WO2020217018A1

WO2020217018A1 - Continuous thermal insulation of pipes for transporting fluids

Info

Publication number: WO2020217018A1
Application number: PCT/FR2020/050678
Authority: WO
Inventors: Renaud DASSONVILLE; Raphaël DAUPHIN; Henri-Jacques Wattez
Original assignee: Perenco
Priority date: 2019-04-24
Filing date: 2020-04-21
Publication date: 2020-10-29
Also published as: FR3095491A1; CO2021014095A2; TN2021000215A1; FR3095491B1; BR112021021249A2; MX2021012959A; GB2597188A; GB2597188B

Abstract

The invention consists in an insulated pipe (1) for transporting fluids, comprising at least a plurality of insulated-pipe (1) sections comprising an internal pipe (2) that is able to transport a fluid and is inserted coaxially in an external sheath (3), said external sheath (3) and said internal pipe (2) forming, between one another, an annular zone (4) for insulating the fluid transported in the internal pipe (2) from the outside environment surrounding the external sheath (3). The two ends (5; 6) of the internal pipe (2) are able to be connected mechanically to the ends (5; 6) of the internal pipes (2) of other insulated-pipe (1) sections, and the two ends (7; 8) of the external sheath (3) are able to be connected mechanically to the ends (8) of the external sheaths (3) of other insulated-pipe sections.

Description

Continuous thermal insulation of pipes for transporting fluids

The present invention relates to a thermally insulated pipe for transporting a fluid, for example oil or gas, and a method of assembling such a pipe.

The invention applies in particular to installations for the production of crude oil, on land or at sea, but more generally it also applies to the transport of any effluent which cannot be exported at ambient temperature or whose cooling would reduce, for example, the efficiency of treatment downstream of the production area.

Such installations require the installation of conduits between the well heads and the facilities for treating fluids produced (oil, water, gas) or injected (water, gas), and between these treatment facilities and the export terminals or importation of treated effluents. These pipes have lengths which can range from a few tens of meters to a few kilometers or even tens of kilometers.

Depending on the characteristics of the effluent transported and the ambient conditions in which the pipes are operated, it may be necessary to maintain a minimum temperature inside the pipe during the circulation of the effluent transported and in the event of stopping the flow of water. effluent in the pipe.

Ensuring a minimum circulation temperature will limit the pressure drops in the pipe by maintaining the viscosity of the effluents transported at levels lower than those which would result from the temperature of the ambient environment in which the pipe is installed. In addition, maintaining the transported effluent at a sufficiently high temperature will prevent, or at least limit, solid deposits on the inner wall of the pipes. For example, by keeping the temperature in the pipe above the temperature at which the paraffins appear.

Ensure a minimum temperature in the event of traffic stopping for a period sufficient to allow either re-circulation or Draining the line will prevent clogging of the lines. For example, this can happen in the case of formation of paraffins during the transport of an effluent containing hydrocarbons with a high paraffin content, or in the case of the formation of gas hydrates for the transport of an effluent containing gas and water under pressure.

Many solutions exist for maintaining such pipes at temperature. Known solutions consist in maintaining the temperature either by reheating (one speaks of active solutions) or by insulation (one speaks of passive solutions).

The object of the invention relates more particularly to so-called passive solutions for maintaining the temperature inside the pipe by its insulation. The invention relates more specifically to the structure and implementation of insulated subsea pipelines, although, of course, it can also be implemented on land.

For simple subsea pipelines, different passive insulation solutions exist. One of the known passive solutions consists in applying to earth, most often in the factory, an insulating material directly on sections of steel tubes. In this case, the insulating material must resist the external environment of the pipe, in particular sea water and the external pressure applied to the pipe when it is underwater. The factory-installed insulation may be a pressure-resistant foam or plastic material. Factory insulated pipe sections have

necessarily lengths limited to about 12 m in general. These insulated tubes can then be pre-assembled in sections of a few tens of meters on land. This pre-assembly is commonly carried out by welding between the sections of tubes and then by thermal insulation of the welded zone by adding, for example, localized insulation. This pre-assembly makes it possible to achieve the greatest length that can be handled by boats or barges laying underwater pipe. This length depends on the selected installation support and can be approximately 12 m, 24 m or 48 m depending on the number of pre-assembled pipe sections. These insulated tubes can also be assembled in sections of greater lengths in the case of a so-called installation. “Unwound”, but here again, this requires welding at each joint and the reconstitution of the thermal insulation at the welded joints.

