Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02356675 2001-06-21
1998P08652WO
PCT/DE 99/03947
Description
Semi-submersible deadweight cargo vessel
The invention relates to a semi-submersible
deadweight cargo vessel. Such cargo vessels are used
principally for transporting large and heavy bulk
materials and are distinguished by a tonnage of far more
than 10,000 t. In contrast to conventional cargo vessels
in which the cargo is loaded and unloaded with cranes, and
which are therefore subject to limits in terms of the
dimensions of the freight to be transported, semi-
submersible deadweight cargo vessels are particularly
suitable for transporting bulky items, for example
complete oil drilling platforms, port crane systems or
medium-sized to large water vessels or parts thereof. For
this purpose, according to the invention, semi-submersible
deadweight cargo vessels are composed of a front part in
which the drive system and the command and crew rooms are
located, and a rear part which is essentially embodied as
a hollow-walled float which has ballast tanks and a planar
transport platform.
By flooding the ballast tanks it is possible to
submerge the semi-submersible deadweight cargo vessel to
such an extent that the transport platform sinks below the
water line so that floatable cargo, or cargo which is
loaded on a pontoon for example, can be placed on it or
removed from it. Conversely, by freeing the ballast tanks
it is possible to raise the transport platform under the
cargo to be transported in order to load on said cargo. In
addition to this float-on/float-off method, cargo can also
simply be loaded and unloaded with what is referred to as
the roll-on/roll-off method by raising or lowering the
transport platform of the semi-submersible deadweight
cargo vessel to the level of the quay.
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It is known to provide cargo vessels with an
electric vessel's drive. In diesel-electric systems, the
electric propeller motor is usually supplied by generators
which are driven by diesel engines and/or gas turbines. A
diesel-electric drive requires higher investment costs in
comparison with diesel engines which are coupled directly
to the vessel's propeller, but it provides the advantage
or more efficient use and makes possible a high torque on
the propeller shaft, even under very large load
conditions. In addition, with diesel-electric drives there
is no risk of inadequate machine control if the propeller
leaves the water, for example in rough seas.
In conventional diesel-electric drives, all the
electric parts of the system are accommodated inside the
vessel, and engines, gear mechanisms and drive shafts are
aligned flush with one another. Other unsatisfactory
aspects of this are the occurrence of high mechanical and
hydrodynanic losses and restricted maneuverability in
comparison with propellers which are driven from outside
the vessel. A comparatively uneconomical consumption of
fuel is also disadvantageous.
The periodical Schiff & Hafen, issue 11/1979,
discloses a semi-submersible vessel in the article
"Condock I" for carrying lighters or floating containers,
which vessel is designed with floatable and freeable
bottom and side tanks for loading and unloading cargo in
accordance with the float-on/float-off and/or roll-
on/roll-off method, and has, as main machine, a diesel
engine in the rear part of the vessel. In order to improve
the maneuverability, a transverse thrust device is
provided in the forebody.
The object of the invention is to disclose a
semi-submersible vessel which can keep its position
without the aid of tugs or anchors and which has a large,
planar loading platform suitable for carrying bulky goods.
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The object is achieved in that the diesel
engines are part of a diesel-electric drive system, the
diesel-electric drive system being arranged in the
forebody and supplying power to at least one electric
azimuth rudder propeller arranged under the stern, the
loading area being embodied as a planar transport
platform and the azimuth rudder propellers permitting,
together with the transverse thrust device, precise
position control during lowering, even when there is a
considerable wind force.
It is advantageous to arrange the
diesel-electric drive system in the forebody so that
optimum utilization is made of the space available on
the vessel with respect to the transportation
suitability of the deadweight cargo vessel. An
arrangement of the essential pieces of equipment in the
forebody ensures maximum possible variability for
loading and unloading cargo onto and off the transport
platform in the afterbody, which is not subject to any
structural restrictions in this way.
It is also advantageous to drive the azimuth
rudder propeller by means of an electric motor which is
arranged outside the vessel and which is fed by at
least one generator driven by the main machines. The
use of electric motors which are arranged outside the
vessel for driving one or more azimuth rudder
propellers provides the advantage of particularly good
maneuvrability. This drive technology which is known in
practice under the designation SSP is distinguished in
this case by a low level of vessel resistance with a
very wide variety of vessel bodies and does not require
any additional cooling because the water flowing around
the electric motor has a cooling effect. Furthermore,
the SSP drive is associated with low use and
maintenance costs.
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Azimuthing rudder propellers are already known,
for example as in the brochure from ABB "Azimuthing
Electric Propulsion Drive" but this drive for the types
of vessel specified in this brochure
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was not selected according to the criteria of the
design of the loading area and the self-positioning of
the vessels equipped with it.
According to a further feature of the
invention, the azimuth rudder propeller is embodied as
an azimuthing rudder double propeller. Double
propellers are associated with higher procurement and
maintenance costs in comparison with single screws, but
providing two propellers makes it possible to have a
smaller propeller diameter, enabling the semi-
submersible deadweight cargo vessel to be constructed
with a smaller draft, which reduces costs. According to
one advantageous development of the invention, the
transverse thrust device is also driven electrically,
contributing to making the design of the deadweight
cargo vessel fuel-efficient and cost-effective.
