Triple-shell pipe for transporting cryogenic liquid

Abstract

The invention relates to the field of pipelines, or pipes, for transporting cryogenic liquids over long distances. More particularly, the invention relates to thermally insulated triple-shell pipes comprising three tubes (2, 3, 4) arranged one inside the other, wherein the tubes define an internal annular space (6) and an external annular space (7), wherein the annular space (7) comprises a silica-based microporous thermal insulator (8), and wherein the annular space (6) does not comprise any insulating material; wherein connecting parts (9) connect the three tubes (2, 3, 4) in pairs, the connecting parts being located in the annular spaces (6, 7); and wherein, in the case of the connecting parts (9) connecting tubes made of materials with different thermal coefficients, tubular transition parts are positioned between the connecting parts (9) and at least one of the two tubes.

Description

Triple-jacketed pipeline for the transport of cryogenic liquid

[0001] The invention relates to the field of liquefied gas transport infrastructure, and more particularly to pipelines, or conduits, used to transport cryogenic liquids over long distances. The triple-walled conduits according to the invention are particularly suitable for transporting liquefied hydrogen or helium. Similar conduits are known from document US4014369 A.

[0002] Cryogenic liquids have many applications, for example:

[0003] - for nitrogen, in cooling, cryopreservation, dimensional contraction of objects before insertion into a tight housing (in the automotive industry), testing or inerting of products in the electronics industry,

[0004] - for oxygen, in rocket propulsion, medical oxygen, steelmaking for steel production,

[0005] - for argon, as a thermal insulator, in bulbs or solder baths,

[0006] - for helium, in the space industry and scientific research (e.g. for superconductors),

[0007] - for Liquefied Natural Gas (LNG), as a more sustainable alternative to traditional hydrocarbons.

[0008] - for liquefied hydrogen, as a vector and means of energy storage with the advantage of not generating CO2 during combustion.

[0009] In view of these growing applications, commercial exchanges of cryogenic liquids have increased significantly, creating a significant need for industrial or scientific cryogenic installations and for longer, safer, cost-effective and more efficient cryogenic fluid transfer lines (in terms of efficiency and ease and speed of their assembly) for aerial, buried or underwater installations.

[0010] In the field of insulated cryogenic fluid transport pipes, insulated transfer lines have been used for several years. For the most robust, they consist, for example, of double-jacketed pipes comprising two concentric tubes:

[0011] - the inner tube is the pipe in which the cryogenic fluid circulates; this inner tube is inserted into an outer tube,

[0012] - the outer tube, into which the inner tube is inserted, is of a diameter such that an annular space is created between the two tubes.

[0013] In these double-jacketed pipes, the annular space is used to install thermal insulation, such as multi-layer insulation coupled with a high vacuum (absolute pressure less than 10 -4 mbar) combined with spacers to prevent the multi-layer insulation from crushing under the weight of the inner tube and the fluid carried or a microporous insulation coupled with reduced pressure (absolute pressure less than 10 mbar at room temperature).

[0014] This double jacket system with thermal insulation in the annulus requires the use, for the internal tube, of materials compatible with cryogenic temperatures. In order to allow the installation of straight and / or buried pipes (without longitudinal flexibility elements such as bellows or expansion lyres) the use of an alloy with a low coefficient of thermal expansion such as Invar ®is particularly advantageous. Indeed, the thermal stresses appearing in the inner tube of the double-jacketed pipe during cryogenic heating are mechanically dimensioning. In the case of a stainless steel inner tube, this type of pipe therefore requires special regular junctions (every few tens of meters) between the inner tube and the outer tube as well as a flexibility element to allow relative movements between the inner tube at cryogenic temperature and the outer tube at ambient temperature. These junctions, which are therefore necessary to avoid rupture of the pipe, constitute areas of lower thermal insulation, which harms the overall thermal performance of the pipe.

[0015] To address some risks of failure of internal or external pipes, insulated pipes with a third jacket have been proposed.

[0016] Triple-jacketed pipes have the advantage of providing a double barrier in the event of a leak in the tube carrying the fluid or a rupture of the outer tube. These constructions also incorporate connecting pieces connecting and holding the different tubes together, the function of which is to ensure the control of thermomechanical constraints and the displacements of the different tubes, however generating thermal bridges along the pipe and increased heat loss.

[0017] Thus, a triple-envelope LNG transport pipe was proposed by the applicant (FR 2862741). It consists of an inner tube with a low thermal expansion coefficient material such as Invar. ®, an intermediate tube made of carbon steel or stainless steel and an outer tube made of carbon steel. Thermal insulation is placed in the inner annular space; additional insulation may be placed in the outer annular space to reduce the impact of thermal bridges at the junction pieces between the inner tubes.

[0018] Document US20150219243 also details a triple pipeline for long-distance LNG transportation using the same arrangement.

[0019] A particularity of deep cryogenics is the increased need for thermal insulation because the cooling efficiency decreases with temperature, so it is necessary to spend 10 W of electricity to provide 1 W of cooling at 77K but 40 W at 20K. The economic impact of the same heat exchange coefficient (expressed in W / (m².K) is thus multiplied by 5 between the two temperatures (x4 for efficiency, x 1.25 for the temperature differential). Another characteristic is the amplification of mechanical constraints linked to expansion and contraction phenomena.

[0020] A known way to improve the performance of thermal insulators is to reduce the gas pressure in the annular space. However, maintaining a low pressure is hampered by the fact that, since hydrogen is a highly diffusive gas, this pressure can tend to increase over the long term by diffusion through the internal pipe. In addition, the leakage of cryogenic liquid into the internal annular space, in addition to the loss of efficiency, risks damaging the insulator, thus reducing the thermal insulation performance and, ultimately, weakening the pipe.

[0021] A triple pipe for LNG transport is also known from document FR2865262. This pipe also has nanoporous insulation in the inner annulus and spacers to protect it from being crushed between the inner tube and the intermediate tube. In addition, it uses concrete in the outer annulus to ballast it. Thus, it does not solve the aforementioned problem.

