Note: Descriptions are shown in the official language in which they were submitted.
A VESSEL AND A METHOD OF MANAGING ICEBERG MOVEMENT
THEREWITH
The present invention relates to a vessel and a method of managing iceberg
movement therewith.
In cold or arctic maritime environments, floating ice can be a significant
issue
for the operation of vessels and off-shore installations. Different types of
floating ice may be encountered, for example, sea ice and ice of land origin.
=
Sea ice is ice formed from the freezing of water at the surface of the sea.
Continual freezing of the sea will increase the sea ice cover and
concentrations
of pack ice. This can lead to areas where sea ice can become an impediment
or danger to shipping. For example, ice can nip a ship where the ice forcibly
presses against the hull of a ship. In a worst case scenario, the ship can
become beset in the ice where the ship is completely surrounded by ice and is
unable to move. One form of ice management for sea ice typically involves ice
breaker vessel clearing a path through the pack ice for another vessel.
.. Another type of floating ice found in the sea is ice of land origin. Ice of
land
origin is ice formed on land in a glacier from fresh water. In some parts of
the
world, glacial ice flows into the sea and projects out from the coastline
above
the sea bed. This projection is called an ice shelf and is a principle source
of
freshwater ice floating in the sea. As the sea and the weather erodes and
melts
the front edge of the glacier in the sea, icebergs calve from the ,calving
line of
the ice shelf.
Icebergs can calve from the ice shelf in different sizes and shapes due to
variation in weather, sea and ice conditions. The sizes of icebergs are
generally
classified as follows:
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Height above
Iceberg type Iceberg size the sea Length (m) Weight (MT)
surface (m)
About the size¨L
Growler H <1 L <5 W - 0.001
of a car
Bergy Bit Small building 1 < H < 5 5 5 L < 15 W - 0.01
Small Berg House 5 5. H < 15 15 5_ L < 60
W -0.1
Medium Berg Ship 15 5 H <45 60 5 L <120 W 2.0
Large Berg Stadium 45 5 H < 75 120 5- L<
200 W - 10
Very Large
Skyscraper H > 75 L > 200 W> 10
Berg
Hereinafter, the term iceberg will be used to refer to any floating ice in the
sea
which originates from a glacier. In this way, the term iceberg used in this
application refers to growlers, bergy bits, small bergs, medium bergs, large
bergs, very large bergs etc.
Icebergs which have calved from the ice shelf are detached and are free to
drift
in the sea. Iceberg movement in the sea is dependent on factors such as wind,
currents and the parameters of the icebergs themselves. Typically, icebergs
will drift away from the ice shelf towards warmer areas. For example, in the
northern hemisphere, icebergs will normally drift south. Overtime, the iceberg
will reduce in size and change shape due to melting or further calving. Due to
the variation of the shape and size of icebergs, icebergs do not move with a
regular pattern.
This means that iceberg movement must be monitored in case, icebergs drift
into shipping lanes which can pose a significant collision risk to shipping
traffic.
With sufficient iceberg monitoring, vessels can adjust their heading to avoid
drifting icebergs.
However, icebergs can also pose a risk to offshore installations and maritime
traffic servicing the offshore installations. An offshore installation can be
an
offshore drilling rig, an off shore windfarm, a pipe laying vessel, an
offshore
drilling vessel or any other static or temporarily static off shore
installation.
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= CA 3010166 2020-03-10
Drifting icebergs can pose significant risk to offshore installations. The
icebergs
can collide with and damage the offshore installations. Alternatively,
icebergs
can gouge troughs in the seabed if the iceberg is big enough or the coastal
waters are shallow enough. In this way, an iceberg can damage or sever
submersed pipes, cables, fibre optics and the like.
Operational safety requirements of offshore installations may require the
temporary or permanent evacuation of the installation if an iceberg drifts too
close. This means that the commercial operation of the offshore installation
may have to be paused losing significant amounts of money. In a worst case
scenario, if an offshore drilling platform stops operating, then it if may not
be
possible to recommence drilling operations due to technical or commercial
feasibilities.
This means ice management of the icebergs is required to ensure icebergs do
not, drift close to offshore installations. Often this requires altering the
heading
of a drifting iceberg.
One known technique for controlling the movement of an iceberg is discussed
in CA2115690. This describes a towline which is looped around the iceberg
and the free ends of the looped towline are pulled by a towing vessel. A
problem
with this arrangement is that small bergs, bergy bits or growlers may be too
small. These smaller icebergs may have a centre of mass that is high enough
that the iceberg tumbles due to the pulling force of the towline on the
iceberg.
If the iceberg tumbles, then it will not stay engaged to the towline and will
have
to be re-secured. Furthermore, these smaller icebergs may have a smoother
surface due to their extensive melting and weathering. This means that there
are less ice features for the towline to gain purchase and the towline will
slip
off.
W02014/145861 discloses another technique for controlling the movement of
an Iceberg by using the propeller wash from a vessel to direct the iceberg. In
this way, the rear of a vessel is directed towards the iceberg and the mass of
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CA 3010166 2020-03-10
the water moved by the propellers is directed to the submerged part of the
iceberg. The problem with this arrangement is that vessel must be manoeuvred
and repositioned next to the iceberg many times in order move the iceberg a
significant distance. This can be a very arduous task for the vessel's
captain,
as well as resulting in high fuel consumption and excessive wear on machinery.
Another known technique is to use a vessel mounted water monitor or a fire
fighting (FIFI) water cannon for directing jet of water at the iceberg. The
problem with this arrangement is that the water monitor is exerting a force on
the top portion of the iceberg which is out of the water. Most of the mass of
the
iceberg is below water and therefore this may not be particularly efficient at
moving the iceberg or again cause tumbling of the iceberg. The use of a water
monitor can also be problematic because spray is often redirected by the
surface of the iceberg back to the vessel. The freezing water spray may result
in severe icing on the vessels' surface. The layer of ice on the vessel can be
dangerous for the crew and cause increased maintenance of the vessel. Using
a water monitor may also be ineffective in rough seas due to the inability to
keep the water jet targeted on the iceberg.
