U.S. patent application number 14/916563 was filed with the patent office on 2016-07-28 for apparatus and method for deploying an object to a sea floor.
This patent application is currently assigned to Soil Machine Dynamics Limited. The applicant listed for this patent is SOIL MACHINE DYNAMICS LIMITED. Invention is credited to John Graeme Walker.
Application Number | 20160215476 14/916563 |
Document ID | / |
Family ID | 49123724 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160215476 |
Kind Code |
A1 |
Walker; John Graeme |
July 28, 2016 |
APPARATUS AND METHOD FOR DEPLOYING AN OBJECT TO A SEA FLOOR
Abstract
A deployment apparatus for deploying an object to a sea floor is
disclosed. The deployment apparatus comprises a body and an
attachment part mounted to the body for releasably attaching an
object to the apparatus. Thrusters provide thrust to transport the
apparatus having an object attached thereto, and inflatable tanks
mounted to the body have adjustable buoyancy.
Inventors: |
Walker; John Graeme;
(Wallsend, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SOIL MACHINE DYNAMICS LIMITED |
Wallsend Tyne and Wear |
|
GB |
|
|
Assignee: |
Soil Machine Dynamics
Limited
Wallsend Tyne and Wear
GB
|
Family ID: |
49123724 |
Appl. No.: |
14/916563 |
Filed: |
September 2, 2014 |
PCT Filed: |
September 2, 2014 |
PCT NO: |
PCT/EP2014/068553 |
371 Date: |
March 3, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F 9/003 20130101;
E21B 15/02 20130101; B63G 2008/002 20130101; B63G 8/001 20130101;
E02F 5/109 20130101; H02G 1/10 20130101; E21B 19/002 20130101; F16L
1/168 20130101; E21B 41/0007 20130101; E02F 3/9225 20130101; E21B
41/04 20130101; B63B 2211/06 20130101; F16L 1/16 20130101 |
International
Class: |
E02F 9/00 20060101
E02F009/00; B63G 8/00 20060101 B63G008/00; E02F 3/92 20060101
E02F003/92; E21B 41/04 20060101 E21B041/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 6, 2013 |
EP |
13183324.6 |
May 12, 2014 |
GB |
1408386.9 |
Jun 26, 2014 |
GB |
1411426.8 |
Claims
1. An apparatus for deploying an object to a sea floor, the
apparatus comprising: a body; at least one attachment device
mounted to the body for releasably attaching an object to the
apparatus; at least one thrust generating device mounted to the
body for providing thrust to transport the apparatus having an
object attached thereto; and at least one buoyant device mounted to
said body and having adjustable buoyancy, wherein at least one said
buoyant device comprises at least one tank adapted to be filled
with air and/or gas by means of a conduit connected to a vessel
located at the sea floor.
2. The apparatus according to claim 1, further comprising at least
one conduit adapted to be releasably connected to at least one said
tank for filling said tank with air and/or gas from a vessel
located at the sea floor.
3. The apparatus according to claim 2, further comprising at least
one release device for releasing at least one said conduit from the
corresponding said tank.
4. The apparatus according to claim 1, wherein at least one said
buoyant device comprises at least one buoyant member adapted to be
moved between a respective first position, for transport from a
vessel to said first location, and a second position, for transport
from said first location to a second location on the sea floor.
5. The apparatus according to claim 4, wherein at least one said
buoyant member is pivotable between said first and second
positions.
6. An apparatus for deploying an object to a sea floor, the
apparatus comprising: a body; at least one attachment device
mounted to the body for releasably attaching an object to the
apparatus; at least one thrust generating device mounted to the
body for providing thrust to transport the apparatus having an
object attached thereto; and at least one buoyant device mounted to
said body and having adjustable buoyancy, wherein at least one said
buoyant device comprises at least one buoyant member adapted to be
moved between a respective first position, for transport from a
vessel to said first location, and a second position, for transport
from said first location to a second location on the sea floor.
7. The apparatus according to claim 6, wherein at least one said
buoyant member is pivotable between said first and second
positions.
8. The apparatus according to claim 6, wherein at least one said
buoyant device comprises at least one tank adapted to be filled
with air and/or gas.
9. The apparatus according to claim 6, wherein at least one said
tank is adapted to be filled with air and/or gas by means of a
conduit connected to a vessel located at the sea surface.
10. The apparatus according to claim 9, further comprising at least
one conduit adapted to be releasably connected to said at least one
said tank for filling said tank with air and/or gas from a vessel
located at the sea floor.
