Method for installing at least one sleeve around a portion of an underwater pipe for transporting fluids

Abstract

The invention relates to a method for installing at least one sleeve around a portion of an underwater pipe for transporting fluids, the sleeve being formed by two half-shells (8a, 8b), the method comprising maintaining, in a mainly vertical position, the pipe, the two half-shells of the sleeve being gripped on the side of their inner face by means of a sleeve-loading system (100) positioned on one side of the pipe, aligning the two half-shells with the axis (Y-Y) of the pipe, gripping the two half-shells by their outer face by means of a sleeve positioning and unlocking system (200) positioned on a side of the pipe opposite that of the sleeve-loading system, pivoting each half-shell about an inner axis (Z-Z) aligned with the axis of the pipe in order to close it onto a portion of the pipe, positioning the sleeve along the axis of the pipe, fully closing and locking the two half-shells onto the pipe portion, and removing the sleeve positioning and unlocking system.

Description

Description Title of the invention: Method for installing at least one sleeve around a portion of an underwater fluid transport pipe Technical Field

[0001] The present invention relates to the general field of underwater fluid transport pipes providing the bottom-surface connection for the transfer of hydrocarbons, for example oil and gas, from underwater production wells. This type of bottom-surface connection can also be used to transfer other fluids between the surface and the seabed, such as for example treated water or carbon dioxide.

[0002] More specifically, it relates to a method of installing buoys (or sleeves for suppressing vortices from the current surrounding the pipe and associated vibrations) around a portion of an underwater bottom-surface connecting pipe, as well as a system for implementing such a method, and uses of such a method. Prior art

[0003] In the field of offshore oil and gas production, subsea pipes called "risers" are pipes that are usually rigid or solid, but sometimes also flexible, providing the connection between a floating support, such as a floating production, storage and offloading unit (or FPSO for "Floating Production, Storage and Offloading"), and the seabed, particularly at great depths.

[0004] Among this type of risers, the Steel Catenary Riser (or SCR) is known, which is a common method of connecting a subsea pipeline to a deepwater floating oil production platform. SCRs are used to transfer fluids such as oil, gas, injection water, etc. between platforms and subsea pipelines.

[0005] Also known as the "Steel Lazy Wave Riser" (or SLWR) is a steel pipe used in such a way as to allow some flexibility to absorb the movements caused by waves and ocean currents. The so-called "lazy wave" configuration refers to the specific shape given to this type of underwater pipe. In fact, this pipe is deliberately arranged in such a way as to form one or more undulations (shaped waves) in order to allow greater flexibility and better absorption of the float's movements due to currents or waves.

[0006] These undulations are obtained by placing a plurality of buoyancy modules (buoy type) around a portion of the pipe, either spaced apart from each other (according to a distributed distribution of buoyancy), or joined to each other (according to a continuous distribution of buoyancy).

[0007] An SLWR pipeline offers several advantages over an SCR pipeline. It reduces the mechanical stresses placed on the pipeline, which increases its lifespan and reduces the risk of failure. It allows for greater vertical or lateral offsets of the floating unit to which it is connected at the surface. In addition, it offers better protection against severe weather events such as storms, allowing the pipeline and float to move more freely. This additional freedom is particularly important at great depths where the impact of surface and pipeline movements is greater on the stress levels in the steel.

[0008] Alternatively, subsea bottom-to-surface connecting pipelines can be constructed from single-length pipeline elements that are assembled on board the laying vessel, then connected to the already constructed pipeline section and finally lowered into the sea as they are connected. This laying can be carried out using a J- or S-shaped laying tower positioned on the laying vessel.

[0009] With J-lay, the subsea pipeline is typically lowered from the lay vessel almost vertically. This type of lay requires a tower substantially vertical on which the individual pipe elements are brought one after the other using a loading arm from a horizontal position on the deck of the laying vessel to be assembled and welded to the already constructed pipe section held from the laying tower. After the welding operations and the application of a coating to improve protection against corrosion or to apply thermal insulation, the new individual pipe element thus connected to the already constructed pipe section is lowered into the sea by moving the laying vessel forward by an advance corresponding generally to the length of the individual pipe element.

