FR2721681A1 - Process for constructing oil pipes and pipe produced - Google Patents

Abstract

The pipes (1) are each made up of two co-axial tubes (10, 20) between which is placed a filling casing (15). The casing (15) is made of insulating material and/or ballasting material. The casing (15) is not placed at the junction sections (26, 32) of the internal tubes provided at each of the two opposite longitudinal ends of the pipe or the internal tube (10). The pipe (1) also has a coupling sleeve (3) which slides on the outside tubes.

Description

 The present invention relates to the design and production of pipes, with particular reference, as a p-é ~ ered application, to pipes such as pipelines commonly called pipelines, which are installed at sea, to serve â convey fluids consisting in particular of petroleum products, in the form of gases or hydrocarbons' guides.

 To constitute such pipes, it is usual to use pipes which are prefabricated and brought to the site, on barge at sea ("off-shore"), and to connect them end to end on site, as and when measure that the pipe is laid in the open sea, passing step by step from a next ac pipe. To do this, we have already, if not used industrially, at least proposed or tried different techniques, both for the design of pipes and fittings as for the assembly and the implementation process.

 There is, however, one circumstance which does not appear to have been taken into account in all its dimensions.

 This is the apparent weight that driving must intrinsically present if one wants to avoid having to bury it at the bottom of the sea so that it does not move under the effect of waves and currents. But also, one cannot resolve this question without at the same time treating the difficulties which one meets on the level of the connections, in particular to ensure a uniform continuity in the mechanical and thermal properties along the finished pipe, or by neglecting the needs related to the marine environment and the temporary efforts to be faced during the mounting and laying of successive pipes.

 To these requirements of industrial practice, the invention provides a new solution, in particular in that the connection between two successive pipes implies a freely sliding sleeve but glued to the pipes at the junction between two successive pipes and / or by the the fact that the different pipes consist in their main part of two coaxial tubes, generally of steel, between which is interposed a filling by which they are both insulated and weighted, and preferably also made relatively impermeable to water. The fluid to be conveyed, consisting of a petroleum product in general, in the preferred application example, circulates inside the internal tube, or transport tube, while the external tube can be easily chosen to play the role of a protective tube protecting the intermediate filling from the aggressiveness of sea water and the shocks that the pipe is likely to have to undergo in c use bear.

 In accordance with one of the characteristics of the invention, the filling formed in the annular envelope space separating the two tubes from the pipes consists essentially of concrete, therefore of a cement binder coating stones and gravel as materials for load, concrete constituting a preferred ballast material.

 According to another characteristic of the invention, a filling material interposed between the coaxial tubes of the pipes consists essentially of a cellular material with closed pores, such as expanded glass or an equivalent plastic foam.

In this case, the pipe according to the invention finds advantage in the qualities of impermeability and insulation of this type of material. In particular, the water-repellent nature of glass or similar materials means that the slight leaks which can always occur through minimal cracks in the external tubes, or especially through the connections between successive pipes, do not propagate along the pipe. and do not go so far as to possibly attack the fluid transport tubes.

It is however more advantageous to combine the two preferred materials, by enveloping the waterproof heat-insulating material that is expanded glass, or a similar closed-pore material, with a ballast layer formed from concrete poured in the factory, the concrete also being able to serve as a binder coating separate blocks of expanded glass and ensuring the homogeneity of the filling envelope throughout the annular volume between the two tubes. In particular, the filling can thus consist of a concrete envelope layer, around '' an envelope of smaller diameter formed by blocks of expanded concrete, themselves embedded in a cement binder coating the whole and loaded in a different way, in particular with loads of smaller particle size
According to the invention, the internal conveyor tube is continuously extended at each of the longitudinal ends of the corresponding pipe, by a junction section where it is bare, beyond the current part of the pipe equipped with the intermediate filling and the external protective tube. .At this level, a connection device between two successive pipes in accordance with the invention involves, in addition to the joining sections of two pipes presented aligned end to end, its own filling envelope as well as a coupling sleeve intended to cover fitting assembly. This extends over a junction zone whose length covers not only that of the junction sections of the internal tubes, but also on either side, an end section of the external tubes corresponding to the current parts of the pipes. I1 is advantageously free sliding on the external tubes of the two pipes, at least on their end sections intervening in the junction zone.

 According to the invention, continuity of the mechanical and thermal properties of the pipe as a whole is ensured by selecting for the constituent elements of the connector substantially the same materials or materials equivalent to those used in the current part of the pipes. Thus, the coupling sleeve is preferably of cylindrical annular shape and made of steel, with a wall thickness equivalent to that of the external tubes of pipes.