[0022] The applicant has developed a new triple-walled pipe, which addresses these problems and is particularly suitable for the transport of cryogenic liquids and more particularly for deep cryogenics. This pipe can be used in an underground, underwater or aerial environment. The choice of materials used for its various elements and the specific arrangement of the various elements make it possible to very significantly reduce the thermomechanical stresses within the pipe, thus making it possible to generate pipe sections of the order of a kilometer, free of any connecting parts. In the pipe according to the invention, the presence of connecting parts to avoid thermomechanical stresses is thus no longer necessary except at the bends of these pipes. Thus, the pipe according to the invention has a particularly improved efficiency, and is particularly easy and quick to assemble.The pipe according to the invention also has particularly improved safety and reliability. On the one hand, in the event of a leak of the cryogenic liquid through the inner tube, the thermal performance of the pipe is maintained: by guaranteeing the same temperature conditions outside the pipe, a leak from the tube carrying the cryogenic liquid therefore remains without any impact outside the pipe. On the other hand, the very particular arrangement of the pipe according to the invention makes it possible to associate it with a control device for the purpose of detecting leakage from the inner tube or permeation through the inner tube. The simplified structure of the sections of the pipe allows, if necessary, easy replacement of the defective part.

[0023] The pipeline as developed by the applicant therefore makes it possible to respond to the technical problems posed by the pipelines of the prior art and by the growth of the market for the transport of cryogenic liquids.

[0024] The applicant has developed a new triple-walled pipeline that is easy and quick to assemble. This pipeline, which is particularly suitable for the transport of cryogenic liquids, has a particularly high efficiency and offers improved safety.

[0025] Thus, an object of the invention is a pipe suitable for the transport of a cryogenic liquid, thermally insulated, characterized in that it comprises three tubes arranged one inside the other: an internal tube made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 , an intermediate tube made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm-1 .K -1 ,an outer tube made of carbon steel, stainless steel, or an austenitic alloy comprising from 22 to 27% by weight of manganese, said three tubes arranged one inside the other defining an internal annular space between said internal tube and said intermediate tube and an external annular space between said intermediate tube and said external tube,

[0026] the outer annular space comprising a microporous silica-based thermal insulator, the inner annular space not comprising any thermal insulating materialconnecting pieces connecting said three tubes arranged one inside the other two by two, located in the outer and inner annular spaces, and provided with at least one orifice so as to allow the circulation of gas in the inner and outer annular spaces, said pieces being made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 mm-1.K-1 , stainless steel, Inconel ® or an austenitic alloy comprising 22 to 27% by weight of manganese, in the case of connecting pieces connecting tubes made of materials with different thermal coefficients, tubular transition pieces positioned between the connecting pieces and at least one of the two tubes, said transition pieces being made of a material with a thermal coefficient intermediate to that of the connecting piece and the tube on which it is positioned.

[0027] This particular configuration makes it possible in particular to limit the use of flexibility and expansion absorption elements between the inner and intermediate tubes at cryogenic temperature and the outer tube at ambient temperature, such as bellows or expansion lyre.

[0028] The applicant has developed modular elements particularly suitable for constituting the pipe according to the invention, which also allow rapid and easy assembly of the latter at the installation site.

[0029] Thus, one of these modular elements, another object of the invention, is a section of pipe suitable for the transport of a cryogenic liquid characterized in that it comprises: three tubes arranged one inside the other: an internal tube made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 , an intermediate tube made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1,an outer tube made of a carbon steel, a stainless steel, or an austenitic alloy comprising from 22 to 27% by weight of manganese,said three tubes arranged one inside the other defining an internal annular space comprised between said internal tube and said intermediate tube and an external annular space comprised between said intermediate tube and said external tube,the external annular space comprising a microporous thermal insulator based on silica, the internal annular space not comprising any thermal insulating material,connecting pieces (9) connecting said three tubes arranged one inside the other (2, 3, 4) two by two, located in the external (7) and internal (6) annular spaces, and provided with at least one orifice so as to allow the circulation of gas in the internal (6) and external (7) annular spaces, said pieces being made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 mm-1.K 1, of a stainless steel, of an Inconel® or of an austenitic alloy comprising 22 to 27% by weight of manganese, in the case of connecting pieces (9) connecting tubes made of materials with different thermal coefficients, tubular transition pieces positioned between the connecting pieces (9) and at least one of the two tubes, said transition pieces being made of a material with a thermal coefficient intermediate to that of the connecting piece and the tube on which it is positioned.

[0030] Another of these modular elements, also the subject of the invention, is a pipe connector as described above, the connector being characterized in that it comprises: three tubes arranged one inside the other: an internal tube made of a material with a thermal expansion coefficient less than or equal to 2.10 -6 mm -1 .K -1, an intermediate tube made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 ,an outer tube made of carbon steel, stainless steel, or an austenitic alloy comprising from 22 to 27% by weight of manganese, said three tubes arranged one inside the other defining an internal annular space between said internal tube and said intermediate tube and an external annular space between said intermediate tube and said external tube,

[0031] the external annular space comprising a microporous silica-based thermal insulator, connecting pieces connecting said three tubes arranged one inside the other two by two, located in the external and internal annular spaces, provided with at least one orifice so as to allow the circulation of gas in the annular spaces, said pieces being made of an alloy with an expansion coefficient less than or equal to 2.10 -6 mm -1 .K -1 , stainless steel, Inconel ®, or an austenitic alloy comprising from 22 to 27% by weight of manganese), in the case of connecting pieces connecting tubes made of materials with different thermal coefficients, tubular transition pieces are positioned between the connecting pieces (9) and at least one of the two tubes, said transition pieces being made of a material with a thermal coefficient intermediate to that of the connecting piece and the tube on which it is positioned, at the level of the connecting piece connecting said outer tube and said intermediate tube, an outer overlayer of microporous thermal insulation based on silica, surrounded by an outer connecting tube made of carbon steel, stainless steel, or austenitic alloy comprising from 22 to 27% by weight of manganese, said outer connecting tube being welded at its ends to the outer tube of the fitting.

[0032] Another of these modular elements, also the subject of the invention, is another pipe connector as described above, the connector being characterized in that it comprises:three tubes arranged one inside the other:an internal tube made of a material with a thermal expansion coefficient less than or equal to 2.10 -6 mm -1 .K -1 , an intermediate tube made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 ,an outer tube made of carbon steel, stainless steel, or an austenitic alloy comprising from 22 to 27% by weight of manganese, said three tubes arranged one inside the other defining an internal annular space between said internal tube and said intermediate tube and an external annular space between said intermediate tube and said external tube,

[0033] the external annular space comprising a microporous silica-based thermal insulator, connecting pieces connecting said three tubes arranged one inside the other two by two, located in the external and internal annular spaces, provided with at least one orifice so as to allow the circulation of gas in the annular spaces, said pieces being made of an alloy with an expansion coefficient less than or equal to 2.10 -6 mm -1 .K -1 , stainless steel, Inconel ®, or an austenitic alloy comprising from 22 to 27% by weight of manganese), in the case of connecting pieces connecting tubes made of materials with different thermal coefficients, tubular transition pieces are positioned between the connecting pieces and at least one of the two tubes, said transition pieces being made of a material with a thermal coefficient intermediate to that of the connecting piece and the tube on which it is positioned, at the level of the connecting piece connecting said external tube and said intermediate tube, a layer of thermal insulation at right angles to said connecting piece is located in the inner annular space.

