Note: Descriptions are shown in the official language in which they were submitted.
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Ice brs.akinq system for floating body
Field of the Invention
The invention relates to an ice breaking system for floating bodies and to a
method for
position stabilisation using a corresponding system.
Background of the Invention
Ice breaking systems for floating bodies or ships are known. JP 59 179493 A
discloses
a system and a method wherein ballast tanks, particularly in the keel region
of the ship
bottom, are used in order to pump over ballast water from starboard to port
and in-
versely so as to thereby achieve a heeling movement of the ship. Due to this
weight
displacement the ice can then be broken, supported by the lateral bulb
formations in the
bow region.
A system working in a different way is known from US 3 939 789. Corresponding
to this
document a drillship operating in ice is equipped in the bow region with a
floodable
chamber. Furthermore a bow projecting in a flat manner over an ice sheet is
provided.
This front flooding or trimming chamber can be rapidly flooded due to
relatively large
openings in the bottom and side region so that sinking of the bow in relation
to the nor-
mal waterline takes place and in this way the ice present below the bow is
broken. By
introducing compressed air into this chamber the trimming chamber is blown out
again.
A division of the trimming chamber is provided so that heeling of the bow and
ship to-
wards port and starboard can be brought about.
However, there is a risk in this design of the ship of chunks of ice being
brought into the
chamber during flooding which may block the corresponding openings during
blowing-
out.
Another system according to US 3 850 125 shows, with a drillship operating in
ice, a
spur-like bow and to the front and to the rear a respective chamber in the
bottom region
of the ship, which chamber can be flooded or blown out. In this way it is
possible to
raise and lower the bow with an ice breaking effect.
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The disadvantages hereby lie also in the risk of the chambers icing up and a
relatively
complex structure of the compressed air means for blowing out the
corresponding
tanks.
A floating body with a drill tower is described in US 3 872 814. The drill
tower is hereby
located on a floating semi-submersible rig with two lateral tubular floating
bodies. These
floating bodies are equipped to the rear and to the front with flooding areas.
It is hereby
possible to bring about, by flooding the front chamber, a sinking and at the
same time
an ice breaking effect against an ice sheet or drift ice. This is further
favoured through
periodic blowing out of the front chamber and flooding of the rear chamber. A
heeling
movement of the drilling rig can also be controlled with this semi-submersible
rig. How-
ever, construction of the required compressed air systems necessitating
relatively high
resources and the risk of icing up of the flood chambers are also present
here.
A further embodiment with ice breaking effect is disclosed by JP 58 224887, in
which a
solid ballast weight can be drawn from the front to the rear in the keel
region in order to
hereby bring about a pitching of the ship with the bow against an ice sheet
and thereby
to exert an ice breaking function.
In order to also facilitate lateral movements of a ship, for example according
to DE 42
08 682 B4 an ice breaker is equipped both with jet propulsions and with
rotatable pro-
pulsion units so that lateral movements are also-facilitated.
However, the known systems predominantly have the disadvantages that they are
formed too inefficiently and that there is a high risk of icing up of the
trimming tanks and
that the blowing-out of the chambers and the weight displacement is carried
out too
slowly in most cases.
The present invention to overcome the aforementioned disadvantages and in
particular
to create an ice breaking system for floating bodies in ice or in case of ice,
in particular
for drillships and research ships or platforms, in ice fields, pack ice or
drift ice and the
like, which reliably facilitates stationary positioning of a ship body or ship
over a point on
the seabed and to indicate a corresponding method for stationary positioning.
