Section 1 Anchoring equipment (2024)

Parent topic: Chapter 9 Anchoring and Towing Equipment

1.1 General

1.1.1For self-propelled units to be assigned the figure (1) in the character of Classification, the anchoring equipment, i.e. anchors, cables, windlass and winches, etc. necessary for the unit during ocean voyages or location moves, is to be as required by this Section. The Regulations governing the assignment of the figure (1) for equipment are given in Pt 1, Ch 2, 2 Definitions, character of classification and class notations.

1.1.2When the equipment fitted to the unit is designed primarily as positional mooring equipment, consideration will be given to accepting the proposed equipment as equivalent to the Rule requirements but only if the arrangements are such that it can be efficiently used as anchoring equipment. See also Pt 1, Ch 2, 2.3 Character Symbols and Pt 3, Ch 10 Positional Mooring Systems.

1.1.3Where the Classification Committee has agreed that anchoring and mooring equipment need not be fitted in view of the particular service of the unit, the character letter N will be assigned, see also Pt 1, Ch 2, 2.2 Modes of operation.

1.2 Equipment number

1.2.1The requirement for anchors, cables, wires and ropes is to be based on an Equipment Number calculated as follows:

Equipment Number =

where

moulded displacement in transit condition, in tonnes

projected area perpendicular to wind direction when at anchor, in m²

projected area parallel to wind direction when at anchor, in m²

In calculating the areas and :

Masking effect can be taken into account for columns;
Open trusswork of derricks, booms and towers, etc. may be approximated by taking 30 per cent of the block area of each side, i.e. 60 per cent of the projected area of one side for double sided trusswork.
When calculating projected areas, account is to be taken of topside process facilities. Special consideration will be given to structure extending outside of the Rule length, L.

1.3 Determination of equipment

1.3.1The basic equipment of anchors and cables is to be determined from Table 9.1.1 Equipment - Anchors and chain cables and associated notes. Table 9.1.1 Equipment - Anchors and chain cables is based on the following assumptions:

1.4 Anchors

1.4.1Two anchors are to be fitted and arranged so that they may be readily dropped should an emergency occur.

1.4.2The mass of each anchor is to be as given in Table 9.1.1 Equipment - Anchors and chain cablesexcept that one anchor may weigh seven per cent less than the Table weight so long as the total weight of the two anchors attached to the cables is not less than twice the tabular weight for one anchor.

1.4.3Anchors are to be of 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 a considerable change of section.

1.4.4Positional mooring anchors of the type which are generally similar to conventional marine anchors but 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 normally be accepted as anchoring equipment in accordance with these Rules.

1.4.5 If ordinary ship type stockless bower anchors, not approved as high holding power anchors, are to be used as Rule equipment, the mass of each anchor is to be not less than 1,33 times that listed in Table 9.1.1 Equipment - Anchors and chain cables for the unit’s Equipment Number.

1.4.6The requirements for manufacture, proof testing and identification of anchors are to be in accordance with 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).

