NL2026122B1

NL2026122B1 - Method, system and assembly for releasing a submergible load from a floater

Info

Publication number: NL2026122B1
Application number: NL2026122A
Authority: NL
Inventors: Langver Berry; Verschueren Yves
Original assignee: Boskalis Bv Baggermaatschappij
Priority date: 2020-07-23
Filing date: 2020-07-23
Publication date: 2022-03-28

Abstract

The invention relates to a method for releasing a submergible load from a floater, wherein the method comprises the steps of: providing a floater and a releasable coupler; coupling the floater to a submergible load with the use of the releasable coupler; attaching a position determiner to the floater, to the submergible load and/or to the releasable coupler; by the position determiner, determining the current position of the position determiner; comparing the determined current position with a target position of the position determiner, in order to determine an offset; when the offset is within a predetermined range, releasing the releasable coupler so as to at least partly release the submergible load from the floater.

Description

P138595NL00 Method, system and assembly for releasing a submergible Load from a floater

BACKGROUND The invention relates to a method for releasing a submergible load from a floater, Furthermore, the invention relates to a system and an assembly for releasing a submergible load from a floater.

A known method to install a submergible cable is to provide a buoyant member or floater and to couple the submergible cable to the floater with the use of releasable couplers. To install the submergible cable, the releasable couplers are released to release the submergible cable from the floater and to allow it to submerge towards the bottom of a body of water or sea.

The known method for installing a submergible cable is to install the submergible cable at a landfall location along a target route of the cable between a shore station and an offshore location. The submergible cable is connected between the shore station and an installation vessel for the cable. Prior to releasing the submergible cable from the floater, the floater with the coupled submergible cable is Lo be positioned above the target route of the cable by the installation vessel, possibly with the help of one or more support vessels.

In the known method the floater with the submergible cable is positioned with the assistance of a human observer who is located at or near the shore station. The human observer uses a line of sight method wherein the human observer focuses on a fixed point at the horizon and makes an educated guess about the position of the floater with respect to a straight line between the shore station and the fixed point at the horizon. The human observer gives directions to the installation vessel and/or to the support vessels based on his educated guess of the position of the floater in order to position the floater with the coupled submergible cable above the target route. When according to the human observer the floater is sufficiently positioned above the target route he may indicate that the submergible cable is to be released from the floater to allow it to submerge towards the bottom of the body of water.

SUMMARY OF THE INVENTION According to the known method, the floater with the coupled submergible cable is exposed to, amongst others, currents, waves and wind that induce motions to the floater. These motions make it hard to position the floater at or close to the target route prior to releasing the submergible cable. Additionally, the method relies on the visual perception of the human observer which may be negatively influenced by external factors such as sunlight reflecting on the water, darkness or twilight, wind, or obstructions within the line of sight of the human observer. The known method is dependent among others on these external factors in regard of whether the method can be executed. As the known method is affected by the mentioned external factors, the known method can be performed only when the external factors are absent or minimal. This is disadvantageous as it limits the available time for releasing the submergible cable. A further disadvantage of the known method is that it is less suitable for target routes of the submergible cable that comprise curves or bends. With such target routes the human observer may not have suitable reference points to make an educated guess about the location of the floater with respect to the target route. As more and more submergible cables are installed at locations having obstacles around which the cable should be routed, the time needed for performing the known method for target routes that comprise curves or bends may become unreasonably long.

It is an object of the present invention to provide a method, a system and an assembly for releasing a submergible load from a floater that is less dependent on external factors.

According to a first aspect, the invention provides a method for releasing a submergible load from a floater, wherein the method comprises the steps of: providing a floater and a releasable coupler; coupling the floater to a submergible load with the use of the releasable coupler; attaching a position determiner to the floater, to the submergible load and/or to the releasable coupler; by the position determiner, determining the current position of the position determiner; comparing the determined current position with a target position of the position determiner, in order to determine an offset; when the offset is within a predetermined range, releasing the releasable coupler so as to at least partly release the submergible load from the floater.