Summary of the Invention
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As an aspect of the present invention, there is provided a floating body or
ship body with
an ice breaking system, the system comprising: at least one front floating
body region or
bow region projecting over a line of a water area on the floating body or ship
body; at
least one trimming tank provided in a front floating body region or bow region
and at
least one trimming tank provided in a rear floating body region or ship body
region; and
a system for filling the trimming tanks with liquid and emptying the trimming
tanks, to
increase weight with a filled trimming tank and to reduce the weight with an
emptied
trimming tank, for producing at least an ice breaking, pitching movement of
the front
floating body region or bow region, wherein: at least one trimming channel
connects the
front and rear trimming tank to each other in terms of flow two trimming
channels are
provided in a region of opposing sides of the body or opposing sides of the
ship,
trimming tanks and trimming channels are formed as a closed trimming system,
trimming tanks and trimming channels are protected against icing outwardly by
cofferdams of the floating body or ship body, the system for filling and
emptying the
trimming tanks comprises at least one fluid conveying system which is provided
in terms
of flow between the trimming tanks, and front and rear trimming tanks can be
filled and
emptied in terms of weight in an opposing manner periodically in order to
produce an
ice breaking, pitching movements, wherein at least one of the front trimming
tank and
rear trimming tank is provided with sub-divisions and can also be operated as
lateral
trimming tanks to produce a heeling movement of the floating body or ship
body.
As another aspect of the present invention, there is provided a method for
position
stabilisation of a floating body or ship with an ice breaking system as
described herein,
wherein a drift direction of the ice or the ocean current is determined, the
floating body
or ship is oriented against the drift direction of the ice or the ocean
current, the ice
breaking system of the floating body or ship body is set in operation, and a
dynamic,
relative movement of the floating body or ship body is carried out in a
magnitude of the
drift speed against the drift direction of the ice or the ocean current.
Due to the increasing importance of the arctic oceans having regard to
exploration for
economically accessible oil fields and other raw materials and minerals,
research ships,
drillships and floating platforms which can be held stationary are
increasingly necessary
which in spite of the ocean current and drifting ice sheets must maintain
their position as
intended above the seabed in a stationary manner.
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which in spite of the ocean current and drifting ice sheets must maintain
their position as
intended above the seabed in a stationary manner.
The inventive system and the method thus consider these requirements. An
essential
core thought is thereby to provide in the bow or front region of the ship body
a front
trimming tank which is provided as far forward as possible and as high as
possible at a
distance from the keel line. In contrast herewith, a second trimming tank is
provided in
the rear region according to the distance and height, whereby both trimming
tanks are
connected to each other in terms of flow by means of at least one trimming
channel. In
case of one trimming channel the latter extends centrally in the longitudinal
direction of
the keel line.
The design with two trimming channels which are placed in opposing side
regions of the
floating body or ship is particularly advantageous.
Due to the preferred arrangement of the front and rear trimming tank above the
water
line a closed system is realised together with the trimming channels. The
trimming tanks
can, however, also be arranged as desired corresponding functionally to the
ship. An
anti-frost arrangement is hereby to be considered, particularly having regard
to energy
saving. As the system must also be fully functioning at relatively low arctic
outside tem-
peratures, also at under -35 C, a trimming fluid, in particular water with a
high salt con-
tent or with additives which considerably reduce the freezing point of the
trimming me-
dium is used. The tanks and trimming channels are outwardly protected where
possible
against icing by cofferdams. In order to protect against icing of the tanks
and / or trim-
ming channels heating of these installations can also be carried out as
required.
In arctic ocean regions in which a ship or a floating platform is to be
positioned exten-
sively stationarily over a drill hole there is the problem ¨ in case of more
or less closed
ice covering or a drift of pack ice ¨ that the ship which is to be held
stationary would drift
with the ice. Drift speeds of approximately 0.5 kn (knots) or less can thus
arise from
slowly changing directions.
The ship must therefore be able to position itself in such situations
dynamically, possibly
at an angle or even transversely to the drift direction of the ice or the
ocean current, for
example over the corresponding sea position.
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According to the method it is provided for position stabilisation of such a
ship body in ice
or in case of ice, particularly using a corresponding ice breaking system,
that on the one
hand the drift of the ice and / or the ocean current is / are determined. It
is provided that
in the presence of an ice drift the ship body is designed and manoeuvred so
that in par-
5 ticular its front region points against the drift direction of the ice or
the ocean current and
the ice breaking system of the ship body is set in operation.
In dependence upon the equipping of the ship body with corresponding
underwater
drive units, which can be designed for example as propulsion units rotatable
by
360 and/or jet propulsions in the bow or stern, a ship equipped in this way
can be held
approximately diagonally or even transversely to the drift direction of the
ice or the
ocean current stationarily above the seabed. The ice breaking systems can
hereby also
support the stationary positioning of the ship body in case of ice through the
production
of heeling movements and / or pitching movements.