Table 9.1.1 Equipment - Anchors and chain cables

Equipment number		Equipment Letter	High holding power anchor mass, in kg	Stud link chain cable
Exceeding	Not exceeding			Length per anchor, in metres	Diameter, in mm
Exceeding	Not exceeding			Length per anchor, in metres	Grade U1	Grade U2	Grade U3
50	70	A	140	110	14	12,5	—
70	90	B	180	110	16	14	—
90	110	C	230	110	17,5	16	—
110	130	D	270	110	19	17,5	—
130	150	E	310	137,5	20,5	17,5	—
150	175	F	360	137,5	22	19	—
175	205	G	430	137,5	24	20,5	—
205	240	H	500	137,5	26	22	20,5
240	280	I	590	165	28	24	22
280	320	J	680	165	30	26	24
320	360	K	770	165	32	28	24
360	400	L	860	192,5	34	30	26
400	450	M	970	192,5	36	32	28
450	500	N	1080	192,5	38	34	30
500	550	O	1190	192,5	40	34	30
550	600	P	1300	220	42	36	32
600	660	Q	1440	220	44	38	34
660	720	R	1580	220	46	40	36
720	780	S	1710	220	48	42	36
780	840	T	1850	220	50	44	38
840	910	U	1990	220	52	46	40
910	980	V	2140	247,5	54	48	42
980	1060	W	2290	247,5	56	50	44
1060	1140	X	2470	247,5	58	50	46
1140	1220	Y	2660	247,5	60	52	46
1220	1300	Z	2840	247,5	62	54	48
1300	1390	A†	3040	247,5	64	56	50
1390	1480	B†	3240	275	66	58	50
1480	1570	C†	3440	275	68	60	52
1570	1670	D†	3670	275	70	62	54
1670	1790	E†	3940	275	73	64	56
1790	1930	F†	4210	275	76	66	58
1930	2080	G†	4500	275	78	68	60
2080	2230	H†	4840	302,5	81	70	62
2230	2380	I†	5180	302,5	84	73	64
2380	2530	J†	5510	302,5	87	76	66
2530	2700	K†	5850	302,5	90	78	68
2700	2870	L†	6230	302,5	92	81	70
2870	3040	M†	6530	302,5	95	84	73
3040	3210	N†	6980	330	97	84	76
3210	3400	O†	7430	330	100	87	78
3400	3600	P†	7880	330	102	90	78
3600	3800	Q†	8330	330	105	92	81
3800	4000	R†	8780	330	107	95	84
4000	4200	S†	9250	330	111	97	87
4200	4400	T†	9700	357,5	114	100	87
4400	4600	U†	10100	357,5	117	102	90
4600	4800	V†	10600	357,5	120	105	92
4800	5000	W†	11000	371,5	122	107	95
5000	5200	X†	11600	371,5	124	111	97
5200	5500	Y†	12100	371,5	127	111	97
5500	5800	Z†	12700	371,5	130	114	100
5800	6100	A*	13400	371,5	132	117	102
6100	6500	B*	14100	371,5	—	120	107
6500	6900	C*	15000	385	—	124	111
6900	7400	D*	16000	385	—	127	114
7400	7900	E*	17500	385	—	132	117
7900	8400	F	18500	385	—	137	122
8400	8900	G*	19500	385	—	142	1127
8900	9400	H*	20500	385	—	147	132
9400	10000	I*	22000	385	—	152	132
10000	10700	J*	23500	385	—	157	137
10700	11500	K*	25000	385	—	157	142
11500	12400	L*	26500	385	—	162	147
12400	1340	M*	29000	385	—	—	152
13400	14600	N*	31500	385	—	—	157
14600	16000	O*	34500	385	—	—	162
NOTES
1. Consideration will be given to the acceptance of equipment differing from these requirements on units which are classed for restricted service (generally those with geographical limitations ensuring service in sheltered or shallow waters only).
2. Special consideration will be given to units which are unmanned during towed voyages and transfer moves.

1.5 High holding power anchors

1.5.1Anchors of designs for which approval is sought as high holding power anchors are to be tested at sea to show that they have holding powers of at least twice those of approved standard stockless anchors of the same mass. For holding power test requirements relating to high holding power anchors, see 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.

1.5.2High holding power anchors are to be of a design that will ensure that the anchors will take effective hold of the sea bed without undue delay and will remain stable, for holding forces up to those required by Pt 4, Ch 9, 1.5 High holding power anchors 1.5.1, irrespective of the angle or position at which they first settle on the sea bed when dropped from a normal type of hawse pipe. In case of doubt, a demonstration of these abilities may be required. The anchors are not to require prior adjustment or special placement on the sea bottom.

1.6 Chain cables

1.6.1The minimum sizes and lengths of chain cables are to be as required by Table 9.1.1 Equipment - Anchors and chain cables.