[0034] This type of connection has the advantage of allowing the external surface of the pipe to be maintained with a constant diameter, without excess thickness even at the connections.

[0035] Another of the modular elements, also the subject of the invention, is a section-end piece for a pipe according to the invention, the section-end piece being characterized in that it comprises:a first part for closing the external annular space welded on the one hand to an external tube and on the other hand to an intermediate tube, said part comprising one end of the intermediate tube adapted to constitute an extension to the intermediate tube of the pipe, and one end of the external tube adapted to constitute an extension to the external tube of the pipe,a second part for closing the internal annular space welded on the one hand to one end of the extension of the intermediate tube of the part for closing the external annular space and on the other hand to the internal tube, said internal tube comprising one end adapted to constitute an extension to the internal tube of the pipe,in the external annular space (7), a layer of microporous thermal insulation based on silica,connecting pieces (9) connecting said three tubes arranged one inside the other (2, 3, 4) two by two, located in the external (7) and internal (6) annular spaces, and provided with at least one orifice so as to allow the circulation of gas in the internal (6) and external (7) annular spaces, said pieces being made of a material with a thermal expansion coefficient less than or equal to 2.10-6 mm-1.K-1, of a stainless steel, of an Inconel® or of an austenitic alloy comprising 22 to 27% by weight of manganese, in the case of connecting pieces (9) connecting tubes made of materials with different thermal coefficients, tubular transition pieces positioned between the connecting pieces (9) and at least one of the two tubes, said transition pieces being made of a material with a thermal coefficient intermediate to that of the connecting piece and the tube on which it is positioned.,

[0036] This end section allows, at each end of the pipe, to close the internal and external annular spaces.

[0037] Another of the modular elements, also the subject of the invention, is a bent section for a pipe as described above, the bent section comprising: three tubes arranged one inside the other: an internal tube made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 ,an intermediate tube made of a material with a coefficient of thermal expansion of a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1,an outer tube made of carbon steel, stainless steel, or an austenitic alloy comprising from 22 to 27% by weight of manganese,said three tubes arranged one inside the other defining an internal annular space between said internal tube and said intermediate tube and an external annular space between said intermediate tube and said external tube,the external annular space comprising a microporous silica-based thermal insulator,said tubes arranged one inside the other having a curvature at an angle between 30° and 90°connecting pieces (9) connecting said three tubes arranged one inside the other (2, 3, 4) two by two, located in the external (7) and internal (6) annular spaces, and provided with at least one orifice so as to allow the circulation of gas in the internal (6) and external (7) annular spaces, said pieces being made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1, of a stainless steel, an Inconel® or an austenitic alloy comprising 22 to 27% by weight of manganese, in the case of connecting pieces (9) connecting tubes made of materials with different thermal coefficients, tubular transition pieces positioned between the connecting pieces (9) and at least one of the two tubes, said transition pieces being made of a material with a thermal coefficient intermediate to that of the connecting piece and the tube on which it is positioned.

[0038] This bent section allows changes of direction to be introduced into the triple-walled pipe, depending, for example, on the terrain on or in which it is installed.

[0039] According to other optional characteristics each of these different objects may include, optionally and independently, one or more of the following characteristics, alone or in combination: the material with a coefficient of thermal expansion less than or equal to 2.10-6 mm -1 .K -1 constituting the inner tube and / or the intermediate tube is an iron-nickel alloy comprising from 34.0% to 38.0% nickel, preferably from 35.0% to 37.0% nickel, or even from 35.5% to 36.5% nickel, the connecting or closing parts are made of an iron-nickel alloy comprising from 34.0% to 38.0% nickel, preferably from 35.0% to 37.0% nickel, or even from 35.5% to 36.5% nickel, the inner tube and / or the intermediate tube have a thickness of at least 3 mm, the microporous thermal insulator has a density of between 40 kg.m -3 and 250 kg.m -3 , between 70 kg.m -3 and 190 kg.m -3 , preferably between 100 kg.m -3and 160 kg.m -3 , and / orthe silica-based microporous thermal insulator comprises at least 50% silica, at least 60% silica, preferably at least 70% silica.

[0040] According to other optional features, the pipe according to the invention may include, optionally and independently, one or more of the following features, alone or in combination: the pipe comprises a segment of at least 10 m, at least 50 m, 100 m, 1 km, 5 km, 10 km or even at least 15 km in which the external and internal annular spaces do not contain any connection, in particular no connection as described previously.the pipe comprises a bent section as described above and one of the fittings described above placed upstream and downstream of said bent section, a gas is circulated in the internal annular space, said gas having, at the circulation pressure in the internal annular space, a liquefaction temperature lower than the cryogenic liquid transported in the pipe, one end of which is coupled to at least one means for analyzing the gas circulating in the internal annular space, or the pressure in the external annular (7), at ambient temperature, before cooling the pipe, is less than or equal to 10 mbar. Brief description of the figures

[0041] Other advantages and characteristics of the invention will appear on reading the following description given by way of illustrative and non-limiting example, with reference to the appended Figures.

[0042] The figure represents a section of a pipe section 1 according to an embodiment of the present invention.

[0043] The figure represents a pipe end section 30 according to an embodiment of the present invention.

[0044] The figure represents a connector 20 for connecting sections 1 of pipe according to an embodiment of the present invention. The white space between the two connecting pieces 9 is purely conventional to indicate that these two pieces are separate; these two pieces as well as all the elements of the connector 20 are of course welded together.

[0045] The figure represents a connector 21 for connecting sections 1 for pipe according to another embodiment of the present invention called bayonet connection. The white space between the two connecting pieces 9 is purely conventional to indicate that these two pieces are separate; these two pieces as well as all the elements of the connector 21 are of course welded together.

[0046] The figure represents a cross-sectional view of a pipe section 1 according to an embodiment of the present invention.