During performing the method according to the invention, the position determiner, for example, is arranged on the floater. By determining the current position of the position determiner, for example periodically, the current position of at least a part of the floater is determined accordingly. By comparing the determined current position of the position determiner with a predetermined target position of the submergible load, which target position may be placed on a predetermined target route, an offset between the determined current position and the target position is determined. On basis of the offset, an operator knows whether the position determiner and, thus, the associated part of the floater is too far away from the target position, or is close enough to the target position.

When it is determined, that the determined current position of the position determiner is too far away from the target position, the operator can adjust the position of the position determiner in order to move the latter towards the target position.

When it is determined that, the determined current position of the position determiner is close enough to the target position, i.e. the offset is within the predetermined range, the releasable coupler may be released in order to release the submergible load at least partly.

Due to the position determiner, there is no longer a need for a human observer to make an educated guess of the position of the floater, such that the method according to the invention is less affected or in the ideal case not affected by external factors.

In an embodiment the step of attaching a position determiner to the floater, to the submergible load and/or to the releasable coupler, comprises the step of attaching two or more position determiners to the floater, to the submergible load and/or to the releasable coupler, the method comprising for each of the two or more position determiners the steps of: determining the current position of the position determiner; and comparing the determined current position with a target position of the position determiner, in order to determine an offset.

In an embodiment thereof the step of providing a floater and a releasable coupler, comprises the step of providing two or more releasable couplers, the method comprising the step of coupling the floater to the submergible load with the use of the two or more releasable couplers.

In an even further embodiment thereof the submergible load is an elongated load, and wherein the step of coupling the floater to the submergible load with the use of the two or more releasable couplers, comprises the step of arranging the two or more releasable couplers along the longitudinal direction of the submergible load, preferably at a predetermined distance from each other.

5 For instance, the method according to this embodiment is used for releasing the elongated submergible load, such as a cable, an umbilical, or a pipeline, which may be flexible along its length. By attaching multiple position determiners along the length of the elongated submergible load, the elongated submergible load is divided into sections defined by the multiple position determiners, wherein the determined current position of each position determiner represent a current position of at least a part of an associated section of the elongated submergible load.

Each of the sections of the elongated submergible load has at least one releasable coupler, which is in operative relation to the position determiner of the respective section. This allows the elongated submergible load to be released section wise, therewith granting advantageously more control to the operator over positioning of the elongated submergible load.

In an embodiment the method comprises the step of associating each of the two or more position determiners to at least one of the two or more releasable couplers, the method comprising for each of the two or more position determiners the step of: when the offset is within a predetermined range, releasing the associated at least one of the two or more releasable couplers so as to at least partly release the submergible load from the floater.

The two or more position determiners can be used to divide, for example, the elongated submergible load into sections. By associating each of the position determiners to one or more releasable couplers, each of the sections of the elongated submergible load is provided with one or more releasable couplers. In this way, releasing of the elongated submergible load can be performed section wise.

In an embodiment thereof the submergible load is released from the floater in a sequential manner along the longitudinal direction of the submergible load.

When releasing, for instance, a submergible cable it may be desirable to start the releasing of the submergible cable at a first end and then progressively release the submergible cable towards the opposite end.

According to the present embodiment, it is possible to release the releasable coupler that is closest to the first end of the submergible load when the associated position determiner is within the predetermined range and to then sequentially release the subsequent releasable couplers along the length of the submergible cable.

In an embodiment the method comprises the steps of: providing a remote monitoring device; transmitting, preferably by a transceiver, the determined current position of the position determiner and/or the determined offset, from the position determiner to the remote monitoring device; and monitoring the determined current position of the position determiner and/or the determined offset by the remote monitoring device.

According to this embodiment, the determined current position and/or the determined offset are transmitted to and can be monitored at a location that is remote from the submergible load.

Advantageously, this embodiment provides the possibility to control releasing of at least a part of the submergible load from a location remote from the submergible load.

In an embodiment the method comprises the step of: when it is determined that the determined offset is outside the predetermined range, adjusting the position of the position determiner based on the determined current position of the position determiner and/or the determined offset.