11. The apparatus according to claim 10, further comprising at
least one release device for releasing at least one said conduit
from the corresponding said tank.
12. The apparatus according to claim 1, further comprising at least
one power supply for operating at least one implement releasably
mountable to at least one said attachment device.
13. The apparatus according to claim 12, wherein at least one said
power supply comprises at least one hydraulic power unit.
14. The apparatus according to claim 1, wherein the apparatus is
adapted such that the centre of mass of the apparatus with an
implement mounted thereto when suspended in air is at a different
location from the centre of buoyancy of the apparatus with an
implement mounted thereto when suspended in water.
15. The apparatus according to claim 14, wherein at least one power
supply is arranged adjacent an edge of the apparatus.
16. The apparatus according to claim 1, further comprising at least
one aperture for enabling flowing material to pass
therethrough.
17. The apparatus according to claim 1, further comprising at least
one implement adapted to be releasably attached to at least one
said attachment device.
18. The apparatus according to claim 17, wherein the implement
comprises at least one sea floor removal device and/or at least one
locating device for locating at least one elongate object in a
trench.
19. The apparatus according to claim 17, wherein the implement
comprises at least one sealing device for sealing an oil and/or gas
well.
20. A method of deploying an object to a sea floor, the method
comprising:-- attaching an object to at least one attachment device
of an apparatus according to claim 1; deploying the apparatus and
object by means of a cable from a vessel to a first location on a
sea floor; increasing buoyancy of at least one said buoyant device;
and moving the object to a second location on the sea floor by
means of at least one said thrust generating device.
21. The method according to claim 20, further comprising deploying
said apparatus and object to said first location through an
aperture in a vessel located in sea ice.
22. The method according to claim 20, further comprising deploying
said object to the sea floor at said second location by generating
downward force on the apparatus by means of at least one said
thrust generating device.
23. The method according to claim 20, wherein the step of
increasing said buoyancy comprises filling at least part of at
least one said buoyant device with air and/or gas.
24. An apparatus for displacing material from a sea floor, the
apparatus comprising: a body: at least one thrust generating device
mounted to the body for providing thrust to transport the
apparatus; and at least one displacement device for generating a
flow of water to the sea floor to displace material therefrom.
25. The apparatus according to claim 24, wherein at least one said
thrust generating device is adapted to provide thrust having a
vertical component.
26. The apparatus according to claim 24, wherein at least one said
displacement device comprises at least one fan.
Description
[0001] The present invention relates to an apparatus and method for
deploying an object to a sea floor, and relates particularly, but
not exclusively, to an apparatus and method for deploying an
implement or structure to a sea floor from a vessel through sea
ice.
[0002] It is known to deploy structures or implements to the seabed
through sea ice, for example in Arctic regions, by connecting guide
wires extending from an aperture in a deck of an icebreaker vessel
to the seabed, and then guiding the structure or implement into
position along the guide wires. However, this arrangement suffers
from the drawback that the location of the structure or implement
on the seabed can only be within a limited lateral distance of the
region of the seabed directly below the vessel. This in turn limits
the range of applications in which the structure or implement can
be used.
[0003] U.S. Pat. No. 3,633,530 discloses a submarine working
vehicle having floating tanks which can be filled with air by means
of an air supply conduit connected to a surface vessel. However,
this arrangement suffers from the drawbacks that it can only work
effectively on even or smooth seabed surfaces, and the size of the
working vehicle that can be deployed from a given size of surface
vessel is severely limited.
[0004] Preferred embodiments of the present invention seek to
overcome one or more of the above disadvantages of the prior
art.
[0005] According to an aspect of the present invention, there is
provided an apparatus for deploying an object to a sea floor, the
apparatus comprising:--
[0006] a body;
[0007] attachment means mounted to the body for releasably
attaching an object to the apparatus;
[0008] thrust generating means mounted to the body for providing
thrust to transport the apparatus having an object attached
thereto; and
[0009] buoyant means mounted to said body and having adjustable
buoyancy;
[0010] wherein the buoyant means comprises at least one tank
adapted to be filled with air and/or gas by means of a conduit
connected to a vessel located at the sea surface.
