Mooring of ships - forces
Course no. 1
1
Purpose of mooring
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To bring the ship alongside
To keep the ship alongside
To assist the ship when un-mooring
2
Design criteria of mooring configurations
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Based on the forces acting upon the ship
 Wind
 Current
 Waves
 Swell
 Other ships passing by (suction effect)
 Location of the berth – Protected or sea berth
 Types of ship – size, displacement, draught
etc.
3
Example: Mooring of VLCC’s
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Often moored outside the harbours along sea berths
Forces are so great that no winch is capable of bringing
the ship alongside
Tugs are always used when mooring and leaving berth
The only criteria is the holding force of the winches
The ship must be maintained in position related to the
shore manifold (chiksans)
4
Mooring winch with undivided drum
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Mooring winches – Divided drum-polyprop
octopus
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Chicksan
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Chicksan
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One of the biggest problems
with the fixed
loading/discharging systems
is the restricted liberty of
movement of the ship
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If one of the limits is
breached => ESD-system
activated
8
Different materials for ropes
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Different configurations
 All steel wire ropes (equipped or not equipped
with tails)
 All ropes are synthetic
 Mixed systems (synthetic + steel wire rope)
 New materials
9
Steel wire rope + tail
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Purpose of the tail is to add elasticity to account for
change in tidal heights
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To protect against chafing cover splice of the tail with
leather or plastic
The tail is connected to the steel wire rope by means of
a Tonsberg shackle or a Mandal shackle
In case of frequent use tails are changed every 18
months
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10
Tonsberg shackles
Mandal Shackle
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Synthetic mooring
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Biggest problem is elasticity
It can give an important « sway »
(balancer) to the ship (breaking out)
3 mooring ropes – different materials –
same length (50 m), MBL and load
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Steel wire
Polyprop
Nylon
–
–
–
0.3m elongation
5m elongation
8 m elongation
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Synthetic mooring
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A side effect is sagging
The « sag » is function
of:
  m-n
 Weight of the
mooring line
 Tension in the line
 Water depth (suction
effect)
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Shallow Water Effects
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Squat effect
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Mixed mooring systems
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Mix of wire ropes and synthetic ropes
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Certainly NOT the best configuration but the
most common one.
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If possible use steel wire rope as springs
and breasts and use synthetic ropes as
head- and stern line
16
New materials
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Composite materials
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Expensive but excellent mooring system
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Kevlar –Aramid ropes are very strong, light
and show little sagging. They react fast in
case of breaking out of the ship.
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Two mooring lines using the same bollard
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Efficient mooring
The efficiency of a mooring rope depends on the
following factors
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Material (steel wire or synthetic – elongation &
MBL)
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Length
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Angles
• in the horizontal plane
• in the vertical plane
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Function of the different ropes
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Head- and stern lines & the springs are stabilising the
ship alongside
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Breast line will prevent the ship to break free from
the berth
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Breast lines must be as perpendicular as possible to
the ships longitudinal axis
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Springs must be as parallel as possible to the berth
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Recommendations
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The function of springs and breast lines is clear.
 Springs are preventing longitudinal movement, while
 Breast are opposing transversal movements.
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The function of head and the stern lines depends on their
angle with the longitudinal axis.
• Great angle => they serve mainly as breast line
while
• Small angle => stopping longitudinal movement
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The ideal configuration will rarely be achieved.
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To obtain a perfect mooring configuration their must be a
perfect harmony between the ships equipment ,
disposition on board and the configuration ashore
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Berthing ships is always a matter of compromises
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Following recommendations have been
published by the OCIMF = Oil Company
International Maritime Forum
The recommendations are valid for a tanker
moored alongside a T-berth
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Recommendations based on OCIMF – Effective
mooring
1.
The horizontal angles of head-, stern- and
breast lines < 15°
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Mooring Dolphin
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Recommendations based on OCIMF – Effective
mooring
The vertical angle with the horizontal plane
must be < 25°
2.
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The effective force is proportional to the cosine of the
angle
If the angle is 25° the line is effective for 91%
If the angle is 45° the efficiency is reduced to 71%
=> Springs & breasts must be long enough
and not to steep
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Springs & Breasts
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Recommendations based on OCIMF – Effective
mooring
3.
Breast lines are most effective is  on the
longitudinal axis.
If  is 45° we have to increase the force in the breast
line till 141 ton to obtain an effective transversal
force of 100 ton
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Recommendations based on OCIMF – Effective
mooring
4.