Embodiments of the present invention aim to address the aforementioned
problems.
According to an aspect of the present invention there is a method of managing
iceberg movement with a vessel comprising: directing a wash of water
.. generated by at least one first propulsor of the vessel at the iceberg;
opposing
a force from the at least one first propulsor with thrust from at least one
second
propulsor of the vessel; and moving the iceberg and the vessel along a desired
heading.
This means that vessel can maintain an operative position with respect to the
iceberg to guide the iceberg along a desired heading without numerous
manoeuvring operations to move the iceberg.
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Optionally, at least one first propulsor and the at least one second
propulsors
are' one or more of: a propeller, a thruster, or an azimuth thruster.
Optionally,
the at least one first propulsor and the at least one second propulsor are bow
thrusters. Optionally, the at least one second propulsor is a foremost bow
thruster. Optionally, the at least one second propulsor is also a stern
thruster.
Optionally, the at least one first propulsor and the at least one second
propulsor
are stern thrusters. Optionally, at least one first propulsor and the at least
one
second propulsor are azimuth thrusters. Optionally, the at least one first
propulsor is a first propeller and the at least one second propulsor is a bow
thruster and a second propeller.
Optionally the method comprises correcting the position of the vessel with
respect to the iceberg with the thrust from the at least one second propulsor.
In
this way, the at least one second propulsor can counteract the force of the at
least one first propulsor.
Optionally, the correcting comprises determining a magnitude and vector of a
resultant force exerted on the vessel from the at least one first propulsor;
and
determining a magnitude and vector of the thrust from the at least one second
propulsor to compensate for the resultant force.
Optionally, the method comprises determining a distance between the vessel
and the iceberg.
Optionally, adjusting the distance between the vessel and the iceberg if the
determined distance not within, a predetermined distance range. Optionally,
adjusting the distance comprises controlling the at least one first and / or
the
second propulsors.
Optionally, the force and the turning moment on the vessel generated by at
least one first propulsor and by the at least one second propulsor of the
vessel
are in equilibrium.
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CA 3010166 2020-03-10
=
In a second aspect of the invention, there is a vessel for managing movement
of an iceberg comprising: at least one first propulsor arranged to generate
and
direct a wash of water at the iceberg; at least one second propulsor arranged
to provide thrust in a direction opposing a force from the at least one first
propulsor, wherein the vessel is arranged to move together with the iceberg
along a desired heading.
In a third aspect of the invention, there is a method of managing iceberg
movement with a vessel comprising: directing a mass of water towards a target
portion of the iceberg; opposing a force of the directed water mass with at
least
one propulsor of the vessel; controlling the at least one propulsor to
maintain a
predetermined distance between the vessel and the iceberg; and
moving the vessel and iceberg along a desired heading.
Optionally, the directing the mass of water comprises either directing a water
jet from a water monitor mounted on the vessel and / or directing a wash of
water generated by at least one other propulsor of the vessel at the iceberg.
Optionally, the method comprises stabilizing the water monitor.
Optionally, the method comprises selecting a target portion of the iceberg.
In a fourth aspect of the invention, there is provided a vessel for moving an
iceberg comprising: at least one water ejector arranged to direct mass of
water
towards a target portion of the iceberg; at least one propulsor arranged to
provide thrust in a direction opposing a force of the directed water mass;
a controller configured to control the at least one propulsor and maintain a
predetermined distance between the vessel and the iceberg, wherein the vessel
is arranged to move together with the iceberg along a desired heading.
Optionally, the at least one water ejector is one or more of the following: a
water
monitor, a propeller, a thruster;or, an azimuth thruster.
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CA 3010166 2020-03-10
=
Optionally, the at least one propulsor is one or more of the following: a
propeller,
a thruster, or an azimuth thruster.
Various other aspects and further embodiments are also described in the
following detailed description and in the attached claims with reference to
the
accompanying drawings, in which:
Figure 1 shows a side view of a vessel for managing movement of an iceberg;
Figures 2 to 7 shows different schematic plan views of a vessel managing
movement of an iceberg according to different embodiments;
Figure 8 shows a schematic view of a vessel for managing movement of an
iceberg;
Figure 9 shows a flow diagram of a method of managing movement of an
iceberg according to an embodiment;
Figure 10 shows another flow diagram of a method of managing movement of
an iceberg according to another embodiment;
Figure 11 shows a flow diagram of a method of managing the distance between
the vessel and the iceberg when the vessel is managing movement of the
iceberg.
Figure 1 shows a side view of a vessel 100 for managing the movement of an
iceberg 102. The iceberg 102 comprises a submersed portion 104 and a
projecting portion 106 above the surface 108 of the water. Typically, the
volume
of the submersed portion 104 of the iceberg 102 is greater than the projecting
portion 106. Often, the ratio of the submersed portion 104 to the projecting
portion 106 is 8:1. As mentioned above, the term iceberg can cover all sizes
of
icebergs. The method of managing iceberg movement described in the
embodiments is particularly suitable for growlers, bergy bits and small bergs.
The iceberg 102 as shown in Figure 1 is one or more of a growler, a bergy bit
and / or a small berg. Nevertheless, the method of managing iceberg
movement described in the embodiments hereinafter can be applicable to any
size of iceberg.
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CA 3010166 2020-03-10
The vessel 100 as shown in Figure 1 is an anchor handling tug supply (AHTS)
vessel. In other embodiments, other types of vessel can be used such as a
platform supply vessel (PSV), multipurpose support vessel (MSV) tug boats, ice
breaker, patrol boat, coast guard vessel, navy vessel, fire-fighting vessel,
or any
other suitable vessel for managing the movement of icebergs.