In this way a relative movement of the ship body in the magnitude of the drift
speed or
the ocean current against the drift direction of the ice is produced so that
the ship body
or the ship can be held stationary for example over a seabed point, for
example a drill
hole.
The position of the floating body itself is therefore determined for example
by means of
GPS or other positioning means and on the basis of the drift speed and drift
direction of
the ice ascertained the ship is orientated with its ice breaking function so
that on the
bow and / or stern side the re-trimming of the trimming medium into the front
and rear
tank produces the pitching, ice breaking function. On the other hand the
orientation of
the ship with the necessary relative speed contrary to the drift speed can be
produced
through bow and / or stern jet propulsions possibly in combination with
electromechani-
cal or diesel mechanical propulsion units so that the ship is held stationary
over a drill
hole. The propulsion units can be arranged in a pod-like manner on the ship
bottom or
be integrated into the hull of the ship body.
The ice breaking function of the ship and the re-trimming of the corresponding
medium
in and to the trimming tanks are usefully carried out with a frequency which
is adapted
to the drift speed of the ice and thereby achieves an efficient ice breaking
effect.
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As an improved ice breaking effect is also achieved through heeling movements
of the
ship, lateral trimming tanks are also provided in the region of the side
walls, in particular
above the water line, so that heeling movements can be produced through re-
trimming
thereof. The lateral trimming tanks are usefully arranged in pairs and
opposite the ship's
centre line. Having regard to an improvement of the rolling and pitching
movements of
the ship a plurality of lateral trimming tanks are preferably provided in
pairs, whereby
they are then arranged distributed in the longitudinal direction of the ship.
The ice breaking function in the sense of trimming - ice breaking can be
further im-
proved in that the pitching or rolling movements of the ship through the re-
trimming into
the tanks from front to rear and inversely can be produced in combination with
the re-
trimming processes in the lateral trimming tanks and a resulting heeling
movement.
As re-trimming of the trimming medium is to be achieved in the closed system
from the
rear to the front trimming tank in as short a time as possible on the one hand
large pipe
cross-sections are provided in the trimming channels, for example of between 1
to 4 m
in diameter, and high power fluid conveying means, for example as hydro-
mechanical
pumping means, are integrated in the closed trimming system.
The corresponding fluid conveying means can provide for example conveying
rates
which allow in joint operation the pumping over of 500 to 1000 t trimming
medium from
the rear to the front in 10 to 30 s.
For re-trimming for example from the front trimming tank into the rear
trimming tank,
however, the kinetic energy of the oscillating water mass during re-trimming
is also used
as a supplement to the high conveying rate of the conveying means. In this
respect so
to speak the rear vibrating water mass is also used to pump over the trimming
medium
in order to be able to re-trim the trimming medium even more quickly for
example from
the front trimming tank into the rear trimming tank.
The trimming channels are preferably brought as far as the corresponding
conveying
means with full volume in the pipes so that immediately the whole flow volume
is avail-
able with a re-trimming process.
This system can be supplemented by corresponding retention or non-return means
which can in particular be operated and switched bi-directionally.
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In dependence upon the trimming medium used the fluid conveying means can also
be
designed to work hydraulically or pneumatically.
In order to achieve a best possible pitching effect of the ship to break the
ice it is prefer-
able to arrange the front and rear trimming tank with a height distance which
is as great
as possible from the keel line or bottom line of the floating body.
The front and rear trimming tank are thus offset extremely far to the front
and rear and
provided as far as possible at the height of the. main deck. In order to
protect and pre-
vent freezing of the trimming medium the tanks and the trimming channels are
prefera-
bly secured outwardly behind cofferdams.
It is also possible to equip the front and rear trimming tanks with sub-
divisions, in par-
ticular in the plane of the ship's centre line, whereby weight loads can also
be produced
alternately to the sides of the ship and the heeling movements for lateral ice
breaking
can thus be improved.
Having regard to the production of pitching or rolling movements of the
floating body it is
possible to also provide only one, in particular a front trimming tank.
This individual trimming tank can be flooded with existing drawn in seawater
and be
blown out for emptying.