Table 9.1.2 Anchor equipmant chain grades

Grade	Material	Tensile strength
Grade	Material	N/mm²	kgf/mm²
U1	Mild steel	300–490	(31–50)
U2(a)	Special quality steel (wrought)	490–690	(50–70)
U2(b)	Special quality steel (cast)	490–690	(50–70)
U3	Extra special quality steel	690 min.	(70 min.)

1.6.3Grade U1 material having a tensile stress of less than 400 N/mm² (41 kgf/cm²) is not to be used in association with high holding power anchors. Grade U3 material is to be used only for chain 20,5 mm or more in diameter.

1.6.4The form and proportion of links and shackles are to be in accordance with Ch 10 Equipment for Mooring and Anchoring of the Rules for Materials.

1.6.5As an alternative to the chains listed in Table 9.1.1 Equipment - Anchors and chain cables, consideration will be given to the use of the following:

Chain cables of Grades R3, R3S and R4 in accordance with Ch 10, 3 Offshore Mooring chain cables of the Rules for Materials.
Wire rope meeting the requirements of the Rules for Materials.

In this case, the length and breaking strength of the wire rope will be specially considered.

1.7 Arrangements for working and stowing anchors and cables

1.7.1A windlass or winch of sufficient power and suitable for the type of cable is to be provided for each of the anchor cables. Where Owners require equipment significantly in excess of Rule requirements, it is their responsibility to specify increased windlass or winch power.

1.7.2The windlasses or winches are to be securely fitted and efficiently bedded to suitable positions on the unit. The structural design integrity of the bedplate is the responsibility of the Builder and windlass manufacturer.

1.7.3The following performance criteria are to be used as a design basis for the windlass:

The windlass is to have sufficient power to exert a continuous duty pull over a period of 30 minutes of:

36,79 N (3,75 kgf) – for Grade U1 chain,

41,68 N (4,25 kgf) – for Grade U2 chain,

41,6 N (4,75 kgf) – for Grade U3 chain,

where is the chain diameter, in mm.
The windlass is to have sufficient power to exert, over a period of at least two minutes, a pull equal to the greater of:
1. short-term pull:
  1,5 times the continuous duty pull as defined in Pt 4, Ch 9, 1.7 Arrangements for working and stowing anchors and cables 1.7.3.(a).
2. anchor breakout pull:
  16,24
where

is length of chain cable per anchor, in metres, as given by Table 9.1.1 Equipment - Anchors and chain cables

is the mass of high holding power anchor, in kg, as given in Table 9.1.1 Equipment - Anchors and chain cables
The windlass, with its braking system in action and in conditions simulating those likely to occur in service, is to be able to withstand, without permanent deformation or brake slip, a load, applied to the cable, given by:
(44 – 0,08) N

(44 – 0,08) kgf )

where

is given in Table 9.1.3 .

NOTE

The performance criteria are to be verified by means of shop tests in the case of windlasses manufactured on an individual basis. Windlasses manufactured under LR’s Type Approval Scheme will not require shop testing on an individual basis.

Cable grade

Windlass used in conjunction with chain stopper Chain stopper not fitted

U1 4,41 (0,45) 7,85 (0,8)

U2 6,18 (0,63) 11,0 (1,12)

U3 8,83 (0,9) 15,7 (1,6)

1.7.4Where shop testing is not possible and Type Approval has not been obtained, calculations demonstrating compliance with Pt 4, Ch 9, 1.7 Arrangements for working and stowing anchors and cables 1.7.3 are to be submitted, together with detailed plans and an arrangement plan showing the following components:

Shafting.
Gearing.
Brakes.
Clutches.

1.7.5During trials on board the unit, the windlass should be shown to be capable of raising the anchor from a depth of 82,5 m to a depth of 27,5 m at a mean speed of not less than 9 m/min. Where the depth of water in the trial area is inadequate, suitable equivalent simulating conditions will be considered as an alternative.

1.7.6The cable is to be capable of being paid out in the event of a power failure.