Another known passive solution consists in applying to land, also usually in the factory, an insulation that is not resistant to sea water or to external pressure on the sections of steel tubes forming the pipe. In this case, the insulation is then encapsulated in a sheath which is able to withstand the pressure. Most often, it is another steel tube forming by welding at the ends of the tube to isolate a sealed annular space between the inner tube (the pipe) and the outer tube (the sleeve). These prefabricated isolated sections are also typically about 12m, 24m or 48m in length. They can also be assembled in sections of greater lengths in the case of “unrolled” installation. Again, this requires two welds at each joint since it is necessary to weld together the tubes forming the pipe and also the tubes forming the sleeve which surrounds the pipe and its insulation.

In both cases, with the exception of unrolled laying, the pre-assembled insulated tube sections, of variable but limited length

(generally around 12 m, sometimes around 24 m or 48 m), are then transported and then assembled together on site to form the pipe. This final assembly is achieved by welding the ends of the sections placed end to end. These welding operations are generally carried out on the laying boat or barge. After the pre-assembled pipe sections have been welded together, it is still necessary to isolate the weld area. The insulation of the weld area is carried out a posteriori by fixing an insulating piece attached or by casting the insulating piece in place around the pipe.

Document FR 3 056 628 A1 describes the assembly of an insulated pipe of the pipe-in-pipe type by connecting pipe sections to one another. The pipe sections consist of an internal casing and an outer casing held concentrically between them by anti-slip and self-centering devices. These devices allow, only when they are deactivated, a sliding limited by shoulders between the inner shell and the outer shell. The ends of the inner shell and the outer shell of one section of pipe are mechanically welded to the respective ends of the inner shell and outer shell of another section of pipe.

Document FR 2 879 715 A1 describes the assembly of an insulated pipe of the pipe-in-pipe type by interconnecting several pipe sections. These pipe sections each consist of an internal pipe and an outer casing. They are interconnected by means of forged junction pieces assembled at the ends of the internal pipes and external shells by welding. Then the junction pieces facing each other are also connected to each other by welding.

In the case of unrolled laying, sections of isolated pipe of several hundred meters or even a few kilometers can be laid at once. However, this requires both large infrastructures on land to pre-fabricate these insulated sections and store them on large coils or carousels, and dedicated laying means which are heavy and very expensive. Moreover, these heavy means are very specific and only present in certain geographical areas, which makes their mobilization even more expensive when it comes to installing a pipe far from existing infrastructure.

These existing methods are both expensive and time consuming to implement. Indeed, they first of all require the prefabrication of pre-insulated pipe sections in factories or specialized sites on land. This prefabrication includes welding and installation of insulating materials. Then, it is necessary to carry out the welding on site of these prefabricated sections as described above, or to implement the laying techniques in unrolled which require heavy specific means both on land and at sea. Finally, it is necessary to insulate after welding the cold spots created at each welded joint between the prefabricated or assembled sections at sea. The object of the invention is to provide a solution for the passive insulation of pipes that is significantly less expensive and easier to implement than the known passive solutions.

To this end, a first aspect of the invention consists of an insulated pipe section for transporting fluids comprising an internal pipe capable of transporting a fluid, inserted coaxially in an outer sleeve, said outer sleeve and said inner pipe forming between them a zone annular allowing the fluid transported in the internal pipe to be isolated from the external environment surrounding the external sheath. A first end and a second end of the internal pipe are each adapted to be

assembled by mechanical seamless connection respectively to a second end of an inner pipe of a second insulated pipe section, and to a first end of an inner pipe of a third insulated pipe section; and a first end and a second end of the outer sleeve are each able to be assembled by mechanical seamless connection respectively to a second end of an outer sleeve of the second insulated pipe section and a first end of the outer sleeve of the third section isolated driving.

Thus, insulation is obtained continuously by assembling the tubes directly on site, without requiring welding or creating cold spots in the main part of the pipe.

Advantageously, the first and second ends of the internal pipe have complementary configurations capable of allowing their interlocking respectively with the second and first ends of the internal pipes to which they are intended to be connected.

Preferably, the first and second ends of the outer sheath have complementary configurations suitable for allowing them to fit together with the second and third ends of the outer sheaths to which they are intended to be connected. Preferably, the inner pipe is slidably mounted in the outer sheath.

Advantageously, the length of the outer sheath is substantially equal to that of the inner pipe after connections.

Preferably, the annular zone located between the inner pipe and the outer sheath is held by at least one spacer housed in the annular zone, and made of a thermally insulating material and facilitating sliding between the inner pipe and the outer sheath.

Advantageously, a thermal radiation barrier is applied to the outer face of the inner pipe and / or the inner face of the outer sheath.

According to a second aspect of the invention, there is provided an insulated pipe for transporting fluids which is made by successive mechanical connections of internal pipes and outer sleeves of the isolated pipe sections as defined above.

Advantageously, the insulation is provided by the formation of a partial air vacuum in the annular space formed by the continuous junction of the annular zones separating the internal pipes from the outer sleeves of the pipe sections assembled together.