The vessel 100 can be used for various marine operations such as anchor
handling, towing, supply of offshore installations, and fire-fighting. The
vessel
100 comprises one or more winches (not shown) for handling towlines and
.. anchors of offshore installations such as oil rigs. The vessel 100
comprises an
open aft portion 110 for storing and managing anchors. Figure 1 shows that
the open aft portion 110 is clear from anchors and towlines for the purposes
of
clarity. The open aft portion 110 may comprise one or more cranes (not shown)
for lifting and moving objects. The vessel 100 can use the winch together with
a towline for towing an iceberg 102, if required. Alternatively, the towline
can
be attached to a capstan or bollard secured to the deck of the vessel 100 when
towing an iceberg 102. The method of towing icebergs 102 with a towline and
vessel is known and will not be discussed in any further detail.
The vessel 100 comprises a plurality of propulsors for moving the vessel
through the water. In some embodiments, the propulsors are one or more of
the following: a propeller, a thruster, or an azimuth thruster. The vessel 100
can have any number or configuration of propulsors. The vessel 100 as shown
in Figure 1 comprises two propellers 122a, 122b of which the starboard
propeller 122b is shown in Figure 1. Figure 2 shows a port propeller 122a and
a starboard propeller 122b. The two propellers 122a, 122b are both coupled to
a diesel two stoke engine 800 (schematically shown in Figure 8) or each
propeller 122a, 122b is coupled to a separate diesel two stroke engine 800.
Alternatively, the two propellers 122a, 122b can be driven by one or more
diesel
.. 4 stroke engines 800. In other embodiments, the propulsors can be powered
with a diesel electric engine with or without a direct coupling. Under normal
sailing, the propellers 122a, 122b are principally used for moving the vessel
100
in a direction towards the bow 126 of the vessel 100. When the propellers
122a,
122b are reversed, the vessel 100 will move in a direction towards the stern
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CA 3010166 2020-03-10
128. In some embodiments, the vessel 100 only has one propeller 122, 700
(e.g. see Figure 7) mounted along the centreline A-A (see Figure 2). In other
operations, the direction of the propellers 122a, 122b can be reversed with
respect to each other. This will be discussed in more detail with respect to
Figure 5.
=
A rudder 124 is positioned aftwards of each propeller 122a, 122b for steering
the vessel 100. The rudder 124 is used for directing a wash 140 which is a
mass of water moved by the propellers 122a, 122b. Each propeller 122a, 122b
can have a nozzle 138 which is a hollow tube which surrounds each propeller
122a, 122b for increasing the propulsive force of the respective propellers
122a,
122b.
The vessel 100 comprises plurality of bow thrusters 112, 114, 116 and a
plurality of stern thrusters 118, 120. Each of the bow thrusters 112, 114, 116
and the stern thrusters 118, 120 are mounted in a tunnel 130. For the purposes
of clarity only one tunnel 130 has been labelled. The tunnel 130 is a hollow
tube integral with the hull 132 of the vessel 100 and is open at both sides,
e.g.
port side 206 and starboard side 200 of the hull 132. This means a thrust
force
can be imparted at either side of the vessel 100. The tunnel 130 which is
integral with the hull 132 of the vessel 100 maintains a compact form and
reduces drag on the thrusters 112, 114, 116, 118, 120 when the vessel 100 is
moving forwards.
The bow thrusters 112, 114, 116 and the stern thrusters 118, 120 provide a
side
force with respect to the vessel 100. In this way, the thrusters 112, 114,
116,
118, 120 increase the manoeuvrability of the vessel 100. In some
embodiments, the thrusters 112, 114, 116, 118, 120 are driven by an electric
motor 802 (schematically shown in Figure 8). The electric motor 802 is powered
by a diesel engine which may be an auxiliary engine (not shown) in addition to
the diesel engines 800 driving the propellers 122a, 122b. Optionally, the
electric motor 802 can also drive the propellers 122a, 122b. Alternatively,
the
electric motors 802 can be powered from the same engine 800 which drives the
propellers 122a, 122b. Additionally or alternatively, the electric motors 802
of
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CA 3010166 2020-03-10
the thrusters 112, 114, 116, 118, 120 are powered by a battery (not shown). In
other embodiments, the thrusters 112, 114, 116, 118, 120 are driven by a
diesel
engine 800 and gearing and linkages (both not shown) couple the engine 800
to the thrusters 112, 114, 116, 118, 120. In operation, one or more thrusters
112, 114, 116, 118, 120 can generate a thrust on aside of the vessel 100. All
the thrusters 112, 114, 116, 118, 120 can generate a thrust on the same side
of the vessel 100 or on different sides of the vessel 100. This will be
discussed
in further detail with respect to Figures 2, 3 and 4.
In other embodiments, one or more of the propellers 122a, 122b or the
thrusters
112, 114, 116, 118, 120 are replaced with azimuth thrusters 600,602 (as shown
in Figure 6). The azimuth thruster 600, 602 is housed in a pod and is also
known as an "azipod''. The azimuth thruster 600, 602 is rotatable by an angle
(azimuth) around a horizontal plane parallel with a main horizontal plane of
the
vessel 100. In this way, the azimuth thruster 600 can direct thrust in any
direction. Similar to the thrusters 112, 114, 116, 118, 120, the azimuth
thrusters
600, 602 can be driven by an engine 800 or an electric motor 802.