In one preferred embodiment, the transverse
thrust device in the forebody can be controlled from a
central navigation console in the wheelhouse and from
two bridge side wings of the semi-submersible
deadweight cargo vessel, in order to ensure maximum
visibility when maneuvering. This is also promoted if,
according to a further advantageous feature of the
invention, the flooding and freeing of the bottom and
side tanks can be controlled from a control console on
the rear side of the wheelhouse.
The switching and signaling boards of the
semi-submersible deadweight cargo vessel are expediently
accommodated in a sound-insulated machine control room
in order to damp the level of sound emitted by the
vessel's machinery. For this purpose, it is also
advantageous to provide, according to a further feature
of the invention, the main machines with sound dampers.
T_n order to make operating costs particularly
low, according to one advantageous development of the
invention, the diesel
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engines can be operated with heavy oil which has a
viscosity of approximately 3,500 s Redwood. Low operating
costs are also promoted if, according to one further
advantageous development of the invention, diesel engines
which can be operated with marine diesel oil are provided
as auxiliary machines. The auxiliary machines are
advantageously installed here on a vibration-damped base
so that a minimum possible noise level is generated.
According to one further feature of the
invention, the exhaust gas line of the drive system is
movably arranged in order to ensure maximum possible
variability with respect to operating of lines in a
favorable way with respect to sounds.
Further details and advantages of the subject
matter of the invention emerge from the following
description of a preferred exemplary embodiment. In the
associated drawing, in particular:
Fig. 1 shows a side view of a semi-submersible
deadweight cargo vessel;
Fig. 2 shows a plan view of the semi-submersible
deadweight cargo vessel according to FIG. 1,.and
Fig. 3 shows a side view of an azimuth rudder double
propeller.
The semi-submersible deadweight cargo vessel
illustrated in figures 1 and 2 has an overall length of
156 m. The length between the casting lengths is 145 m.
The cargo deck has a length of 126 m, a width of 32.26 m
and a free cargo area of approximately 4,065 mz. The
height of the sides in the vicinity of the cargo deck is
10 m, while the draft of the semi-submersible deadweight
cargo vessel is 7.50 m with freeboard and 19.0 m with
the cargo deck lowered.
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The semi-submersible deadweight cargo vessel
has a dead weight of 18,000 t with freeboard. This is
composed of 2,000 t heavy oil (HFO 380) which serves as
fuel for the main machines, 172 t marine diesel oil
which is used as fuel for the auxiliary machines and
for which a loading capacity of approximately 200 m3 is
present, 300 t fresh water, for which there is a
corresponding loading capacity of 300 m3, 25 t
lubricating oil, 20 t supplies for the crew, 20 t spare
parts and 15,463 t payload. The average molded draft is
approximately 7.5 m with this dead weight in sea water
with a specific density of 1,025 t/m3. This corresponds
to the draft with freeboard.
The semi-submersible deadweight cargo vessel
also has a loading capacity of approximately 40 m3 for
dirty oil and of approximately 5 m3 for waste water.
Accommodation for 22 crew members and 16 passengers is
provided in the forebody, above the foredeck. 3 diesel
engines with a rotational speed of approximately
720 min-1, which serve as the main machines, are also
arranged on the forebody. With the diesel engines which
are embodied as 9-cylinder series-mounted machines it
is possible to generate electrical power of
approximately 3,645 kW each. With electrical losses of
approximately 8.7% of the generator when driving, and
without supplying the vessel's electrical system, a
power of 8,675 kW can thus be made available.
The semi-submersible deadweight cargo vessel is
also equipped with two auxiliary machines, embodied as
diesel engines, for generating power for the vessel's
electrical system, said machines supplying a generator
power of 720 kW each with a rotational speed of
720/900 min-1. A third diesel generator, which has a
rotational speed of 1800 min-1 and a generator power in
accordance with the SOLAS regulations is provided for
when the vessel is docked and for emergencies.
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Two azimuth rudder double propellers, which are
each driven by means of electric motors arranged
outside the vessel
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and can generate an operating speed of 14 kn are used
as the vessel's drive. This drive, which is referred to
as an SSP drive (illustrated in fig. 3) is supplemented
by two electrically driven transverse thrust devices
which improve the maneuverability and stability of the
deadweight cargo vessel. Trials have shown that the
lowered deadweight cargo vessel can be readily
controlled precisely against a wind force of 6 to 7
Beaufort using the two transverse thrust devices.
A multiplicity of winches are provided for
fastening the cargo on the cargo deck. Sound protection
measures, for example the spatial separation of machine
rooms and accommodation, noise-proofing encapsulation
of the accommodation on the foredeck or sound damping
for the main machines, ensure ergonomic working
conditions. The semi-submersible deadweight cargo
vessel can be lifted from the lowered draft of 18 m to
a draft of 7.50 m within 4 hours by pumping empty the
ballast tanks using compressed air. As a result of the
low consumption by the main machines of 46.98 mT/24 hr
it is possible for the semi-submersible deadweight
cargo vessel, which can also be a dock vessel depending
on the application, to be at sea for a period of 34.6
days longer, basing the calculation on 360 days, than
comparable conventional vessels. This means that
additional cargo can be transported for the same
operating costs. The high fuel efficiency is also due
to the fact that, depending on requirements, just one
or two diesel engines of the main machines are
operated. Last but not least this also allows for
ecological factors.
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