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Title:
SUBSEA SENSOR SYSTEM USING MANEUVERABLE TOOL FOR ROV FREE INSTALLATION AND MAINTENANCE OF SUBSEA SENSOR CARRIERS
Document Type and Number:
WIPO Patent Application WO/2018/091574
Kind Code:
A1
Abstract:
A system and methods that facilitates the launch and recovery of a subsea sensor carrier from a ship with a winch without the use of an ROV, wherein the system includes * a launch and recovery tool (40) that comprises an interface for optical signals, operated by an operator in a control room of a vessel, thrusters (8) for maneuvering the tool, locking means for releasable locking to a sensor carrier, * a sensor carrier (41) that comprises space and a structure that can carry the subsea sensors (30), releasably lockable to a docking structure (42) on the sea bed, a connection interface (26) for connecting the sensor carrier to an infrastructure cable (22) * a docking structure (42) that comprises a receptacle (23) for the connection interface (26) and guide means (20, 21) for guiding the sensor carrier into alignment with the docking structure.

Inventors:
TORKELSEN, Terje (Nordeideveien 25C, 5251 Søreidgrend, N-5251, NO)
Application Number:
EP2017/079417
Publication Date:
May 24, 2018
Filing Date:
November 16, 2017
Export Citation:
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Assignee:
METAS AS (Nedre Åstveit 12, 5106 Øvre Ervik, N-5106, NO)
International Classes:
B63C7/16; E21B41/00; E21B41/04
Domestic Patent References:
WO2013114138A22013-08-08
WO2001021478A12001-03-29
WO2013050411A22013-04-11
Foreign References:
GB2496608A2013-05-22
Other References:
RIGAUD V ET AL: "New methods for Deep Sea Intervention on Benthic Laboratories - DESIBEL Project", OCEANS '98. CONFERENCE PROCEEDINGS. NICE, SEPT. 28 - OCT. 1, 1998; [IEEE OCEANS CONFERENCE], NEW YORK, NY : IEEE, US, vol. 1, 28 September 1998 (1998-09-28), pages 352 - 356, XP002157034, ISBN: 978-0-7803-5046-5
None
Attorney, Agent or Firm:
ONSAGERS AS (P.O. Box 1813 Vika, 0123 Oslo, N-0123, NO)
Download PDF:
Claims:
CLAIMS

A system for launch and recovery of one or more su bsea sensors (30) from a ship with a crane and/or winch, characterized in that the system comprises:

a. A sensor carrier (41) comprising a sensor carrier frame (46) within which is arranged the sensors,

b. A launch and recovery tool (40) comprising a frame (33) with an open bottom, arranged to be placed over and about the sensor carrier frame (46), said launch and recovery tool further comprising

i. First locking means for releasably locking into engagement with the sensor carrier,

ii. a connection point for a winch wire (1) from a crane or winch on a vessel, and

iii. a plurality of thrusters for maneuvering the launch and recovery tool, said thrusters controllable by an operator on the vessel.

The system according to claim 1, further comprising a docking station (42) arranged on the seabed, said docking station having a shape corresponding to the shape of the sensor carrier frame (46) , wherein the sensor carrier is arranged to be guided by the thrusters into position on top of the docking station, assisted by guide means (20, 21, 31, 39) arranged on the sensor carrier and the docking station respectively, the sensor carrier further comprising a second locking means for releasable connection to the docking station, the second locking means actuated by a locking tool (15) on the launch and recovery tool (40).

The system according to claims 1 or 2, wherein the launch and recovery tool, sensor carrier and/or docking station are essentially pyramidal or conical in shape.

The system according to one of the preceding claims, wherein the launch and recovery tool

(40) further comprises one or more cameras (12) for visual feedback during the

maneuvering, and the winch wire comprises a cable for transmitting optical signals.

