable, the towline should be buoyant.
20.5 Operations
20.5.1 When an anchor mass is more than 30 kilogrammes, an efficient mechanical means
should be provided for handling the anchor.
20.5.2 There should be a strong securing point on the foredeck or equivalent structure
and where appropriate a fairlead or roller at the stem head.
20.5.3 Operation in Area Category 0, 1, 2, 3 or 4
20.5.3.1 Vessels certificated to operate in Area Categories 0, 1, 2, 3 or 4 should be
provided with at least two anchors (one main and one spare or two main) and cables,
subject to section 20.1 and in accordance with the requirements of Table 20.1 or 2. Twin
propulsion, high speed vessels that do not normally anchor as part of their operational
procedures may carry a single larger anchor to a recognised Classification Society
standards sizes, see 25.9.7.
20.5.3.2 Anchors of equivalent holding power may be proposed and provided, subject to
approval by the Certifying Authority.
20.5.4 Operation in Area Category 5 and 6
20.5.4.1 Vessels certificated to operate in Area Category 5 and 6 should have an anchor
of sufficient mass for the size and type of vessel. Local conditions i.e. tide, currents
etc. should also be considered when choosing the anchor.
TABLE 20.1
ANCHORS AND CABLES – for vessels up to 15m
| Length of vessel
|
Anchor Mass Note 3
|
Anchor Cable Diameter Note 1, 3
|
|
|
Main
|
Spare
|
Main Chain
|
Rope Note 2
|
Spare Chain
|
Rope Note 2
|
| (metres)
|
(kg)
|
(kg)
|
(mm)
|
(mm)
|
(mm)
|
(mm)
|
| 6
|
8
|
4
|
6
|
12
|
6
|
10
|
| 7
|
9
|
4
|
8
|
12
|
6
|
10
|
| 8
|
10
|
5
|
8
|
12
|
6
|
10
|
| 9
|
13
|
5
|
8
|
12
|
6
|
10
|
| 10
|
16
|
6
|
8
|
12
|
6
|
10
|
| 11
|
19
|
7
|
8
|
12
|
6
|
10
|
| 12
|
22
|
10
|
10
|
14
|
8
|
12
|
| 13
|
25
|
12
|
10
|
14
|
8
|
12
|
| 14
|
28
|
12
|
10
|
14
|
8
|
12
|
| 15
|
30
|
15
|
10
|
14
|
8
|
12
|
TABLE 20.2
ANCHORS AND CABLES – for Vessels over 15m
| Loaded Displacement
|
Anchor Main Note 3
|
Anchor Spare Note 3
|
Anchor Chain diameter. Note 1,3,5
|
| (Tonnes)
|
(kg)
|
(kg)
|
(mm)
|
| 25
|
30
|
30
|
10
|
| 50
|
40
|
40
|
12
|
| 75
|
50
|
50
|
12
|
| 100
|
75
|
75
|
13.5
|
| 125
|
90
|
90
|
13.5
|
| 150
|
100
|
100
|
13.5
|
| 175
|
125
|
125
|
16
|
| 200
|
130
|
130
|
17.5
|
| 225
|
150
|
150
|
17.5
|
| 250
|
180
|
180
|
17.5
|
| 275
|
225
|
225
|
17.5
|
| 300
|
230
|
230
|
17.5
|
| 350
|
240
|
240
|
17.5
|
| 400
|
245
|
245
|
17.5
|
| 450
|
250
|
250
|
19
|
| 500
|
255
|
255
|
19
|
| 550
|
260
|
260
|
19
|
| 600
|
265
|
265
|
19
|
| 650
|
270
|
270
|
20
|
| 700
|
300
|
300
|
20
|
| 750
|
360
|
360
|
20
|
Notes:
Chain cable diameter given is for short link chain.
1 Chain cable diameter given is for short link chain. Chain cable should be sized in
accordance with EN 24565 (covered by BS 7160), or equivalent.
2 The rope diameter given is for nylon construction. When rope of another construction
is proposed, the breaking load should be not less than that of the nylon rope specified
in the table.
3 When anchors and cables are manufactured to imperial sizes, the metric equivalent of
the anchor mass and the cable diameter should not be less than the table value.
4 For the purposes of this section, mean length is defined as:-
(Length + Length on waterline) / 2
5 Where rope is used the breaking strength of the rope or wire should be equivalent to
that of the chain specified in the Table.