According to this embodiment, the position of the position determiner is adjusted when it is determined that the determined offset based on a previous determined current position is outside the predetermined range. Hence, the method according to this embodiment advantageously provides the capability to adjust the position of the position determiner, in order to bring the offset within the predetermined range, such that the submergible load will be located at or sufficiently close to the target position after release thereof. In the context of the present patent application, it is noted that the submergible load, or a part thereof, may be actively repositioned by the vessel, support vessels or cables that are attached to the submergible load.

In an embodiment the submergible load is selected from a group comprising a cable, an umbilical and a pipeline.

In an embodiment the step of providing a floater and a releasable coupler, comprises the step of providing a floater with multiple sub-floaters, and multiple releasable couplers; and wherein the step of coupling the floater to the submergible load with the use of the releasable coupler, comprises the step of coupling each of the multiple sub-floaters to the submergible load with the use of at least one of the multiple releasable couplers. With elongated submergible loads such as the cables and pipelines which have a great length, it is advantageous to use multiple floaters or sub-floaters in order to provide adeguate support to the submergible load along the length thereof.

In the context of the present patent application, it is noted that the sub-floaters may be distinct buoys which are spaced apart from each other along the submergible load.

In an embodiment the method comprises the step of: connecting the submergible load to a shore station, wherein the submergible load extends away from the shore station when the submergible load is at least partly released from the floater. According to this embodiment the cable may be connected to the shore station prior to releasing it from the floater, therewith providing a solid starting point for the submergible load to be released. After connecting the cable to the shore station the cable is then released from the floater, preferably in a sequential manner along the longitudinal direction of the submergible load in a direction away from the shore station.

In an embodiment the step of by the position determiner, determining the current position of the position determiner, comprises the step of by the position determiner, periodically determining the current position of the position determiner, preferably determining the current position of the position determiner within periods of maximum ten seconds, more preferably within periods of maximum five seconds. By periodically determining the current position of the position determiner the power consumption of the location determiner is reduced to extend the operating time thereof, adjustment of the position of the position determiner can be followed live or nearly live. As an operator is enabled to follow adjustment of the position of the position determiner live or nearly live, the operator is enabled to respond to the adjustment relatively quick, for example when the operator observes that the position determiner is moving away from the target position.

In an embodiment the method comprises the step of: switching the position determiner into a sleep mode or into an active mode. The active mode is used when releasing the submergible load. The sleep mode is used when no position information is required, for instance during preparation works or during downtime. The sleep mode reduces power consumption of the position determiner to extend the operating time thereof.

In an embodiment the method comprises the step of: deploying the submergible load and the floater together from a vessel, from an offshore location or from the shore.

According to a second aspect, the invention provides a system for releasing a submergible load, wherein the system comprises a floater, a releasable coupler configured for coupling the floater to the submergible load, a position determiner configured for being attached to the floater, the submergible load and/or the releasable coupler, and a controller that has an operable connection with the position determiner, wherein the position determiner is configured for determining the current position of the position determiner, wherein the controller is configured for comparing the determined current position with a target position of the position determiner, in order to determine an offset, and wherein the controller is configured for, when the offset is within a predetermined range, controlling release of the releasable coupler so as to at least partly release the submergible load from the floater.

The system according to the second aspect of the invention has at least the same technical advantages as the method according to the first aspect of the invention, which will not be repeated hereafter.

It is noted in the context of the present patent application that controlling release of the releasable coupler so as to at least partly release the submergible load from the floater may involve indicating to an operator that the offset is within the predetermined range, therewith enabling the operator to decide whether or not to release the releasable coupler.

In an embodiment the system comprises two or more position determiners that are configured for being attached to the floater, the submergible load and/or the releasable coupler.

In an embodiment the system comprises two or more releasable couplers configured for coupling the floater to the submergible load.

In an embodiment each of the two or more position determiners is associated to at least one of the two or more releasable couplers.

In an embodiment the floater comprises multiple sub-floaters and the system comprises multiple releasable couplers for coupling the sub-floaters to the submergible load.

In an embodiment the position determiner comprises a global navigation satellite system (GNSS) receiver. The GNSS receiver may relate to systems such as GPS, GLONASS, BeiDou or Galileo.

In an embodiment thereof the system comprises a global navigation satellite system augmentation device, such as a RTCM transmitter, that has an operable connection at least with the controller. The GNSS augmentation device may be used to improve the accuracy of the determined current position of the GNSS receiver and thus of the position determiner. Therewith, the accuracy of determining the position of the position determiner and the associated part of the submergible load is increased.