The system according to one of the preceding claims, wherein the launch and recovery tool

(40) comprises a gyro (9) and a position sensor (10) as a means for determining position and is arranged to communicate with a dynamic positioning system of the vessel.

The system according to one of the preceding claims, wherein the guide means for guiding the sensor carrier on to the docking station comprises a plurality of funnel shaped members

(21) arranged at the bottom of the sensor carrier, said funnel shaped member arranged to receive corresponding guide pins (20).

7. The system according to one of the preceding claims, wherein the sensor carrier (41) comprises a cable connection device in the form of a movable stab plate connector (26) , arranged to mate with a receptacle (23) on the docking station (42) for connecting cables from the sensor carrier to an infrastructure cable (22), said stab plate connector movable by a connection tool (24) arranged on the launch and recovery tool (40).

8. A method for installing sensors on or near the seabed, characterized in that the method comprises:

a. Providing a launch and recovery tool (40) and a sensor carrier (41) according to any one of claims 1-7,

b. Connecting a winch line from a vessel to the launch and recovery tool,

c. Releasably connecting the launch and recovery tool (40) to the sensor carrier (41) d. Lowering the launch and recovery tool (40) to the seabed.

e. Disconnecting the launch and recovery tool from the sensor carrier.

9. The method according to claim 8, further comprising the steps of

a. Providing a docking station (42) according to one of claims 2-7, installed on the seabed

b. Navigating to, and landing the sensor carrier on top of the docking station by means of an operator on the vessel controlling the thrusters of the launch and recovery tool,

c. Locking the sensor carrier to the docking station,

d. Connecting the sensor carrier to a cable connection interface on the docking station,

10. A method for retrieving sensors from an installed position on or near the seabed, said

sensors being arranged in a sensor carrier (41) characterized in that the method comprises: a. Providing a launch and recovery tool (40) and a sensor carrier (41) according to any one of claims 1-7,

b. Connecting a winch line from a vessel to the launch and recovery tool,

c. Lowering the launch and recovery tool (40) to the vicinity of the sensor carrier, d. Navigating to, and landing the launch and recovery tool on top of the sensor carrier by means of an operator on the vessel controlling the thrusters of the launch and recovery tool,

e. Locking the launch and recovery tool to the sensor carrier,

f. Retrieving the sensor carrier to the vessel.

11. The method according to claim 10, wherein the sensor carrier is releasably connected to a docking station (42) on the sea bed, the sensors of the sensor carrier connected to the docking station by a stab plate connector (26) movable by traveling screws (25), the method further comprising the steps of

a. Actuating the traveling screws (25) to disconnect the stab plate connector, b. Actuating a locking tool (15) on the launch and recovery tool (40) to unlock the sensor carrier from the docking station.

12. The method according to any one of claims 8-11, wherein the launch and recovery tool is in communication with a dynamic positioning system of the vessel and controlled by dedicated software and/or system for topside control.

Description:
SUBSEA SENSOR SYSTEM USING MANEUVERABLE TOOL FOR ROV FREE INSTALLATION AND

MAINTENANCE OF SUBSEA SENSOR CARRIERS

FIELD OF THE INVENTION

The present invention relates to subsea sensor carriers, typically used for ocean observatories and environmental monitoring. More specifically the invention relates to tools and methods for launch and recovery for maintenance of sensor carriers.

BACKGROUND OF THE INVENTION- DESCRIPTION OF THE RELATED ART

Currently, subsea sensor carriers are typically installed from a ship using a crane/winch, as hanging in a wire connected via lifting lugs, a spreader or similar means. One or more ROV's are needed in the operation. An ROV is used to position the sensor carrier before it is landed in the designated position on the seabed or on a template structure. For cabled sensor carriers, an ROV connects the sensor carrier to the existing cable infrastructure. There are several disadvantages to using an ROV:

• A heavy armored umbilical and an underwater tether winch is required

• For deep water, the increased size, weight, and powering capacity needed for an ROV

umbilical cable creates even greater technical and economic challenges.