Turning back to Figure 1, control of the vessel 100 is achieved by manual
controls 808 such as joysticks, helm, wheel etc. (shown schematically in
Figure
8) located in the bridge 134. The bridge 134 is usually located in position
such
that the crew members have good visibility of the vessel 100 and the
surrounding sea. The bridge 134 as shown in Figure 1 has 360 degree visibility
of the sea surrounding the vessel 100. This means that crew members
operating the vessel 100 can safely and easily control the vessel 100
irrespective of whether the vessel 100 is moving forwards, backwards or side
to side. In other embodiments,=the vessel can be autonomously Controlled with
a dynamic positioning module 804 and a vessel control module 806 (as shown
in Figure 8). Use of the dynamic positioning module 804 will be discussed in
further detail together with Figure 8 below.
When any of the propulsors e.g. thrusters 112, 114, 116, 118, 120 or the
propellers 122a, 122b are in operation, the propulsors move a wash 140 which
is a mass of water forced away from the vessel 100. The reaction force of the
CA 3010166 2020-03-10
vessel 100 due to the propulsors causes the vessel 100 to move. Figure 1
shows a wash 140 caused by one the starboard propeller 122b. The wash 140
is Moving in the direction of the arrow away from the stern 128 of the vessel
100 and towards the iceberg 102. Whilst the wash 140 is associated with one
of the propellers 122, a similar wash 140 is generated with the thrusters 112,
114, 116, 118, 120 when they are directed at the submersed portion 104 of the
iceberg 102. For example, the wash 202 is shown in Figure 2 which is
associated with the aftmost bow thruster 112.
The wash 140 expands in a cone shape 136 as the mass of water propagates
from the propeller 122b. If the draft of the vessel 100 is of sufficient
magnitude,
then the propellers 122 or the thrusters 112, 114 ,116, 118, 120, cause a wash
14() with a cone shape that entirely impacts the submersed portion 104 of the
iceberg 102. In some embodiments, the vessel 100 can be trimmed so that the
propellers 122 and / or the thrusters 112 are directed downwards to the
submersed portion 104 of the iceberg 102. This means that the wash 140 will
be less likely to be directed to the water surface 108. In some embodiments,
the vessel 100 can be trimmed so that the propellers 122 and / or the
thrusters
112 are directly upwards to the submersed portion 104 of the iceberg 102 if
the
cone 136 of the wash 140 is entirely or partially directed below the bottom of
the iceberg 102. In this way, if the draft of the iceberg is less than
expected,
the cone 136 of the wash 140 can be directed to entirely impact the submersed
portion 104 of the iceberg 102. In some embodiments, the position of the
thrUster 112, 114, 116, 118, 120 are approximately 5.5m below the water
surface 108.
Turning to Figures 2 and 9, the management of the iceberg 102 movement will
be discussed in more detail. Figure 2 shows a schematic plan view of the
vessel 100 managing the movement of the iceberg 102. Figure 9 shows a flow
diagram for the steps of the method of managing movement of the iceberg 102.
The vessel 100 is positioned broadside to the iceberg 102. In this way, the
starboard side 200 of the vessel 100 is nearest the iceberg 102. The vessel
100 is positioned at a distance Dv from the iceberg 102.
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CA 3010166 2020-03-10
In some embodiments, the vessel 100 is positioned at a distance Dv between
10m to 25m. In some embodiments, the distance Dv is 15m which provides a
= balance between effective thruster force imparted to the iceberg 102 and
safety
of the vessel 100. At a distance of 15m the decrease in thruster force is
approximately 3% than when the vessel is at 10m, but the increased distance
reduces the risk of the vessel 100 colliding with the iceberg 102 or ice
calving
from the iceberg 102. The bow thrusters 112, 114, 116 in some embodiments
= have a 1180kW rating and can generate a thruster force of 171. However,
the
force of the wash 140 decreases as a function of distance from the bow
thruster.
For example, the bow thruster 112, 114, 116 can generate a force of
approximately 10T at a distance of 10m and 7T at a distance of 25m.
In other embodiments, the thrusters 112, 114, 116, 118, 120 can be of any
power rating and generate any required thruster force. In some embodiments,
the thruster force generated by the thrusters 112, 114, 116, 118, 120 is above
3.5T. In other embodiments, the thruster force generated by the thrusters 112,
114, 116, 118, 120 is between 3.5T and 20T.
The bow thrusters 112, 114, 116 are aligned with the iceberg 102. The bow
thrusters 112, 114, 116 are positioned at different points along the
longitudinal
axis or centreline A-A of the vessel 100. The foremost bow thruster 116 is
located closest to the bow 126 along centreline A-A. The foremost bow thruster
116 is positioned at distance x2 from the centre C of the vessel 100. The
aftmost
boW thruster 112 is located closest to the centre C of the vessel 100 at a
distance xi from the centre C. The middle bow thruster 114 is located between
the foremost bow thruster 116 and the aftmost bow thruster 116.
Figure 2 shows the aftmost bow thruster 112 directing thrust at the iceberg
102.
The vessel 100 is positioned such that the thruster 112 generates a wash 202
which exerts a force Fi against the iceberg 102 as shown in step 900 in Figure
9. Accordingly, the turning moment resulting from the aftmost bow thruster 112
Mi on the vessel 100 is Fi=xi. The turning moment Mi exerted on the vessel
100 due to the thrust from the aftmost bow thruster 112 causes the vessel 100
to yaw in an anticlockwise direction away from the iceberg 102.
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CA 3010166 2020-03-10
In order to keep the vessel 100 in substantially the same position and
orientation with respect to the iceberg 102, the foremost bow thruster 116
generates a thrust F2 to oppose the force from the wash 202 of the aftmost bow
thruster 112 as shown in _step 902 as shown in Figure 9. In this way, the
foremost bow thruster 116 generates an opposing, counter acting wash 204 to
yaw the vessel in a clockwise direction towards the iceberg 102. Accordingly,
the. turning moment M2 resulting from the foremost bow thruster 116 on the
vessel 100 is F2=x2. The turning moments Ml, M2 should balance in order to
maintain the vessel 100 substantially stationary with respect to the iceberg
102.