[0010] The pipe is then lowered gradually into the water and placed on the bottom, gradually joining pieces of pipe there. The welding and coating operations are typically carried out in an assembly station located below the main part of the tower and above the section of pipe being laid. The individual pipe elements are therefore typically brought by the loading arm into a vertical position in the tower above the assembly station, transferred to said tower via the (pipe gripping) clamps of said arm and those of the tower, then translated vertically to be joined at the assembly station to the section of pipe already assembled and being laid in the water.

[0011] There are several methods of installing buoyancy modules around a SLWR pipeline constructed using the J-lay.

[0012] For distributed distribution, the buoyancy modules can be pre-installed on the deck of the pipelaying vessel after the pipe unit has been assembled and before it is lifted to the pipelaying tower by the loading arm. The pipe unit is then lifted to the pipelaying tower with its buoyancy modules closed and locked in translation and rotation on a portion of the pipelaying element.

[0013] Although a proven method, this approach generally requires maintaining empty spaces (exclusion zones) on the pipe element to allow manipulation by the loading arm and its grippers, as well as by the gripping elements (grippers) in the tower. It is therefore not possible to achieve a continuous distribution with this installation method.

[0014] It is also known to use a V-trolley system. This system, located for example in the assembly station of the laying tower below the tower clamps, is used to load the buoyancy modules onto the pipe element once the unit length section has been connected to the pipe being laid and held by the tower.

[0015] Such a system thus theoretically allows for a continuous distribution of buoyancy modules around the pipe. However, it is limited to small buoyancy modules (because they must pass through the tower assembly station) and it is a manual (or semi-manual) system. In addition, this system also requires space available in said assembly station, to supply buoyancy modules but also to move and approach the section of pipe to be equipped. However, assembly stations can sometimes be cluttered with equipment necessary for connecting the section of pipe of unit length to the section of pipe being laid. For example, we can note the presence of the elements necessary for welding the two sections of pipe, for checking this weld or for the thermal or anti-corrosion coating after this weld.In this case, the V-Trolley system cannot be installed in the assembly station.

[0016] To achieve a continuous distribution of the buoyancy modules with an efficient laying rhythm, the semi-automatic buoy loading system described in publication W02022 / 070160 A1 has been proposed. This system allows the buoyancy modules to be loaded and installed on the pipe element after it has been welded into the laying tower and thus eliminates interference problems with the laying tower and the clamps of the loading arm and the tower. However, this solution requires having a significant space available for the positioning and operations of said loading system, space that may not always be available, depending on the architecture of the vessel deck, the tower and the assembly station. For example, for the SAIPEM FDS laying vessel, this equipment would not have could not be used as designed because the assembly station did not allow these operations. Statement of the invention

[0017] The invention therefore aims to propose a method for installing buoyancy modules which makes it possible to obtain both a distributed distribution and a continuous distribution of the buoyancy modules and which can be used on most laying vessels.

[0018] According to the invention, this object is achieved by means of a method for installing at least one sleeve around a portion of an underwater fluid transport pipe, the sleeve being formed by two half-shells each having an internal face intended to be in contact with the pipe and an external face opposite the internal face, the method comprising: a) maintaining the pipe in a mainly vertical position; b) gripping the two half-shells of the sleeve on their internal face side by means of a sleeve loading system which is positioned on one side of the pipe; c) aligning the two half-shells of the sleeve with the axis of the pipe by positioning them on either side of the pipe;d) gripping the two half-shells of the sleeve by their external face by means of a sleeve positioning and locking system which is positioned on one side of the pipe opposite that of the sleeve loading system; e) pivoting by means of the sleeve positioning and locking system of each half-shell of the sleeve around an internal axis aligned with the axis of the pipe to close it at least partially on a portion of the pipe; f) positioning the sleeve thus assembled along the axis of the pipe by means of the sleeve positioning and locking system; (g) the complete closing and locking of the two half-shells of the sleeve on the pipe section; and (h) the removal of the sleeve positioning and locking system