In an embodiment the position determiner comprises a storage medium configured for storing the determined current positions of the position determiner.

In an embodiment the position determiner comprises a battery for providing power to the position determiner.

In an embodiment the position determiner comprises a transceiver configured for transmitting data to and/or for receiving data from an external device. Preferably the transceiver is provided with a data simcard.

Alternatively, the transceiver is configured to be operable in a (local) Wi-Fi network, or in a (local) radiofrequency network.

In an embodiment the system comprises a remote monitoring device, and wherein the position determiner is configured for transmitting the determined current position and/or the determined offset of the position determiner to the remote monitoring device, and wherein the remote monitoring device is configured for monitoring the received determined current position of the position determiner and/or the determined offset.

According to a third aspect, the invention provides an assembly comprising the system for releasing a submergible load according to the second aspect of the invention, a submergible load that is to be released from the system, and a vessel for handling the system and/or the submergible load.

The assembly according to the invention has at least the same technical advantages as described in relation to the method according to the first aspect of the invention, which will not be repeated hereafter.

The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be elucidated on the basis of an exemplary embodiment shown in the attached schematic drawings, in which: Figure 1A shows a part of a system according to the invention for releasing a submergible load from a floater, according to a first embodiment of the invention; Figure 1B shows a part of the system for releasing a submergible load from a floater, according to an alternative embodiment of the invention; Figure ZA shows a top view of the system for releasing a submergible load from a floater of figure 1A, wherein the system extends between a shore station and an installation vessel; Figures 2B-2D show steps of a release method according to an embodiment of the invention for releasing the submergible load from the floater;

DETAILED DESCRIPTION OF THE INVENTION Figures 1 and 2A-D show a system 1 for releasing a submergible load 2 from a buoyant member or floater 3 according to an exemplary embodiment of the invention. The system 1 extends between a vessel 10 on a sea and a shore station 11 on a shore of the sea. The submergible load 2 can be a pipeline, an umbilical or a cable for a subsea infrastructure, e.g. a powercable or a cable for data communication. The floater 3 is releasably coupled to the submergible load 2. In the coupled state, the floater 3 has a longitudinal direction L that extends parallel or substantially parallel to the elongate direction of the submergible load 2. Typically, the submergible load 2 and the floater 3 are deployed together from a vessel or the shore.

Figure 1A shows a part of the system 1 and the submergible load 2 in more detail. The floater 3 is formed by an inflatable or air-filled tube 30 with a buoyancy that is sufficient to at least partially support the submergible load 2 at sea. The submergible load 2 is coupled to the floater 3 with a plurality of releasable couplers 4. In this exemplary embodiment each releasable coupler 4 is arranged circumferentially and/or in a loop around the combination of the submergible load 2 and the releasable coupler 4. However, it 1s noted that different releasable coupler configurations, e.g. a configuration in which one or more releasable couplers 4 are looped individually around the submergible load 2 and the floater 3, are also feasible. The submergible load 2 is coupled to the floater 3 at a plurality of consecutive coupling positions that are distributed evenly along and/or spaced apart over the length of the floater 3. The releasable couplers 4 comprise a strap 8 and a releasable clip 5 to retain the floater 3 to the submergible load 2. The release clip 5 comprises a first clip member 51 and a second clip member 52. Each clip member 51, 52 is connected to an end of the strap 8. The clip members 51, 52 are arranged to releasably engage each other, thereby closing and/or completing the loop of said strap 8 and/or retaining the strap 8 around the combination of the submergible load 2 and the floater 3. In this exemplary embodiment, each clip member 51, 52 comprises a not shown hook at one end, an aperture at another end and a reaction surface extending in between both ends. The hook of each clip member 51, 52 releasably snap-fits into the aperture of the other clip member 51,

