Note: Descriptions are shown in the official language in which they were submitted.
CA 02854533 2016-01-25
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BULWARK LIFE BOAT PROTECTION
The present invention relates to a protective arrangement suitable for free
fall
lifeboats.
Free fall lifeboats are use on offshore vessels and constructions. The davit
with
life boat is a permanent installation through the lifetime of the vessel or
construction,
where the lifeboat is in a standby position for release in case of an
emergency. The
lifeboat davits are situated at places where there is a free course to sea, so
that the
lifeboat can fall directly into the sea at a distance from the construction,
in case of
emergency and release.
On most offshore constructions, the davit is arranged above reach of green sea
and waves, and thereby direct exposure to sea water. However, as there is a
tendency
towards smaller constructions offshore, there is also an increasing problem
that the
davit cannot be arranged as high above sea level as desired. This is also a
problem on
FPSO's where it is difficult for the vessel to adjust to the direction of the
surrounding
waves.
It is estimated that the impact force in heavy green sea can be as high as 400
tons per square meter in short wave impacts. Such forces can easily harm the
construction of the davit and lifeboat.
There is therefore a need for a protection system of free fall lifeboats
systems,
which can prevent waves from reaching the davit and lifeboat system.
The object of embodiments of the present invention is to provide an efficient
protection for a free fall lifeboat arrangement against wave impacts on the
offshore
construction or vessel on which the lifeboat arrangement is situated.
This is obtained by a protective assembly for bulwark with opening, comprising
a
frame assembly, a membrane connected to the frame assembly in a distended way,
and
perforating means. The frame assembly and the perforating means comprises
anchoring
means suitable for side-by-side anchoring to the bulwark structure surrounding
the
opening. The perforating means are arranged movable towards the frame assembly
by
means of a moving weight, such as a free fall lifeboat, in such a way that the
membrane is perforated.
The membrane may provide protection against breaking waves and green sea
impact forces, thereby ensuring a safe residence for the lifeboat even at
levels within
reach of the surrounding sea. This ensures a quick escape in an emergency
situation, a
perforating means being pushed by a falling lifeboat, will perforate the
membrane so
that the lifeboat can fall into the sea without delay. This gives a highly
efficient way of
forcing the lifeboat through the protective assembly.
In one aspect of the invention, the frame assembly comprises membrane
handling means suitable for lifting and lowering the membrane in relation to
the
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bulwark opening. If the emergency situation rises during calm weather, where
there is not a need for protection against waves, the membrane can be lowered,
leaving a free passage for the lifeboat. It is also thinkable that the
membrane can
be removed for maintenance or replacement of parts of or the complete lifeboat
and/or davit.
In a further aspect of the invention, the perforating means comprises
rotatable members provided with cutting means, the cutting means facing the
frame assembly, when anchored to a bulwark. As the perforating means provide
cutting means of rotatable members, the passage of a lifeboat past the
perforating
io means will automatically rotate the rotatable members forwards towards
the
membrane. This movement will move the cutting means into the membrane,
tearing it apart to leave a free passage for the falling lifeboat. As the
cutting action
is promoted by the falling lifeboat, it is independent of power supply, which
can be
essential in emergency situations such as a fire, where power can be cut off.
In one aspect of the invention, the perforating means further comprises
integrated rotating means suitable for moving the perforating means towards
the
frame structure or membrane. The rotating means can forward the rotatable
members with cutting means towards the membrane, so that a falling lifeboat
pushes the cutting means directly into the membrane. As the cutting action
starts
almost simultaneously with the lifeboat passing, the risk of the membrane
slowing
down the lifeboat is minimised.
In yet another aspect of the invention, the perforating means is anchored to
the bulwark structure between the frame assembly or membrane and a free fall
lifeboat or davit, at a predefined distance from the frame assembly or
membrane.
As the perforating means are arranged at a distance from the membrane,
there is a free space for the membrane to yield under impact forces from
breaking
waves without getting in contact with the cutting means. Furthermore, as the
cutting means are facing the membrane on the rotatable members, the opposite
side of the rotatable members will serve as a protection for the lifeboat
against the
cutting means. This way, the lifeboat will not risk damages due to passing the
bulwark passage in direct contact with the perforating means of the protective
arrangement.
In one aspect of the invention, the frame assembly comprises rotating
means such as swivels, the membrane being connected to the frame assembly by
means of wires passing over the swivels, the wires further being connected to
a
winch. As the membrane is provided with a winching system it is possible to
lower
and rise the membrane, opening and closing the lifeboat passage in a bulwark
depending on needs and weather conditions.
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In one aspect of the invention, the wires holding the membrane are
arranged in guides on each side of the membrane. The guides will ensure a
stable
anchoring of the membrane. If the membrane is lowered or risen, the guide can
also promote a controlled movement of the membrane and adjacent structures.