The individual trimming tank can, however, also be connected with lateral
intermediate
tanks to form a closed system so that the trimming medium can be pumped over,
but
remaining moreover in the trimming system.
The number and arrangement of the trimming tanks, in particular for producing
the
pitching of the ship, is arranged and designed in the overall function with
the trimming
channels in such a way that the largest possible trim moments can be produced
in the
ship in relatively short time intervals.
By way of a supplement to the preferred closed trimming system it is useful
having re-
gard to different fields of application of such a ship to also realise,
alternatively or in
combination with the closed trimming system, an outwardly open trimming
system.
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It is thus desirable also having regard to repair to be able to connect in
particular the
front and rear trimming tank via fluid lines outwardly to the seawater in
order to thereby
be able to realise auxiliarily or alternatively a trimming process.
The manoeuvrability of the ship is further improved in that additionally to
the main drives
further direct or indirect drive means, in particular bow and stern jet
propulsions, are
present, possibly in combination with for example electromechanical propulsion
units,
whereby the latter mostly comprise rotation regions of 0 to 3600 in pod-like
suspen-
sions.
Precisely this drive combination allows a corresponding floating body or a
ship to also
be held, in case of drift and ocean current, stationarily over a drill hole or
a defined posi-
tion on the seabed, in particular through computer control.
The trimming system described within the scope of this invention is
advantageously de-
signed to be computer controlled and can be used not only in ice-covered water
but also
with an open water area. The trimming processes usually take place fully
automatically
whereby a semi-automatic function is also conceivable. The computer controlled
trim-
ming allows a plurality of trimming processes and adjustments. Both rolling
and pitching
movements as well as heeling movements of the floating body can thus be
controlled. It
is also possible to realise the periodic frequency in dependence upon
predefined angles
to be achieved during pitching processes or heeling processes or also a
combination
thereof.
As there is a need for re-trimming processes which are as rapid as possible
and this is
to be realised in adaptation to the required frequency for the ship movements,
fluid con-
veying means are required which facilitate a flow speed in the trimming
channels with
up to approx. 8 m/s.
In comparison with this, pumping-over processes take place in ballast water or
liquids at
approximately 3 m/s.
Pneumatic drives, for example blower fan units, can be used as fluid conveying
means
which have their threshold at approximately 10 m / head of water. Centrifugal
pumps
are already more advantageous in contrast therewith but wherein the control
should be
even quicker in the opposite direction of effect.
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Propeller drives and impeller drive systems have proved to be particularly
suitable for
the rapid re-trimming processes.
The system for position stabilisation is therefore to be adapted on the one
hand in rela-
tion to the synchronisation with the drift speed of the ice and on the other
hand in rela-
tion to the pitching and rolling frequency of the ship having regard to the
ice breaking
function. In order to improve the ice breaking function the ship hull is also
to be de-
signed to be projecting far out in particular at the bow and stern end.
This is obviously supplemented for the whole ship hull through the necessary
design of
the ship walls and the ship bottom for the corresponding ice class.
An improvement of the ice breaking effect in heeling movements is achieved
through
projection of the ship side walls.
Having regard to the ice breaking function maximum trimming and heeling angles
can
also be predefined which should be considered in the re-trimming process for
the rolling
and heeling of the ship.
=
In order to improve the re-trimming process having regard to time the trimming
channels
should constantly be filled with trimming medium at least as far as the feed
pumps and
the opposing empty trimming tank should have no remaining fluid. During the
pumping-
over process it is to be ensured in particular that no air reaches inside the
pumps in or-
der to avoid damage through cavitation.
A re-tvimming process can be started in this way with full volume available
without delay
and with corresponding diameter dimensioning of the trimming channels can also
be
concluded with a re-trimming volume of 500 to 1000 t between 10 and 20 S.