[0011] By providing thrust generating means for providing thrust to
transport the apparatus having an object attached thereto, and
buoyant means having adjustable buoyancy, this provides the
advantage of enabling the apparatus with an object releasably
attached thereto to be transported from a vessel to a first
location on the seabed by means of a cable, and then to a second
location on the seabed by means of the thrust generating means
subsequently to increasing the buoyancy of the combined apparatus
and object by increasing the buoyancy of the buoyant means. This in
turn provides the advantage of enabling objects to be deployed to
subsea locations laterally further from the location of a vessel
than is presently possible, thereby enabling deployment to a wider
range of locations. Providing at least one tank adapted to be
filled with air and/or gas by means of a conduit connected to a
vessel located at the sea surface provides the further advantage of
enabling a larger upthrust to be generated than is possible for an
apparatus having on-board air tanks, thereby enabling larger
objects to be manipulated.
[0012] The apparatus may further comprise at least one conduit
adapted to be releasably connected to at least one said tank for
filling said tank with air and/or gas from a vessel located at the
sea surface.
[0013] The apparatus may further comprise release means for
releasing at least one said conduit from the corresponding said
tank.
[0014] This provides the advantage of avoiding the need for a
remotely operated vehicle for releasing the conduit.
[0015] The buoyant means may comprise at least one buoyant member
adapted to be moved between a respective first position, for
transport from a vessel to said first location, and a second
position, for transport from said first location to a second
location on the sea floor.
[0016] This provides the advantage of enabling the lateral
dimensions of the apparatus to be minimised while passing through
an aperture on the vessel, thereby maximising the size and payload
of the apparatus that can be used for a given vessel aperture size.
The advantage is also provided of enabling the buoyant members to
be located in respective lower positions before the buoyancy is
increased, and at respective higher positions subsequently to the
buoyancy being increased, thereby contributing to stability of the
apparatus during deployment.
[0017] At least one said buoyant member may be pivotable between
said first and second positions.
[0018] According to another aspect of the present invention, there
is provided an apparatus for deploying an object to a sea floor,
the apparatus comprising:--
[0019] a body;
[0020] attachment means mounted to the body for releasably
attaching an object to the apparatus;
[0021] thrust generating means mounted to the body for providing
thrust to transport the apparatus having an object attached
thereto; and
[0022] buoyant means mounted to said body and having adjustable
buoyancy, wherein the buoyant means comprises at least one buoyant
member adapted to be moved between a respective first position, for
transport from a vessel to said first location, and a second
position, for transport from said first location to a second
location on the sea floor.
[0023] By providing at least one buoyant member adapted to be moved
between a respective first position, for transport from a vessel to
said first location, and a second position, for transport from said
first location to a second location on the sea floor, this provides
the advantage of enabling the lateral dimensions of the apparatus
to be minimised while passing through an aperture on the vessel,
thereby maximising the size and payload of the apparatus that can
be used for a given vessel aperture size. The advantage is also
provided of enabling the buoyant members to be located in
respective lower positions before the buoyancy is increased, and at
respective higher positions subsequently to the buoyancy being
increased, thereby contributing to stability of the apparatus
during deployment.
[0024] At least one said buoyant member may be pivotable between
said first and second positions.
[0025] The buoyant means may comprise at least one tank adapted to
be filled with air and/or gas.
[0026] At least one said tank may be adapted to be filled with air
and/or gas by means of a conduit connected to a vessel located at
the sea surface.
[0027] The apparatus may further comprise at least one conduit
adapted to be releasably connected to at least one said tank for
filling said tank with air and/or gas from a vessel located at the
sea surface.
[0028] The apparatus may further comprise release means for
releasing at least one said conduit from the corresponding said
tank.
[0029] The apparatus may further comprise power supply means for
operating at least one implement releasably mountable to said
attachment means.
[0030] The power supply means may comprise at least one hydraulic
power unit.
[0031] The apparatus may be adapted such that the centre of mass of
the vehicle with an implement mounted thereto when suspended in air
is at a different location from the centre of buoyancy of the
vehicle with an implement mounted thereto when suspended in
water.
[0032] This provides the advantage of enabling the apparatus to be
used to deploy an implement such as a blow out preventer for
sealing an oil or gas well while enabling an umbilical deploying
the apparatus to avoid damage from harmful products being emitted
from the well. This in turn provides the advantage of enabling the
apparatus to be used for this purpose in shallow water, while
enabling the surface vessel operating the apparatus to be laterally
separate from the well.
[0033] The power supply means may be arranged adjacent an edge of
the apparatus.
[0034] This provides the advantage of simplifying construction of
the apparatus by enabling the weight of the power supply means to
be balanced by the weight of the buoyant means.
