EP1121551A1

EP1121551A1 - Assembly for constructing an underwater system for transporting fluid, energy or signals

Info

Publication number: EP1121551A1
Application number: EP99949055A
Authority: EP
Inventors: Claude Trichard; Eric Pirony; David Trimmings
Original assignee: Novoplastic SA
Current assignee: Novoplastic SA
Priority date: 1998-10-14
Filing date: 1999-10-14
Publication date: 2001-08-08
Also published as: BR9909413A; NO20011838D0; EP1129313A1; PL347185A1; ATE218683T1; NO20011838L; BR9909411A; CZ20011313A3; WO2000022332A1; FR2784734A1; NO20011839L; NO20011840D0; EP1121552A1; AU6207499A; CA2346566A1; DE69901729D1; EP1129313B1; DK1129313T3; WO2000022331A1; CA2346560A1

Abstract

The invention concerns a connection device (11) for sealingly assembling two elements (1a, 1b) of an underwater installation conduit (1), comprising concentrically an inner sheath (2) and an outer sheath (10). The invention is characterised in that it comprises a fitting including a single-piece sleeve (13), whereof the internal passage is adapted to be externally shrunk on sealed to said sleeve two tips, respectively at the two ends of the inner sheath (2) of the two elements (1a, 1b) to be connected, stripped of the outer sheath (10), and comprises at said sleeve (13) two tips two threads in opposite direction respectively, said sleeve (13) comprising on the outside, in a median region, at least a flat section (12), adapted to be clamped by rotating the sleeve (13) with a wrench.

Description

ASSEMBLY FOR THE CONSTRUCTION OF A UNDERWATER TRANSPORT NETWORK OF FLUID, ENERGY, OR SIGNALS

The invention relates to an assembly for building an underwater transport network for fluid, energy, or signals. By "fluid" is meant any body or substance in the liquid or gaseous state, under pressure, capable of being transported in any suitable conduit, sealingly separating said fluid from the outside, for example a pipe or a pipeline.

By "energy" is meant mainly but not exclusively electrical energy, for example a low or high voltage electric current, weak or strong, circulating by any suitable means, isolated from the outside, for example a mono- electric cable. wire or multi-wire.

By "signals" is meant any digital or analog signals supported by a physical quantity, for example optical, circulating in isolation from the outside, for example in a fiber optic cable.

Different circumstances require crossing any aquatic obstacle, such as a river, canal, lake, arm of the sea or ocean, or even an open channel or sewage system, to convey a fluid, energy, or signals, of one point to another.

To do this, different techniques are used to set up or implant submerged one or more composite installation conduits, in which the cables or pipes themselves are pushed, blown or pulled, for example electric cables or pipes .

In the case of small obstacles, the installation duct is put in place by sinking, that is to say by carrying out a directional drilling, passing under the obstacle, the installation duct being hooked to the drilling head, bypassing the obstacle.

As these are relatively long obstacles, the burial technique is currently preferred. This solution consists in burying the installation duct in the basement of the aquatic obstacle using a plow, which is a kind of plow pulled from the aquatic surface by all appropriate means such as boats.

Two techniques or methods of burial are thus known, called direct and indirect respectively. In the case of land transport networks, the installation conduit (s) are traditionally installed with civil engineering work, essentially consisting in digging a trench, installing the conduit in it, then filling the trench. Even if civil engineering can be more or less mechanized, this installation is today particularly expensive.

At the start of the present invention, the Applicant had the idea of using the aquatic networks existing on earth, natural or artificial, to have one or more installation conduits there, instead of proceeding by traditional civil engineering. From this idea, it remained to design a set of elements or components to obtain an installation network:

- likely to descend to the bottom of the water by gravity,

- waterproof vis-à-vis outside water, - and suitable for traction at the time of its installation either from the shore or from a boat.