Brief Description of the Drawings
The invention is explained in greater detail below by reference to schematic
representa-
tions of two embodiments. The drawings show:
Fig. 1 a sectional illustration with a top view from above of a ship equipped
with an ice
breaking system approximately at the height of the main deck, wherein a front,
a rear
CA 02751898 2013-09-27
and two lateral trimming tanks with the connecting trimming channels are shown
with
hatching;
Fig. 2 a vertical section through the ship according to Fig. 1 along the
starboard side
trimming channel with sectional illustration in the front and rear trimming
tank;
5 Fig. 3 a vertical section approximately at the height of the intersection
line 3 ¨ 3 accord-
ing to Fig. 1;
Fig. 4 a vertical cross-section approximately at the height of the
intersection line 4 ¨ 4
according to Fig. 1 and
Fig. 5 a schematic illustration of a bow region of a ship with ice breaking
function and
10 pitching movement of the ship with ice breaking function shown through
three line pat-
terns.
Detailed Description of the Invention
Fig. 1 shows a horizontal section of a ship 1 approximately at the height of
the main
deck with the essential component groups of the trimming system.
In the bow region 2 a front trimming tank 10 and in the stern region 3 a rear
trimming
tank 16 are shown with hatching. The trimming tanks 10, 16 are arranged as far
as pos-
sible in a most frontal position or respectively in an extremely rear position
of the ship.
The front and/or rear trimming tank 10, 16 can be divided into sub-divisions
(SD) and
can also be operated as lateral trimming tanks to produce a heeling movement
of the
ship body 1.
As shown in section in Fig. 2 the trimming tanks 10, 16 are arranged with as
large as
possible distance from the keel line 4 or the ship bottom 7. Due to this
extreme ar-
rangement above the normal water line the force moments acting on the ice
sheet are
considerably improved. =
In the example the trimming tanks 10, 16 are connected in terms of flow with
two trim-
ming channels offset in the outer region of the ship. The trimming channels
12, 13 lie
below the lower level of the trimming tanks 10, 16 but in the normal case
still above the
water line.
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Feed pumps 18, 19 as high power pumps are connected in terms of effect with
the
trimming channels 12, 13 and the trimming medium located therein.
It is also possible to arrange further feed pumps, similarly to in Fig. 1,
offset to the rear
additionally on the trimming channels.
In order to produce a heeling movement of the ship lateral trimming tanks 21
and 22 are
provided on both sides. These lateral trimming tanks 21, 22, are located very
deep in
the ship, as shown in Fig. 2, particularly in the bottom region of the ship.
As shown in Fig. 2, the bow 2 is formed as a fiat bow. This also applies to
the stern 3
which has a very flat region. The bow region can also be designed in the
manner of a
spoon bow. The flat contour to the front and to the rear can also be realised
with a suffi-
ciently projecting stem and stern post in order to be able to exert a good ice
breaking
function.
In the view of the starboard side according to Fig. 2 a drive screw 31 is
shown sche-
matically with shaft bearing 32 and drive unit 33.
In the vertical sectional representation according to Fig. 3, which shows a
section ac-
cording to 3-3 according to Fig. 1, the trimming channels 12, 13 are provided
very far
below in the bottom region of the ship. The shaft bearings 32 and 35 are shown
project-
ing downwardly.
The lateral side walls of the ship 1 are formed as projecting side walls 24,
25 so that in
case of heeling movements an improvement in the ice breaking function is
present.
In the sectional illustration according to Fig. 4 along the intersection line
4-4 it is shown
schematically that the trimming channels 12 or 13 go into the lateral
connection boxes
of the rear trimming tanks 16 and form approximately an L shape in section.
The trimming channels 12, 13 can also comprise a circular diameter having
regard to
the feed pumps 18, 19, whereby this diameter can amount for example to between
1 m
and 4 m.
Having regard to the outward protection the trimming channels and trimming
tanks are
additionally protected through externally lying cofferdams.
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The schematic illustration according to Fig. 5 shows a bow region 2 of the
ship 1 and
the ice sheet 41 drifting against the bow incline 38. Due to the pitching
movement of the
ship through the re-trimming effect into the front and rear trimming tank the
ice breaking
effect is achieved through the upward and downward movement of the bow 2 so
that
the ice sheet 41 is broken up into smaller ice sheet portions 42.
A similar effect is also shown by the heeling movement to the sides with the
supporting
effect of the projecting lateral side walls 24, 25.
The ice breaking system and the corresponding method thus allow floating
bodies or
ships to also be held stationary in the ice of the arctic sea up to certain
ice thicknesses
over a point on the seabed, for example for drilling purposes.