[0019] The method according to the invention is remarkable for its decoupled approach in that the equipment necessary for its implementation (namely the sleeve loading system and the sleeve positioning and locking system) are positioned on either side of the subsea pipeline being laid ("in front" and "behind" it). In particular, in the context of a J-lay of such a pipeline, it may be particularly advantageous to position the sleeve positioning and locking system in the laying tower, and the sleeve loading system on the pipeline section loading arm. Thus, the pipeline section loading arm is used to supply the sleeve positioning and locking system with sleeves using virtually passive, simple and lightweight equipment, which has no (or very little) impact on the operations of the loading arm.

[0020] This results in a partition of functions between the equipment on either side of the pipe being laid on which the sleeves (buoyancy modules or sleeves for suppressing vortices from the current surrounding the pipe and associated vibrations) must be installed, making it possible to optimize the simplicity of this equipment by making the best use of available resources. The method according to the invention makes it possible to free up space "in front of" the pipe being laid (the sleeve positioning and locking system being installed "behind" the pipe) and therefore potentially to optimize / unblock space on the ship's deck.

[0021] Such a configuration is made possible by the fact that the sleeves are presented by their external face by the sleeve loading system located on one side of the pipe and passing around it. The sleeve positioning and locking system located on the other side of the pipe therefore simply has to catch the sleeves in the conventional manner by holding them by their external face and to close them on the pipe before lock (with some position adjustments on the horizontal plane and along the pipe).

[0022] This decoupled approach thus allows to optimize the distribution, position, size and operation of the sleeve loading and positioning and locking systems according to the organization of the ship deck, the tower and the assembly station and their environments and resources. In particular, in the context of the SAIPEM FDS vessel, this approach made it possible to use the space resource available in the tower and combine it with the loading arm to provide buoyancy modules to the pipe in the tower, after the connection of a unit length element to the pipe being laid held by the tower, and therefore by having more freedom of operation regarding the different pipe gripping systems in the tower, to achieve a continuous distribution of buoyancy modules on the SAIPEM FDS vessel.

[0023] Of course, the application of the method according to the invention is conceivable to other laying vessels having the laying tower located at the rear of the vessel (as for the SAIPEM FDS but with potentially different architectures of laying tower and loading arm). More generally, the method according to the invention applies to other architectures of laying vessels and in particular to architectures in which the laying tower is located in the middle of the vessel, and the pipe during laying passes through a so-called "moonpool" system (a central well in the deck of the vessel).

[0024] The method according to the invention also applies to ships for which the laying tower is located on the side of the ship or to ships which do not lay the pipe using a J-process but for example a roll-out method (another laying method where the pipe is pre-assembled on land and wound onto a reel before being "unrolled" at sea, again with a passage through a substantially vertical position in which the buoyancy modules or sleeves are installed. The method according to the invention can make it possible in these different cases to optimize the arrangement of the loading system and the positioning and locking system by locating them on either side of the pipe where usually, these two systems form only one, located on a single side of the pipe.

[0025] Preferably, the sleeve loading system is located on the side of the respective inner face of the half-shells of the sleeve, while the sleeve positioning and locking system is located on the side of the respective outer face of the half-shells of the sleeve.

[0026] In one embodiment, step c) comprises a rotational movement of the sleeve loading system. In this case, prior to step d), a translation step of the sleeve positioning and locking system in a substantially horizontal direction may be provided.

[0027] In another embodiment, step c) comprises a rotational movement followed by a translational movement of the sleeve loading system in a substantially horizontal direction.

[0028] In yet another embodiment, step c) comprises a rotational movement followed by a vertical translational movement, followed by a translational movement of the sleeve loading system in a substantially horizontal direction.

[0029] During step a), the pipe is advantageously maintained in a position forming an angle of between 45° and 100° relative to the horizontal.

[0030] The invention also relates to a system for implementing the method as defined above, comprising: - a sleeve loading system which is intended to be positioned on one side of a pipe and which comprises means for gripping the two half-shells of the sleeve on their respective internal face; and - a system for positioning and locking the sleeves which is intended to be positioned on an opposite side of the pipe and which comprises means for gripping the two half-shells of the sleeve on their respective external face.