Thus, the annular space can be the subject of a partial vacuum from one end of the pipe after the pipe has been laid without underwater intervention or offshore means.

Preferably, the insulated pipe further comprises an intermediate internal pipe having a first end capable of being connected to the second end of the internal pipe of the last insulated pipe section and an intermediate outer sleeve having a first end capable of being connected to the second end of the last section of pipe insulated and mounted on the intermediate internal pipe so as to take up the tensile and compressive forces, and whose respective lengths are adapted to accommodate the difference in length between all the internal pipes connected between them and all of the external sheaths connected to each other. Advantageously, the insulated pipe also comprises an insulated pipe initiation section capable of being connected by a second end to the first end of the internal pipe and to the first end of an outer sheath of the first insulated pipe section in order to hermetically closing one of the ends of the annular space, and having at one end a pipe start fixing flange; and an insulated pipe termination section adapted to be connected by a first end to the second end of the intermediate inner pipe and to the second end of an intermediate outer sleeve in order to hermetically seal the other end of the annular space, and having at a second end a pipe termination fixing flange.

According to a third aspect of the invention, there is provided a method of assembling an insulated pipe for transporting fluids as defined above, which comprises the following steps:

• an approach step from an isolated pipe section to

assemble to one or more pre-positioned pipe sections;

• a step of connecting the internal pipe in which the first end of the internal pipe of an insulated pipe section to be assembled is mechanically connected without welding with the second end of the internal pipe of a pre-insulated pipe section

positioned;

• an external sheath connection step in which the first end of the outer sheath of an insulated pipe section to be assembled is mechanically connected without welding with the second end of the outer sheath of a pre-positioned insulated pipe section; and

• repeating the above steps to assemble at least one section of isolated pipe to the last section of isolated pipe

previously assembled.

Advantageously, the method of assembling an insulated pipe for transporting fluids further comprises the following steps: • before the step of connecting the internal pipe, a first sliding step of the outer sleeve of the pipe section to be assembled in order to release the first end of the internal pipe to be connected; and

· Before the step of connecting the outer sleeve, a second sliding step of the outer sleeve of the pipe section to be assembled towards the outer sleeve of the already assembled pipe section.

Preferably, the assembly method further comprises the following steps:

· A step of connecting a first end of the intermediate internal pipe to the second end of the internal pipe of the last insulated pipe section;

• a step of inserting the intermediate outer sheath around the intermediate inner pipe; and

· A step of connecting a first end of the intermediate outer sheath to the second end of the outer sheath of the last section of insulated pipe.

Advantageously, in the assembly method:

• the first step is to assemble the first insulated pipe section to the initiation pipe section; and

• the last step is to assemble a second end of the intermediate inner pipe and a second end of the intermediate outer sleeve to the termination pipe section.

Preferably, the assembly method further comprises a step of establishing a partial air vacuum in the continuous annular space formed by the connection of all the annular zones of the pipe sections connected to each other.

It should be noted that the efficiency of the insulation compared to its low cost of implementation makes it possible to consider other applications for the insulation of pipes than those conventionally envisaged with existing technologies which are reserved for the transport of pipes. 'non-exportable effluents at room temperature and with high added value. For example, the It is conceivable to implement the invention in order to conserve heat and thus allow better efficiency of a separation process downstream of the pipe. Due to the low cost of the invention, even if the effluent could be transported in an uninsulated pipe without this leading to excessive deposition or pressure drops, it is possible to envisage its isolation.

Other characteristics and advantages of the invention are demonstrated by the following description of non-limiting examples of embodiments of the various aspects of the invention. The description refers to the appended figures which are also given by way of non-limiting exemplary embodiments of the invention:

[Fig. 1] Figure 1 shows schematically an isolated pipe diagram in partial section;

[Fig. 2] Figure 2 shows a side view in partial section of an isolated pipe section;

[Fig. 3] Figure 3 shows a side view in partial section of an insulated pipe initiation section;

[Fig. 4] Figure 4 shows a side view in partial section of an insulated pipe termination section;

[Fig. 5a] Figure 5a shows the method of assembling a first insulated pipe section to an insulated pipe initiation section;

[Fig. 5b] FIG. 5b represents a first step of the method

assembly of the constituent sections of an insulated pipe;

[Fig. 5c] FIG. 5c represents a second step of the method

assembly of the constituent sections of an insulated pipe;

[Fig. 5d] FIG. 5d represents a third step of the method

assembly of the constituent sections of an insulated pipe;

[Fig. 5e] FIG. 5e represents a fourth step of the method

assembly of the constituent sections of an insulated pipe;