In one aspect of the invention, the rotatable members are formed as
elongated arms provided with rotatable fastening means at one end of the arm
and
cutting means along one side of the arm. The elongated arms gives a light and
slim
holding structure for the cutting means, which makes it easy to move or rotate
the
arms in an emergency situation.
io In one aspect of the invention, the elongated arms are tapered, the
fastening means anchoring the arms to the bulwark, being situated at the
widest
end of the arm. A tapered form of the elongated arms ensures a sufficient
anchoring interface between the arm and the bulwark. The attachment of cutting
means such as knifes, knife blades, shear blades, piercers or any other means
suitable for perforating a membrane, to the arm will normally be less material
and
space requiring than the anchoring of the rotatable arm to the bulwark. It is
therefore an advantage to save material and weight by trimming away excess
material from the arm parts surrounding the cutting means.
In one aspect of the invention the membrane is connected to the frame
assembly by means of fixing clamps in a fixing frame holding fixing elements
arranged on predefined edge areas of the membrane. The frame assembly can be
anchored directly on the bulwark surface, thereby providing a further
attachment
means for the membrane. The fixing frame can also be integrated in the frame
assembly. The fixing assembly with fixing frame and fixing elements will
provide a
further reinforcement of the attachment of the membrane to ensure that it
withstand the forces from the surrounding sea.
The invention also relates to an offshore construction comprising at least one
protective assembly described above. The use of protective assemblies on an
offshore construction, such as platforms, vessels, FPSOs or the like, makes it
possible to place the lifeboat davit within reach of the sea, without the risk
of waves
striking or harming the davit and lifeboat. Thereby, the protective assembly
makes
it possible to use freefall lifeboats on constructions and vessels of smaller
sizes,
where it is not possible to place the davit above reach of the sea. As
freefall
lifeboats provide a safer escape means than lighter constructions, the
assembly can
improve safety in offshore environments.
The invention further relates to the use of a protective assembly as
described above, as a protective assembly for a free fall lifeboat and davit
situated
in a marine environment.
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The invention will now be further explained by means of the attached
drawings of non-limiting embodiments of the invention, where:
Fig. 1 shows a free fall lifeboat and davit arrangement with a first
embodiment of a protection system according to the invention, in passive
position.
Fig. 2 shows the protection system of fig. 1 in an activated position.
Fig. 3 shows the protection system in fig. 1 hit by a wave.
Fig. 4 shows a second embodiment of the protection system.
Fig. 5 shows an outline of a fall movement pattern for a free fall life boat
io being released from a davit.
Fig. 6-8 show detailed views of three following positions for a free fall
lifeboat hitting and passing through a protective system according to the
invention.
Fig. 9 shows a front view of a membrane and rotatable members.
Fig. 10 shows an example of a fixing arrangement for a protection
membrane.
Fig. 11a-lib shows the fixing arrangement of fig. 10 in released position.
Fig. 12 shows an example of a side support for the membrane.
Fig. 1 shows a free fall lifeboat 1, davit arrangement 2 and a bulwark 20
provided with a protection system 3 according to the invention, in passive
position.
The protective system comprises a frame assembly 4 holding a protective
membrane 5 being held in a releasable or adjustable way. This will be further
explained below. Between the protective membrane 5 and the lifeboat, there is
membrane perforating means 7. The membrane perforating means 7 comprises
rotatable members 8 and cutting means 9.
If there is an emergency situation and the life boat must pass the membrane
to escape the platform or the like, the life boat will force the rotatable
members 8
out towards the membrane, and the cutting means 9 will cut openings in the
membrane to enable to lifeboat to unobstructed pass the protection system.
Fig. 2
shows the rotatable members 8 turned towards the membrane 5 and the cutting
means 9 in position to cut through the membrane. The rotatable members 8 can
be
provided with further opening means 16, which can move the rotatable members 8
towards the membrane prior to a launch.
Fig. 3 shows a visualisation of how the protection system 3 will function
when a wave hits the protection system arranged on the bulwark 20 in front of
the
lifeboat davit 2. The membrane 5 is mounted at a distance from the membrane
perforating means 7. As there is a natural flexibility in the membrane, the
membrane will yield when being hit by a wave, thereby absorbing the impact
force
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of the wave and direct the water masses away from the opening in the bulwark
dedicated to the passage 10 for a lifeboat. The maximum pressure of a breaking
wave can be up to 400 tons/m2 and it is essential that the protection system
and
membrane can withstand such impacts. As the protection system prevents the
5 waves from reaching the lifeboat and davit, there will be no damages to
these,
even in extreme weather.
As the membrane withstand the impact forces of green sea and other rough
weather conditions, it is possible to lower the arrangement of the lifeboat
davit
towards the sea surface while maintaining a safe residence even at heights
below
io expected wave heights of the surrounding sea.
Fig. 4 shows a side view of a free fall lifeboat with davit and a second
embodiment of the protection system 3. The protection system comprises a frame
assembly 4, membrane wires or ropes 14 and a holding mechanism (not shown)
holding a protective membrane 5, signal line 6 and winch 15. Furthermore,
there is
provided membrane perforating means 7 arranged at a distance behind the
membrane 5, between the protective membrane 5 and the lifeboat 1. The
membrane perforating means comprises at least one rotatable member 8
comprising cutting means 9.