 In this context and in accordance with a preferred alternative embodiment of the invention, a filling ring to be inserted on site, in the area of the two connecting sections of the internal tubes welded end to end, consists of rigid prefabricated elements, d thermal insulation and / or ballasting, advantageously made either of expanded glass or of similar plastics material with closed pores, or of cement, or even of a combination of these two materials. I1 seems that for the convenience of implementing the process which is the subject of the invention, it is particularly advantageous to produce such a filling ring from rigid staves or shells, in particular from two semi-annular elements each covering half of the circumference of the internal tubes, which are intended to be assembled on site, in particular by means of a compatible binder.

 On the other hand, it is desirable in the context of the invention that the sleeve is, at least on its inner face, with a substantially continuous and smooth surface, that is to say free from corrugations interfering with the outer surface of the protective tubes. This does not prevent that, without obstructing a capacity of free sliding on the pipes, its internal surface includes corrugations or other form of roughness facilitating the effects of plating and the adhesion of a filling having a function of binder as will be seen later. I1 advantageously has an inside diameter greater than the outside diameter of the outer protective tubes, so as to provide a clearance between the two, for example between 5 and 30 mm, and preferably between 10 and 15 mm. As a result, it is easy to slide the sleeve over the pipes to bring it into the appropriate position during the connection operations, regardless of any misalignment between the external tubes, often caused by manufacturing defects and / or by deviations from assembly during the welding of the internal tubes, and whatever the ovalization tolerances of the external tubes and of the coupling sleeve.

 According to another characteristic of the invention, in the concretization of which intervenes the advantageously provided clearance between the outside diameter of the outer protective tubes and the inside diameter of the coupling sleeve, the constituent elements of the pipes and of the connector are used for setting using a method according to the invention which, during assembly on site at sea, comprises a step making it possible to make each connection zone between successive pipes at best coherent with the current parts of these pipes and intimately linked with them. This stage consists in injecting under pressure a liquid binder, but fast hardening, in any space or interstice remaining free at the junction between two successive tubes. The injection is advantageously carried out through the wall of the coupling sleeve.

 According to preferred embodiments of the invention, such a binder, capable of hardening other than by evaporation of diluent only, can be of mineral nature, which will be the case of hydraulic binders of the cement family, or of mainly nature organic as are the compositions based on resins and adhesives hardening by polymerization, whether by the effect of free radicals, by that of promoters or crosslinkers, or by any other process. Examples of particularly advantageous organic resins include epoxy resins accompanied by an additional hardener and, where appropriate, a crosslinker, adhesives based on polyester resin, polyurethane resins and polymerizable elastomer resins. that such a list of binders is not limiting, it should also be understood that such binders can be used in the context of the invention in any combination in which they are technically compatible, the advantage of such combinations being, according to the cases, to reduce the costs, to improve the power of adhesion with respect to the steel, the glass, or the cellular material chosen, to reduce the time necessary for hardening, to improve the quality of the bonding by contact and resistance to friction stresses which arise when, as usual, the pipe being laid is subjected to tensile forces in the longitudinal direction.

 A particular embodiment of the invention will now be described in more detail which will make it better understand the essential characteristics and the advantages, it being understood however that this embodiment is chosen by way of example and that it is in no way limiting.

Its description is illustrated by the accompanying drawings, in which
- Figure 1 shows in longitudinal section a prefabricated pipe according to the invention.

 - Figure 2 shows two pipes end to end during on-site connection operations.

 - Figure 3 shows, still in longitudinal section, the same two pipes once connected.

 - Figure 4 shows a schematic cross-sectional view of the same assembly at the junction between the two pipes.

 - Figure 5 shows a sectional view similar to Figure 4, but this time through the middle or running part of a pipe.

 For the sake of clarity, the same elements will often be designated below by the same reference numbers and the representation of the drawings is schematic, without necessarily necessarily respecting the same scale in dimensions.

 In accordance with the invention in the particular embodiment described and illustrated by the figures, a pipeline for petroleum products, in particular for gaseous or liquid hydrocarbons, is mounted on site on a barge in the open sea, from series of pipes all identical to each other, by end-to-end connection of successive pipes which are added step by step to the pipe being installed at the bottom of the sea.

 The assembly being of the double-walled type and intermediate envelope made of thermal insulation and ballasting materials, each pipe is prefabricated in the factory and constituted as shown in FIG. 1. Between two coaxial cylindrical steel tubes, namely a conveyor tube internal 10 and an external protective tube 20, it can be seen that in practice, the envelope 15 for filling the intermediate annular space is formed from filling materials of two different types in the particular case under consideration.

 In fact, during manufacturing in the factory, blocks 22 of water-repellent cellular material, more particularly here of expanded glass, were placed on the internal tube 10, all around the latter, and then concrete, as a filling material with hydraulic cement binder, in the space left free between the blocks themselves and between the blocks and the tubes. By this, two concentric envelopes were formed, the first 16 around the inner tube being formed by blocks of expanded glass coated with concrete and the second being a continuous layer of concrete 23 against the inner surface of the outer tube.