52. Other configurations of mutually engaging and releasable clip members 51, 52 will be apparent to one skilled in the art. Between the reaction surfaces, the release clip 5 defines an intermediate space from which a release force can be applied onto the reaction surfaces for releasing and/or disengaging the clip members 51, 52. The system 1, in the exemplary embodiment of figure 1A, further comprises a hose 6 extending in a release direction R alongside, substantially parallel to and/or in the longitudinal direction L of the floater 3. Preferably, the hose 6 is of the lay-flat type, meaning that in a resting state, in which the pressure inside the hose 6 1s equal or substantially equal to the ambient pressure, the hose 6 is arranged to lie flat or substantially flat. The hose 6 may be expanded from the resting state into an expanded state, in which the hose 6 has a substantially circular cross section. In the expanded state the hose 6 has a diameter that is considerably smaller than the diameter of the floater 3. The hose 6 does not serve to substantively contribute buoyancy to the floater 3.

As shown in figure 1A, the hose 6 has a first end 61 that ís connected to a source 7 of pneumatic or hydraulic pressure upstream with respect to the release direction R and a second end 62 that is located downstream of the pressure source 7 in the release direction R. The hose 6 is arranged to extend alongside the submergible load 2 and/or the floater 3 in the release direction R from one releasable clip 5 to the next along a plurality of the clips 5. At each releasable clip 5, the hose 6 is inserted, accommodated, enclosed and/or sandwiched between the respective clip members 51, 52 of the releasable clip 5. In its resting state, the hose 6 is arranged to lie flat or substantially flat in between the opposite reaction surfaces of the respective clip members 51, 52 without exerting any substantial forces onto the reaction surfaces.

The pressure source 7 comprises a manually controllable pump 70 with an output opening 71 for connection to the first end 61 of the hose 6, a control member 72 for controlling the pressure of the pump 70 through the output opening 71, a flow meter, a pressure Sensor Oor a pressure gauge 73 and a pressure release opening 74 for releasing the pressure inside the hose 6. The pump 70 is preferably connected to a source of hydraulic fluid, most preferably water. Alternatively, the pump 70 may be arranged to provide pneumatic pressure by drawing air from the environment.

The system 1 further comprises a not shown pig or a plug that is insertable into the hose 6 at the first end 61 and that is dimensioned to travel inside and/or through the hose 6 in the release direction R towards the second end 62. The plug has a substantially circular cross section with a largest diameter that 1s equal, substantially equal or slightly smaller than the inside diameter of the hose 6.

The plug has a leading end that is arranged to face in the release direction R. The leading end of the plug is provided with a wedge that tapers in the release direction R and that is arranged to be driven into the space between the first clip member 51 and the second clip member 52. The largest diameter of the wedge is larger than the intermediate space between the first clip member 51 and the second clip member 52 so that the wedge can only forcefully pass through or in between the clip members 51,

52.

Figure 1A shows the situation in which the pressure P has been increased to an extent in which the plug has started to travel through the hose 6 from the first end 61 thereof towards the second end 62 in the release direction R. The submergible load 2 is still coupled to the floater 3 with the use of a plurality of the releasable couplers 4 looped around the combination of the submergible load 2 and the floater 3. The straps 8 of the releasable couplers 4 are held or retained by a plurality of the previously discussed releasable clips 5. The plug has already passed and released the first of the plurality of releasable clips 5. The first clip member 51 and the second clip member 52 of said released clip 5 have been disengaged, resulting in the ends of the strap 8 being disconnected. The submergible load 2 becomes separated from the floater 3 at the location of said released clip 5 and starts to submerge under the influence of its own weight.

Figure 1B shows an alternative embodiment of the system 1 that comprises substantially the same features as the system 1 as shown in figure 1A. Corresponding features are not reintroduced and are referred to with the same reference numbers. The alternative system 1 lacks the hose 6 and the source 7 of pneumatic or hydraulic pressure for releasing the releasable couplers 4. The clips 5 may be released manually, for instance by pulling a not shown rope that is attached to one of the clip members 51, 52 from a support vessel near the system 1. In the alternative system

1 the position determiners 20A-F 2 are attached to the floater 3 at a plurality of consecutive reference positions that are further spaced apart from each other over the length of the floater 3 and/or submergible load 2 as compared to the system 1 as shown in figure 1A.