[0031] Advantageously, the gripping means of the sleeve loading system comprise gripping fingers capable of cooperating with orifices made in the respective internal face of the half-shells of the sleeve.

[0032] Also advantageously, the gripping means of the sleeve positioning and locking system comprise at least one pair of grippers each capable of gripping a half-shell of the sleeve by its external face.

[0033] In this case, each of the clamps is preferably mounted on a cradle which is intended to receive a sleeve half-shell and which is articulated around an internal axis aligned with the axis of the pipe, said cradle being able to be pivoted around its internal axis to at least partially close the sleeve half-shell on a portion of the pipe.

[0034] The sleeve loading system may comprise a pivoting support. As for the sleeve positioning and locking system, it may comprise a support which can move in a direction substantially parallel to the axis of the pipe in order to be able to adjust the position of the sleeves along said pipe, as well as a structure which can move in a mainly horizontal direction making it possible to approach the pipe in a manner substantially perpendicular to the axis thereof.

[0035] The invention also relates to a use of the method as defined above for the installation of a plurality of positive buoyancy sleeves forming buoys around a portion of an underwater pipe providing a bottom-surface connection for the transport of hydrocarbons or another fluid.

[0036] In this use, the subsea pipeline may be constructed by a J-lay technique, with the buoys being installed around a portion of the pipeline prior to lowering that portion into the sea.

[0037] In this case, the subsea pipeline is advantageously constructed on a pipelaying vessel using a J-lay, with the buoy positioning and locking system positioned in a J-lay tower, and the buoy loading system positioned on a pipe section loading arm.

[0038] Additionally, the buoys can be installed around the pipeline portion spaced apart or joined together.

[0039] The invention also relates to a use of the method as defined above for the installation of sleeves for suppressing vortices from the current and associated vibrations around a portion of an underwater pipe providing a bottom-surface connection for the transport of hydrocarbons or another fluid. Brief description of the drawings

[0040] [Fig. 1] Figure 1 is a side view of the rear of a laying vessel capable of using the method according to the invention.

[0041] [Fig. 2] Figure 2 is a perspective view of a positive buoyancy sleeve forming a buoy that can be installed around a portion of pipe using the method according to the invention.

[0042] [Fig. 3] Figure 3 is a cross-sectional view of a portion of underwater pipeline around which a buoy has been installed.

[0043] [Fig. 4] to [Fig. 11] Figures 4 to 11 illustrate different steps of the installation method according to the invention. Description of the embodiments

[0044] The invention relates to a method for installing at least one sleeve around a portion of an underwater fluid transport pipeline, and in particular a portion of SLWR type pipeline which is constructed using J-laying.

[0045] J-laying is a technique known in the offshore industry for laying subsea pipelines. This type of laying requires the use of a laying vessel such as the one partially shown in Figure 1.

[0046] In the example of Figure 1, such a laying vessel 2 comprises a J-shaped laying tower 4 which is mounted substantially vertically at the rear of the vessel. A loading arm 6 is mounted on the lower end of the tower around a horizontal joint XX so as to be able to pivot between a horizontal position in which it can receive individual pipe elements present on the deck of the laying vessel, and a vertical position in which it can transfer the unitary driving elements to the J-laying tower (in Figure 1, three positions of the loading arm are shown: a horizontal position, a vertical position (backed against the tower), and an intermediate position).

[0047] Vibrations induced by ocean currents that generate vortices on submerged pipelines are known to increase drag and can lead to structural fatigue. A known solution to suppress these vibrations is to modify the flow along the pipeline, interrupting the production of vortices so that they act less coherently. To this end, propellers with the same axis as the pipeline and formed by fins are added. These propellers formed by fins are commonly called "VIV strakes" for "Vortex Induced Vibrations" strakes in English. Such propellers can be installed on a pipeline via sleeves supporting the propellers.