• The ROV is not easy to maneuver and operations performed by an ROV can be time

consuming

• A large ROV crew is needed, typically (1) an intendant, (2) an operator, (3) a navigator and often more staff (due e.g. to work shifts). To sum up, the amount of time, cost of equipment and personnel used makes ROV operations costly.

The majority of the su bsea sensors need to be retrieved to surface for regular maintenance or for repair of damage at some point in their life cycle, again currently requiring the need for an ROV. There is a need, therefore, for a simpler and more cost effective solution for the launch and recovery of sensor carriers for subsea sensors. SUMMARY OF THE INVENTION

The present invention has as its object providing a solution that overcomes the disadvantages of the prior art by creating a system that removes the need for expensive ROV operations for launch and recovery in relation to installation and maintenance of subsea sensor carriers, or at least providing an alternative solution.

More specifically the invention provides a system and methods that facilitates the launch and recovery of a subsea sensor carrier from a ship with a winch without the use of an ROV, wherein the system comprises · a launch and recovery tool that comprises an interface for optical signals, a control room, control software, a system for maneuvering the tool, locking bolts adapted to lock into a sensor carrier, a locking tool for activating the locking section on the sensor carrier and a connection tool for activating the connection section on the sensor carrier.

• a sensor carrier that comprises space and a structure that can carry the subsea sensors, a locking section for locking the sensor carrier to a docking structure, a connection section for connecting the sensor carrier to a cable interface on the docking structure, for example in form of a stab plate on the sensor carrier and a receptacle on the docking structure.

• a docking structure that comprises an interface for the locking section on the sensor carrier to lock into and a cable connector interface for the connection section on the sensor carrier to connect to.

The purpose of the launch and recovery tool is to launch and retrieve the sensor carrier without needing assistance from an ROV. The tool is adapted for being handled by a winch as hanging in a wire from an installation ship. The ship will preferably have a dynamic positioning system and a heave compensated winch. The sensor carrier is designed to carry a variety of different sensors, such as environmental sensors, advanced acoustic sensors, cameras and tools for subsea operations. The sensor carrier provides a stable and protected platform for the sensors and the necessary equipment and interface for power- up, operating and monitoring the sensors. The sensor carrier can be placed directly on the seabed or connected to a docking structure. The purpose of the docking structure is to provide a rigid foundation for the sensor carrier and a connection to the infrastructure of cables, providing power and signal. The connection section on the sensor carrier, for example in the form of a stab plate connector, can connect to a stab plate receptacle on the docking structure without assistance of an OV. The docking structure is designed according to one aspect for 20 years of deployment and is typically preinstalled together with the cabled infrastructure.

The launch and recovery tool is connected to lifting means on the installation ship by a lifting wire, preferably containing power and/or signal cables such as an optical signal cable. The launch and recovery tool can alternately be provided with a battery enabling it to operate for a limited time on battery power.

For topside control, a special software is used for operating the connection and locking functions on the launch and recovery tool, maneuvering of the tool, operation and monitoring of all sensors and cameras on the tool. All operations may be performed in a control room from a dedicated computer terminal with keyboard, joysticks and several monitors.

The launch and recovery tool includes means for maneuvering the tool and its payload in the correct position. The means for positioning comprises thrusters, for example four thrusters, one in each corner of the launch and recovery tool, in addition to using the winch and the ship's dynamic positioning system. The invention is not limited to the use of four thrusters. Two, three and even more thrusters placed in different locations than in the corners can be used. The thrusters are operated using a joystick controller. The software converts the directional commands from the joystick into correct direction and power on all four thrusters. For navigation, the navigator uses several cameras together with lights, a gyro for heading information and sensors for depth and height above the seabed. At least one of the cameras may be installed on a pan and tilt unit for better control of the camera view for navigational purposes. All cameras and sensors are controlled and monitored from the specialized software.