In this way, the foremost bow thruster 116 requires a thrust less than the
aftmost
bow thruster 112. Accordingly, by using the foremost bow thruster 116 to
maintain the position of the vessel 100, less power and fuel is required than
if
another thruster such as the middle bow thruster 114 is used. Whilst the
turning
.. moments Mi, M2 are balanced, the vessel 100 will not yaw about the centre
C.
However, where there are only.two opposing forces Fi, F2 as shown in Figure
2 which are offset along the centreline A-A to balance the turning moments,
the
forees F1, F2 are unequal. Whilst, the iceberg 102 and the vessel 100 will
move
along the desired heading, the vessel 100 will move slowly with respect to the
iceberg (e.g. towards or away from) the iceberg 102 due to the unequal
opposing forces Fi, F2 Nevertheless, the vessel 100 will have to perform less
manoeuvres than because relative movement between the vessel 100 and the
iceberg 102 is small.
In an alternative embodiment, based on the arrangement shown in Figure 2,
the thrusters 112, 116 are positioned at the same distance from the centre C
along the centreline A-A. However, the thrusters 112, 116 are positioned
vertically above each other at different heights from the bottom of the hull.
In
this case both the opposing forces F1, F2 and the turning moments M1, M2 are
equal.
In some embodiments, the captain or crew member of the vessel 100 can
manually adjust the power of the foremost bow thruster 116 and the aftmost
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CA 3010166 2020-03-10
bow thruster 112 to adjust the distance Dv of the vessel 100 from the iceberg
102. In this way, the captain of the vessel 100 can maintain the distance Dv
of
the, vessel 100 with respect to the iceberg 102. In some
embodiments, the
captain of the vessel 100 can maintain the position and the orientation of the
vessel 100 with respect to the iceberg 102. Accordingly, the vessel 100 and
the iceberg 102 move together along a desired heading.
In other embodiments, the vessel control module 806 can balance the turning
moments Ml, M2 of the bow thrusters 112, 116. This means that the captain of
the vessel 100 can manually select the amount of thrust being directed to the
iceberg 102 and the vessel will 100 will remain in position with respect to
the
iceberg 102. This will be discussed in further detail with respect to Figure
10
below.
In this way, the vessel 100 moves the iceberg 102 along a desired heading as
shown in step 904 in Figure 9. The vessel 100 continues moving the iceberg
102 until the corrected heading of the iceberg 102 is no longer a risk to
shipping
traffic of offshore installations. For example, in some embodiments, the
vessel
100 may only need to move the iceberg 102 a few degrees off its original
heading. Once the heading of the iceberg 102 has been sufficiently adjusted,
then the vessel 100 can move away from the iceberg 102 and perform another
operation.
The method of managing movement of the iceberg 102 with a vessel 100 as
described in reference to the embodiment is more fuel efficient that other ice
management techniques. For example, a typical water monitor can require a
system power of 1600kW and will generate a water flow of 2400m3/h. This
creates a water flow force of 'approximately 3.5t at a distance of 10m. A
comparable force from the bow thrusters requires a power of 1000kW. This
means the fuel consumption is reduced which can be significant for an ice
moving operation lasting many hours.
Furthermore, the method of managing ice movement can be faster than using
a water monitor because a greater peak force is available from the bow
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CA 3010166 2020-03-10
thrusters 112, 114, 116. In this way, the duration of ice movement operations
can be reduced if the bow thruster 112 is operated at 100% power.
Another embodiment will now be described in reference to Figure 3. Figure 3
shows a schematic plan view of the vessel 100 managing the movement of the
iceberg 102. The embodiment as shown in Figure 3 is substantially the same
as the embodiment shown in Figure 2 except that an aftmost stern thruster 118
is used to control the yaw motion of the vessel 100.
Figure 3 shows only two bow thrusters 112, 116 and one stern thruster 118 for
the purposes of clarity. The same reference numbers have been used to refer
to the same features as described in reference to Figure 2.
In the arrangement in Figure 3 the thrusts generated by the foremost bow
thruster 116 and the aftmost bow thruster 112 are equal and opposite. In some
embodiments, the thrusters 112, 116 generate a thrust of 17T each. This
makes manual control of the vessel 100 easier. In this way, a thrust power
setting of the aftmost bow thruster 112 can be selected for generating a
required
= wash 202. At the same time the vessel control module 806 controls the
foremost bow thruster 116 to generate the same thrust to counteract the wash
202 directed towards the iceberg 102.
Since the thrust of the thrusters is equal, the turning moments Ml, M2
respectively associated with the aftmost bow thruster 112 and the foremost bow
thruster 116 will be unbalanced. Accordingly, a third thruster is required to
balance the yawing motion of the vessel 100.
Accordingly, the aftmost stern thruster 118 generates a thrust to counter the
resultant force of the bow thrusters 112, 116. The aftmost stern thruster 118
is
positioned on the centreline A-A at a distance x3 from the centre C. The stern
thruster 118 generates a smaller thrust creating wash 300. The turning moment
resulting from the aftmost Stern thruster 118 M3 on the vessel 100 is F3.x3.
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If the bow thrusters 112, 116 are operating at an equal thrust, then the
vessel
100 will tend to rotate in an anticlockwise direction. That is, the turning
moments Mi, M2 from the aftmost bow thruster 112 and the foremost bow
thruster 116 will be unbalanced. In this case, aftmost stern thruster 118 will
direct the thrust on the port side 206 as shown in Figure 3. Accordingly, the
turning moment Mi from the aftmost bow thruster 112 and the turning moment
M3 from the aftmost stern thruster 118 equal the turning moment M2 from the
foremost bow thruster 116. This means that the vessel 100 will not yaw about
the centre C.
Optionally, the force F2 of foremost bow thruster 116 and the force F3 of the
aftmost stern thruster 118 equal the force Fi from the aftmost bow thruster
112.