The system 1 comprises multiple position determiners 20A-F secured to the releasable couplers 4 respectively, wherein each of the position determiners 20A- F is configured to determine its current position C1-6. Since each position determiner 20A-F is secured to the floater 3, the respective position determiner 20A-F accordingly determines the current position of at least the part of the floater 3 to which the respective position determiner 20A-F is secured. The system 1 is provided with a non-shown controller, for example on board of the vessel 10, operably connected to each of the position determiners 20A-F. The controller is configured to receive the determined current positions Cl-6 and to compare the determined current position Cl-6 of each of the respective position determiners 20A-F to a predetermined target position T1-6 of each of the respective position determiners Z0A-F along a target route T of the submergible load 2. The target route T may be based on and/or correspond to a pre-laid trench for the submergible load 2 or a predetermined course of the submergible load 2. The current position Cl-6 and the predetermined target position T1-6 are compared in order to determine an offset D1-6 for each of the position determiners 20A-F that represents the difference between the current position Cl-6 and the target position Tl-6 of the respective position determiner 20A-F, As shown in figure 1A, in this example the position determiners 20A-F are attached to the strap 8 of the releasable coupler 4 and therewith to the floater 3 and to the submergible load 2. The position determiners Z20A-F are attached to the floater 3 at a plurality of consecutive reference positions ‘that are distributed evenly along and/or spaced apart over the length of the floater 3 and/or submergible load 2. In this example the reference positions of the position determiners 20A-F coincide with the coupling positions of the releasable couplers 4. However, it is noted that the reference positions of the position determiners 20A-F are independent of the coupling positions of the releasable couplers 4. Each of the position determiners 20A-F is associated to at least one of the two or more releasable couplers 4. When each position determiner 20A-F is associated with multiple releasable couplers 4, it is possible to release the submergible load 2 in sections or its entirety at once. Typically, the floater 3 is provided with position determiners 20A-F with a spacing of the position determiners 20A-F of preferably 50 meters, wherein the spacing can be adjusted in light of the load characteristics and the environmental conditions. The position determiners 20A-F are located substantially at the top of the floater 3 in order to avoid obstructions that may hinder or block signals from and to the position determiners 20A-F, especially to avoid obstructions above the position determiners 20A-F. In this example, each position determiner 20A-F comprises a global navigation satellite system receiver, or GNSS receiver, for determining the current position Cl-6 of the position determiner 20A-F, a transceiver for transmitting and/or receiving data e.g. the determined current position C1-6, and a power source for powering the position determiner 20A-F. The system 1 may comprise a non-shown GNSS augmentation device, such as a RTCM transmitter, that has an operable connection at least with the controller. The GNSS augmentation device may enable GNSS correction to the determined current positions C1-C6, in order to improve the accuracy of the determined current position Cl-6 of the GNSS receiver of the position determiner 20A-F.

The system 1 may comprise not shown remote monitoring devices, for example on board of the vessel 10 and/or located on shore, configured for monitoring the determined current positions C1-6 and/or the determined offsets D1-6 of the position determiner 20A-F. The remote monitoring device receives data that comprises the determined current position C1-6 and/or the determined offset D1-6 and displays the determined current position C1-6 and/or the determined offset D1-6 to a user, e.g. the operator of the system 1. In this example the system comprises a first remote monitoring device that is located on the shore near the shore station 11 and a second remote monitoring device that is located on the vessel 10. Both remote monitoring devices identically display the determined current position C1-6 and/or the determined offset D1-6 to ensure that the respective users have the same information during the release operation.

In short, the submergible load 2 is initially positioned above the sea bottom near the target route T of the submergible load 2. When the offset Dl1-6 of the respective position determiners 20A-F is within a predetermined range, the submergible load 2 is dropped onto or released towards the sea bottom by terminating the coupling between the floater 3 and the submergible load 2, thereby releasing the submergible load 2 from the floater

3. Preferably the predetermined range of the offset D1-6 is between 0 and 1 meter, more preferably between 0 and 0.05 meter.

Figures 2A-D show a release sequence for releasing the submergible load 2 from the floater 3. In this example the submergible load 2 is released from the floater 3 in a sequential manner along the longitudinal direction L of the floater 3, more specifically the submergible load 2 is sequentially released from the floater 3 in a direction away from the shore station 11 towards the vessel 10 along the longitudinal direction L of the floater 3.