[0047] The relative scales of the different objects or elements are not respected to allow for good visualization. The figures presented here are purely illustrative. Description of embodiments

[0048] The inventive principle of the present invention is based on the integrated configuration of three tubes arranged one inside the other, combined with a microporous thermal insulator arranged in the outer annular space. This unique technical concept allows for optimal insulation and a significant reduction of thermomechanical stresses over long distances. All proposed assembly variants, such as connectors, elbow sections and end pieces, are specific adaptations of the basic inventive principle, which is based on a structure of three tubes arranged with a microporous thermal insulator in the outer annular space. These adaptations make it possible to meet assembly, flexibility and integration requirements in particular layout configurations, while maintaining the overall technical effect of optimal insulation and reduction of thermomechanical stresses.

[0049] The term "pipeline" within the meaning of the present invention refers to an assembly for conveying one or more fluids or fluidized products from point A to point B. In a particular embodiment, the pipe according to the invention allows the transport on land, underground or above ground, or at sea, of one or more fluids or liquefied products from a fixed tank to a mobile tank in a so-called export terminal or from a mobile tank to a fixed tank in an import terminal. An example of a mobile tank may be a ship transporting said fluids or liquefied products over intercontinental distances. As mentioned below, the pipes according to the invention are particularly suitable for the transport of cryogenic liquids, such as liquid nitrogen, liquid oxygen, liquid argon, helium, Liquefied Natural Gas (LNG), or even liquid hydrogen.The terms "conduit" and "pipeline" are interchangeable here and can be used interchangeably.

[0050] The term "tube" according to the meaning of the present invention refers to a pipe or conduit for conveying a fluid or a mixture of fluids, and / or which may also comprise in its lumen another tube and / or another material. The pipe according to the present invention is thus made up of several tubes arranged one inside the other.

[0051] The name "annular" or the terms "annular space" are used interchangeably. For the purposes of the present invention, they refer to the space formed between two tubes arranged one inside the other, said space being able to receive a circulation of fluid and / or be filled with a material.

[0052] The term "cryogenic fluid" according to the present invention refers to cryogenic liquids such as liquid nitrogen, liquid oxygen, liquid argon, liquid helium, Liquefied Natural Gas (LNG), or liquid hydrogen. In a preferred embodiment, the cryogenic liquids have a temperature lower than that of liquid nitrogen (-196°C / 77 K, so-called deep cryogenic temperatures). In another preferred embodiment, the cryogenic fluid is liquid hydrogen or liquid helium. In an even more preferred embodiment, the cryogenic fluid is liquid hydrogen (liquid at 20 K). The terms cryogenic fluids and cryogenic liquids are used herein interchangeably and are interchangeable.

[0053] The term "coefficient of thermal expansion" is well known in the art and is a measure of the reversible change in volume or length of a material with temperature. As mentioned above, contact with cryogenic fluids that have particularly low temperatures can generate phenomena of shrinkage or expansion of materials that generate mechanical stresses on the elements they constitute.

[0054] Unless otherwise provided, the intervals mentioned are understood to include the limits. Thus, for example, a quantity described as being between 5 and 10 or ranging from 5 to 10 may have the value 5 or 10. For example, unless otherwise provided, a quantity described as less than or greater than 10 may have the value 10.

[0055] A first object of the invention is therefore the pipe as developed by the applicant which has particularly improved thermal efficiency and safety.

[0056] Thermally insulated pipe suitable for the transport of cryogenic fluid

[0057] The pipe according to the invention is insulated and thermally adapted to the transport of a fluid or a mixture of fluids, preferably cryogenic, as mentioned above; certain embodiments are described more precisely below.

[0058] A pipe according to the present invention is in a triple-tube configuration or, in English terminology, pipe-in-pipe-in-pipe (PIPIP). Thus, a pipe according to the present invention comprises three tubes 2, 3, 4 arranged one inside the other as illustrated in and in.

[0059] A pipe according to the present invention thus comprises a first tube, called internal tube 2, defining a lumen (or internal space) 5 intended for the circulation of a cryogenic fluid.

[0060] The inner tube 2 is suitable for transporting one or more fluids, preferably cryogenic fluids. Thus, the inner tube 2 is suitable for transporting a cryogenic fluid or a mixture of cryogenic fluids at a temperature less than or equal to -160°C, preferably less than or equal to -190°C. In a particularly preferred manner, the inner tube 2 is suitable for transporting a cryogenic fluid or a mixture of cryogenic fluids at a temperature less than or equal to -250°C.

[0061] The inner tube 2 is thus suitable for transporting cryogenic fluids such as liquefied natural gas (LNG), liquid nitrogen, liquid oxygen, argon, liquid hydrogen or liquid helium, preferably liquid hydrogen or liquid helium.

[0062] The inner tube 2 is made of a material having a low coefficient of thermal expansion, preferably a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 . When the inner tube 2 is in operation in the pipe, that is to say during the circulation of a cryogenic fluid in the internal space 5 (or lumen) of the inner tube 2, using a material with such a coefficient of thermal expansion makes it possible to avoid the higher mechanical stresses generated during shrinkage phenomena being greater than the elastic limit of the material without it being necessary to add longitudinal flexibility elements such as bellows or expansion lyres like other pipes of the prior art. This thus makes it possible to avoid breakages of the inner tube 2 of the pipe and prolongs its service life.

[0063] Thus, the material constituting the inner tube 2 may be an iron-nickel alloy comprising at least 34.0% nickel, preferably at least 35.0% nickel and even more preferably at least 36.0% nickel. In a further preferred embodiment, the material constituting the inner tube 2 may be an iron-nickel alloy comprising from 34.0% to 38.0% nickel, preferably from 35.0% to 37.0% nickel, or even from 35.5% to 36.5% nickel. In a particularly preferred embodiment, said iron-nickel alloy comprises 36.0% nickel. In another particularly preferred embodiment, said iron-nickel alloy is an Invar ® . Invars have expansion coefficients that are particularly suitable for transporting cryogenic fluids. Also, Invar-type alloys ®have some of the mechanical properties, such as yield strength and tensile strength, which are higher at cryogenic temperatures than those measured at room temperature. A mechanical sizing of the tube carried out with the mechanical properties of Invar ® at room temperature is therefore conservative for a cryogenic line. In an effort to optimize sizing by reducing the thickness of the Invar tube ® for cryogenic application it can be considered to use the mechanical properties of Invar ® at cryogenic temperature to adapt the dimensions of the pipe elements in order to optimize its production costs and performance.