[0048] The sleeves that are installed around the pipe by the method according to the invention may be VIV suppression sleeves. Such sleeves are formed of two half-shells each having an internal face intended to be in contact with the pipe and an external face opposite the internal face. The external face of these half-shells carries hydrodynamic fins which are for example arranged in a helix around the axis of the pipe in order to modify the flow along it.

[0049] Alternatively, the sleeves which are installed around the pipe may be positively buoyant sleeves forming buoys, such as the buoy 8 shown in Figures 2 and 3.

[0050] The buoy 8 is formed by two half-shells 8a, 8b each having a geometric shape which corresponds to half of a cylinder with an internal face intended to be in contact with the pipe 10 and an external face opposite the internal face.

[0051] The half-shells 8a, 8b of the buoy can be produced by rotational molding and the hollow volume of these half-shells can be filled with a lightening material, for example polymers, syntactic foams, or even special resins, suitable to ensure adequate upward hydrostatic thrust and to withstand operating pressures in the water body.

[0052] In addition, the buoy 8 can be configured, if necessary, to limit the vortices induced by the currents on the pipe, and the associated vibrations. For this purpose, the external face of the half-shells 8a, 8b can carry hydrodynamic fins 12 (i.e. the “VIV strakes”) which are, for example, arranged in a triple helix around the axis YY of the pipe.

[0053] In connection with Figures 4 to 11, an embodiment of the method according to the invention for installing a buoy (such as that of Figures 2 and 3) around a portion of pipe which is being laid by means of a laying vessel (such as that partially shown in Figure 1) will now be described.

[0054] Of course, the process described below applies identically to the installation of a sleeve for suppressing vibrations induced by vortices.

[0055] As a prerequisite to the method, as shown in Figure 1, the pipe 10 is held in the laying tower 4 in a mainly vertical position, i.e. it forms an angle with respect to the horizontal of between 45° (angle 1 in Figure 1) and 100° (angle a2 in Figure 1) (the vertical being the 90° position and (the 45° angle corresponding to the tower leaning towards the front of the laying boat).

[0056] The method according to the invention involves the use of a sleeve loading system which is positioned on one side of the pipe, and a sleeve positioning and locking system which is positioned on an opposite side of the pipe.

[0057] For example, as shown in Figure 1, the sleeve loading system 100 is positioned on the loading arm 6 of the laying vessel 2 at the front of the pipe 10 (relative to the direction of advance of the laying vessel), while the sleeve positioning and locking system 200 is positioned in the tower 4 of the laying vessel at the rear of the pipe 10.

[0058] As shown in Figure 4, the sleeve loading system 100 comprises means for gripping the two half-shells 8a, 8b of the sleeve on their respective internal face.

[0059] For example, these gripping means may be in the form of gripping fingers 102 which are capable of cooperating with orifices (not shown in the figures) made at the level of the respective internal face of the half-shells 8a, 8b of the sleeve. These gripping fingers 102 are retractable and are mounted on a support structure 104 secured to the loading arm of the laying ship.

[0060] In a first step of the method according to the invention, the half-shells of the sleeve are loaded onto the sleeve loading system 100 by means of the gripping fingers 102 thereof. This loading is carried out while the loading arm of the laying vessel is in a horizontal position aligned with the deck of the vessel.

[0061] The next step of the method shown in Figure 5 consists of aligning the two half-shells 8a, 8b of the sleeve with the axis YY of the pipe 10 by positioning them on either side of the latter. This alignment is achieved by bringing the two half-shells towards the pipe by presenting them by their respective external face.

[0062] For this purpose, this step is carried out here by first rotating the loading arm of the laying vessel - and therefore the sleeve loading system 100 - around the vertical joint XX of the laying tower (figure 1) to bring it into a mainly vertical position as shown in figure 1.

[0063] As shown in Figure 6, the sleeve positioning and locking system 200 then performs a translation in a substantially horizontal direction towards the sleeve loading system 100.