[Fig. 5f] FIG. 5f represents a fifth step of the method

assembly of the constituent sections of an insulated pipe; [Fig. 6a] FIG. 6a shows a side view of an intermediate internal pipe;

[Fig. 6b] Figure 6b shows a side view of an intermediate outer sheath;

[Fig. 7a] Figure 7a shows the method of assembling the intermediate internal pipe to the last section of isolated pipe;

[Fig. 7b] FIG. 7b represents a first step of the method

assembly of the intermediate outer sleeve to the last section of insulated pipe;

[Fig. 7c] FIG. 7c represents a second step of the method

assembly of the intermediate outer sleeve to the last section of insulated pipe; and

[Fig. 7d] Figure 7d shows the method of assembling the termination section of an insulated pipe to the intermediate inner pipe and the middle outer sleeve.

In the following, the description of the invention is given in the context of an isolated subsea pipe intended to transport an effluent of petroleum origin from an extraction well to a processing terminal. This context of implementation of the invention is described only to facilitate understanding of the invention, but can in no way be considered as limiting for it. The same is true for all the other examples of implementation of the various characteristics constituting the invention described below for illustrative purposes only.

Figure 1 shows an isolated pipe obtained by assembling several sections of isolated pipe 1. Indeed, an isolated pipe section 1 has a limited length, generally between one and several tens of meters, it is therefore necessary to connect a sufficient number of insulated pipe sections 1 to cover the distance between the upstream and downstream terminals of the pipe to which it is directly connected. The connection upstream of the insulated pipe, for example with a wellhead on an offshore platform, is made by a pipe start fixing flange 32 which is connected to the first insulated pipe section 1 by a pipe section d. 'initiation 10 (see figure 3). The downstream connection of the insulated pipe, for example with a feed point of a processing terminal, is made by a termination flange 29 which is connected to the rest of the insulated pipe by a pipe termination section 25 ( see figure 4). Overall, the insulated pipe is in the form of an inner tube enveloped by an outer tube with an annular space formed between these two tubes. This annular space makes it possible to thermally isolate the fluid transported inside the inner tube from the ambient medium surrounding the outer tube. In fact, in the case of an underwater pipe, the temperature prevailing around the pipe increases the viscosity of the fluid transported and can cause the formation of solid residues, for example the paraffin contained in the fluid if the latter is a hydrocarbon, or gas hydrate formation, which may clog the line.

FIG. 2 shows an insulated pipe section 1 constituting the pipe before its assembly. The insulated pipe section 1 is in the form of a double-cased tube comprising an internal pipe 2 located coaxially inside an outer sheath 3. An annular zone 4 is thus formed between the inner pipe 2 and the sheath. external 3. In fact, to assemble two contiguous isolated pipe sections 1, the two internal pipes 2 and the two outer sheaths 3 facing each other are mechanically connected. Thus, the junction of the annular zones 4 forms a continuous annular space between the inner tube and the outer tube of the insulated pipe as illustrated in FIG. 1. In order to ensure good insulation of the fluid transported in the insulated pipe, the annular space can be filled with an insulating material or, as described below, the insulation can also be obtained by generating an air vacuum. partial in the annular space.

The assembly of the isolated pipe sections 1 is based on the modularity of the pipe. For this, the length of the outer sleeve 3 is substantially equal to that of the inner pipe 2.

The inner pipe 2 and the outer sheath 3 are typically made of steel. However, other materials can be used, for example, depending on the stresses induced by the environment in which the pipe is laid, or by the physicochemical characteristics of the fluid to be transported. The assembly of the insulated pipe sections 1 is carried out on a single assembly station, called a “station”, by mechanical connection without welding of the two ends facing the two insulated pipe sections to be assembled. As shown in Figure 2, the inner pipe has at its two distal ends 5 and 6, on one side a female connector 5 and on the other side a male connector 6. Similarly, the outer sheath 3 has at its two ends distal 7 and 8, on one side a female connector 7 and on the other side a male connector 8. For convenience, the female connectors 5 and 7 are all on the same side of the insulated pipe section 1 and the

male connectors 6 and 8 on the other side but an alternate configuration is also possible.

Thus, the assembly of the isolated pipe sections 1 is achieved by successive and reciprocating interlocking of the internal pipes 2 intended to transport the fluid and which therefore resist the internal pressure exerted by the transported fluid, and of the external sleeves 3 which resist the pressure. ambient pressure and which also allow the resumption of the installation forces of the assembly formed by the internal pipes and their external sheaths.

The annular zone 4 formed between the internal pipe 2 and the external sheath 3 is guaranteed by spacers 9 made of a material which does not conduct much heat, such as for example polyethylene or

polyurethane, which makes it possible to limit local heat losses by conduction at the points of contact between the spacers 9 and on the one hand the outer surface of the internal pipe 2 and on the other hand the inner surface of the outer sheath 3. These spacers 9 are fixed to the outer surface of the inner pipe 34 and provide a low coefficient of friction with the inner surface of the outer sleeve 37 so as to allow relative movement of the inner pipe 2 in the outer sleeve 3.