Figure ZA shows the submergible load 2 that extends between the shore station 11 and the vessel 10. The floater 3 is along its full length coupled to the submergible load 2. The current positions Cl1-6 are different from the target positions T1-6 of the position determiners 20A-F, which results in varying offsets D1-6 for the respective position determiners 20A-F. Based on the determined current position Cl and/or offset Dl of the first position determiner 20A, in this example the position determiner 20A that is closest to the shore station 11, the first position determiner 20A is re-positioned in order to locate the first position determiner 20A closer to or at the target position Tl at the target route T. Re-positioning or adjusting the position of the first position determiner 20A may be performed by the vessel 10 or a support vessel that is attached to the floater 3 and/or the submergible load 2. Alternatively the first position determiner 220A may be positioned by current, waves and/or wind acting on the system 1 and/or the submergible load 2. When the first position determiner 20A is positioned sufficiently at or near the target route T the releasable couplers 4 that are associated with the first position determiner 20A are released to partly release the submergible load 2 from the floater 3. Preferably the releasable couplers 4 are released sequentially in the release direction R from the shore station 11 towards the vessel 10. When the associated releasable couplers 4 have released the submergible load 2 the above described steps are repeated for the second position determiner 20B, in this example the position determiner 20B that is second closest to the shore station

11. Subsequently the above described sequence is repeated for the other position determiners 20C-F.

Figure 2B shows a state of the system 1 during the release sequence in which the system 1 is partly released from the submergible load 2 and is partly coupled to submergible load 2. The system 1 is partly released from the submergible load 2 along two position determiners 20A-B and partly coupled to the submergible load 2 along four position determiners 20C-F. The current positions Cl-2 of the two position determiners 20A-B substantially coincide with the respective target positions T1-2 and the current positions C3-6 of the four position determiners 20C-F are different from the respective target positions T3-6. Figure 2C shows a state of the system 1 during the release sequence in which the system 1 is partly released from the submergible load 2 and is partly coupled to submergible load 2. The system 1 is partly released from the submergible load 2 along four position determiners 20A- D and partly coupled to the submergible load 2 along two position determiners 20E-F. The current positions Cl-4 of the four position determiners 20A-D substantially coincide with the respective target positions T1-4 and the current positions C5-6 of the two position determiners 20E-F are different from the respective target positions T5-6.

Figure ZD shows a state of the system 1 at the end of the release sequence in which the system 1 is fully released from the submergible load 2 along all position determiners 20A-F. The current positions Cl-6 of the position determiners 20A-F substantially coincide with the respective target positions T1-6.

Alternatively, the submergible load 2 can be released from the floater 3 in its entirety at once.

It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention.

Claims

CONCLUSIONS

A method of releasing a submersible cargo from a float, the method comprising the steps of: providing a float and a releasable coupler; coupling the float to a submersible payload using the releasable coupler; attaching a positioner to the float, to the submersible cargo and/or to the releasable coupler; by the position determiner, determining the current position of the position determiner; comparing the determined current position with a target position of the position determiner to determine a difference (offset); when the difference is within a predetermined range, releasing the releasable coupler to at least partially release the submersible cargo from the float.

The method of claim 1, wherein the step of attaching a positioner to the float, to the submersible cargo and/or to the releasable coupler comprises the step of attaching two or more positioners to the float, to the submersible charge and/or to the releasable coupler, the method for each of the two or more positioners comprising the steps of: determining the current position of the positioner; and comparing the determined current position with a target position of the position determiner to determine a difference.

The method of claim 1 or claim 2, wherein the step of providing a float and a releasable coupler comprises the step of providing two or more releasable couplers, the method comprising the step of coupling the float to the submersible cargo using the two or more releasable couplers.

The method of claim 3, wherein the submersible cargo is an elongate cargo, and wherein the step of coupling the float to the submersible cargo using the two or more releasable couplers comprises the step of applying the two or more releasable couplers along the longitudinal direction of the submersible cargo, preferably at a predetermined distance from each other.