1.7.7Windlass performance characteristics specified in Pt 4, Ch 9, 1.7 Arrangements for working and stowing anchors and cables 1.7.3 and Pt 4, Ch 9, 1.7 Arrangements for working and stowing anchors and cables 1.7.5 are based on the following assumptions:

One cable lifter only is connected to the drive shaft.
Continuous duty and short-term pulls are measured at the cable lifter.
Brake tests are carried out with the brakes fully applied and the cable lifter declutched.
The probability of declutching a cable lifter from the motor with its brake in the off position is minimised.
Hawse pipe efficiency assumed to be 70 per cent.

1.7.8An easy lead of the cables from the windlass or winch to the anchors and chain lockers or wire storage drum is to be arranged. Where cables pass over or through stoppers, these stoppers are to be manufactured from ductile material and be designed to minimise the probability of damage to, or snagging of, the cable. They are to be capable of withstanding without permanent deformation a load equal to 80 per cent of the Rule breaking load of the cable passing over them.

1.7.9The chain locker is to be of a capacity and depth adequate to provide an easy direct lead for the cable into the chain pipes, when the cable is fully stowed. Chain or spurling pipes are to be of suitable size and provided with chafing lips. If more than one chain is to be stowed in one locker then the individual cables are to be separated by substantial divisions in the locker.

1.7.10Provision is to be made for securing the inboard ends of the cables to the structure. This attachment should have a working strength of not less than 63,7 kN (6,5 tonne-f) or 10 per cent of the breaking strength of the chain cable, whichever is the greater, and the structure to which it is attached is to be adequate for this load. Attention is drawn to the advantages of arranging that the cable may be slipped in an emergency from an accessible position outside the chain locker.

1.7.11Where wire rope cables are used, these are to be stored on suitable drums. The lead to the drums is to be such that the cables will reel onto the drums reasonably evenly. If the drums are designed to apply the full winch hauling load to the cables then the arrangements, using spooling gear or otherwise, are to ensure even reeling of the cables onto the drums.

1.7.12Fairleads, hawse pipes, anchor racks and associated structure and components are to be of ample thickness and of a suitable size and form to house the anchors efficiently, preventing, as much as practicable, slackening of the cable or movements of the anchor being caused by wave action. The plating and framing in way of these components are to be reinforced as necessary. Columns, lower hulls, footings and other areas likely to be damaged by anchors, chain cables and wire ropes, etc. are to be suitably strengthened.

1.7.13The design of the windlass is to be such that the following requirements or equivalent arrangements will minimise the probability of the chain locker or forecastle being flooded in bad weather:

a weathertight connection can be made between the windlass bedplate, or its equivalent, and the upper end of the chain pipe;
access to the chain pipe is adequate to permit the fitting of a cover or seal, of sufficient strength and proper design, over the chain pipe if the sea is liable to break over the windlass; and
for column-stabilised units, see Pt 4, Ch 7, 4.7 Weathertight integrity related to stability 4.7.2.

1.7.14All anchors are to be stowed to prevent moving during transit.

1.8 Testing of equipment

1.8.1All anchors and chain cables are to be tested at establishments and on machines recognised by LR and under the supervision of LR’s Surveyors or other Officers recognised by LR, and in accordance with the Rules for Materials.

1.8.2Test certificates showing particulars of weights of anchors, or size and weight of cable and of the test loads applied are to be furnished. These certificates are to be examined by the Surveyors when the anchors and cables are placed on board the unit.

1.8.3Steel wire ropes are to be tested as required by the Rules for Materials.

36,79 N (3,75 kgf)	– for Grade U1 chain,
41,68 N (4,25 kgf)	– for Grade U2 chain,
41,6 N (4,75 kgf)	– for Grade U3 chain,

Cable grade
Cable grade	Windlass used in conjunction with chain stopper	Chain stopper not fitted
U1	4,41 (0,45)	7,85 (0,8)
U2	6,18 (0,63)	11,0 (1,12)
U3	8,83 (0,9)	15,7 (1,6)