[0064] Depending on the implementation of the installation method according to the invention, the alignment of the two half-shells of the sleeve with the axis of the pipe can be carried out differently. For example, such an alignment can comprise a rotational movement followed by a translational movement of the system of loading the sleeves in a substantially horizontal direction. Alternatively, this alignment may comprise a rotational movement followed by a vertical translational movement, followed by a translational movement of the sleeve loading system in a substantially horizontal direction.

[0065] The sleeve positioning and locking system 200 is positioned on the side of the pipe which is opposite to that by which the sleeve loading system 100 is positioned.

[0066] The system for positioning and locking the sleeves 200 comprises means for gripping the two half-shells 8a, 8b of the sleeve by their external face.

[0067] For example, the system for positioning and locking the sleeves 200 may comprise one or more pairs of clamps 202 each capable of gripping a half-shell 8a, 8b of the sleeve by its external face.

[0068] More specifically, each of the pairs of clamps 202 is advantageously mounted on a cradle 204 which is intended to receive a half-shell of sleeve. These cradles are mounted on a support 206 which is integral with the laying tower of the laying ship and which can move in a substantially horizontal direction by means of, for example, jacks (not shown in the figures). Advantageously, the system for positioning and locking the sleeves comprises, for each cradle, two pairs of clamps which are spaced longitudinally from one another.

[0069] As shown in Figure 7, the pairs of clamps 202 of the sleeve positioning and locking system 200 are closed (by actuation of a control cylinder for example) to grip the two half-shells 8a, 8b of the sleeve.

[0070] It will be noted that the pairs of clamps and the cradles of the sleeve positioning and locking system are designed not to interfere with the hydrodynamic fins 12 of the sleeve, for example by being inserted between two adjacent fins and engaging with notches 14 made on the periphery of the half-shells 8a, 8b of the sleeve (see figure 2).

[0071] In the next step illustrated in Figure 8, the sleeve loading system is withdrawn by first releasing the gripping fingers from the inner face of the sleeve half-shells 8a, 8b (these now being held by the clamps 202 of the sleeve positioning and locking system 200), then pivoting the loading arm of the laying tower to its horizontal position.

[0072] Furthermore, the positioning and locking system of the sleeves 200 can adjust its axial position relative to the pipe 10 by making small movements (by means of the jacks connected to the support 206).

[0073] The next step of the method consists of closing (at least partially) each half-shell 8a, 8b of the sleeve on a portion of the pipe 10.

[0074] For this purpose, as shown in Figure 9, each cradle 204 of the sleeve positioning and locking system is articulated around a vertical internal axis ZZ which is aligned with the axis YY of the pipe so as to be able to be pivoted around this internal axis (for example by means of a jack not shown in the figures) to at least partially close the sleeve half-shell which it receives on a portion of the pipe 10.

[0075] In the next step (figure 10), the sleeve thus assembled on the pipe portion is correctly positioned vertically along the Y-Y axis of the pipe 10 by means of the sleeve positioning and locking system.

[0076] The sleeve positioning and locking system then completely closes the two sleeve half-shells 8a, 8b on the portion of the pipe 10, then these are locked onto the portion of the pipe, for example by strapping or screwing.

[0077] As shown in Figure 11, the cradles 204 of the sleeve positioning and locking system open in order to release the pipe 10 provided with its sleeve 8. The sleeve positioning and locking system can then be withdrawn from the pipe.

Claims

Claims 1. Method for installing at least one sleeve around a portion of an underwater fluid transport pipe, the sleeve (8) being formed by two half-shells (8a, 8b) each having an inner face intended to be in contact with the pipe (10) and an outer face opposite the inner face, the method comprising: a) maintaining the pipe (10) in a mainly vertical position; b) gripping the two half-shells (8a, 8b) of the sleeve (8) on their inner face side by means of a sleeve loading system (100) which is positioned on one side of the pipe; c) aligning the two half-shells of the sleeve with the axis (YY) of the pipe by positioning them on either side of the pipe;d) gripping the two half-shells of the sleeve by their external face by means of a sleeve positioning and locking system (200) which is positioned on a side of the pipe opposite that of the sleeve loading system; e) pivoting by means of the sleeve positioning and locking system of each half-shell of the sleeve around an internal axis (ZZ) aligned with the axis of the pipe to close it at least partially on a portion of the pipe; f) positioning the sleeve (8) thus assembled along the axis of the pipe by means of the sleeve positioning and locking system; g) completely closing and locking the two half-shells of the sleeve on the portion of pipe; and h) removing the sleeve positioning and locking system.

