LECTURE LAYOUT
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Definition
Developments of container ship concept
Aspects of container ship design
Main dimensions: length, breadth, depth, draft
Containers
Container stowage and securing
Hullform
Stability
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DEFINITION
• Containerisation can be considered as a total
transportation concept.
• The cargo is handled in a utilised form suitable
for carriage by sea, road, rail and inland
waterways.
• Container ship is the seaborn link in the chain.
• Containerisation offers a true door to door
service.
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DEVELOPMENT OF CONTAINER SHIP CONCEPT
• The first container ships were converted from
tankers to carry unitised cargo.
• After the developments container ships became
• complex,
• highly specialised vessels
to maximise the benefits to be gained from high
cargo handling rates and reduced port time.
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DEVELOPMENT OF CONTAINER SHIP CONCEPT
• The design philosophy has changed from its
early form because of:
• the changes in the world economy
• changes in the trading pattern,
• major world political events.
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DEVELOPMENT OF CONTAINER SHIP CONCEPT
• The first container ships had low carrying
capacity, because the origin ships were designed
to carry bulk cargoes.
• The development of specialised container
carrying vessels resulted in increases in
container capacity for a given volume.
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DEVELOPMENT OF CONTAINER SHIP CONCEPT
• The first ships were carrying around
– 1200 TEU (twenty-foot equivalent units)
– with the service speed 22 knots.
• The first large container ship were designed in
the late 1960’s.
• The size and speed of the ships increased to take
the advantage of the economy.
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DEVELOPMENT OF CONTAINER SHIP CONCEPT
• The large ones upto
– 3000 TEU
– were powered by twin or triple screw steam or diesel
plant
– to give service speed of around 26 knots.
• After a number of years of successful operation
these vessels were badly hit by rising fuel coasts.
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DEVELOPMENT OF CONTAINER SHIP CONCEPT
• Many of the vessels were re-engined to single
screw diesel plant.
• The reduction in speed resulted in
– fuller forms
– with the associated advantage of the vessels being
able to carry
• required capacity with much reduced main dimensions.
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ASPECTES OF CONTAINER SHIP DESIGN
• A container ship can be
• a pure container carrier,
• a container/RoRo carrier,
• a general cargo vessel with a container carrying capability.
• A container ship can carry:
• a cargo handling equipment or not.
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ASPECTES OF CONTAINER SHIP DESIGN
• The cargo securing equipment can be different
types.
• Modern cargo vessels have container carrying
facility but restricted by:
• small hatch area/deck area ratio,
• deck stowage resulted from stability consideration,
• relatively low ballast of vessels can be another restriction.
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ASPECTES OF CONTAINER SHIP DESIGN
• The design of pure container ships is based on
the cargo unit to be carried.
• The dimensions, hullform and general layout
being developed to maximise the capacity.
• Different cargo securing equipment are used to
minimise the risk of cargo damage or loss.
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ASPECTES OF CONTAINER SHIP DESIGN
• A pure container vessel can be a
• deep sea vessel,
• feeder vessel to provide a container distribution service
• A modern deep see vessel has a capacity of
– 2500+ TEU
– with a service speed of 18-24 knots.
• Feeders have the smaller capacity
– around 500-1000 teu
– 16-18 knots.
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ASPECTES OF CONTAINER SHIP DESIGN
• The large vessels operate on well defined liner
route with land based cargo handling
equipment.
• On the other hand feeders are usually operate
between the ports without proper shore based
equipment, so have cargo handling equipment.
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MAIN DIMENSIONS
• The main dimensions of container ships are
based on the physical size of the containers to
be accommodated.
• For a specified container capacity, the
dimensions of the vessel will be determined by
the number of bays, rows and tiers.
• Dimensions also depend on the navigational
futures such as the Panama canal etc.
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MAIN DIMENSIONS
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LENGTH
• Length of a container ship can be calculated by
adding:
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length of the cargo space,
length of the machinery space,
length of the fore peak space,
length of the aft peak space.
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LENGTH
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LENGTH
• The length of the cargo space is a function of:
• number of container bays,
• the length of the containers,
• required clearances to accommodate the container
securing device,
• necessary allowance for structural members should be
taken into account.
• Cargo handling equipment such as cranes should be
calculated in cargo space length.
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LENGTH
• For preliminary design work, it can be
assumed that the length required for each
container is (l+1.5) m where l is length of a
container (Munro-Smith, 1975) by making
allowances for clearance and cross-ties. The
LBP of the ship is the sum of the container
portion, engine-sterntube and portion
forward. Thus:
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LENGTH
LBP = Lc + Le + Lf + LBCC
where Lc = Container portion = Nx.(l+1.5)
Nx = Number of containers in the length.