For coarse guiding of the launch and recovery tool when landing on top of the sensor carrier, the base section of the launch and recovery tool comprises a frame structure comprising a plurality of ring segments, for example four, with a diameter large enough to go on the outside of an upper part of the sensor carrier's frame. The ring segments will help center the launch and recovery tool on the sensor carrier. The sensor carrier has a frame with upper corners. An upper part of each of the corners of the sensor carrier's frame structure will fit into guide slots between these ring segments. These slots will assure the correct rotational guiding. Thrusters can be used to rotate the tool into these slots if needed. An additional upper ring on the tool frame structure with smaller diameter will land on top of the sensor carrier, and make sure the tool is landed in the correct vertical position. According to this aspect, there is no need for guide wires. For coarse guiding of the sensor carrier during landing on top of the docking structure, the sensor carrier comprises one or more guide funnels at the bottom, for example a guide funnel placed diagonally in each corner, with the docking structure comprising a corresponding number of guide pins, for example also placed diagonally on the top of its frame in each corner. After entry of the coarse guide pins into the guide funnels, the sensor carrier will be steered into one or more, for example four, smaller guide pins for final guiding. These four guide pins are located on top of the docking structure, one in each corner. Correspondingly, a small guide hole is located at the bottom of each corner of the sensor carrier.

For carrying the sensor carrier to the seabed, the launch and recovery tool includes one or more locking bolts adapted to lock into the sensor carrier for releasable locking. According to one aspect, one bolt may be arranged in each corner of the lower part of the launch and recovery tool. Each locking bolt comprises a rod that can be pushed/pulled by a hydraulic piston into/out of a corresponding through hole on the sensor carrier.

The launch and recovery tool also comprise a locking tool for activating the locking section on the sensor carrier for releasable locking to the docking structure. The locking tool comprises one or more hydraulic actuators that moves one rod each on the sensor carrier. Each rod again activates a mechanical device each on the sensor carrier that pushes/pulls a rod into a corresponding locking hole in the docking structure.

When the sensor carrier is confirmed locked in to the docking structure, a connection operation can be activated by a connection tool on the launch and recovery tool. The connection operation is provided by a connection section on the sensor carrier comprising a stab plate with connectors that are arranged to mate with matching receptacles on the docking structure. The connection tool on the launch and recovery tool is comprised of one or more hydraulic motors on the launch and recovery tool that are used to operate trawling screws. Turning the trawling screws, which are connected to the stab plate, moves the stab plate on the sensor carrier down and mates it with the receptacles on the docking structure. Typically, there are two or more connectors on the stab plate. One for power and one for optical fiber signals for the sensor carrier. Extra connectors can be used if for instance a locally remote sensor platform (satellite) are to be used.

The invention provides a method of using the system to launch a sensor carrier and connect it to a docking structure. The method includes a ship winch to lower the launch and recovery tool assembly close to a docking structure on the seabed. The launch and recovery tool assembly is comprised of the launch and recovery tool with the sensor carrier locked in. The method further includes maneuvering the launch and recovery tool assembly, in correct position above the docking structure, using the tool's own maneuvering system. When the launch and recovery tool assembly is maneuvered into the correct position above the docking structure, it is landed out on top of the docking structure. Final rotational adjustments are done by use of the maneuvering system. Cameras are used to verify the correct rotational orientation before locking the sensor carrier into the docking structure by use of the locking section on the sensor carrier. When the sensor carrier is confirmed locked in to the docking structure by use of cameras, the connection tool on the launch and recovery tool activates the connection section on the sensor carrier. After full connection of the stab plate connectors is confirmed, the launch and recovery tool is unlocked from the sensor carrier and recovered to the ship.