Springs offer the greatest holding power in the
longitudinal direction. Their length is  60
meters
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Recommendations based on OCIMF – Effective
mooring
5.
The impact of the head and the stern lines on the
total holding power of the mooring configuration is
less important than the influence of springs and
breasts. This mainly because these lines are too long.
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Never the less they are important to compensate the
dynamical forces.
30
Recommendations based on OCIMF – Effective
mooring
6.
Very short lines must be avoided. They always take
the most important part of the load, especially when
the ship is moving
Short length = important vertical angle
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Short breast lines
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Long breast line: 52ton load is sufficient to obtain an
effective holding power of 50 ton
Short breast line: Load has to be increased till 88 ton
to obtain same result
32
Recommendations based on OCIMF – Effective
mooring
All the mooring ropes in the same group
(working in the same direction) must have
the same tension.
7.
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If not, the weakest line will break first. Total load
will have to be received by the remaining lines =>
increased risk of breaking (chain reaction)
Groups are aft spring + head lines, Stern lines +
forward spring, breast lines
33
Recommendations based on OCIMF – Effective
mooring
8.
Their must be an equilibrium between the 4 groups:
head- and stern lines, springs and breasts.
Optimal mooring configuration is determined after studying the
static and dynamical forces for a specific berth.
Example: Proposed configuration (Direction of the wind: 110°)
4 breast lines (aft) + 1 stern line
3 headlines + 3 breast lines (fore)
34
Recommendations based on OCIMF – Effective
mooring
9.
The number of lines is function of the size of
the ship and the prevailing weather conditions
A – Panamax (75.000 dwt) - 12 lines (2 headlines – 4 breasts – 4
springs – 2 stern lines: 2 –2 – 2 fore and aft)
B – VLCC (150.000 dwt) 16 lines (4 headlines – 4 breasts – 4
springs – 4 stern lines: 4 –2 – 2 fore and aft)
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Mooring configurations bulk carriers
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Cape Size: 4 –2 – 2 (fore and aft)
Panamamax: 4 –1– 1 (fore and aft)
Handy Size: 4 –1 (fore and aft)
Mini Bulker: 3 –1 (fore and aft)
Mini Bulker – moored so it can shift forward and
backwards during loading/discharging
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Mooring configurations
bulk carriers
Recommendations based on OCIMF – Effective
mooring
10.
Mooring lines must be passed ashore using the
deck fittings (fairleads) because of friction and
the curvature relation.
Curvature relation =  curvature deck fitting/ 
mooring line
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Mooring of ship TVS 1ste kan
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Deck fittings
OCIMF equipment:
Panama
hawse- hole Pedestal
Fairleads
(Chaumard)
Info
Suez & Panama Canal
42
Suez Canal
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Total length is 190.25 km
Water surface width is 280.345 m
Width between the buoys is 195.215 m
Canal depth is 22.5 m
Maximum ship draught allowed is 62ft
Speed allowed for loaded carriers is 13 km/h
Speed allowed for unloaded carriers is 14 km/h.
Average transit time is 14 hours
43
Suez Canal
Panama Canal
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The Panama Canal is approximately 80 kilometers.
The Canal uses a system of locks
The locks function as water lifts: they raise ships from
sea level (the Pacific or the Atlantic) to the level of
Gatun Lake (26 meters above sea level)
45
Panama Canal
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Each set of locks bears the name of the townsite where
it was built: Gatun (on the Atlantic side), and Pedro
Miguel and Miraflores (on the Pacific side).
The maximum dimensions of ships that can transit the
Canal are: 32.3 meters in beam; draft 12 meters in
Tropical Fresh Water; and 294.1 meters long
The narrowest portion of the Canal is Culebra Cut
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Panama Canal
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Gatun Lock
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Gaillard
Cut
Pedro Miguel Locks
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Mira Flores Locks
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4-roller fear
lead Towing
Bracket
Smit Towing Bracket
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Chocks and buttons
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Bits and Bollards
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Panama chocks
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Roller Chocks
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Roller Fairleads
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Towing pads (point d’attache pour le
câble de remorque)
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Mooring alongside a classic berth (quay)
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Mooring alongside
a classic berth
(quay)
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Mooring alongside a T-berth
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Mooring with 2 anchors
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Ship to ship
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SPM – Single Point Mooring Buoy
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SPM - buoy
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SPM - buoy
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FPSO – single point mooring
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FSO - operations
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STL – Submerged Turret Loading
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STP – Submerged Turret Production
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STP – Submerged Turret Production
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