[0064] Considering that the pipe can be exposed to variable temperatures, and that the properties of the materials vary according to the temperature to which they are exposed, the inner tube 2 according to the present invention has a thickness of 3.0 mm to 15.0 mm, for inner tubes 2 with a diameter typically between 88.9 mm and 914.0 mm, which corresponds to a dimensioning taking into account the physical properties of an Invar type material. ® at room temperature or cryogenic. As previously explained, certain mechanical properties of Invar type alloys ®, such as yield strength and tensile strength, are better at cryogenic temperatures than at room temperature. Thus in one embodiment, considering cryogenic temperatures; the inner tube 2 has a thickness between 3.0 mm and 5.0 mm. Such a thickness allows for resource savings considering the improved properties of the Invar ® at cryogenic temperatures.

[0065] For obvious safety reasons and to ensure optimal sealing of the internal tube 2 which is in direct contact with the cryogenic fluid, it may nevertheless be preferable for the internal tube 2 to have a thickness of between 5.0 mm and 10.0 mm, for internal tubes 2 with a diameter typically between 88.9 mm and 914.0 mm; this thickness corresponds to a dimensioning determined from the physical properties of the Invar type material. ® at room temperature.

[0066] A pipe according to the present invention comprises a second tube, called intermediate tube 3, said intermediate tube 3 being arranged around the internal tube 2. Thus, the internal wall of the intermediate tube 3 and the external wall of the internal tube 2 define an internal annular space 6.

[0067] The intermediate tube 3 is made of a material having a low coefficient of thermal expansion, preferably a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 .

[0068] Thus, the material constituting the intermediate tube 3 may be an iron-nickel alloy comprising at least 34.0% nickel, preferably at least 35.0% nickel and even more preferably at least 36.0% nickel. In a particular embodiment, the material constituting the intermediate tube 3 may be an iron-nickel alloy comprising from 34.0% to 38% nickel, preferably from 35.0% to 37.0% nickel, or even from 35.5% to 36.5% nickel. In a particularly preferred embodiment, said iron-nickel alloy comprises 36.0% nickel. In a particularly preferred embodiment, said iron-nickel alloy is an Invar ® .

[0069] In a preferred embodiment, the inner 2 and intermediate 3 tubes are made of materials with identical coefficients of thermal expansion. In an even more preferred embodiment, the inner 2 and intermediate 3 tubes are made of the same material. In an even more preferred embodiment, the inner 2 and intermediate 3 tubes are made of the same Invar ® .

[0070] The intermediate tube 3 of the pipe according to the present invention has a thickness of 3.0 mm to 10.0 mm, for intermediate tubes 3 with a diameter typically between 88.9 mm and 914.0 mm. Thus in one embodiment, considering the mechanical properties at cryogenic temperatures; the intermediate tube 3 has a thickness of between 3.0 mm and 5.0 mm.

[0071] For the same safety reasons as those mentioned for the internal tube 2, it may nevertheless be preferable for the intermediate tube 3 to have a thickness of between 5.0 mm and 10.0 mm, for intermediate tubes 3 with a diameter typically of between 88.9 mm and 914 mm; this thickness corresponds to a dimensioning determined from the physical properties of the Invar type material. ® at room temperature.

[0072] In a particular configuration of the pipe according to the invention, the internal tube 2 and the intermediate tube 3 are made of an Invar ® , and said inner tube 2 has a thickness of between 5.0 and 10.0 mm and said intermediate tube 3 has a thickness of between 3.0 and 5.0 mm. That is to say that the dimensions of the inner tube 2 and intermediate tube 3 are made taking into account the mechanical properties of the Invar ®at room temperature and cryogenic temperature respectively. Such a configuration has the advantage of meeting safety requirements by providing a particularly large thickness for the internal tube in which the cryogenic fluid circulates while optimizing costs due to the use of a smaller quantity of material for the intermediate tube 3. It should in fact be considered that materials with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 , in particular the Invar ® , are relatively expensive compared, in particular, to stainless steels, usually used for cryogenics. In the accidental case of a leak from the internal tube 2 during operation, the intermediate tube 3 will then have to withstand the pressure of the cryogenic fluid while it is already at cryogenic temperature.

[0073] The internal annular space 6 contributes to the double confinement of the cryogenic fluid provided by the pipe according to the invention, in particular in the event of a leak or alteration of the internal tube 2. It also contributes to the good insulation of the internal tube 2. This internal annular space 6 according to the invention does not, however, comprise any thermal insulating material. In the pipe according to the invention, the internal annular space 6 is thus dedicated to preserving the integrity of the system: it allows in particular the installation of one or more means allowing:

[0074] – The removal by pumping of the permeant gas from the fluid vein to the internal annulus, the pipe is then provided with such pumping means to evacuate the permeant gas; and / or

[0075] – Monitoring the pressure within this annulus, an increase in pressure being a sign of a leak of fluid through the internal tube 2; thus the pipe according to the invention can be provided with sensors making it possible to detect an increase in pressure in the internal annulus 6; and / or

[0076] – The sweeping of the inner annulus 6 by a carrier gas, associated with detection, to identify more quickly any permeation of the cryogenic fluid towards the inner annulus; the pipe is then associated with means for circulating said carrier gas as well as possibly means for analyzing it, for example by mass spectrometry, to identify early any leak event. In a particular embodiment, the sweeping is carried out continuously and in a loop and the pressure in the inner annulus 6 is kept sufficiently low so that there is no condensation of the cryogenic fluid transported in the inner annulus 6. It is understood that the carrier gas is chosen from gases having a liquefaction temperature, at the pressure to which the inner annular space 6 is subjected, lower than that of the cryogenic fluid transported by the inner tube 2.Thus, for example, if the cryogenic fluid transported by the pipe in the lumen of the internal tube 2 is liquid hydrogen (liquefaction temperature -253°C / 20 K), helium can be chosen as the carrier gas (liquefaction temperature -269°C / 4.13 K).

[0077] This is however not incompatible with a localized presence of thermally insulating panels at certain connections 21 as described below. The pipes 100 comprising these connections 21 nevertheless remain made up of segments of at least 10 m, at least 50 m, at least 100 m, at least 1 km, at least 5 km, at least 10 km, at least 15 km, or even more, in which the internal annular space 6 does not comprise any thermal insulating material.