Le = Length of engine room and after peak
tank
Lf = Length of fore peak tank.
LBCC = Length between most forward cargo
hold and collision bulkhead.
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LENGTH
• As a first approximation
– the length of the aft peak tank can be taken as
3.5% of LBP.
– The length of fore peak tank can be taken as 5%
LBP and
– length of space forward of container length can
be taken as 10% LBP.
LBP=0.035 LBP+Le+LC+0.1 LBP+0.05 LBP
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BREADTH
• Breadth is a function of the size of the container
units and calculated using the number of
container rows.
• The gaps between containers depend on the type
of stowage equipment.
• Breadth is very important to the stability. It is
great concern in the design and operation of
container ships then any other vessel type.
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BREADTH
• Containers have a standard width of 2.43 m.
However, each container requires an
allowance for clearance, guides, etc. of
about 240 mm (Munro-Smith, 1975) so that
each container requires a width of 2.67 m.
Thus the number of rows (Ny) cells located
transversely in the ship require 2.67 Ny m.
Since the width available for containers is
about 80 percent of the ship's breadth B,
then
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BREADTH
0.80 B = 2.67 Ny
B = 3.34 Ny
Ny : Number of tiers of containers in holds.
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BREADTH
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VISION
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DEPTH
• It is a function of the size of the container unit
with the vertical gaps between the adjacent
containers and the height of the tank top in the
holds.
• The number of tiers of containers to be carried
in the hold will be dependent on the proportion
of the total capacity of the vessel to be carried
under the deck.
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DEPTH
• The rate of under container numbers is around
40-60 % of the total capacity.
• Container ships are associated with large
freeboard and light loaded drafts.
• The light draft is due to the low density of the
cargo .
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DEPTH
• This results low displacement according to the
physical size of the vessels.
• Container ships are deep vessels to
accommodate the under deck stowage results in
the large freeboard.
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DEPTH
The depth of the ship is in generally controlled
by the number of containers to be carried
vertically. Thus:
D=Nz H + DB where
Nz = Number of tiers of containers in holds
H = Height containers
DB = Depth of double bottom.
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CONTAINERS
• The most common container sizes are 20 and 40
foot ISO standard containers.
• There are some other container sizes which are
not commonly used.
• The problem of the container ship design occurs
if the different size of containers should be
carried.
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CONTAINERS
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CONTAINER STOWAGE AND SECURING
• In the holds usually cell guides system is used
for stowage and securing.
• The system reduces the chance of container
damage and speeds up the loading and
unloading process.
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CONTAINER STOWAGE AND SECURING
• A typical cell guide system consists of groups of
four vertical guides constructed from steel angle
bars into which the containers are lowered
running the full depth of the vessel from hatch
coaming level down to the top tank.
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CONTAINER STOWAGE AND SECURING
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CONTAINER STOWAGE AND SECURING
• The tolerance into the guides must be small thet
shifting of the containers is minimised and that
the container spreader can be easily engaged
when removing containers.
• With this system fastening of the individual
containers is unnecessary as all of the static and
dynamic forces generated by the containers are
transmitted directly into the ship structure by the
cell guide members.
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CONTAINER STOWAGE AND SECURING
• There are leading equipment on top of the cell
guides in both the longitudinal and transverse
directions.
• The above deck containers are affected by static
and dynamic forces.
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CONTAINER STOWAGE AND SECURING
• These forces limit the securing equipment and
number of tiers usually 3 or 4 tires are used.
• Twist locks and lashing roads are commonly
used above deck securing equipment.
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CONTAINER STOWAGE AND SECURING
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CONTAINER STOWAGE AND SECURING
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HULLFORMS
• Afterbodies of container ships are generally
characterised by wide transom stern which
provide aided stability, increased hold volumes
and increased deck areas.
• This increases in powering due to large wetted
surface area, hence frictional resistance and the
increased tendency to slam.
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HULLFORMS
• Another disadvantage of this, flat sections above
the propeller will cause vibration.
• The fore body will have a bulb to promote the
cancellation of the bow wave. This reduces
wave making resistance.
• Fore body will usually be V shaped in order to
improve stability and increase deck area and
underdeck container capacity.
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STABILITY
• The stability of container ships is perhaps the
most important aspect of their design.
• Vertical centre of gravity is very high because
of above deck containers, therefore container
ships have to be operated with some amount of
ballast.
• In order to minimise the amount of ballast the
heavier containers can be carried in the bottom
tiers and the lighter or empty ones being carried
on-deck, then VCG is reduced.
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