[0035] The apparatus may further comprise at least one aperture for
enabling flowing material to pass therethrough.
[0036] This provides the advantage of assisting operation of the
apparatus in deploying a blow out preventer.
[0037] The apparatus may further comprise at least one implement
adapted to be releasably attached to said attachment means.
[0038] The implement may comprise sea floor removal means and/or
locating means for locating at least one elongate object in a
trench.
[0039] The implement may comprise sealing means for sealing an oil
and/or gas well.
[0040] According to a further aspect of the present invention,
there is provided a method of deploying an object to a sea floor,
the method comprising:--
[0041] attaching an object to attachment means of an apparatus as
defined above;
[0042] deploying the apparatus and object by means of a cable from
a vessel to a first location on a sea floor;
[0043] increasing buoyancy of said buoyant means; and
[0044] moving the object to a second location on the sea floor by
means of said thrust generating means.
[0045] The method may further comprise deploying said apparatus and
object to said first location through an aperture in a vessel
located in sea ice.
[0046] The method may further comprise deploying said object to the
sea floor at said second location by generating downward force on
the apparatus by means of said thrust generating means.
[0047] This provides the advantage of assisting in locating the
object.
[0048] The step of increasing said buoyancy may comprise filling at
least part of said buoyant means with air and/or gas.
[0049] According to a further aspect of the present invention,
there is provided an apparatus for displacing material from a sea
floor, the apparatus comprising:
[0050] a body:
[0051] thrust generating means mounted to the body for providing
thrust to transport the apparatus; and
[0052] displacement means for generating a flow of water to the sea
floor to displace material therefrom.
[0053] By providing thrust generating means mounted to the body for
providing thrust to transport the apparatus, this provides the
advantage of enabling a displacement apparatus such as an excavator
to be used independently of a surface vessel, thereby enabling
access to previously inaccessible locations.
[0054] The thrust generating means may be adapted to provide thrust
having a vertical component.
[0055] This provides the advantage of enabling a downward thrust to
be generated by the apparatus, to counteract an upward thrust
generated by the displacement means, thereby enabling a
displacement means of higher power to be used.
[0056] The displacement means may comprise at least one fan.
[0057] Preferred embodiments of the present invention will now be
described, by way of example, and not in any limitative sense, with
reference to the accompanying drawings, in which:--
[0058] FIG. 1 is a schematic view of a known deployment
apparatus;
[0059] FIG. 2 is a schematic perspective view of a first jetting
apparatus in a transport condition thereof for use with the
apparatus of FIG. 1;
[0060] FIG. 3 is a perspective view of a first chain cutting
apparatus in a transport condition thereof for use with the
apparatus of FIG. 1;
[0061] FIG. 4 is a side view of the apparatus of FIG. 3 in a
deployed condition thereof and mounted to the deployment apparatus
of FIG. 1;
[0062] FIG. 5 is a side view of the apparatus of FIG. 2 in a
deployed condition thereof and mounted to the deployment apparatus
of FIG. 1;
[0063] FIG. 6 is a perspective view of an excavator apparatus of a
first embodiment of the present invention;
[0064] FIG. 7 is a front view of a second chain cutter apparatus
mounted to the deployment apparatus of FIG. 1;
[0065] FIG. 8 is a perspective view of the chain cutter and
deployment apparatus of FIG. 7;
[0066] FIG. 9 is a perspective view of a drilling apparatus mounted
to the deployment apparatus of FIG. 1;
[0067] FIG. 10 is a side view of the drilling apparatus and
deployment apparatus of FIG. 9;
[0068] FIG. 11 is a perspective view of a rotary cutter mounted to
the deployment apparatus of FIG. 1;
[0069] FIG. 12 is a perspective view of a digger head for replacing
the rotary cutter of FIG. 11;
[0070] FIG. 13 is a perspective view of a drill for replacing the
rotary cutter of FIG. 11;
[0071] FIG. 14 is a perspective view of a well construction skid
mounted to a deployment apparatus embodying the present
invention;
[0072] FIG. 15 is a perspective view of a well construction
component mounted to the deployment apparatus of FIG. 14;
[0073] FIG. 16 is a plan view of a deployment apparatus of a
further embodiment of the present invention;
[0074] FIG. 17 is a side view of the apparatus of FIG. 16;
[0075] FIG. 18 is an end view of the apparatus of FIG. 16;
[0076] FIG. 19 is a side view of the apparatus of FIG. 17 being
lowered from a surface vessel; and
[0077] FIG. 20 is an end view of the apparatus of FIG. 18 being
lowered from a surface vessel.