As indicated above, the insulation is obtained by making an air space in the annular zone 4 separating the internal duct 2 from the external sheath 3. Additionally, the insulation can be improved by making a partial vacuum in the same annular zone 4.

Additionally, the insulation is improved by the installation of a barrier anti thermal radiation (not shown) which can be obtained, for example, by a reinforced aluminum foil wound on the outer surface of the internal duct 34, or by a suitable coating (aluminum or equivalent) applied thereon or on the internal surface of the outer sheath 37, or on both. Other methods of making a thermal radiation barrier are also possible.

FIG. 3 shows an initiation pipe section 10. As indicated above in relation to FIG. 1, the initiation pipe section is intended to provide the mechanical connection with the terminal through which the assembly of the pipe is started. the driving. This connection is made by the start-of-pipe fixing flange 32. The point of initiation of the assembly of the insulated pipe may be located upstream of the pipe or downstream depending on the direction of flow of the fluid to be transported in depending on what will be most practical for laying the insulated pipe. The start-of-pipe clamp 32 is located at a distal end 12 of an inner initiation pipe 11 of the initiation pipe section 10. The other distal end 13 of the inner initiation pipe 11 is. configured to fit on the shape

complementary configured at the antagonistic distal end of the internal pipe 2 of the first insulated pipe section 1 to be assembled. In Figure 3, the distal end 13 of the inner initiation pipe 11 is a male connector but it could just as easily have been a female connector. The inner initiation pipe 11 is partially enveloped by an outer initiation sheath 14, the distal end of which 15 located on the side of the start of the pipe fixing flange 32 is connected to the inner initiation pipe 11 in order to 'ensure the sealing of the annular space on the side of the insulated pipe through which its installation is initiated. The connection between the outer initiation sleeve 14 and the inner initiation pipe 11 can be made in different ways such as welding or crimping. The other distal end 16 of the outer initiation sheath 14 is configured to interlock with the complementary shape configured at the opposing distal end of the outer sheath 3 of the first insulated pipe section 1 to be assembled (see FIG. 1). In Figure 3, the distal end 16 of the outer initiation sheath 14 is also a male connector but it could just as well be a female connector. It should be noted that the distal end 16 of the outer initiation sheath 14 which is intended to be nested, is set back from the corresponding distal end of the inner initiation pipe 11. As explained below. , this longitudinal offset makes it possible to release the connector from the distal part 13 of the internal initiation pipe 11. At least one spacer 9 makes it possible to maintain the annular zone between the internal initiation pipe 11 and the external initiation sheath 14 .

Symmetrically, Figure 4 shows a pipe termination section 25. As indicated above in relation to Figure 1, the pipe termination section 25 is intended to provide the mechanical connection with the terminal on the side of which the terminal is terminated. pipe assembly. This connection is made by the pipe termination flange 29. The pipe termination fixing flange 29 is located at a distal end 28 of an internal termination pipe 26 belonging to the termination pipe section 25. The other distal end 27 of internal termination conduit 25 is configured to interlock with the complementary shape configured at the opposing distal end of inner conduit 2 of the last insulated conduit section 1 to be assembled (see Figure 1). In FIG. 4, the distal end 31 of the internal termination pipe 26 is a complementary connector of the corresponding connector of the initiation pipe section 10. The internal termination pipe 26 is enveloped by an external termination sheath 30, whose distal end 31 located on the side of the pipe termination flange 29 is connected to the internal termination pipe 26 in order to seal the annular space on the side of the insulated pipe through which its installation is completed . The connection between the external termination sheath 30 and the internal termination pipe 26 can also be made in different ways, such as welding or crimping. The other distal end 31 of the outer terminating sheath 30 is configured to fit over the complementary shape configured at the opposing distal end of another outer sheath (see Figure 4). In FIG. 4, the distal end 31 of the external termination sheath 30 is also a female connector. It is It should be noted that, for the termination section 25, the distal end 31 of the external termination sheath 30 which is intended to be nested extends beyond the corresponding distal end 27 of the internal termination pipe 26. This offset longitudinal between on the one hand the distal end 27 of the internal termination pipe 26 and on the other hand that 31 of the external termination sheath 30 makes it possible to make up for the withdrawal between the distal ends 16 and 13 of the section of the pipe. initiation 10 (see figure 3). At least one spacer 9 makes it possible to maintain the annular zone between the internal termination pipe 26 and the external termination sheath 30.