When the forces on opposing sides of the vessel 100 are equal, then the vessel
= 100 will remain at a fixed distance with respect to the iceberg 102.
Alternatively, if the vessel 100 is positioned so that the iceberg 102 is
nearest
the port side 206 of the vessel 100, then the aftmost stern thruster 118 will
generate a thrust on the starboard side 200 as shown by the dotted arrow in
= Figure 3. Additionally, if the sea is rough, then the thrust of the bow
thrusters
112, 116 may not be directed in the intended direction or the bow thrusters
112,
116 may break the surface 108 of the water. Accordingly, the aftmost stern
thruster 118 may need to generate thrust on the starboard side 200.
In an alternative embodiment, the thrust to counter the resultant force of the
bow thrusters 112, 116 can be generated by the middle bow thruster 114. This
is less preferable because more thrust will be required to counter the
resultant
force consuming more fuel. Furthermore, thrusters 112, 114, 116 can "cross
talk" when in operation in opposing directions. That is, wash from one
thruster
can interact with the intake from another thruster. In some embodiments,
thrust
is generated by separated thrusters. In some embodiments, the thrusters 112,
116 generating thrust are separated by a distance of at least 5m to 10m.
Indeed, another embodiment there can be any number of bow thrusters and
any two of the thrusters can generate the wash 202 and the counter acting wash
204.
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Reference will now be made to Figure 4 which shows a schematic plan view of
the vessel 100 managing the movement of the iceberg 102. Figure 4 is the
same as the embodiments described in reference to Figures 2 and 3. For the
purposes of clarity, the bow thrusters 112, 114, 116 have not been shown.
The vessel 100 comprises two, stern thrusters 118, 120. The foremost stern
thruster 120 is located closest to the bow 126 along centreline A-A. The
aftmost
stern thruster 118 is located closest to the stern 128 of the vessel 100. The
.. principle of operation is the same as the embodiment as described in
reference
to Figure 2. In this way, the foremost stern thruster 120 creates a wash 400
to
push the iceberg 102 and the aftmost stern thruster 118 creates a counter
acting wash 402. Advantageously, the arrangement as shown in Figure 4 may
be .preferable in some rough sea conditions because less of the vessel 100 is
broadside to the iceberg 102. In this way, it is easier to escape from the
proximity of the iceberg 102.
Similar to Figure 2, the turning moments of the stern thrusters 118, 120 will
be
required to stop the vessel 100 yawing. In another embodiment (not shown for
.. brevity), a bow thruster 116 (not shown in Figure 4) can be used to counter
the
yawing motion caused by the stern thrusters 118, 120. Accordingly, the
operation is the same as that discussed in reference to Figure 3. In another
embodiment, there can be any number of stern thrusters and any two thrusters
can be used to create a wash 400 and a counter acting wash 402.
Reference will now be made to Figure 5. Figure 5 shows a schematic plan view
of the vessel 100 managing the movement of the iceberg 102. Figure 5 is the
same as the embodiments discussed in reference to Figures 2 to 4 except that
the propellers 122b, 122a are used to create the wash 140. Figure 5 is the
plan
view, of the embodiment as shown in Figure 1.
The vessel 100 approaches the iceberg 102 from the stern 128. The starboard
propeller 122b is engaged in the forward direction. This creates the wash 140
which is directed at the iceberg 102. In order, to counter the forward thrust
from
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the starboard propeller 122b, the port propeller 122a is engaged in a reward
direction. This creates an opposing, counteracting wash 500. This passes
under the hull of the vessel 100 and is indicated by the dotted arrow. Since
the
coOnter acting wash is directed underneath the hull 132, the propellers 122a,
122b may need to be operated at different power levels to compensate for
turbulence caused by the counteracting wash 500 interacting with the hull 132.
Alternatively, both propellers 122a, 122b can be operated at an equal power
level, but in opposite directions.
When the propellers 122a, 122b are in operation, this generates a turning
moment and the vessel 100 will yaw about its centre in an anticlockwise
direction. Accordingly, one or more bow thrusters 116 generate p counter yaw
wash 502 to the port side 206 of the vessel 100. If the direction of the
propellers
122a, 122b is reversed, then the bow thrusters 116 may generate the wash 502
on the starboard side 200 of the vessel.
The arrangement as shown in Figure 5 may be preferable because the stern
128 is nearest the iceberg 102.. This means that a smaller cross section of
the
vessel 100 is exposed to the iceberg 102 when compared to the vessel 100
being broadside to the iceberg 102. This means that the propellers 122a, 122b
can be operated in a forward direction to move quickly away from the iceberg
102. Furthermore, by using the propellers 122a, 122b to create the wash for
moving the iceberg 102, the fuel efficiency can be further increased.
Another embodiment will now be described in reference to Figure 6. Figure 6
shows a schematic plan view of the vessel 100 managing the movement of the
iceberg 102. Figure 6 is the same as the embodiments described in reference
to Figures 1 to 5 except that the port and starboard propellers 122a, 122b are
replaced respectively with port and starboard azipods 600, 602.
The port and starboard azipods 600, 602 are rotatable about any azimuth as
indicated by the dashed azipods. The position of the dash azipods is such that
the rotation axis of the azimuth thruster are aligned parallel with the
centreline
A-A of the vessel 100.
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=
The azipods 600, 602 as shown in Figure 6 are locked in a position (e.g. 90
degrees) where the rotation axis of the azimuth thruster are perpendicular to
the centreline A-A of the vessel 100 and aligned along axis B-B. This means
that the starboard azimuth thruster 602 generates a wash 604 in the direction
of the starboard side 200 _for moving the iceberg 102 and the port azimuth
thruster 600 generates a counteracting wash 606 in the direction of the port
side 206.
