OCIMF_Mooring_Equipment_Guidelines_(Second_Edition)

Steel wire lines with an independent wire rope core (IWRC) are strongly recommended over fibre
core sleel wire lines for several reasons. An IWRC st.eel .... 'ire line has a much greater resistance to
crushing, higher MBL for a given diameter and greater strength retenfion when bent.

For mooring VLCCs. i.t is recommended t,hat as a minimum a 42 mm (J t ") djameter 6 x 37 class

1 WRC preformed, heavily drawn galvanized wire line (minimum tensile strength of 180 kg/rnm2)
with a typical MBL of 115 rnt (1128 kN) be specified.

6.2.3 Corrosion Protection

Corrosion protect ion can be provided by galvanising of individual wires. So-called 'commercial gal-
vanising' is inadequate for marine application. 'Heavy' galvanising should be carried out in ac-
cordance with lIS 3525 or DIN E 1548. These standa rds specify tbe zinc weight per wire surface as
a function of wire diameter. The zinc weight ranges from about J 00 glm for a 1.0 mm^2 diameter
wire 10 220g/mZ for a 2.5mm diameter or greater wire. The DIN E 1548 values are slightly higher
for normalised wires.

6.2.4 Bend Radius

Wire ropes will lose strength when bent over a radius. This is a major factor in the design of

shipboard equipment for wire rope, since items such as winch drums and fairleads must have an

adequate diameter or surface radius. Tbe recommended minimum values lisled in sections 7 and 8

are based on lines with the recommended independent wire rope core. A fibre core (ope will Jose

more strength at a given bend ratio tban an IWRC rope. This is clearly shown in Fig. 6.2.

As a general rule, a minimum bend ratio of 12 is recommended. Where this would create problems

with the si ze of the fitti ng, a ratio of 10 is an acceptable compromise for items such as universal

roller fairleads.

95

.-JI

~f--Cl 90

Qzo. w

a:wo

o[:!:a:

U.(/)W

O"g;^85

~~~

wYu. u<to

a:wa: w

o.al BO

75 ~ ____ ~ ____ -L ____ ~~ ____ ~ ____ ~ ____ ~ ____ ~ ____ ~

8 to 12 14 16 18 20

BENDING RATIO Did

Where D z Diameter 01 Bill. Bollard. Fairlead, Etc.

d .. Diameter ot Wire Rope

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FIGURE 6.2: EFFECTS OF BENDING ON WIRE ROPE STRENGTH

6.2.5 Maintenance, Handling and inspection

These subjects arc dealt with in Appendix B.

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