The invention provides a method of using the system to recover a sensor carrier that is connected to a docking structure. The method includes lowering the launch and recovery tool by a winch close to a sensor carrier connected to a docking structure on the seabed. The method further includes maneuvering the launch and recovery tool into the correct position above the sensor carrier, using the tool's own maneuvering system. When the launch and recovery tool is in correct position, it is landed out on top of the sensor carrier. Final rotational adjustments are done by use of the maneuvering system. Cameras are used to verify the correct rotational orientation before locking the launch and recovery tool into the sensor carrier. When the locking is confirmed by use of cameras, the connection section on the sensor carrier disconnects the stab plate connectors from the receptacles on the docking structure. When the connectors are confirmed disconnected visually, the sensor carrier is released by retracting the locking rods out of the locking holes on the docking structure. The sensor carrier can then be recovered to the ship by the launch and recovery tool.

The invention provides a method of using the system to launch a sensor carrier on the seabed. The method includes lowering a launch and recovery tool assembly by a winch close to the seabed. The launch and recovery tool assembly is comprised of the launch and recovery tool connected to the sensor carrier. The method further includes maneuvering the launch and recovery tool assembly in correct position above the seabed using the tools own maneuvering system. When the launch and recovery tool assembly is in the correct position, it is landed out on the seabed. The launch and recovery tool is then unlocked from the sensor carrier and recovered to the ship.

The invention provides a method of using the system to recover a sensor carrier from the seabed. The method includes lowering the launch and recovery tool by a winch close to the sensor carrier on the seabed. The launch and recovery tool is maneuvered in the correct position above the sensor carrier using the launch and recovery tools own maneuvering system. When the launch and recovery tool is in correct position, it is landed out on top of the sensor carrier. Final rotational adjustments are done by use of the maneuvering system. Cameras are used to verify the correct rotational orientation before locking the launch and recovery tool to the sensor carrier. When the locking is confirmed the launch and recovery tool and the sensor carrier are recovered to the ship.

B EIF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail with reference to the attached drawings, where: FIG. 1 illustrates the system according to the invention, before the sensor carrier, carried by the launch and recovery tool, is landed on the docking structure

FIG 2 illustrates the system of FIG. 1, with the sensor carrier landed on the docking structure, ready for locking and connection to the docking structure.

FIG 3 illustrates the system of FIG. 1 and 2, where sensor carrier is connected to the docking structure and the launch and recovery tool is released from the sensor carrier and being recovered back to the ship.

FIG. 4 illustrates the system according to the invention, before the sensor carrier, carried by the launch and recovery tool, is landed on the seabed

FIG. 5 illustrates the system of FIG. 4, where the sensor carrier, carried by the launch and recovery tool, is landed on the seabed

FIG. 6 illustrates the system of FIGS. 4 and 5, where the launch and recovery tool is released from the sensor carrier and being recovered to the ship.

FIG 7 illustrates the launch and recovery tool according to the invention FIG 8 illustrates the sensor carrier according to the invention FIG 9 illustrates the docking structure according to the invention FIG 10 illustrates an alternative embodiment of the invention. DETAILED DESCRIPTION

The basic operation of the system of the invention is illustrated in Figs 1-6, as discussed immediately below. More detailed aspects of the components are discussed further below with reference to Figs 7-10.

Reference is made to FIG. 1, illustrating the system according to the invention; more specifically the launch and recovery tool 40 is locked into the sensor carrier 41, ready for landing on the docking structure 42. The assembly is launched as hanging from a ship in a lifting wire 1. Control signals to the launch and recovery tool are provided via the lifting wire. Power for the launch and recovery tool may be provided by a power cable integrated into the lifting wire or be provided from batteries included in the tool itself. The launch and recovery tool's includes a system for maneuvering that is used to position the tool and sensor carrier in the correct position above the docking structure. Reference is then made to FIG. 2, illustrating that the sensor carrier 41 has been landed on top of the docking structure 42. After landing, the sensor carrier is locked in to the docking structure. The sensor carrier is then connected to the docking structure using a connection section on the sensor carrier. Reference is then made to FIG. 3, illustrating that the launch and recovery tool 40 has been unlocked from the sensor carrier and ready for recovery to the ship.