[0078] Referring to FIG. 1, a known deployment apparatus 2 forming
part of an undersea remotely operated vehicle (ROV) has a body 4
having an attachment point 6 for a lifting cable 8, and an
attachment part 14 for enabling releasable attachment of an object
or implement such as a jetting vehicle 16 (FIG. 2) to the
attachment part 14 for enabling releasable attachment of an
implement to the deployment apparatus 2, as well as vertical
thrusters 18 and horizontal thrusters 20 arranged at respective
corners of the body 4 for moving the apparatus 2 between the first
and second locations.
[0079] FIGS. 14 and 15 show a deployment apparatus 2 embodying the
present invention. The deployment apparatus 2 has a body 4 having
an attachment point 6 (FIG. 15) for a lifting cable 8 and a pair of
buoyant members in the form of inflatable tanks 10, 12 pivotably
attached to the body 4 and moveable between a first position, for
transporting the apparatus 2 from a surface vessel (not shown) to a
first location on the sea bed, as shown in FIG. 14, and a second
position, for transporting from the first location to a second
location on the sea bed, as shown in FIG. 15. The deployment
apparatus 2 is also provided with an attachment part 14 for
enabling releasable attachment of an object or implement such as a
jetting vehicle 16 (FIG. 2) to the attachment part 14 for enabling
releasable attachment of an implement to the deployment apparatus
2, as well as vertical thrusters 18 and horizontal thrusters 20
arranged at respective corners of the body 4 for moving the
apparatus 2 between the first and second locations.
[0080] Referring to FIGS. 2 and 5, tracked jetting vehicle 16 for
releasable attachment to the deployment apparatus 2 of FIG. 1 or 14
has a body 22 having a connector (not shown) for connection to a
hydraulic power unit (not shown) provided in the deployment
apparatus 2. A jetting device 24 is moveable between a transport
position (FIG. 2) and a deployment position (FIG. 5) for removing
debris from a trench to enable location of a cable or pipeline (not
shown) into the trench, and a pair of tracks 26 for moving the
jetting device 24 along the trench.
[0081] Referring now to FIGS. 3 and 4, a first chain cutting
apparatus 28 for locating a cable (not shown) in a trench has a
body 30 having an attachment part for removable attachment to the
deployment apparatus 2 of FIG. 1 or 14, and an attachment (not
shown) for connection to the hydraulic power unit of the deployment
apparatus 2. A chain cutter 32 is mounted to the body 30 and is
pivotably moveable between a transport position (FIG. 3) and a
cutting position (FIG. 4) for cutting a trench. A cable guide 34 is
pivotably mounted to the body 30 and is moveable between a
transport position (FIG. 3) and a deployment position (FIG. 4) in
which it guides a cable into a trench cut by the chain cutter 32.
The chain cutter is advanced along the seabed by means of tracks 36
to cut the trench.
[0082] FIG. 6 shows a remotely operable excavator apparatus 39
embodying the present invention. The apparatus 39 has a body 40
removably mounted to the deployment apparatus 2 of FIG. 1 or 14 and
a mass flow excavation unit 42 for removing debris from a trench
cut by the chain cutting apparatus 28 of FIGS. 3 and 4 mounted to
the body 40. The body 40 has skids 41 for location on the sides of
the trench. The excavation unit 42 has a pair of fans 43 (only one
of which is shown in FIG. 6), each of the fans 43 being arranged in
a respective water inlet 45. The fans 43 cause water to be drawn
into the inlets 45 and eject a high pressure stream of water from
outlet 47 to displace debris from the trench.
[0083] FIGS. 7 and 8 show a second chain cutting apparatus 44
mounted to the deployment apparatus 2 of FIG. 1 or 14 and having a
body 46 supporting a pair of trench cutters 48 for cutting a trench
on opposite sides of a pipeline 50 which is subsequently laid into
the trench. The trench cutters 48 are propelled along the trench by
means of tracks 52.
[0084] FIGS. 9 and 10 show a drilling apparatus 54 having a coring
drill base 56 to enable core samples to be taken from the seabed.
The drilling apparatus 54 is mounted to the deployment apparatus 2
of FIG. 1 or 14 and comprises a body 58 supporting the drill base
56.