Advantageously, the axis of rotation 608, 610 of the port and starboard
azipods
600, 602 are aligned on the axis B-B. This means that the thrust of azipods
600, 602 is not offset. This means that the wash 604, and the counteracting
wash 606 are aligned along axis B-B. In this way, the thrust of the azipods
600,
602 can be equal and the vessel 100 does not experience any yawing motion.
In some embodiments, the azipods 600, 602 are in addition to other propulsors
such as propellers and thrusters. In some embodiments, the azipods 600, 602
are mounted in different locations on the vessel 100. If the azipods 600, 602
are offset from each other along the centreline A-A, then another propulsor
will
be required to counter the resulting yawing motion as discussed in reference
to
Figures 3, 4, and 5.
The thrusters 112, 114, 116, 118, 120 can be used to make minor adjustments
to the position of the vessel 100 with respect to the iceberg, for example,
due
to wind and currents.
Turning to Figures 7 and- 10, another embodiment will now be discussed.
Figure 7 shows a schematic plan view of the vessel 100 managing the
movement of the iceberg 102. Figure 10 shows a flow diagram of a method of
managing iceberg movement according to another embodiment.
The vessel 100 as shown in Figure 7 has a simple arrangement with a single
propeller 700 and a single bow azimuth thruster 702 mounted on the centreline
of the vessel. Operation of the vessel 100 is the same as discussed with
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reference to Figure 5 except that no thrusters are required to counter a
yawing
motion.
The vessel 100 further comprises a stern mounted water monitor 704. The
water monitor 704 is for targeting the projecting portion 106 of the iceberg
102
above the surface 108 of the water. This means that the vessel 100 can direct
a mass of water with a water jet 706 from the water monitor 704 and / or with
a
wash 708 from the propeller 700 as shown in step 1000 of Figure 10. In other
embodiments, there can additionally or alternatively be a bow mounted water
monitor 138 as shown in Figure 1.
When the vessel 100 is directing a water jet 706 or a wash 708 to the iceberg
102, the vessel generates forceto oppose the directed mass of water as shown
in step 1002 of Figure 10. Step 1002 is the same as the step 902 in Figure 9.
In a less preferred embodiment, the water jet 706 can be opposed with another
jet of water (not shown) from the bow mounted water monitor 138.
The propulsors 700, 702 are. controlled to maintain the vessel 100 at a
predetermined distance between the iceberg 102 and the vessel 100 as shown
in step 1004 of Figure 10. As mentioned with respect to Figure 10, the captain
can manually maintain the distance of the vessel 100 at a predetermined
distance from the iceberg -102. Alternatively, the vessel control module 806
controls the propulsors based on sensor information and vessel information to
maintain a relative distance to the iceberg 102.
= 25
In another embodiment, the embodiment using a water monitor shown in Figure
7 can be combined with any of the embodiments discussed in reference to
Figures 1 to 6.
The process of maintaining the distance between the vessel 100 and the
iceberg 102 will be discussed in further detail with respect to Figures 8 and
Figures 11. Figure 8 shows a schematic view of a vessel for managing
movement of an iceberg. Figure 11 shows a flow diagram of a method of
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managing the distance between the vessel and the iceberg when the vessel is
managing movement of the iceberg.
Turning to Figure 8, the vessel 100 comprises a plurality of different modules
for controlling one or more aspects of the vessel 100. The modules may be
implemented on hardware, firmware or software operating on one or more
processors or computers. A single processor can operate the different module
functionalities or separate individual processors, or separate groups of
processors can operate each module functionality.
The vessel 100 further comprises modules for determining parameter
information relating the vessel 100. Figure 8 is a non-exhaustive list of the
different control modules of a vessel 100. The vessel 100 comprises a vessel
control module 806 for controlling the movement, positioning and orientation
of
the vessel 100 by sending instructions to the propulsors e.g. the propellers
122a, 122b, 700, the thrusters 112, 114, 116, 118, 120 and/or azipods 600,
602. The vessel control module 806 can control one or more other aspects of
the vessel 100 such as the water monitor 704, 138.
The vessel control module 806 receives position information from a dynamic
positioning module 804. The dynamic position module 804 receives positioning
information from one or more inputs such as a global positioning system (GPS)
814, global navigation satellite system (GLONASS) 816, and a compass 818
for determining the current position and heading of the vessel 100. The
dynamic positioning module 804 can receive additional positioning input
information from other input sources, if required. The dynamic position module
804 sends target position information to vessel control module 806. The target
position information received from the dynamic positioning module 804 is
position information for moving the vessel 100 from a current position to a
desired target position of the vessel 100. For example, the target position
information can be position information for maintaining the vessel 100 in a
static
position for the vessel 100 or a maintaining the vessel on a course or
heading.
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=
The vessel 100 further comprises an iceberg distance module 810 for
determining the distance of the iceberg 102 from the vessel 100. The dynamic
positioning module 806 may not receive information relating to the relative
position of the iceberg with respect to the vessel 100. Accordingly, iceberg
distance information is separately obtained. In some embodiments, the iceberg
distance module 810 is incorporated in the dynamic positioning module 810.
The iceberg distance module 810 comprises at least one distance sensor 812
for determining the distance between the vessel 100 and the iceberg 102. The
at least one distance sensor 812 can be a laser range finder, LIDAR, RADAR,
SONAR, a camera, ultrasonic distance detector or any other suitable sensor for
determining distance of an object. The laser range finder measures the time
for reflected light to be detected to determine the distance of the iceberg.