A method according to claim 2 and claim 3 or claim 4, comprising the step of associating each of the two or more positioners with at least one of the two or more releasable couplers, the method for each of the two or more position determiners comprises the step of: when the difference is within a predetermined range, releasing the associated at least one of the two or more releasable couplers to at least partially release the submersible cargo from the float.

The method of claim 5, wherein the submersible cargo is released from the float in a sequential manner along the longitudinal direction of the submersible cargo.

The method of any preceding claim, wherein the method comprises the steps of: providing a remote monitoring device; transmitting, preferably by a transceiver, the determined current position of the position determiner and/or the determined difference, from the position determiner to the remote monitoring device; and monitoring the determined current position of the position determiner and/or the determined difference by the remote monitoring device.

The method of any preceding claim, wherein the method comprises the step of: when it is determined that the determined difference is outside the predetermined range, adjusting the position of the position determiner based on the determined current position of the position determiner and /or the particular difference.

A method according to any one of the preceding claims, wherein the submersible cargo is selected from a group comprising a cable, an umbilical and a pipeline.

The method of any preceding claim, wherein the step of providing a driver and a releasable coupler comprises the step of providing a driver having a plurality of sub-floats, and a plurality of releasable couplers, and wherein the step of coupling of the float having a submersible payload using the releasable coupler, comprising the step of coupling each of the plurality of sub-floats to the submersible payload using at least one of the plurality of releasable couplers.

A method according to any preceding claim, wherein the method comprises the step of: connecting the submersible cargo to a shore station, the submersible cargo extending away from the shore station when the submersible cargo is at least partially released from the float.

A method according to any one of the preceding claims, wherein the step of determining the position determiner's current position by the position determiner comprises the step of the position determiner periodically determining the current position of the position determiner, preferably determining of the current position of the locator within periods of maximum ten seconds, more preferably within periods of maximum five seconds

A method according to any one of the preceding claims, wherein the method comprises the step of: switching the positioner into a sleep mode or into an active mode.

A method according to any preceding claim, wherein the method comprises the step of: deploying the submersible cargo and the float together from a vessel, from an offshore location or from the coast.

15. A submersible cargo release system, the system comprising a float, a releasable coupler configured to couple the float to the submersible cargo, a positioner configured to be attached to the float, to the submersible payload and/or to the releasable coupler, and a control unit having an operable connection to the positioner, the positioner being configured to determine the current position of the positioner, the control unit being configured to compare the determined current position with a target position of the position determiner to determine a difference, and wherein the control unit is configured to, when the difference is within a predetermined range, control release the releasable coupler to at least partially release the submersible payload give from the float.

The system of claim 15, including two or more positioners configured to be attached to the float, to the submersible cargo and/or to the releasable coupler.

The system of claim 15 or 16, including two or more releasable couplers configured to couple the float to the submersible cargo.

The system of claims 16 and 17, wherein each of the two or more positioners is associated with at least one of the two or more releasable couplers.

A system according to any one of claims 15-18, wherein the float comprises a plurality of sub-floats and the system comprises a plurality of releasable couplers for coupling the sub-floats to the submersible Cargo.

A system according to any one of claims 15-19, wherein the position determiner comprises a global navigation satellite system (GNSS receiver) receiver.

A system according to any one of claims 15-20, wherein the position determiner comprises a supplemental device for a global navigation satellite system, such as an RTCM transmitter, which has an operable connection to at least the control unit.

The system of any of claims 15-21, wherein the position determiner comprises a storage medium configured to store the determined current positions of the position determiner.

A system according to any one of claims 15-22, wherein the position determiner is provided with a battery for powering the position determiner.

A system according to any one of claims 15-23, wherein the position determiner comprises a transceiver configured to send data to and/or receive data from an external device, preferably wherein the transceiver comes with a data SIM card.

The system of any of claims 15-24, wherein the system includes a remote monitoring device, and wherein the position determiner is configured to transmit the determined current position and/or the determined difference from the position determiner to the remote remote monitoring device, and wherein the remote monitoring device is configured to monitor the received determined current position of the position determiner and/or the determined difference.

An assembly comprising the submersible cargo release system of any one of claims 15 to 25, a submersible cargo to be released from the system, and a vessel for handling the system and/or the submersibles. cargo.