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(main items of a standard type under study)
| Length LOA |
306.0 meters |
Lightship Displacement |
87,900 mt |
| Beam |
50.0 meters |
Gas Cargo Weight |
19,600 mt |
| Hull Depth |
27.4 meters |
Deadweight |
40,600 mt |
| Full Load Draft |
10.3 meters |
Service Speed |
18 knots |
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Crew |
36 person |
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| On the basis of the above particulars,
explanations are being given as follows: |
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| a. |
She is expected to be a little smaller as
compared with Kumanogawa, a VLCC built at Sakaide Dockyard of Kawasaki Shipbuilding
Corporation: LOA 333 meters, Beam 60 meters and Draft 19.2 meters. In the meantime,
comparing with Golden Gate Bridge, an Over Panamax-sized containership, the CNG carrier is
somewhat larger with a view to LOA 284.7 meters, Beam 40 meters and Draft 12.5 meters. |
| b. |
You will find her characteristics when you
compare her *lightship displacement, 87,900 mt with 42,038 mt of Kumanogawa and 24,824 mt
of Golden Gate Bridge. How different it is from the other two! That difference is
attributed to her heavy tanks where CNG is stowed. |
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*Lightship displacement means her displacement
when there are no crew, cargo, bunker oil nor water, etc. onboard. It is equivalent to her
tare weight itself. |
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| Diagram No.1 General Arrangement |
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Diagrams 2 and 3 illustrate a tank module named
"Pipe Tank Module" into which CNG is poured for sea transportation.
One module combine 24 pipes with each pipe being about 1 meter in diameter and 36 meters
in length. She is equipped with 100 sets of modules. She is loaded with 2,400 gigantic
pipes. Consequently, her lightship displacement becomes much bigger than any other kind of
ship. In a sense, we may as well call her "A Carrier of Pipes."
Further to explain, CNG is loaded into the pipes compressed at about 130 barometric
pressures and carried at a low temperature. As compared with the compression ratio of one
six hundredth (1/600) of LNG (liquefied natural gas), it is the case that the CNG’s
ratio stands lower. However, arrangements are made to heighten the CNG’s compression to
one three hundredth (1/300) in volume by compressing and keeping CNG at a low temperature.
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| Diagram No. 2 Pipe Tank Module |
Diagram No. 3 Pipe Tank Module ( plan view ) |
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| Equipment for cargo
operations |
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Let’s see how CNG is put into the pipes.
In the case of carriers of LNG and LPG (liquefied petroleum gas), manifolds are usually
situated at the center of the hull, which connects pipes from ashore for
loading/discharging operations. As you can see from Diagrams 4 and 5, the CNG carrier
performs loading/discharging operations, mooring her bottom of the bow with a buoy where a
gas transferring pipe named Submerged Turret Nozzle (STL) is installed.
Her method is better because loading/discharging operations are operable with safety even
in the case of atmospheric and sea weather conditions being a little bad; it is proved
that the system has already been used for the operations of oil tankers in the North Sea. |
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Diagram No. 4
Loading/Discharging Operations & STL |
Diagram No. 5
Submerged Turret Nozzle(STL) |
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The CNG carrier’s speed is expected to be 18
knots per hour. In usual cases, propulsion system rotates propeller through direct
connection of a 2-cycle diesel engine with a propeller shaft. In her case, we are
examining deployment of an electric propulsion system. It is the first time for us to try
this.
More exactly, we are planning to install a gigantic motor instead of diesel engine and
rotate propellers through connecting a motor shaft with a propeller shaft. Power for
rotating the propellers is supplied from a generator. |
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| The merits of the new propelling system are: |
| a. |
It will make possible to widen an engine room and
give more flexibility for arrangements therein, i.e. securing a wider tank space, etc. |
| b. |
It will be possible to set a number of rotations
more minutely. |
| c. |
In the case of the propelling system with a
diesel engine, power is more consumed when cargo operations are on: an extra burden bears
on power supply. In the meantime, in the case of the system with motors, no power is used
for propelling at berth and an additional power supply will be possible for cargo
operations. |
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| In the meantime, the demerits are: |
| a. |
Required capacity of generating power becomes
larger: there is a need for either increase in output of power per generator and engines
or an increase in number of generators and engines installed onboard. |
| b. |
There is a need for new maintenance plans by
introducing the new system. |
| c. |
In the case of the propelling system with a diesel
engine, power is more consumed when cargo operations are on: an extra burden bears on
power supply. In the meantime, in the case of the system with motors, no power is used for
propelling at berth and an additional power supply will be possible for cargo operations. |
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We have to manage to make this project successful
with new ideas and wisdom.
Finally, the project is being promoted in cooperation with American Bureau of Shipping
(ABS). Last April, EnerSea acquired "Approval in Principle" from ABS that
assures us safety and achievability of the entire design.
Your kind understanding and support of this project is highly appreciated. |