This is the object of the present invention. A complementary and optional object of the present invention aims to immobilize and retain such a network on the submerged bottom. According to the invention, an assembly for the construction of an underwater transport network for fluid, energy, or signals, comprises at least two installation elements or conduits connected using a connection device, and a traction device for pulling on the duct (s), - each duct comprising an inner sheath surrounded by a sealing layer forming a peripheral ballast and optionally an outer sheath, the traction device comprising two elements put in place by screwing on the end of the duct, so as to enclose the wall of said duct over its entire periphery,

- And the connection device (s) being made in a single piece of the sleeve type, which has two opposite ends.

The present invention is now described with reference to the accompanying drawing, in which:

FIG. 1 schematically represents a sealed underwater network for the transport of fluid, energy, or signals, obtained by assembling the elements or components of the assembly according to the invention defined above,

FIG. 2 is a view in longitudinal section of an embodiment of the composite duct,

FIGS. 3 to 5 show, in cross section, four different embodiments of a composite installation duct according to the invention,

FIG. 6 represents, in axial or longitudinal section, a connection device in accordance with the invention placed on two adjacent ends of two installation duct elements, the latter also being in accordance with the invention,

FIGS. 7 and 8 represent, respectively, a longitudinal and axial section and a cross section through its middle of a connector belonging to the connection device shown in FIG. 6,

FIGS. 9 and 10 show, respectively in vertical axial section and in top view, a device for immobilizing on the underwater bottom, a duct element according to the present invention,

FIG. 11 represents a traction device according to the invention, placed in the free end of an installation duct according to the invention,

FIGS. 1 2 and 13 respectively show in axial and front section, the anti-creep ring of the device in FIG. 1 1,

FIG. 14 is a partial sectional view on an enlarged scale of detail A of FIG. 1 2, - Figure 15 is a cross-sectional view of another embodiment of the composite conduit.

Figures 1 6 and 17 schematically represent laying methods for an installation duct according to the invention. - Figure 18 shows in section an alternative embodiment of the connection device associated with the installation conduit according to the invention.

In accordance with FIG. 1, an earth structure 50 has been represented comprising a part immersed in an aqueous area, the bottom 17 of which is submerged by the latter.

It is on this bottom 17 submerged that is installed the installation network or underwater transport according to the invention, obtained by assembling the elements or components previously defined. In accordance with FIGS. 2 to 4, this network is obtained mainly with duct elements 1 of composite installation.

Each composite installation duct 1 includes:

- an inner sheath 2 obtained for example by extrusion of an appropriate plastic material, - and a peripheral ballast 3, integral outside and with the sheath 2, extending around and along the length of the latter, the weight per unit length of said conduit is determined to at least partially counteract the thrust generated by the displacement of the liquid volume of said conduit. The weight per unit length of the empty installation pipe 1 must therefore be greater than the mass of water displaced. The immersion of the conduit 1 should however not be too fast or too slow.

The laying system risks blocking on the one hand when the installation duct is too heavy and falls too quickly towards the bottom 17 and on the other hand when the installation duct 1 is too ^" light and is driven by the current. The optimal immersion speed depends on the advancement speed of the installation system and therefore on the installation method itself.

Advantageously, the weight differential of the duct 1. installation is between 10 and 30% of the weight of the displaced water, depending on the diameter of said duct and the installation method used. According to the embodiment shown in Figure 2, the peripheral ballast 3 is produced by helical winding around the inner sheath 2 of two metal strips 4 and 5, relatively heavy. Each strip 4 and 5 is wound by forming a gap 4a or 5a, that is to say by forming spiers 4b, 5b spaced apart and whose juxtaposed edges delimit spaces. This winding is carried out with covering of the internal interstices 4a by the external turns 5b of the external strip 5. The interstices 4a and 5a are filled with a sealing material 30, such as petroleum gel, powder or equivalent filling material opposing with the passage of water or other fluid, both longitudinally and transversely.

In accordance with the invention, the conduit 1 therefore comprises a sealing means comprising a metallic armor whose weight per unit of length is calibrated to contribute to or serve as a peripheral ballast 3.

The sealing means may also include a metallic strip 31, of small thickness disposed around and along the length of the inner sheath 2, the edges of which are contiguous and in a sealed manner (FIGS. 4, 5 and 1 5 for example). The sealing material 30 is more advantageously produced with a vegetable-based grease to meet the anti-pollution criteria and standards.