2. Method according to claim 1, wherein the sleeve loading system (100) is located on the side of the respective internal face of the half-shells of the sleeve, while the sleeve positioning and locking system (200) is located on the side of the respective external face of the half-shells of the sleeve.

3. Method according to one of claims 1 and 2, in which step c) comprises a rotational movement of the sleeve loading system (100).

4. Method according to claim 3, further comprising, prior to step d), a step of translating the system for positioning and locking the sleeves (200) in a substantially horizontal direction.

5. Method according to one of claims 1 and 2, in which step c) comprises a rotational movement followed by a translational movement of the sleeve loading system (100) in a substantially horizontal direction.

6. Method according to one of claims 1 and 2, in which step c) comprises a rotational movement followed by a vertical translational movement, followed by a translational movement of the sleeve loading system (100) in a substantially horizontal direction.

7. Method according to any one of claims 1 to 6, in which, during step a), the pipe (10) is maintained in a position forming an angle of between 45° and 100° relative to horizontal.

8. System for implementing the method according to any one of claims 1 to 7, comprising - a sleeve loading system (100) which is intended to be positioned on one side of a pipe (8) and which comprises means (102) for gripping the two half-shells (8a, 8b) of the sleeve on the side of their respective internal face; and - a system for positioning and locking the sleeves (200) which is intended to be positioned on an opposite side of the pipe and which comprises means (202) for gripping the two half-shells of the sleeve on the side of their respective external face.

9. System according to claim 8, in which the gripping means of the sleeve loading system (100) comprise gripping fingers (102) capable of cooperating with orifices made in the respective internal face of the half-shells of the sleeve.

10. System according to one of claims 7 and 8, in which the gripping means of the system for positioning and locking the sleeves (200) comprise at least one pair of clamps (202) each capable of gripping a half-shell of the sleeve by its external face.

11. System according to claim 10, in which each of the clamps (202) is mounted on a cradle (204) which is intended to receive a sleeve half-shell and which is articulated around an internal axis (ZZ) aligned with the axis (YY) of the pipe, said cradle being able to be pivoted around its internal axis to at least partially close the sleeve half-shell on a portion of the pipe.

12. A system according to any one of claims 8 to 11, wherein the sleeve loading system (100) comprises a pivoting support (104).

13. System according to any one of claims 8 to 12, in which the system for positioning and locking the sleeves (200) comprises a support (206) capable of moving in a direction substantially parallel to the axis (YY) of the pipe in order to be able to adjust the position of the sleeves along said pipe.

14. System according to claim 13, in which the system for positioning and locking the sleeves (200) further comprises a structure capable of moving in a mainly horizontal direction making it possible to approach the pipe in a manner substantially perpendicular to the axis thereof.

15. Use of the method according to any one of claims 1 to 7 for the installation of a plurality of positive buoyancy sleeves forming buoys (8) around a portion of an underwater pipe (10) providing a bottom-surface connection for the transport of hydrocarbons or another fluid.

16. Use according to claim 15, in which the underwater pipeline is constructed by a J-laying technique, the buoys being installed around a portion of the pipeline prior to lowering this portion into the sea.

17. Use according to claim 16, wherein the subsea pipeline is constructed on a laying vessel (2) using a J-lay, the buoy positioning and locking system (200) being positioned in a J-lay tower (4), the buoy loading system (100) being positioned on a loading arm (6) of the pipeline sections.

18. Use according to one of claims 16 and 17, in which buoys are installed around the portion of the pipe, being spaced from each other or being joined to each other.

19. Use of the method according to any one of claims 1 to 7 for the installation of sleeves for suppressing vortices from the current and associated vibrations around a portion of an underwater pipe providing a bottom-surface connection for the transport of hydrocarbons or another fluid.

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