Container Ships and Their Design
8. OOCL
9. Yang Ming
10. Pacific International Lines Future Of Container Vessels
Container vessels represent a majority in terms of the packaged cargo ferried across the world.
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Container Ships and Their Design
On account of the relevance and the ever-increasing demand for better maritime cargo transportation channels, there has been huge strides in the container ships’
domain.
Such advancements are expected to grow even more in the days to come.
In the coming days, container ships have a lot more challenges to face, but Container shipping industry will always stand strong.
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Upcoming changes in rules/
regulations, increasingly stringent environmental laws, competitive market, introduction of new
technologies, increase in marine traffic in relation to increase in carrying
Capacity of the vessels will be its preeminent problems.
Container Ships and Their Design
Design of Container Ships
The design of the concomitant container vessel is decisive. The hull is akin to the conventional Bulk Carriers and General cargo ships which are built around a solid keel. The lower part of the vessel has a significant effect on the
construction of the ship. There are lower decks, Engine room and plentiful of ballast and Fuel Tanks. The Cargo holds are the places where the under deck Containers are loaded.
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Inside the hold, there are cell guide arrangements which guide the
container to slot well.
This not only helps the crane operator to slide the container
safely inside the holds but also acts as a guide for them. It is imperative to maintain this cell guide well.
Container Ships and Their Design
Cell Guide in Container Hold
Any damage to the cell guides may lead to critical consequences. These holds are topped by hatch covers, above which the containers are stacked too.
Most of the modern container vessels do not have cranes, but some do have cargo cranes installed on them, especially in vessels of smaller sizes. Ships which have cranes onboard are called as geared container vessels whereas vessels without cranes are called as Gearless container vessels.
These geared container vessels use them for self-loading and discharging at ports where the cargo volume is low. There are also some specialised systems for securing the containers onboard. In most of the container vessels, lift away type of hatch covers are used.
Hatch covers not only increase the carrying capacity but also prevents the water ingress inside the hold & fissure, the containers under the deck and on deck
both. These hatch covers have cleats which must be closed after every cargo operation & before vessel’s departure from any port. Also, within a container ship, there are well-demarcated holds that separate each container from others, which simplifies the entirety of the filing of the containers.
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Container Ships and Their Design
• In essence, container ships are regarded to be a generic reference. Within their ambit, there are several different types of container ships. Each
container vessel is unique and different, with an undiminished operational singularity
• Container ships that are built specifically to fit into the channels of the
Panama Canal are referred to as the Panamax container vessels. These ships can be loaded with a maximum TEU of about 5000 and measure slightly
over 290 metres lengthwise.
• The smallest variance of container vessels is the Small Feeder type. These container vessels can carry loads up to 1000 TEUs. Several developments made to the Feeder categorisation has resulted in the development of the
categories of ‘Feedermax’ and ‘Feeder.’ The former can carry a maximum of about 3,000 TEUs while the latter can carry around 2,000 TEUs.
Container shipping vessels represent a majority in terms of the packaged cargo ferried across the world.
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Container Ships and Their Design
Container Ship Design – The Hull Geometry:
The first and the most prominent design aspect of any ship is the geometry of its hull. Before we understand why hulls of container ships have attained their
characteristic shape, we should first notice the geometry itself.
A visual comparison of the hull of a container ship with that of a bulk carrier or an oil tanker would imply that a container ship’s hull has a finer form than the other two. In other words, the forward and aft sections of a container ship are streamlined, and not fuller like that of a bulk carrier or oil tanker. Why?
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Container Ships and Their Design
Hull of Container Ship
To answer that, we will need first to understand another aspect of the container industry. Goods shipped in containers are often of high value and high priority.
E.g, if a marine diesel engine for a ship being constructed in a shipyard in India is to be shipped in from Germany, the shipment would be made in a container, and is a high priority shipment because the installation of the engine into the engine room is a step in the construction process that would determine the possibility of delays in the later stages of construction.
Also, the equipment needs to be delivered without any impact or damage. Thus, container ships are tightly time-bound ships. They have a very low turnaround time, that is, the time they spend at a port for loading and unloading has to be minimum in order to be able to call the next port without delay. It is due to this reason; container ships fall in the category of high-speed ships.
To achieve high speed, the resistance of the hull needs to be minimised, which is obtained by a fine form hull. In other words, container ship hulls have a low coefficient of buoyancy, ranging from 0.6 to 0.7.
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Container Ships and Their Design
Another notable geometrical characteristic of container ships is the high
prismatic coefficient of the hull-form. That is, the hull section for most of the length of the vessel is almost rectangular. This is done to accommodate a
maximum number of containers below the deck.
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Container Ships and Their Design
Hull Design of Container ship
Midship Section Of Container Ships:
One of the most critical structural drawings that are prepared during the design of a container ship is that of the midship section. The midship section of a ship is prepared with a lot of design and functional considerations in mind, which include the type of cargo, stowage methods to be used by the ship, capacity of the ship, etc. Its midship section often identifies a ship type.
For a typical container ship design, the midship section is shown in the
following figure. What is, however necessary, is to understand the drawing from a designer’s point of view. Some standard features of the midship section of a container ship are discussed below:
• All container ships are double-bottomed, to allow for the double bottom spaces to be used as tanks
• Container ships are also longitudinally framed because the variable loading conditions often result in large hogging and sagging moments, which result in high longitudinal bending stresses
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Container Ships and Their Design
• The shape of the midship section is almost box-like. In the words of a designer, it has high midship area coefficient, ranging from 0.75 to 0.85
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Container Ships and Their Design
Mid Ship Section - Container Ship
• The bilge strake is the angular plate that joins the inner side shell and the tank top plating. Since the presence of this plate would prevent the stowage of
containers at the corner of the section, the length of this strake is kept to a minimum. In most recent cases, however, container ships are not provided with bilge strakes at all, to ensure maximum stowage capacity
• The most important structural feature of a container ship is the torsion box, which we will discuss in detail in one of the following sections
• Container ships are usually equipped with no hatches. That is, the vessel has no continuous main deck running full breadth all along with the ship. This open box-like structure (relate with the midship section figure), enables easy stowage of containers from the tank top to the highest level above main deck level. The only decks are within the double hull, which is more like stringers running full length, and provide passageway along the length of the ship
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Container Ships and Their Design