OCIMF_Mooring_Equipment_Guidelines_(Second_Edition)

1.6 OPERATIONAL CONSIDERATIONS

The above mooring guidelines were developed to optlmize load distribution to the moorings. Tn
practice, final selection of the mooring pattern for a given berth must also take inro account local
operational and weather conditions, pier geomelry and ship design. Some pilots, for example, desire
head and stem lines to assist ships moving into, along, or out of a berth, while others may use spring
lines for this purpose. Head and stem lines would be advantageous at berths wh.ere the mooring
points are too close to !.he ship and good breast lines cannot be provided, or where the bollards
are located so that the spring lines will have an excessive vertical angle in the light condition. These
excessive angles would result in considerably reduced restraint capability.

High winds and currents from cenain directions might make it desirable to have an asymmetrical
mooring arrangement. This could mean placing more mooring lines or breast lines at one end of the
ship.

The other factor to consider is the optimum length of mooring lincs. It would be desirable to
keep aB lines at a vertical angle of less than 25°. For example, if the ship's chock location is 2Sm
above the shore mooring point, Ihe mooring point should be at least SOm horizontally from the
chock.

Long lines are advantageous both from standpoint of load efficiency and line-tending. But where
fibre ropes are used, the increased extension can be a disadvantage by permitting the ship to move
excessively, thereby endangering loading arms. Figure 1.7 i1!uslrates the effects of line lengths on
tiDe-tending requirements.

lS.2m

J' '1 Winch

Tend Lines At These Points (2)~'" ~ :.-.:::. -:..---~------'1 I

1:

___ ----,~ ~~ ~ ~~ ~ Tend L,ne At t I Rise =

__ __ ____ ..e: /. ~ ~ ::::::: .309\1"1 - These Pomts (8) I I

u "2 ___ ~11' ----=: :-- ..... 4.. ~ ~::::::-_ - ~ -^1 I _,.... I 1

rl.. --=----"' ~^61 m ,...-' .~-- 30.5m _ - - - - - ---g

I.

30.Sm

1-_______^6 _'m ________ ---M - -- - --~ -- -- - -~

Ligh1 Ship

Distance From

Bollard To Ship Side

3O.Sm

4S.7m

61m

Minimum No. Tendm9s

Due To 1S.2m Ship Rise

8

4

2

Loaded Ship

I

Notes; • Assume Wire Lines. Yield Strain D 1% Length ~ 0.46m lor 4S.7m Hawser

• Assume No Slack in Wires


• Assume Lines Tended when they reach Maximum Allowable Load

FIGURE 1.7: EFFECT OF LINE LENGTH ON TENDING REQUIREMENTS

1S.2m