FIG. 4, illustrates the system according to the invention; more specifically the launch and recovery tool 40 is locked in to the sensor carrier 41, ready for landing the sensor carrier in the correct position on the seabed. The assembly is launched as hanging from a ship in a lifting wire 1. Control signals to the launch and recovery tool are provided via the lifting wire. Power for the launch and recovery tool may be provided via cable or provided through batteries included in the tool itself. The launch and recovery tools comprises a system for maneuvering that is used to position the tool and the sensor carrier in the correct position above the seabed. Reference is then made to FIG. 5, illustrating that the sensor carrier 41 has been landed on the seabed. FIG. 6, illustrating that the launch and recovery tool 40 has been unlocked from the sensor carrier and ready for recovery.

FIGS. 7-10 are a more detailed illustration of the system of the invention.

As shown in fig 7, the launch and recovery tool comprises a frame 33. The frame comprises a base section 34 and a top section 35, connected by rails 36. Base section 34 comprises guide ring segments 27. According to one aspect, the base section and top sections may be essentially rectangular, with the sides of top section having shorter lengths than the sides of the base section. This provides the launch and recovery tool with an essentially pyramidal or conical shape, with a larger base than top. As seen in Fig 8, the sensor carrier, arranged to carry a payload comprising subsea sensors 30, has a similar pyramidal shape, as does the docking structure shown in Fig 9. The respective shapes of the launch and recovery tool, sensor carrier and docking structure facilitates the landing of one upon the other. Sensor carrier 41 comprises an upper frame part 43, a plurality (preferably four) outwardly sloping legs 44, connected by supporting braces 45, defining an essentially pyramidal sensor carrier frame 46. The payload (30) and other components are arranged within the interior of frame 46.

Fig 7 shows the lifting wire 1 on the launch and recovery tool that may include an optical signal cable for control signals and data transfer of sensor data. All sensors and control data are going through the interface container 2. According to one aspect, the system runs off electronic power from battery containers 3 included in the tool itself. All hydraulic functions are operated from a hydraulic tank 4 with pump and control valves inside. There is also a hydraulic accumulator tank 6 (not visible in this illustration) for immediately and quick release of the hydraulic cylinders running a plurality of locking bolts on the launch and recovery tool. A pressure compensator 7 (not visible in this illustration) is compensating for the compression of the oil in the system as a function of increased pressure due to increased depth. The pressure compensator is maintaining 3 bar over pressure in the hydraulic tank regardless of the operation depth to avoid water penetrating into the hydraulic system at greater depths.

For maneuvering, the tool is equipped with four thrusters 8, a gyro 9 (not visible in illustration), an altimeter 10 and several lights 11 and cameras 12. For final mechanical guiding, the launch and recovery tool includes a guide ring segments 27 that will go on the outside of the sensor carrier, aligning the tool to the center of the sensor carrier. A landing point for the sensor carrier 28, assures the correct vertical alignment.

For coarse guiding of the launch and recovery tool when landing on top of the sensor carrier, the base section 34 of the launch and recovery tool comprises a frame structure 33 comprising a plurality of ring segments 27, for example four, with a diameter large enough to go on the outside of an upper part of the sensor carrier's frame. The ring segments will help center the launch and recovery tool on the sensor carrier. The sensor carrier has a frame with upper corners. An upper part of each of the corners 37 of the sensor carrier's frame structure will fit into guide slots 38 between these ring segments. These slots will assure the correct rotational alignment. Thrusters can be used to rotate the tool into these slots if needed. An additional upper ring 28 on the tool frame structure with smaller diameter will land on top of the sensor carrier, and make sure the tool is landed in the correct vertical position. According to this aspect, there is no need for guide wires. For coarse guiding of the sensor carrier during landing on top of the docking structure, the sensor carrier comprises, as shown in Fig. 8, one or more guide funnels 21 at the bottom, for example a guide funnel placed diagonally in each corner, with the docking structure comprising a corresponding number of guide pins 20, for example also placed diagonally on the top of its frame in each corner. After entry of the coarse guide pins into the guide funnels, the sensor carrier will be steered into one or more, for example four, smaller guide pins 31 arranged on the docking station for final guiding. These four guide pins are located on top of the docking structure, one in each corner.