The sealing material 30 is advantageously made with a grease also coating the turns 4b, 5b so as to provide lubrication of a turn 4b relative to the other 5b. This contributes to obtaining flexibility properties of the installation duct 1. The lubrication of the turns 4b, 5b promotes a slight relative movement of the turns 4b with respect to the turns 5b, which appreciably improves the flexibility of the installation duct 1. This flexibility is very important for the winding of the conduit 1 on storage drums 54 and for its handling. The longitudinal seal, that is to say with respect to the water capable of infiltrating between the metal strips 4, 5, is ensured up to several tens of bars. Advantageously, the fats used are capable of absorbing hydrogen ions, originating from a hydrolysis of water and which are very harmful to optical cables, which absorb said hydrogen ions. This grease also serves as a lubricant vis-à-vis the relative movement of the turns between them and an outer sheath 10 for clamping disposed around the metal armor.

In accordance with the embodiment shown in FIG. 3, the peripheral ballast 3 is a metal armor, formed by a relatively heavy metal strip 6, entirely enveloping the sheath 2 and whose longitudinal edges are either contiguous, and for example welded, either overlapped and grouted with a layer 6a of synthetic material, forming part of the ribbon or subject to a specific contribution. The ribbon 6 is corrugated at 6b to give the reinforced tube, thus formed, the flexibility necessary for its implementation.

Of course, the metal of the peripheral ballast may or may not resist corrosion, and may for example be stainless steel.

According to the embodiments of Figures 4 and 5, the peripheral ballast 3 is a tubular lining surrounding the inner sheath 2. This lining comprises a plastic matrix 7, in which are distributed and embedded metal grains 8, themselves coated with a plastic material 9, different from that of the matrix and having a higher melting point than that of the plastic material of the matrix. This characteristic makes it possible in particular to coextrude, with the metal grains 8, and the inner sheath 2, and the tubular lining.

According to the embodiments of Figures 2, 3, and 4, the peripheral ballast 3 is covered by an outer sheath 10 also obtained by extrusion of a plastic material, for example integral and linked to the ballast. In the embodiment shown in Figure 2, the outer sheath 10 is used to retain the sealing material 30, in this case a grease and contributes to sealing. The outer sheath 10 is also a cohesion agent which maintains the metal armor (s), or an external tightening sheath. This or these metallic armors, in this case two relatively heavy helical sheet metal windings, in combination with the sealing material 30 gives remarkable longitudinal sealing to the duct 1. In addition, these metal armorings providing the peripheral ballast

3, also give the duct 1 according to the invention the necessary mechanical resistance with respect to centripetal compression forces, considerable pressures prevailing inside said duct 1 during blowing operations, inevitable shocks during laying said conduit 1, and pulling forces.

As the mechanical strength is ensured at least in part by the peripheral ballast 3, the installation duct 1 according to the invention has advantages, as remarkable as they are unexpected. Indeed, the outer sheath 10 provides a tightening envelope for the metallic armor and a confinement for the grease. This outer sheath 10 can thus have a relatively small thickness and does not necessarily contribute to mechanically reinforcing the duct 1.

Another very interesting consequence is that the internal sheath 2 can have less pronounced mechanical resistance properties than those usually required for underwater pipes. Again, it is the concentric peripheral ballast 3 which, by virtue of its mechanical resistance properties, of using an inner sheath 2 of smaller thickness, and if necessary less resistant and less expensive. Another remarkable advantage of the installation duct 1 according to the invention lies in its dimensions. The diameter and thickness of these installation conduits 1 is compatible with terrestrial installation conduits that mechanical, physical and chemical constraints much more marked during installation in underwater environment. The connection between a pipe 1 of underwater installation and a land pipe is thus carried out without difficulty.