= 15 Additionally or alternatively, at least one beacon 710 is placed
on the closest
surface of the iceberg 102 to the vessel 100 for measuring the distance. The
beacon 710 can be passive and provide a surface which is better for reflecting
the measurement signals e.g. light, radio waves, sound waves. In this way the
beacon 710 can be made from a reflective material such as foil. In alternative
= 20 embodiments, the beacon 710 can be active and send a signal to the
distance
sensor 812 for measuring the distance. For example, the active beacon 710
can comprises a GPS detector for determining position of the iceberg which is
sent to the distance sensor 812. In some embodiments, the beacon 812 can
be launched from the vessel 100 to the iceberg 102 using a harpoon, drone,
25 cannon or any other suitable means for delivering the beacon 812 to the
iceberg
102.
Turning to Figure 11, the control of the distance between the iceberg 102 and
the vessel 100 will now be discussed. Initially, the vessel 100 approaches the
30 iceberg as indicated in the start step 1100.
As the vessel 100 reaches a predetermined distance Dv from the iceberg 102,
the vessel 100 generates -a wash 708 towards the iceberg 102 to move the
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iceberg 102. Initially, the wash 708 force (F wash) and the countering wash
712
wash,
force (Fcounter wash) are equal as shown in step 1102.
However, due to wind and currents, the vessel 100 may move with respect to
the iceberg 102.
The iceberg distance module 810 the determines the distance Dv between the
vessel 100 and the iceberg 102.. The iceberg distance module 810 determines
whether the current distance Dv is within a predetermined distance range or
.. eqOal to a predetermined distance threshold. In some embodiments, there is
a
range of distances for Dv which provides optimal thrust fuel efficiency when
moving the iceberg and safety of the vessel. As mentioned previously this
distance is between 10m ¨ 25m. By having an acceptable distance range, less
adjustment will be required which will improve fuel efficiency and
maintenance.
In some other embodiments, the target distance Dv is 15m.
In step 1104 as shown in Figure 11, the iceberg distance module 810
determines that the vessel 100 is too close to the iceberg 102. That is the
current vessel distance Dv is less than a safe, optimal distance Doptimal. The
iceberg distance module 810 indicates to the dynamic position module 804
directly or indirectly via the vessel control module 806 that the distance
between
the vessel 100 and the iceberg 102 should be increased. Accordingly, the
dynamic positioning module 804 sends target position information to the vessel
control module 806. The vessel control module 806 then controls the
propulsors such that the wash 708 force (Fwash) is greater than the countering
wash 712 force (Fcounter wash) as shown in step 1106. This is either achieved
by
reducing power to the azimuth thruster 702 and/or increasing power to the
propeller 700. This moves the vessel 100 to the target position, which is
further
away from the iceberg. =
The vessel control module 806 then returns to step 1102 where the wash 708
force (F wash) and the countering wash 712 force (Fcounter 1 are equal.
wash, wash,
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Alternatively, in step 1104 as shown in Figure 11, the iceberg distance module
810 determines that the vessel is too far away from the iceberg 102. That is,
the current vessel distance Dv is greater than the safe, optimal distance
Doptimal.
The iceberg distance module 810 indicates to the dynamic position module 804
directly or indirectly via the vessel control module 806 that the distance
between
the vessel 100 and the iceberg 102 should be decreased. Accordingly, the
dynamic positioning module 804 sends target position information to the vessel
control module 806. The vessel control module 806 then controls the
propulsors such that the wash 708 force (Fwash) .s i less than the countering
wash
712 force (Fcounter wash) as shown in step 1108. This is either achieved by
increasing the power to the azimuth thruster 702 and/or decreasing power to
the propeller 700. This moves the vessel 100 to the target position, which is
closer to the iceberg.
.. In this way, the target position information received from the dynamic
position
module 804 maintains the vessel 100 and the iceberg 102 on a desired heading
as shown in step 1006 in Figure 10. Step 1006 is the same as the step 904 in
Figure 9.
The method as described in reference to Figures 7, 10 and 11 for controlling
the distance between the iceberg 102 and the vessel 100 can be applied to any
of the previously described embodiments in Figures 1 to 6.
In a further embodiment, the water monitor 704 additionally is Controlled by a
water monitor module 820. The water monitor module 820 controls the pump
rate ,of the water jet 706 with the water monitor pump system 822 and the
direction of the water monitor 704 with the water monitor positioning system
824. The water monitor 704 is mounted on a stabilized rotatable gimble or
platform 714. The stabilization of the rotatable gimble or platform 714 is
.. controlled by a water monitor stabilization module 826. The water monitor
stabilization module 826 receives vessel movement information from the vessel
control module 806 and compensates for the yaw, roll, heave and translational
movement of the vessel 100. The vessel control module 806 sends information
to the water monitor module 820 to target a part of the iceberg 102. This can
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CA 3010166 2020-03-10
be a manually selected portion of the iceberg 102. Once the initial water
monitor parameters have been selected (pump rate, relative angle and position
of the water jet), the vessel control module instructed the water monitor
module
820 to keep the water jet targeted on the same portion of the iceberg. The
water monitor module 820 adjust the pump rate and the position of the water
monitor to maintain the water jet 706 fixed in the same place with respect to
the
iceberg independent of movement of the vessel 100 and the distance between
the vessel 100 and the iceberg .102.
The water monitor 704, 138 can be combined with any of the previously
described embodiments. Furthermore, the method described in reference to
Figures 7 and 10 can be combined with any of the previously described
embodiments.
Whilst, the aforementioned embodiments discuss a method managing iceberg
movement with a vessel, the method can be applied to managing movement of
other floating objects in water. For example, a vessel can be used to direct
jetsam, flotsam, floating rubbish, oil spills, floating shipping containers,
or other
debris. Indeed, the method can be applied to any floating object in order to
managing the object's movement in the water. In this way, the term "iceberg"
can be replaced with "object" or "rubbish" etc throughout the application.
In another embodiment two or more embodiments are combined. Features of
one embodiment can be combined with features of other embodiments.
Embodiments of the present invention have been discussed with particular
reference to the examples illustrated. However, it will be appreciated that
variations and modifications may be made to the examples described within the
scope of the invention.
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