Correspondingly, a small guide hole 39 is located at the bottom of each corner of the sensor carrier.

For carrying the sensor carrier to the seabed, the launch and recovery tool includes 4 locking bolts 13 for releasable locking to the sensor carrier. On in each corner of the tool. The locking bolts are activated by hydraulic pistons 29. The locking bolts are pushed into corresponding holes for locking bolts 14 in the sensor carrier shown in FIG. 8.

The launch and recovery tool also comprises a locking tool 15 for activating the locking section on the sensor carrier. The locking sections locks the sensor carrier to the docking structure shown in FIG. 9. The locking tool comprises to hydraulic pistons 15 that moves one rod 16 each on the sensor carrier. These rods again activates two mechanical arms 17 that pushes/pulls a rod 18 into a corresponding through hole 19 on the docking structure. The through hole 19 is on the tip of the template coarse guide pin 20. Two guide funnels 21 are doing the coarse guiding, while four second guide pins 31 position inserted into holes 39 ensure the sensor carrier is in correct position on top of the docking structure before locking the sensor carrier to the docking structure.

The connection section 32 on the sensor carrier can be activated by a connection tool 24 on the launch and recovery tool. The connection tool comprises two hydraulic motors that are used to operate two trawling screws 25 sitting on the sensor carrier. Turning the trawling screws 25, which are connected to a stab plate 26, moves the stab plate 26 on the sensor carrier down and mates it with a receptacle 23 on the docking structure shown in FIG.9. Typically, there are two connectors, one for power and one for optical fiber signals, but in some cases a third connector for locally remote sensor carriers (Satellites).

Alternative design of the launch and recovery tool

According to another aspect, as illustrated in Fig. 10, an embodiment of the invention comprises an alternative solution for guiding the launch and recovery tool when landing on top of the sensor carrier. According this embodiment, two locking bolts arranged on the launch and recovery tool lock into the sensor carrier for releasable locking. In addition, this embodiment comprises an alternative design of the locking tool for activating the locking section on the sensor carrier for releasable locking to the docking structure. The alternative solution can completely replace existing functions or work in parallel to provide more flexible and reliable solution.

For guiding of the launch and recovery tool during landing on top of the sensor carrier, the alternative solution of the launch and recovery tool comprises, as shown in Fig. 10, two combined locking and guiding bolts 46, for example placed diagonally in each corner, with two corresponding guide funnels 48 on the sensor carrier, for example also placed diagonally on the top of its frame in each corner. After entry of the locking and guiding bolts into the guide funnels, the launch and recovery tool will be steered into to correct orientation until it lands out on a landing point for the sensor carrier 28, which assures correct vertical alignment. For carrying the sensor carrier to the seabed, the two locking and guiding bolts 46 are used for releasable locking to the sensor carrier. Each locking and guiding bolt comprises a stopper key 45 that can be rotated and locked into a slot 49 on the guide funnel on the sensor carrier. The stopper key is activated by a hydraulic piston 44.

The locking and guiding bolts also comprise a locking tool for activating the locking section on the sensor carrier. The locking section locks the sensor carrier to the docking structure shown in Fig. 9. The looking tool comprises 1 hydraulic piston 43 in center of each of the locking and guiding bolts. Each hydraulic piston moves a rod 47 in and out of the lower part of the locking and guiding bolt. These two rods activate two mechanical arms 17 that pushes/pulls a rod 18 into a corresponding through hole 19 on the docking structure.