Section 4 Mooring Equipment

401. General

1. The equipment of positioning systems is to have sufficient redundancy. In cases where any single unit of equipment of positioning systems is fitted on board Units, special consideration is to be given to the reliability of such equipment and its components. In cases where the failure of any single unit of equipment may lead to loss of positioning capability, an additional set of such equipment will be required as deemed necessary by the Society.

2. Means are to be provided whereby the normal operations of positioning systems can be sustained or restored even though one unit of equipment becomes inoperative. In the case of driving units, special consideration is to be given for preventing loss of function.

3. The prime movers used for positioning systems are to be designed to operate under the static con- ditions given in Ch 9, Sec 1, 102. as well as under the dynamic conditions given below. Deviation from given values may be permitted, taking into consideration the type, size and service conditions, etc. of the Units in cases where deemed appropriate by the Society.

(1) In the case of ship type and barge-type Units:

Rolling up to 22.5° and simultaneously pitching up to 7.5°

(2) In the case of column-stabilized Units: Dynamic inclination up to 22.5° in any direction

402. Chains, wire ropes, etc.

1. Chains, wire ropes or fibre ropes used for mooring systems are to comply with the requirements given in Pt 4, Ch 8, Sec 4 and Sec 5 of Rules for the Classification of Steel Ships or any standards deemed appropriate by the Society. In cases where the Grade R4 chains specified in Pt 4, Ch 8 of Rules for the Classification of Steel Ships or stronger chains are used, special care is to be taken because repairs by welding for any defects, loose studs and corrosion by weld- ing is, in principle, prohibited for such chains.

2. Intermediate sinkers, intermediate buoys and anchors, sinkers, piles, etc. for seabed mooring points are to be as deemed appropriate by the Society.

403. Chain stoppers or windlasses, winches, etc.

1. Individual equipment of mooring systems is, in principle, to be approved by the Society.

2. Chain stoppers used for mooring systems are to have sufficient strength against the breaking strength of the mooring line as deemed appropriate by the Society. The prototypes of chain stop-

pers are

It is to mooring

to be verified to have sufficient strength against the breaking strength of the mooring line.

be verified that the stress calculated by structural analysis under the awareness that the line is subjected to design maximum loads does not exceed the specified proof stress of

the chain stoppers.

3. Windlasses used for the catenary mooring systems of Units are to comply with the requirements specified in following Sub-paragraph (1) to (3):

(1) Each windlass is to be provided with two independent power-operated brakes. Each brake is to be capable of holding against a static load of at least 50% of braking strength of mooring lines. In cases where deemed appropriate by the Society, one of the brakes may be replaced by a manually operated brake.

(2)

Windlasses are to have sufficient dynamic braking capacity to control the normal combination of loads from anchors, mooring lines and anchor handling vessels during the deployment of an- chors at the maximum design pay-out speed of the windlass.

(3) In cases where a power source for a windlass is lost, power-operated braking systems are to be automatically applied and be capable of holding against 50% of the total static braking capacity of the windlass.

4. The means specified in Sub-paragraph (1) to (4) below are to be provided for controlling catenary mooring systems:

(1) Each windlass is to be capable of being controlled from a position which provides a good view

(2)

(3)

(4)

of the operation.

Means are to be provided at the windlass control position to monitor mooring line tension and windlass power load as well as to indicate the amount of mooring line paid out.

Indicators for mooring line tension, wind velocity and wind direction at the control station of each windlass are to be provided at the manned control position.

Means of communication are to be provided between essential places for mooring operations

(for example, operating position, wheel house, control room, etc.)

5. Means are to be so provided that mooring lines can be released from the Units after any loss of the main power supply.

6. In the case of laying taut mooring lines, the initial tension in all mooring lines is to be coordi- nated to achieve approximate uniformity. Power equipment capable of adjusting the tension of mooring lines is to be provided as necessary.

7. A tension monitoring system is to be provided for each taut mooring line.

404. Fairleaders

1. In cases where chains are used for mooring lines, the standard length of the part where the chain and fairleader make contact is to be not less than 7 times the chain diameter.

2. In cases where wire ropes or fibre ropes are used for mooring lines, the standard length of the part where the wire rope and fairleader make contact is to be not less than 14 times the wire rope nominal diameter.

3. In the case of arrangements that do not comply with the standards given in Par 1 or Par 2 above, detailed analysis in which the effects of bending loads acting on mooring lines is taken into account is to be carried out. Otherwise, mooring analysis is to be carried out modifying the values of the safety factors given in Table 6.1 upto those values deemed appropriate by the Society.