In the shown embodiment, the rotatable members 8 are formed as gates
being provided with cutting means on the surface facing the membrane. If the
lifeboat is released, it will slide towards and into the rotatable members,
forcing
them to pivot outwards, thereby forcing the cutting means through the
membrane,
leaving a free passage for the boat. A signal line activating the system is
linked to
the hydraulic pump for the lifeboat hook.
The membrane 5 is a rectangular fabric with high-strength and durability
towards sea water, which at its corners is held by membrane wires 14 being
arranged on swivels or pulleys 18 in the frame assembly 4 in such a way that
the
wires can be pulled over the pulleys thereby lowering or lifting the membrane
in
relation to the lifeboat passage of the bulwark 20 by means of the winch 15.
The
winch can for example be powered by a servo motor running on UPS. Is is an
advantage of the frame assembly comprises a guide 17 for the wires over the
complete traveling path.
If there is a calm sea in an emergency situation, the membrane can be
lowered in front of the bulwark below the lifeboat passage, leaving the
passage
open. If the lifeboat is released, it will pass between the wires holding the
two sides
of the membrane, above the membrane.
However, if there is rough weather with green sea conditions, the membrane
can be kept as a safeguard in front of the lifeboat. In such situations, the
rotatable
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members with cutting means will rotate into the membrane as the lifeboat
passes,
cutting the membrane open and thereby opening the lifeboat passage. Fig. 5
shows
a partly sectional side view of a lifeboat being released and dropped through
a
protection system according to the invention. The lifeboat will pass between
the two
rotatable members and through the perforated membrane.
Figs. 6-8 show a side view of a falling boat 1 forcing the rotatable members
8 forwards and into the membrane 5. As the rotatable members 8 get in contact
with the membrane 5, the cutting members 9 will cut an opening in the
membrane,
letting the lifeboat pass unobstructed, which is important in an emergency
situation. The cutting members 9 should be sharp and preferably of razor blade
quality to ensure that the membrane is cut open efficiently when needed.
Fig. 9 shows a front view of a membrane and rotatable members with
cutting means showing an example of the positions of the rotatable members in
relation to the membrane. In the shown embodiment, there are two upper
rotatable
members 8' and two lower rotatable members 8". The rotatable members are
arranged as a diagonal cross from the corners of the membrane towards the
centre.
The lifeboat will first hit the rotatable members at the centre of the
membrane. The
cutting means will start cutting an opening in the centre of the membrane and
subsequently outwards making the hole larger and larger while the lifeboat
passes
zo through the membrane.
As the membrane and surrounding structure should withstand heavy impacts
and rough environmental conditions, the holding arrangement for the membrane 5
must be strong and secure. Fig. 10-12 shows an example of a holding
arrangement
for the membrane 5. Fig. 10 shows upper and lower fixing clamps 21 in a fixing
frame 22 holding the membrane 5.
Fig. ha and lib shows the membrane and holding arrangement separated
from each other. The fixing clamps 21 are rotatable arranged in a fixing frame
22
and can be opened to accommodate a membrane and closed to hold the membrane
in position. The membrane 5 is provided with fixing elements 23 e.g. at each
corner
of the membrane. The fixing elements 23 are formed with membrane plate section
24 and flange 25. The membrane plate sections 24 are provided with a hole 26
corresponding to passages in the membrane 5. The holes in the membrane 5 can
advantageously be provided with integrated reinforcing elements in the
passages.
The membrane plate sections 24 of two fixing elements 23 are pressed
towards each side of a passage in the membrane 5, where after a bolt or rod 26
or
the like passing through the fixing elements and membrane, presses the fixing
elements onto the membrane. The flanges 25 are formed to fit into the fixing
clamps 21, in such a way that the flanges 25 are accommodated in the clamps
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when they are in closed position. The fixing clamps are controlled by ordinary
means, such as an electric or hydraulic motor.
Fig. 12 shows a fixing arrangement for the membrane, where the fixing
elements 23 are held directly in the fixing frame 22. The fixing arrangement
shown
is an example of a reinforcing anchoring of the membrane, to ensure that the
membrane can withstand the high forces of breaker waves. The fixing frame 22
can
advantageously be connected directly to the bulwark, e.g. on the surface 19 of
the
lifeboat passage 10 (see fig. 1), so that the membrane is directly stretched
out over
the lifeboat passage. It is also possible to integrate the fixing frame 22 in
the frame
assembly 4. The fixing frame will then be a part of the guiding arrangement
17,
where the membrane can be held by clamps in the fixing frame during normal
operating conditions and be detached if there is an emergency situation where
the
sea is sufficiently calm to expose the lifeboat and davit to the environment.
It has been described a protective assembly for bulwark (20) with opening
(10), to protect a freefall lifeboat situated behind the opening. The assembly
comprises a membrane (5) covering the opening (10) and perforating means (7)
suitable for perforating the membrane (5) in case of emergency to allow the
lifeboat to pass through the opening without being hampered by the membrane.
It
is also described the use of such protective assembly in a marine environment
and
zo an offshore construction being provided with at least one protective
assembly.