The assembly during the progress of the laying of the insulated pipe on the one hand of the internal pipes 2 and on the other hand of the external sleeves 3 is carried out without successive welding, mechanically. This assembly can be accomplished either using connector systems (eg, bolted, screwed, helical or concentric connectors), or by cold interlocking of the ends as used herein to describe the invention. For example, “ZapLok” or “SureLock” type crimping systems or any other equivalent system can be used to produce this interlocking system for the internal pipes 2 and / or the external sleeves 3. One of the advantages of this type of connection is that unlike soldering, the outer coating of the inner pipe 2, which can be covered with the thermal radiation barrier, is preserved during connection. The same goes for the outer sheath 3 and the annular zone 4, which guarantees their continuity throughout the pipe without the need, as with existing solutions, to add new insulation to each connection joint. .

Figures 5a to 5f show an assembly of the different constituent sections 1 and 10 of the insulated pipe with the distal ends of the different internal pipes 2 and 11 carrying male connectors pointing to the right (in the direction of the installation progress) , but the invention is symmetrical and the male connectors can just as easily be arranged in the other direction with the female connectors in the direction of installation. After the initiation pipe section 10 has been positioned, a first Insulated pipe section 1 to be assembled is approached from the side of its connectable end (see FIG. 5a). Then, the inner pipe 2 of the first pipe section 1 to be assembled slides inside the outer sheath 3 in the direction of the initiation pipe section 10 to allow the mechanical connection of the inner pipe 2 of the first section of the pipe. pipe 1 to be assembled with the internal initiation pipe 11 (see FIG. 5b). Then, the inner pipe 2 of the first pipe section 1 to be assembled is mechanically connected with the inner initiation pipe 11 (see Figure 5c). Then, the outer sleeve 3 of the first insulated pipe section 1 to be assembled slides towards the initiation pipe section 10 on the inner pipe 2 which has just been connected to allow the mechanical connection of the outer sleeve 3 of the first section. insulated pipe 1 to be assembled with the external initiation sheath 14 (see FIG. 5 d). The assembly sequence of the first insulated pipe section 1 with the initiation pipe section 10 ends with the mechanical connection of the outer sleeve 3 of the first insulated pipe section 1 to be assembled with the initiation outer sleeve 14 (see figure 5 e). Then, as shown in figure 5f, the steps described above in relation to figures 5a to 5e are repeated to assemble the second insulated pipe section 1 to the first pipe section 1 assembled previously, and so on for all of them. other sections of insulated pipe to be assembled until the desired length of insulated pipe is obtained.

As shown in Figure 5e, a first particular part is assembled at the end of the insulated pipe through which the assembly of the insulated pipe sections 1 has started. This particular part is the initiation pipe section 10 illustrated in FIG. 3 which guarantees at one end of the insulated pipe the sealing of the annular space formed by the junction of the annular zones 4 of all the assembled insulated pipe sections. to each other. Symmetrically, to close and guarantee the tightness of this annular space at the other end of the insulated pipe, another particular part is assembled at the end of the installation sequence of the insulated pipe, this is the section of termination pipe 25 illustrated in FIG. 4 and described above.

Additionally, an intermediate internal pipe 17 and an intermediate external sheath 21 are mechanically connected between, on the one hand, the inner pipe 2 and the outer sheath 3 of the insulated pipe section 1 assembled last, respectively, and on the other hand, the internal termination pipe 26 and the external termination sheath 30 (see FIG. 7d). These two intermediate parts, described below and illustrated in FIGS. 6a and 6b, ensure the absorption of the mechanical tensile and compressive forces between all of the internal pipes 2 and all of the external sleeves 3. They also allow d '' accommodate the difference in length at the end of assembly between all the internal pipes 2 and all the external sleeves 3.

FIG. 6a shows an intermediate internal pipe 17 which has at a first end 18 a female connection so as to be connected by this first end 18 to the internal pipe 2 of section of the insulated pipe 1 laid last. This could be a male connection in the event that the end 6 of the inner pipe 2 of the insulated pipe section assembled last is a female connection. The intermediate pipe 17 ends with a second end 19 intended to be connected to the opposing end 27 of the internal termination pipe 26. The length of the intermediate internal pipe 17 is adapted to the difference in length observed at the end of assembly. of the insulated pipe between, on the one hand, all of the internal pipes 2 and, on the other hand, all of the outer sheaths 3. In addition, a shoulder 20 is provided on the outer surface of the intermediate internal pipe 17 as well than a threaded part 35.