In the embodiments of Figures 4 and 5, the transverse seal in each pipe 1 is provided by a metal strip 31, for example of aluminum which, of small thickness and weight, is independent of the means constituting the ballast 3. This strip is coated on one face with a plastic material the melting point of which is at most equal to that of the plastic material making up the subsequent layers of the conduit and for example of the outer sheath 10 to Figure 4 and the lining 7 in Figure 5. It is arranged longitudinally on said lining 7 or on the inner sheath 2, and so that its longitudinal overlapping edges are grouted by melting the plastic coating during l extrusion of the external layer, namely, sheath 10 and lining 7, respectively for FIGS. 4 and 5. In FIG. 1 5, showing an alternative embodiment of the peripheral ballast 3, it is made up of metallic elements, such as wires or blades 32, of circular, flat, trapezoidal or lozenge cross section, helically wound around the sheath 2, or around an intermediate sheath 2a, making it possible to fix and maintain the longitudinal edges of a metallic strip 31 in sealing contact, having the same structure and the same function as that 31 of the embodiment given with reference to FIGS. 4 and 5.

The intervals between blades or wires 31 are filled with sealing material 30. The assembly is protected by the outer sheath 10 made of synthetic material.

The outer sheath 10 is for example made of polyethylene and polyamide in one or other of the exemplary embodiments of the installation duct 1.

Consequently, according to the invention, the installation duct 1 is composite, and makes it possible to have there, by drawing, blowing, or pushing, any tube or cable, represented by the reference numeral 29 in FIGS. 2 to 5 and 1 5 .

In accordance with FIGS. 6 and 7, the connection device 1 1 comprises a connector 12 for sealingly assembling two elements 1 a and 1 b of conduit 1. Depending on the environment, saline or not, this connector 1 2 is made of metal, or of synthetic material. The connector 12 is preferably made with a stainless steel metallic material, or an aluminum protected by a surface treatment. It comprises a cylindrical sleeve 13, comprising two opposite ends 14a and 14b for the tight fitting of the two ends 2a, 2b of the two inner sheaths 2 of the two adjacent duct elements 1a and 1b, respectively. Each end piece 14a and 14b includes, internally and going from its free end to half the length of the sleeve 13, an inlet chamfer 13a, a cylindrical bore 13b with a groove for an O-ring 33, a threaded part 13c, with an identical pitch but in the opposite direction to that of the other end piece 14a, 14b, and a stop face 13d. The seal 33 and the thread 13c cooperate with the internal sheath 2 of the duct 1, sheath previously stripped over a short length, as shown in FIG. 6.

The connection device 1 1 according to the invention is remarkable in the sense that the sleeve 1 3 consists of a single piece, in which are fitted O-rings 33, which it suffices to turn to obtain a tight connection between the two elements 1 a, 1 b of conduit 1 for installation.

According to another exemplary embodiment of the connection description 1 1 according to the invention but not shown in the figures, the O-rings 33 can be replaced by a sealing material attached to the inner sheath 2 or in each end piece 14a, 14b. As shown in Figures 7 and 8, the connector 1 2 has a central region 1 2a in which the flats 12b give it a polygonal transverse shape, for example hexagonal, allowing the clamping of the connector 12 on two inner sheaths 2, arranged in the extension one from the other. The connection device 1 1 also includes two sheaths

1 5 made of heat-shrinkable plastic. Each sheath 15 is heat-shrunk on the end of each of the duct elements 1 to provide mechanical protection for the peripheral ballast 3 and possibly the outer sheath 10 and to avoid, during the pulls exerted on this duct to move it, that foreign bodies are inserted between the armor or ballast 3 and one or other of the sheaths 2 and 10. Each sheath 1 5 also ensures, at least at low immersion pressures, the tight protection of the components of the duct 1 . In accordance with the invention, the thickness of the sleeve 14 is adapted to match its cylindrical outer surface, substantially with that of the outer sheath 10.

According to an alternative embodiment according to the invention and shown in Figure 18, the two sheaths 1 5 can be replaced by a single heat-shrinkable sheath fitted on a conduit element 1 a, 1 b before mounting the device connection 1 1. After the installation of the connection device 1 1, in this case the screwing of the connector 1 2 on the two ends 2a, 2b of the two inner sheaths 2, the heat-shrinkable sheath is slid on the conduit 1 so as to cover on the one hand the connection zone between the elements 1, 1b of the conduit 1 and the sleeve 13, and on the other hand the sleeve 13 itself.