[0078] A pipe according to the present invention comprises a third tube, called outer tube 4, said outer tube 4 being arranged around the intermediate tube 3. Thus, the inner wall of the outer tube 4 and the outer wall of the intermediate tube 3 define an annular space called outer annular space 7, and the inner 2, intermediate 3 and outer 4 tubes are arranged one inside the other successively.

[0079] The outer tube 4 is made of carbon steel, stainless steel, or an austenitic alloy containing 22 to 27% by weight of manganese. The use of an Invar ® is possible; however, it is not necessary to ensure the transport of a cryogenic fluid in good conditions and is currently undesirable due to the high cost of such alloys.

[0080] The outer annular space 7 of the pipe plays an essential role in the insulation of the pipe and ensures optimal performance of the pipe. The outer annular space 7 comprises a microporous silica-based thermal insulator 8 arranged around the intermediate tube 3, and is subjected to a reduced pressure, measured at room temperature, less than or equal to 20.0 mbar, preferably less than or equal to 10 mbar, less than or equal to 5.0 mbar, less than or equal to 1 mbar, or even less than or equal to 0.1 mbar. It is understood that it is particularly advantageous to establish the lowest possible pressure in the annular space 7. Obviously, this pressure established at room temperature is expected to decrease when the pipe is put into service (or cooled) for the transport of a cryogenic fluid.Thus in a particular embodiment, the pressure in the external annular 7, at ambient temperature, before the pipe is cooled, is between 0.1 mbar and 10 mbar.

[0081] Advantageously, the silica-based microporous thermal insulator 8 is sufficiently rigid to resist, on the one hand, the pressure generated by the mass of the inner tube 2 when it is filled with cryogenic fluid and, on the other hand, the mass of the intermediate tube 3. This makes it possible not to use additional spacers to hold the intermediate tube 3 in the outer tube 4; the insulator 8 being sufficiently strong to itself play the role of spacer between the intermediate tube 3 and the outer tube 4. In one embodiment, the silica-based microporous thermal insulator 8 has a density less than or equal to 250 kg / m 3 , preferably less than or equal to 220 kg / m 3 , less than or equal to 180 kg / m 3 , less than or equal to 150 kg / m3 , or even less than or equal to 100 kg / m 3 . In another embodiment, the microporous silica-based thermal insulator 8 has a density of between 40 kg.m -3 and 250 kg.m -3 , between 70 kg.m -3 and 190 kg.m -3 , preferably between 100 kg.m -3 and 160 kg.m -3 . In a preferred embodiment, the silica-based microporous thermal insulator 8 comprises at least 50% silica, at least 60% silica, preferably at least 70% silica. In a preferred embodiment, the silica-based microporous thermal insulator 8 is Izoflex ® .

[0082] Ideally, the thickness of the internal annulus is reduced to reduce the size of the pipe and reduce the cost of supplying steel tubes. Indeed, the cost of a steel tube is proportional to its mass, which is itself a function of its diameter and thickness. In one embodiment, the thickness of the internal annular space is less than 100 mm, preferably less than 50 mm, or even less than 10 mm.

[0083] The thickness of the thermal insulation layer 8 is between 40 and 150 mm, preferably between 50 and 120 mm, preferably between 60 and 90 mm.

[0084] Spacers can be placed between tubes 2 and 3 to allow efficient welding between, on the one hand, each of the tubes 2 and, on the other hand, each of the tubes 3 of successive sections 1.

[0085] This arrangement and the nature of the tubes 2, 3, 4, the spaces 6 and 7 and the silica-based microporous insulator 8 have the effect of minimizing the mechanical and thermal stresses generated by exposure to environmental temperatures and cryogenic fluids and, thereby, make it possible to envisage pipe segments 100 without intermediate parts which would aim to reduce these stresses by mitigating the effects of expansion and retraction. This makes it possible to envisage, when the terrain and the conditions of installation of the pipe allow it, pipe segments consisting of several sections 1 of pipe and several meters long, or even at least 10 m, at least 50 m, at least 100 m, at least 1 km, at least 5 km, at least 10 km, at least 15 km, or even more. This is particularly advantageous in terms of cost and speed of assembly.Indeed, the pipeline according to the invention is an assembly of different elements including pipeline sections 1 having the structure described above and illustrated in. These individual sections 1 may have a length of between 10 m and 50 m. They are advantageously assembled in a workshop and transported and then used to construct the pipeline at the location of its installation. In the segments consisting of several pipeline sections 1, each of the tubes 2, 3, 4 of each section 1 are simply welded end to end to form a segment of greater length as explained below, of course having continuity of the lumen of the internal tube 2 and also continuity of the internal annular space 6 and the external annular space 7, i.e. connection (in particular without connection 20, 21) in these annular spaces. Such continuity is particularly advantageous.

[0086] Thus, the pipeline according to the invention is advantageously made up of modular elements pre-assembled in the workshop and transported then assembled at the location where the pipeline is to be installed.

[0087] Thus, a pipe according to the invention may be an assembly of several of the following modular elements: pipe section 1 as illustrated in the, pipe end section 30 as illustrated in the which has the role of closing the annular spaces 6 and 7 at the ends of the pipe, connectors 20 or connectors 21 (illustrated in the and 4 respectively), located at least upstream and downstream of the bent zones of the pipe; these parts make it possible to reduce the thermomechanical stresses which occur particularly in these regions, section bent at a determined angle which make it possible to change the orientation of the pipe depending, for example, on the terrain and / or the constraints relating to its location.

[0088] In each of these elements there are tubes 2, 3, 4 as well as annular spaces 6, 7 which are arranged in continuity with each other in the pipe.

[0089] In addition to the pipe sections 1 described above and illustrated, a pipe according to the present invention also comprises at least two end-piece sections 30 (visible in the) at each end. This end-piece section 30 makes it possible to seal the ends of the pipe at the termination of the pipe. This end-piece section 30 is advantageously assembled in a workshop and then transported and welded to the pipe installation site.

[0090] This end-piece section 30 for a pipe comprises: A first closing piece 12 of the external annular space 7 welded on the one hand to an external tube 4 and on the other hand to an intermediate tube 3, said piece comprising one end of the intermediate tube 3 adapted to constitute an extension to the intermediate tube 3 of the pipe, and one end of the external tube 4 adapted to constitute an extension to the external tube 4 of the pipe, A second closing piece 12 of the internal annular space 6 welded on the one hand to one end of the extension of the intermediate tube 3 of the closing piece of the external annular space 7 and on the other hand to the internal tube 2, said internal tube 2 comprising one end adapted to constitute an extension to the internal tube 2 of the pipe, in the external annular space 7, a layer of microporous thermal insulation 8 based on silica.