Figure 6b shows an intermediate outer sleeve 21 which, like the outer sleeves 3, has at each of its ends 22 and 23 a female or male connection to be connected by one end 22 to the outer sleeve 3 of the insulated pipe section 1 placed last, and by its other end 23 to the opposing end 31 of the external termination sheath 30. As for the intermediate internal pipe 17, the The length of the intermediate outer sheath 21 is adapted to the difference in length observed at the end of assembly of the insulated pipe between, on the one hand, all the internal pipes 2 and, on the other hand, all of the outer sheaths 3. At its end located on the side of the termination pipe section 25, the intermediate outer sleeve 21 has a locking flange 24 which extends inwardly thereof. When the intermediate internal pipe 17 is mounted in the intermediate external sheath 21, the locking flange 24 abuts on a face of the shoulder 20 oriented towards the end 19 of the intermediate internal pipe 17 intended to be connected with the internal pipe 26. Before the assembly of the termination pipe section 25, a locking nut 36 is screwed onto the threaded portion 35 to press the locking flange 24 of the intermediate outer sleeve 21 against the shoulder 20 of the inner pipe. intermediate 17 (see figure 7c).

Figures 7a to 7d show the final assembly sequence of the insulated pipe. After the last insulated pipe section has been assembled as shown in figure 5f, the intermediate inner pipe is approached from the free end thereof (see upper part of figure 7a) by its end 18 configured in female connection. . Then, the intermediate internal pipe 17 is connected to the internal pipe 2 of the last insulated pipe section 1 (see lower part of FIG. 7a). After the connection of the intermediate internal pipe 17, the intermediate external sheath 21 is approached to the intermediate internal pipe 17 by its free end (see upper part of FIG. 7b). Then, it is mounted on the intermediate internal pipe 17 until the locking flange 24 abuts against the shoulder 20 (see lower part of Figure 7b). At this stage, the locking nut 36 is screwed onto the threaded part 35 of the intermediate internal pipe 17 to press the locking flange 24 against the shoulder 20 (see FIG. 7c). After tightening the nut 36, the section of termination pipe 25 is approached to the intermediate internal pipe 17 (see upper part of Figure 7d). Then, the female connectors 27 and 31 of the internal termination pipe 26 and the external termination sheath 30 are simultaneously connected by interlocking with respectively the male connector at the end 19 of the intermediate internal pipe 17, and the male connector at the end 23 of the intermediate external sheath 21 which completes the assembly of the insulated pipe by hermetically closing the space annular.

Once the insulated pipe is completely assembled and installed, the annular space is advantageously evacuated by means of a vacuum pump connected via a tapping made at one end of the double jacket of the pipe, for example at the end. of the external termination sheath 30. The insulation of the internal pipe is thus carried out on site very simply once the pipe has been laid, which also allows continuous control of the integrity of the insulation from this tap-off by simply measuring the pressure. in the annular space. In fact, to achieve the insulation of the internal pipe, it is not necessary to create a vacuum. An air gap trapped in the annulus is less effective but sufficient to provide insulation, for example, over a short length of pipe.

Although in the above description, the particular aspects of the invention have been described in the context of an insulated underwater pipe of the “pipe in pipe” type, it could be implemented in other configurations. , in particular for onshore pipelines and / or for the transport of other effluents such as gas.

Claims

1. Insulated pipe section (1) for transporting fluids comprising an internal pipe (2) capable of transporting a fluid, inserted coaxially in an outer sleeve (3), said outer sleeve (3) and said inner pipe (2) forming between them an annular zone (4) making it possible to isolate the fluid transported in the internal pipe (2) from the external environment surrounding the external sleeve (3); said insulated pipe section (1) being characterized in that a first end (5) and a second end (6) of the inner pipe (2) are each able to be assembled by mechanical seamless connection respectively at a second end (6) of an internal pipe (2) of a second insulated pipe section (1), and at a first end (5) of an inner pipe (2) of a third insulated pipe section (1) ; and a first end (7) and a second end (8) of the outer sleeve (3) are each capable of being assembled by mechanical connection without welding respectively to a second end (8) of an outer sleeve (3) of the second insulated pipe section and a first end (7) of the outer sleeve (3) of the third insulated pipe section (1) -

2. Insulated pipe section (1) for transporting fluids according to claim 1 wherein the first and second ends (5; 6) of the internal pipe (2) have complementary configurations capable of allowing their interlocking respectively with the second and first ends (6, 5) of the internal pipes (2) to which they are intended to be connected.

3. Insulated pipe section (1) for transporting fluids according to claim 1 or 2 wherein the first and second ends of the outer sheath (7; 8) have complementary configurations suitable for allowing their interlocking with the second and third ends ( 8; 7) external sheaths (3) to which they are intended to be connected.

4. Insulated pipe section (1) for transporting fluids according to one of claims 1 to 3 wherein the inner pipe (2) is slidably mounted in the outer sleeve (3).