The assembly of several installation duct elements 1 using connection devices 1 1 is therefore liable to undergo significant mechanical forces, insofar as said assembly can have a length ranging from 0.5 to 2 kilometers, for example for the indirect burial method.

The good mechanical strength between the different elements 1 a, 1 b and the connection devices 1 1 is all the more remarkable since the connectors 12 are screwed directly onto the internal sheaths 2, which do not in themselves provide due to the 'localized absence of peripheral ballast 3, sufficient mechanical strength in relation to the stresses and shocks they could undergo. The use of a connection device 1 1 according to the invention in association with a pipe 1 of installation as described previously thus gives surprising results by their reliability within the framework of the methods of installation in underwater environment.

In accordance with FIGS. 9 and 10, a device 1 6 for immobilizing the underwater bottom is obtained, essentially, by molding concrete, the quality of which is suitable for immersion in an aqueous medium. This device comprises a heavy base 18, the lower face 18a of which is concave and surmounted by a part 18F in the shape of a stud, crossed by a through hole 18g, allowing its suspension. Different means 19a, 19b, 19c, in the form of hooks, are provided for fixing an installation duct 1 to the base 1 8. Holes 18b to 18e pass through the base 18, from its lower face to its upper face, for the passage of water during the immersion of the device 16 immobilization. Anchor peaks 20 are distributed around the periphery of the base 18.

The orifices 18b to 18e all advantageously have the same configuration, for example in an arc, and the same dimension. The holes 18b to 18e are also provided in the base

18 isotropically and around an axis of symmetry parallel to the direction of descent towards the bottom 17.

The concavity of the lower face 18a in combination with these orifices 18b to 18e therefore makes it possible to obtain perfect immersion guidance of the immobilization device 1 6. The descent to the bottom 1 7 of the river is thus ensured with better precision, and this thanks to a homogeneous flow of water through the orifices 18b to 18th.

Such an immobilization device 1 6 makes it possible to maintain the conduits 1 on the bottom 17 of the underwater environment, in particular by anchoring on the bottom 17 using anchor peaks 20.

The traction device 21 shown in Figure 1 1 is composed of a core 22, and an outer ring 23. The core 22, of generally cylindrical shape, includes a tapered frustoconical part 22a and, in the extension of the part of small diameter of the cone, a cylindrical part 22b provided with a groove for an O-ring seal 25. The core 22 is extended, beyond the part of large diameter of the cone, by a draw rod 24 provided with 'a hooking eye 24a. This core 22 has diametrical dimensions allowing it to be screwed inside the inner sheath 2.

As a variant of the traction device 21 according to the invention, the cylindrical part 22b provided with a groove by an O-ring seal 25 can be eliminated or replaced by an elongation of the threaded frustoconical part 22a.

As shown in more detail in FIGS. 12 and 13, the outer ring 23, of generally cylindrical outer shape, is provided, at one of its ends, with a hexagonal collar 26 to ensure its wedging in rotation by means of a key. Internally, and starting from this collar 26, it comprises an inlet chamfer 23a, a smooth cylindrical bore 23b, a threaded bore 23c, a clearance groove 23d and an internal shoulder 23e, forming engagement stop. FIG. 14 shows that the threading of the outer ring 23 has a cross-section in a right triangle and therefore forms helical notches 27 opposing all movements in the direction of the arrow 28 of the peripheral ballast 3 or of the outer sheath 10 of the conduit 1 around which the outer ring 23 is arranged. Other threads than that described in FIG. 14 may also be suitable without departing from the scope of the present invention.