 As it appears from FIG. 1, the external tube 20 is shorter than the internal tube 10. It extends over most of the length of the internal tube in all its middle part, constituting the current part of the pipe, but it leaves at the two opposite ends of the inner tube 10 two joining sections 26 and 27 where the inner tube protrudes from the outer tube and where it is devoid of any envelope. The intermediate filling consisting of the materials 22 and 23 stops at the ends of the external tube 20, suitable forms being temporarily placed at these ends when the concrete is poured.

Furthermore, it is useful to provide spacers 24 and 25, which remain in the finished pipe, while they are intended to hold the blocks 22 in place against the internal tube 10 and / or to keep the latter centered in the axis of the outer tube 20 during the pouring and hardening of the concrete.

 The blocks 22 are preferably made of expanded glass in the particular case described. This material has the advantage of being impermeable to water, which means that it retains its insulating properties in the event of seawater leaks which may occur through interstitial cracks in the tubes 20 or at the fittings. formed using the sleeves 3, over the years of use of the submerged pipe at sea. The lightness of this material means that it combines advantageously, in accordance with the invention, with concrete which serves both to drown everything and to ballast the pipes. Weight is an important asset for pipelines, because in many applications, it will avoid having to bury the pipe at the bottom of the sea to ensure its stability. As for the outer casing tube 20, it protects the material filling, and more particularly concrete, of the aggressiveness of sea water and impacts with rocks, anchors and various articles which can strike the pipe.

 It can be seen from FIG. 1 and from FIG. 5 that the blocks 22 are each of parallelepipedal shape, that they are placed end to end along the internal tube 10, and that in the particular case illustrated by FIG. 5, they each have a substantially square section.

It may however be useful, as a variant, to give them a trapezoidal shape, possibly limited by two arcs of circles, with cut sides or not, to better fill an annular space around the tube 10.

 Sizing may involve, for example, for pipes with common lengths of 12, or rather 24 meters, internal diameters of 150 mm, for internal tubes, from 300 to 400 mm for external tubes, with internal tubes protruding longitudinally from 100 mm the outer tubes at each end, taking into account the accessibility requirements for the welding operation, the layer of concrete around the insulation having a thickness of between 10 and 100 mm, in particular around 20 to 30 millimeters . It will be noted that the wall thickness of the external tubes can be relatively reduced, taking into account the fact that its impact and buckling resistance is reinforced by the concrete layer 23.

 If we now refer to Figure 2, we see two pipes II and 12 being connected end to end. The pipe 11 ends the pipe already in place and the next pipe is connected to it 12. Beforehand, a coupling sleeve 3 is engaged by the free end of the pipe 11. This sleeve is of cylindrical annular shape. , with an internal diameter leaving around the outer tubes 20 and 30 respectively of the pipes 11 and 12, a free sliding clearance, sufficient to be able to absorb their possible deformations, and in particular the effects of alignment tolerances and shrinking during welding operations.

Its internal surface, like the external surface of the tubes, is either truly smooth, or preferably rough to improve the effectiveness of the binder by adhesion and jamming. It is preferably of a thickness equal to or slightly greater than that of the outer tube.

 FIG. 2 represents the two pipes 11 and 12 at the moment when their respective internal tubes 10 and 31 have already been welded together in alignment with one another at 4, at the end of their respective joining sections 26 and 32 .

In the free space surrounding these junction sections between the ends of the respective external tubes 20 and 30, there is interposed a filling ring which we have admitted here that it consists of two half-shells 5 and 6. These half-shells shells being made in advance, are preferably made of hardened concrete. However, to improve the continuity of the properties of the pipe from one pipe to another, it is advantageous to provide for embedding in the concrete blocks of the same material as the blocks of expanded glass 23. In other cases, it is possible to make a similar ring consisting only of staves or blocks of expanded glass of appropriate shape and dimensions.

 The next step is to bring the sleeve 3 partially on the end of the pipe 12, so that it covers the entire junction area by its middle part. The length of the sleeve 3 is advantageously chosen, so that it then extends symmetrically over the end sections 33 and 34 of the outer tubes 20 and 30. Its length is chosen to be between 2 and 4 times their diameter. It is for example of the order of 3 to 3.5 meters for a pipe diameter of approximately 400 mm.

 Then, by injection orifices 7, 8 and 9 drilled for this purpose through the wall of the sleeve 3, a curable binder 18 is introduced under pressure, filling all the gaps and interstices remaining free around the filling ring ( possibly inside of it when it is formed from non-embedded blocks), between the two half-shells 5 and 6, between these and the connecting sections 26, 32 of the internal tubes 10, 31, and between the outer tubes 20, 30 (more precisely their end sections 33 and 34) and the sleeve 3 itself. Figures 2 and 3 it can be seen that for reasons of convenience, during injection the sleeve 3 is oriented circularly so that the injection holes are located at the bottom on pipes arranged horizontally during connection operations.