[0091] In one embodiment, the closing parts 12 of the external annular space 7 and of the internal annular space 6 are independently of one another made of a material with a thermal expansion coefficient less than or equal to 2.10 -6 mm -1 .K -1 , stainless steel, Inconel ®or an austenitic alloy comprising 22 to 27% by weight of manganese. Within the same end-piece section 30, the closing pieces 12 may each be made of a material with similar expansion properties (i.e. compatible and considered close by the person skilled in the art) or identical, preferably identical. In a preferred embodiment, within the same end-piece section 30, they are made of a material of identical composition. In another embodiment, the first and second closing pieces are made of a single piece. In this particular embodiment, said end of the inner tube 2 projects beyond the end of the intermediate tube 3 which itself projects beyond the end of the outer tube 4, so as to facilitate the welding operations. In a preferred embodiment, the material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1is an iron-nickel alloy comprising at least 34.0% nickel, preferably at least 35.0% nickel and even more preferably at least 36.0% nickel. In a particularly preferred embodiment, said iron-nickel alloy comprises 36.0% nickel. In an equally preferred embodiment, it may be an iron-nickel alloy comprising from 34.0% to 38.0% nickel, preferably from 35.0% to 37.0% nickel, or even from 35.5% to 36.5% nickel. In a particularly preferred embodiment, said iron-nickel alloy is an Invar ® .

[0092] In a preferred embodiment, the ends of the tubes 2, 3 and 4 of the end-piece section 30 are made of the same material as the ends of the tubes 2, 3, and 4 of the pipe to which they are intended to be connected by welding in the method detailed below. Obviously, the dimensions of the different elements of the end-piece section 30 are of dimensions adapted to be connected to the end of the pipe.

[0093] In a particular embodiment of the end-piece section 30 according to the invention, a layer of thermal insulation 8 is present in the internal annular space 6. This layer aims to complete the insulation of the pipe on the part of the end-piece section 30 not covered by the external annular space 7 comprising a layer of thermal insulation 8. In a preferred embodiment, this layer of thermal insulation 8 present in the internal annular space 6 of the end-piece section 30 also extends partly under the layer of thermal insulation 8 of the external annular space 7, thus allowing optimal insulation at the end of the pipe. In other words, the layer of thermal insulation 8 is located at the right of said closing part 12 in the internal annular space 6.

[0094] A pipeline may also comprise at least one bent section. It will be readily understood that the bent sections are made necessary to allow the pipeline to follow the defined route from point A to point B, taking into account for example the ground conditions, by modifying the orientation of the pipeline according to a defined angle. Typically, the bent section comprises the same elements as those described above for the pipeline section 1, with the difference that each of the tubes 2, 3, 4 of the same bent section has an identical angle of between 30° and 90°. Preferably, the tubes 2, 3 and 4 of the bent section are made of the same material as the tubes 2, 3, and 4 of the pipeline to which they are intended to be connected by welding in the method detailed below.In the same way also, the external annular space 7 comprises a microporous thermal insulator 8 based on silica. Obviously, the diametrical dimensions of the different elements of the bent section are of dimensions adapted to the diametrical dimensions of the different elements of the pipe.

[0095] As mentioned, although the pipe sections 1 of the pipe according to the invention are particularly suitable for limiting the thermomechanical stresses induced in the pipe, the presence of bends (in other words, areas where the pipe is curved) accentuates these stresses in the areas which contain them and makes necessary the presence of connectors 20, 21, as described previously in the summary section, located upstream and downstream of the bends.

[0096] A connector 20 adapted to the pipe of the invention is as described in. This connector 20 is advantageously assembled in the workshop then transported and welded to the place of installation of the pipe.

[0097] Typically, the connector 20 comprises the same elements as those described above for the pipe section 1. Preferably, the tubes 2, 3 and 4 of the connector 20 are made of the same material as the tubes 2, 3 and 4 of the pipe to which they are intended to be connected by welding in the method detailed below. Obviously, the diametrical dimensions of the different elements of the connector are of dimensions adapted to the diametrical dimensions of the different elements of the pipe to which the connector 20 is intended to be connected.

[0098] The connector 20 further comprises connecting pieces 9 connecting the tubes 2, 3, 4 arranged two by two, located in the external 7 and internal 6 annular spaces. They are provided with at least one orifice so as to allow the circulation of gas in the annular spaces 6, 7, said pieces being made of a material selected from an alloy with an expansion coefficient less than or equal to 2.10 -6 mm -1 .K -1 , a stainless steel, an Inconel ® , an austenitic alloy comprising from 22 to 27% by weight of manganese. In a preferred embodiment, the material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1is an iron-nickel alloy comprising at least 34.0% nickel, preferably at least 35.0% nickel and even more preferably at least 36.0% nickel. In a further preferred embodiment, it may be an iron-nickel alloy comprising from 34.0% to 38.0% nickel, preferably from 35.0% to 37.0% nickel, or even from 35.5% to 36.5% nickel. In a particularly preferred embodiment, said iron-nickel alloy is an Invar ® . Within the same connector 20, the connecting pieces 9 may be made of a material with similar expansion properties (i.e. compatible and considered close by the person skilled in the art) or identical, preferably identical. In a preferred embodiment, within the same connector 20, they are made of a material of identical composition.

[0099] As mentioned and visible on the, and mentioned in the summary part of the invention above, an external overlayer 10 of thermal insulation 8 surrounded by an external connecting tube 11 is present on this connection 20. The external connecting tube 11 can be made of carbon steel, stainless steel, or austenitic alloy comprising from 22 to 27% by weight of manganese. In a preferred embodiment, the external connecting tube 11 is made of carbon steel. This connection 20 has the advantage of being easy and quick to assemble in the workshop.

[0100] Although this connector 20 is quite effective in reducing the physical stresses generated at the bends in the pipe according to the invention, it may be advantageous in certain embodiments for the pipe not to have any relief formed by this overlayer on its surface. This is made possible by the implementation of a connector 21 as illustrated in and described in the summary section of the invention above.