When the device is mounted on the end of a duct 1, the outer ring 23 is first placed around this end, possibly as far as the stop of its shoulder 23e on the end face of the duct 1, then the core 22 is engaged, and screwed into the conduit 1. This has the consequence of compressing the wall or walls of the elements making up the conduit 1 between the two threads, respectively 22a of the core 22 and 23c of the ring 23, and ensuring, by encrustation of these threads in said walls, the mechanical connection positive between said conduit 1 and the traction device 21. The seal thus obtained is if necessary doubled by the seal 25.

This very simple assembly is carried out on the installation site and provides an excellent mechanical connection, but also the desired seal in an underwater environment. When moving the conduit 1 by pulling on the device

21, the components of this duct 1 cannot escape by creep since, on one side, they are prevented by the teeth 27 and, on the other side, by the shoulder 23e of the outer ring 23.

The establishment of such underwater networks is carried out using for example existing burial methods.

The direct burial method is thus known, shown diagrammatically in FIG. 16, which consists in burying the installation conduit 1 in a trench 17a dug in the bed of a river 51 using a plow 52 carrying an inert or vibrating bag. This plow 52 is towed by a barge 53 on which the installation duct 1 is stored. The latter is wound on drums 54. The barge 53 is itself pulled by a cable 55 fixed on a tug 56 located substantially in the middle of the river 51 and anchored at the bottom 17. The cable 55 fixed on the tug 56 by the through a winch 57 which makes it possible to pull and move the barge 53 as well as the plow 52.

There is also known an indirect burial method, shown diagrammatically in FIG. 1 7, in which for example several installation conduits 1 are assembled or tied up on a barge 53.

The assembly is then brought to the bed of a river 51 where it is supported on the surface by balloons 60. The conduits 1 are connected to a connection pontoon 61 on the surface to achieve lengths of approximately 0.5 to 2 kilometers. Once in the vertical position of the landfill line, the conduits 1 are poured by removing the balloons 60.

When the bundle of conduit 1 rests on the bottom 17 of the river, a water jet plower allows the bundle of conduits 1 to be buried. The conduits 1 are cast and rest on the bottom 17, at the location identified by the reference 50a.

An anchoring system or an immobilizing device 16 making it possible to keep the beam in place, can also be used in one or other of the methods, replacing burial, when there is no risk of dredging and when the currents are very weak.

It is particularly important to implement such methods, to have conduits 1 whose immersion speed is perfectly controlled so as to avoid blockages of the laying mechanisms. The burial speed and the forward speed of the burial train are therefore linked to the weight of the duct 1, said weight determining its immersion speed.

Furthermore, it is of great importance to be able to connect two conduits 1 easily using the connection device 1 1 either on the barge 53, or on the bottom 17 in the event of accidental rupture. It is also essential to pull on the conduits 1, with a large force to end up two conduits 1 intended to be connected. Such positioning is obtained in a simple and reliable manner with the traction device 21.

Claims

1 / Assembly for the construction of an underwater transport network for fluid, energy, or signals, comprising at least two installation conduits (1) connected using a connection device (1 1) , and a traction device (21) for pulling on the conduit (s) (1),

- each conduit (1) comprising an inner sheath (2) surrounded by a sealing layer forming a peripheral ballast and possibly an outer sheath (10), - the traction device comprising two elements put in place by screwing on the end of the conduit (1) so as to enclose the wall of said conduit (1) over its entire periphery,

- And the connection device (s) (1 1) being made in a single piece of the sleeve type (13), which has two opposite ends (14a, 14b), which are capable of being screwed onto each of the internal sheaths (2) .

2 / assembly according to claim 1, characterized in that it comprises an immobilization device (16) of the duct or conduits (1) for installation on the bottom (17) of the river (51). 3 / assembly according to claim 1 or 2, characterized in that it comprises a heat-shrinkable sheath (15) capable of covering the entire connection area between two conduits (1) of installation connected.

4 / assembly according to any one of claims 1 to 3, characterized in that sealing means, of the O-ring type (33) are reported in each end piece (14a, 14b)

5 / assembly according to any one of claims 1 to 4, characterized in that it is used to implement the direct burial method or the indirect burial method in which the connections of elements (1 a, 1 b) of conduit (1) can be made on the surface or at the bottom (17) of the river.