 The curable binder can be between light, lightly loaded and fluid concrete, if its composition ensures rapid hardening. However, preferably, it is a binder hardening by polymerization and chosen to have good adhesion on the steel constituting the tubes, for example based on polyester resin. Under the injection pressure, such a binder enters the freely sliding clearance left between the external tubes 20-30 and the sleeve 3 by flowing from the middle part towards the ends of the sleeve. To prevent it from overflowing outwards, inflatable seals are placed at its ends and removed once the binder has hardened. It should be noted, however, that it is not always essential for the binder to reach the ends of the sleeve.

 In this way, the invention makes it possible to ensure the desired inertia during laying and during the use of the pipe, homogeneously throughout the latter.

At the time of connection, the internal tubes welded together are sufficient to withstand most of the tensile stresses, while the thickness of the clearance which separates the coupling sleeve from the external tubes can be adapted in order to allow the binder filling this clearance, once hardened, then come and perfect the overall qualities of the pipe in use, by its resistance to friction and bending.

 Naturally, and as it already clearly follows from the above, the invention is not limited to the particular embodiments which have been described by way of preferred examples, of which it encompasses all the variants remaining within the scope of the claims of the patent.

Claims (10)

R E E N DI CAT IONS  1 / A method of constructing pipes such as pipes for petroleum products to be mounted in the open sea, according to which one connects step by step prefabricated pipes, characterized in that said pipes (1) each consist of two coaxial tubes (10 , 20) between which is placed, in the running part of the pipe, a filling envelope (15) of insulating material and / or ballast material, with the exception of connecting sections (26,32) of the internal tubes provided for each of two opposite longitudinal ends of the pipe where the internal tube (10) protrudes in length from the external tube (20), in that the internal tubes of a pipe already in place (11) are welded end to end 'a pipe to be connected (12), after having engaged on the pipe already in place a coupling sleeve (3) having a free sliding clearance on the external tubes of said pipes, elements (5,6) are interposed in material of insulation and / or ballasting re the opposite ends of the external tubes to form a filling ring (36) surrounding said junction sections, said sleeve (3) is then made to slide until it overlaps end sections ( 33,34) of the external tubes on either side of said ring, then a curable binder (18) is injected under pressure through the wall of the sleeve capable of filling the spaces remaining empty in the junction zone and to be bonded the sleeve on the end sections of the outer tubes.  2 / A method according to claim 1, characterized in that one uses as filling materials blocks of expanded glass and / or plastic foam with closed pores, surrounded and coated with concrete and / or a curable binder .  3 / Pipes to be connected to form a pipe by implementing the method according to claim 1, characterized in that they consist in the main part of two coaxial tubes (10,20), generally made of steel, between which is interposed a filling envelope (15) by which they are both insulated and weighted, and preferably further rendered impermeable to water, and in that the internal conveyor tube (10) extends continuously at each of the longitudinal ends of the corresponding pipe, by a joining section (26, 32) where it is bare, beyond the current part of the pipe equipped with the intermediate filling (15) and the external protective tube.  4 / Pipes according to claim 3, characterized in that the filling envelope separating the two tubes of the pipes consists essentially of concrete and / or blocks of expanded glass or other cellular material with closed pores embedded in concrete.  5 / Device for implementing the method according to claim 1, for the connection between two successive pipes of a pipe, each consisting of an internal fluid-carrying tube (10), an external protective tube (20) and an intermediate filling envelope ((15) interposed therebetween, characterized in that it comprises a coupling sleeve intended to cover the whole of the fitting, by implying, in addition to joining sections of the internal tubes (10 , 31) of two pipes presented aligned end to end in its middle part, and on either side, an end section (33,34) of the external tubes of said pipes, as well as a filling ring to occupy a annular space around said junction zones.  6 / Device according to claim 5, characterized in that said sleeve (3) is of cylindrical shape and in that it has a continuous and smooth internal face.  7 / Device according to claim 5 or 6, characterized in that @edit ring consists at least in part of rigid concrete elements which are embedded in a curable binder during cu connection of said pipes to each other.  8 / Device according to any one of claims 5 to - characterized in that said ring consists at least in part of rigid elements of cellular material im @ waterproof to @@ water which are embedded in a hardening binder during the connection of said pipes to each other.  9 / Device according to any one of claims 5 to 3, characterized in that said ring consists at least in part of rigid elements of expanded glass or plastic material with closed pores to be assembled and in that said elements are embedded in a curable binder when connecting said pipes to each other  10 / Device according to 1 any one of claims 5 to 9, characterized in that said sleeve (3) is free play. sliding on the outer tubes of said pipes.