5. Insulated pipe section (1) for transporting fluids according to one of claims 1 to 4 wherein the length of the outer sleeve (3) is substantially equal to that of the inner pipe (2) after connections.

6. Insulated pipe section (1) for transporting fluids according to claim 4 wherein the annular zone (4) located between the internal pipe (2) and the outer sleeve (3) is held by at least one spacer (9). housed in the annular zone (4), and made of an insulating material

thermally and facilitating sliding between the inner pipe (2) and the outer sheath (3).

7. Insulated pipe section (1) for transporting fluids according to one of the preceding claims, in which a thermal radiation barrier is applied to the outer face of the inner pipe (2) and / or the inner face of the outer sleeve (3). ).

8. Insulated pipe for transporting fluids, characterized in that it is produced by successive mechanical connections of internal pipes (2) and of external sleeves (3) of isolated pipe section (1) as defined in the preceding claims.

9. Insulated pipe for transporting fluids according to claim 8 wherein the insulation is provided by the formation of a partial air vacuum in an annular space formed by the continuous junction of the annular areas (4) formed respectively between the pipes. internal (2) and external sheaths (3).

10. Insulated pipe for transporting fluids according to one of claims 8 or 9 further comprising an intermediate internal pipe (17) having a first end (18) adapted to be connected to the second end of the internal pipe (2) of the last insulated pipe section (1) and an intermediate outer sleeve (21) having a first end (22) adapted to be connected to the second end (8) of the last insulated pipe section (1) and mounted on the pipe internal intermediate (17) so as to take up the tensile and compressive forces, and the respective lengths of which are adapted to accommodate the difference in length between all the internal pipes (2) connected to each other and all the external sheaths (3) ) connected to each other.

1 1. Insulated pipe for transporting fluids according to one of claims 8 to 10 comprising:

- an insulated pipe initiation section (10) adapted to be connected by a second end (13; 16) to the first end (5) of the internal pipe (2) and to the first end (7) of a outer sleeve (3) of the first insulated pipe section (1) in order to hermetically close one of the ends of the annular space, and having at a first end (12) a pipe start fixing flange (32); and

- an insulated pipe termination section (25) adapted to be connected by a first end (27; 31) to the second end (19) of the intermediate internal pipe (17) and to the second end (23) of a intermediate outer sheath (3) in order to hermetically close the other end of the annular space, and having at a second end (28) a pipe termination fixing flange (29).

12. A method of assembling an insulated pipe for transporting fluids as defined in claims 8 to 11, said method comprising the following steps:

- an approach step of an isolated pipe section (1) to be assembled with one or more repositioned pipe sections;

- a step of connecting the internal pipe (2) in which the first end (5) of the internal pipe (2) of an insulated pipe section (1) to be assembled is mechanically connected without welding with the second end (6 ) the internal pipe (2) of a pre-positioned insulated pipe section;

- a step of connecting the outer sheath (3) in which the first end (7) of the outer sheath (3) of an insulated pipe section

(1) to be assembled is mechanically connected without welding with the second end (8) of the outer sleeve (3) of a section of pre-insulated pipe. positioned; and

- repeating the above steps to assemble at least one insulated pipe section (1) to the last insulated pipe section (1) previously assembled.

13. A method of assembling an insulated pipe for transporting fluids according to claim 12, further comprising the following steps:

- before the step of connecting the internal pipe (2) a first sliding step of the outer sleeve (3) of the pipe section to be assembled in order to release the first end (5) of the internal pipe (2) to be connected ; and

- Before the step of connecting the outer sheath (3) a second sliding step of the outer sheath (3) of the pipe section to be assembled towards the outer sheath (3) of the already assembled pipe section.

14. Assembly method according to one of claims 12 to 13 of an insulated pipe for transporting fluids according to one of claims 10 to 11, said method further comprising the following steps:

- a step of connecting a first end (18) of the intermediate internal pipe (17) to the second end (6) of the internal pipe (2) of the last section of isolated pipe (1);

- a step of inserting the intermediate outer sheath (21) around the intermediate inner pipe (17); and

- a step of connecting a first end (22) of the intermediate outer sleeve (21) to the second end (8) of the outer sleeve (3) of the last section of insulated pipe (1).

15. Assembly method according to claim 14 of an insulated pipe for transporting fluids according to claim 11, in which:

- the first step is to assemble the first insulated pipe section (1) to the initiation pipe section (10); and

- the last step is to assemble a second end (19) of the intermediate inner pipe (17) and a second end (23) of the intermediate outer sleeve (21) to the termination pipe section (25).

16. Assembly method according to one of claims 12 to 15 of an insulated pipe for transporting fluids according to one of claims 7 to 11, further comprising a step of establishing a partial vacuum of air in the continuous annular space formed by the connection of all the annular zones (4) of the pipe sections connected to each other.