[0085] Referring to FIG. 11 a rotary cutter apparatus 58 has a body
60 removably connectable to the deployment apparatus 2 of FIG. 1 or
14 and a manipulator arm 62 connected to the body 60. Rotary cutter
heads 64 are mounted to a distal end of the manipulator arm 62, and
a suction tube 66 is provided for removal of debris produced by the
cutter heads 64. The rotary cutter heads 64 can be replaced by an
excavator arm 68 cooperating with a suction tube 70 as shown in
FIG. 12 or a digger head 72 as shown in FIG. 13.
[0086] Referring to FIG. 14, a well construction skid 74 for use in
construction of well heads has a body 76 supporting a well
connector 78, the body being 76 removably attachable to the
deployment apparatus 2. In order to mount the well construction
skid 74 to the seabed, the well construction skid 74 is attached to
the deployment apparatus 2 with the buoyant members 10, 12 in their
respective transport positions. The deployment apparatus 2 with the
well construction skid 74 mounted thereto is lowered by means of a
cable 8 attached to cable attachment point 6 (FIG. 15) through an
aperture known as a moon pool in an icebreaking vessel, and lowered
to a first location on the seabed. When the apparatus 2 reaches its
first location, the buoyant members 10, 12 are then pivoted about
their pivot axes by means of a motor or remotely operated vehicle
(not shown) to their working positions (FIG. 15) and an air hose
(not shown) is connected by means of the remotely operated vehicle
to each buoyant member 10, 12 to enable the tanks to be filled with
air to increase the buoyancy of the apparatus 2. Alternatively, an
air hose can be connected to each buoyant member 10,12 at the
surface, so that the buoyant members 10, 12 can be filled with air
as the apparatus 2 is being lowered to the first location on the
sea bed. The air hoses can then be released from the buoyant
members 10, 12 by means of release means such as hydraulic
cylinders on the apparatus 2, thereby avoiding the need for a
remotely operated vehicle. The deployment cable 8 is then
disconnected, and the apparatus 2 with the well construction skid
74 is moved to its second location on the seabed. The well
construction skid 72 is then brought into contact with the seabed
by means of the vertical thrusters 18 and the well construction
skid 74 is secured to the seabed by means of a remotely operated
vehicle. After the well construction skid 74 has been secured to
the seabed, the apparatus 2 is detached from the well construction
skid and returned to the vessel for re-use.
[0087] FIG. 15 shows a further well construction component 78 to be
secured to the seabed by means of the deployment apparatus 2 and a
solid buoyancy member 80 provided on the component 78. The solid
buoyancy member 80 assists in manipulation of the component 78 and
apparatus 2 to the second location, and is left in place in the
component 78 when the component is secured to the second
location.
[0088] Referring to FIGS. 16 to 20, a deployment apparatus 80 of a
second embodiment of the invention has a body 82 having an open
framework having an upper part defining a lift point 84 for an
umbilical (not shown) for lifting the deployment apparatus 80 with
a blow-out preventer (not shown), for sealing an oil or gas well,
mounted to an underside thereof. The deployment apparatus 80 is
lifted from the deck of a surface vessel by means of a hydraulic
A-frame 86 supporting the apparatus. A hydraulic power unit 88 and
other electrical equipment is located adjacent an edge region 90 of
the frame, and air tanks 92, 94 of the apparatus 80 protrude beyond
the edge 96 of the frame opposite to the edge 90 at which the
hydraulic power unit 88 and electrical equipment is located to
compensate for the increased weight on that side of the body. In
this way, the centre of mass 98 of the apparatus 80 with a blow-out
preventer (not shown) mounted thereto is at a location to one side
of a central aperture 100 defined in the frame, and the centre of
buoyancy 102 of the apparatus 80 when submerged is at the centre of
the central aperture 100. The blow-out preventer (BOP) is supported
at a pair of BOP lift points 104, 106 on opposite sides of the
central aperture 100 so that the centre of buoyancy 102 is
generally midway between the two BOP lift points 104, 106. In this
way, when the apparatus 80 is maneuvering the blow-out preventer
towards an oil or gas well by means of horizontal thrusters 108
and/or vertical thrusters 110, harmful material being ejected from
the well passes through the central aperture 100 and thereby does
not cause damage to the umbilical mounted to the vehicle lift point
84, which is located above the centre of mass in air.
[0089] It will be appreciated by persons skilled in the art that
the above embodiments have been described by way of example only,
and not in any limitative sense, and that various alterations and
modifications are possible without departure from the scope of the
invention as defined by the appended claims.
* * * * *