[0101] In the connector 21 for the pipe according to the invention, the thermal insulation layer 8 placed at the right of the connecting piece 9 connecting the external tube 4 and the intermediate tube 3, is arranged in the inner annular 6. This organization allows the continuity of the external surface of the pipe, that is to say without protrusion or bump. In one embodiment, as shown in the, in this connector 21, the thickness of the external annular space 7 is reduced relative to the thickness of the external annular space of the adjacent sections 1. In this embodiment, this reduction allows an increase in the internal annular space 6 to allow the localized introduction of the thermal insulation layer 8 at the right of the connecting piece 9 connecting the external tube 4 and the intermediate tube 3. In this connector 21, the very localized presence of thermal insulation 8 does not lead to a loss of the overall performance of the pipe according to the invention.Furthermore, the insulation in the inner annulus of this connector 21 is placed so as not to cause any particular hindrance for, for example, the establishment of the sweeping of the inner annulus 6 of the pipe by a carrier gas as mentioned above. The composition characteristics of the different elements of these connectors 21 are identical to those of the connectors 20. In particular, within the same connector 21, the connecting pieces 9 may be made of a material with similar expansion properties (i.e. compatible and considered close by the person skilled in the art) or identical, preferably identical. In a preferred embodiment, within the same connector 21, they are made of a material of identical composition.

[0102] In a preferred embodiment, the thermal insulator 8 is in contact with the intermediate tube and, where appropriate, with regard to the connections 20 or 21, with the external tube or the internal tube respectively.

[0103] As mentioned, the arrangement of the pipe elements and the various modular elements act in synergy and make it possible to obtain a pipe that is particularly thermally efficient, safe and suitable for cryogenic fluids and more particularly for cryogenic fluids at liquefaction temperatures such as those of hydrogen or helium.

[0104] In the embodiments according to which the connecting pieces 9 and the tubes to which they are connected are made of materials with different thermal coefficients, it is advantageous to insert between the tubes and the connecting pieces, transition pieces which are made of a material selected from a stainless steel, an Inconel ® or an austenitic alloy comprising 22 to 27% by weight of manganese and which are inserted in continuity with the connecting piece and the tube to which the latter is connected. An inconel ®is known to be a superalloy highly resistant to extreme temperature conditions and corrosion (superalloy) that contains mainly nickel, but also several other metals such as chromium, magnesium, iron or titanium. Thus, there are several Inconel type alloys ® . In particular, an Inconel ® At meaning of the invention refers to a superalloy comprising at least 45% nickel such as, for example and in a non-limiting manner, supra 50 ® , Inconel 600, Inconel 625, or Inconel 718. An Inconel ® is a particularly preferred material for transition pieces, for example when a connecting piece 9 is made of stainless steel and one of the tubes to which it is connected is made of Invar ® .

[0105] According to another aspect, the invention also relates to the methods of assembling the modular elements above which can make up the pipe according to the invention.

[0106] Assembly processes for the various modular elements of the pipeline.

[0107] Despite a triple-envelope architecture, the pipes 100 developed by the inventors are particularly easy and quick to assemble. This ease and speed of assembly is due on the one hand to the arrangements described above as well as to the particular choice of materials for the various components, but also on the other hand to the development of parts pre-assembled in the workshop, which can easily be transported to the site of construction of the pipe (at sea, on land or above ground). This ease of construction and the safety of these pipes 100 can also make it possible to envisage their installation in rugged environments or environments previously considered unsuitable for this. Thus, other objects of the present invention relate to methods of assembling the various modular elements mentioned above, to result in the construction of a pipe according to the invention.

[0108] Another object of the invention therefore relates to a method of assembling the end of a pipe section and a pipe end-piece section 30, which makes it possible to safely close the internal 6 and external 7 annular rings.This method may comprise the following steps:Providing a pipe section end as described above,Providing a pipe section-end piece 30 whose inner 2, intermediate 3 and outer 4 tubes are of a diameter adapted, respectively, to the extension of the inner 2, intermediate 3 and outer 4 tubes of the pipe section end,Welding the end of the inner tube 2 of the pipe section end 1 with the end of the inner tube 2 of the pipe section-end piece 30 adapted to constitute an extension of the inner tube 2 of the pipe section end 1,In a space between the intermediate tube 3 of the end-end piece 30 and the intermediate tube 3 of the pipe section 1, insert two intermediate half-shells made of a material with a thermal expansion coefficient less than or equal to 2.10-6 mm -1 .K -1and weld them each on the one hand to the end of the intermediate tube 3 of the end-piece section 30 adapted to constitute an extension of the intermediate tube 3 of the end of the pipe section 1 and on the other hand to the intermediate tube 3 of the pipe section, then weld the half-shells together,In the external annular space 7, fill a space between the thermal insulation layer 8 of the end of the pipe section 1 and the thermal insulation layer 8 of the end-piece section 30, by adding a thermal insulation layer 8 in continuity with said thermal insulation layer 8 of the end of the pipe section 1 and thermal insulation layer 8 of the end-piece section 30,In a space between the external tube 4 of the end-piece section 30 and the external tube 4 end of the pipe section 1, insert two external half-shells made of carbon steel, stainless steel,or an austenitic alloy comprising from 22 to 27% by weight of manganese and weld them each on the one hand to the end of the external tube 4 of the pipe end section 30 and on the other hand to the external tube 4 of the pipe 1, then weld the half-shells together.,

[0109] In a particular embodiment of the method for assembling the end of a pipe section and a pipe end-piece section 30, a layer of thermal insulation 8 is present in the internal annular space 6 which extends partly under the layer of thermal insulation 8 of the external annular space 7, thus allowing optimal insulation at the end of the pipe whose internal and external annular spaces are closed.

[0110] Another object of the invention relates to a method for assembling two ends of sections 1 of a pipe, which allows the elongation of the pipe according to the invention. This method for assembling two ends of section 1 of pipe may comprise the following steps:Providing two ends of two sections 1, the inner 2, intermediate 3 and outer 4 tubes of which are of a diameter adapted to allow the end-to-end assembly of each of said inner 2, intermediate 3 and outer 4 tubes of the two sections 1,Butting the inner tubes 2 of each of the ends of the two sections 1 of pipe, so that they are joined by one of their ends,Welding the joined ends of the inner tubes 2 of each of the sections,Butting the intermediate tubes 3 of each of the sections to the ends of the intermediate tubes 3 of each of the sections so that they are joined and form a single tube surrounding the inner tube 2,Weld the joined ends of the intermediate tubes 3 of each of the sections,Ensure the continuity of the thermal insulation in the external annular space 7, for example, by adding thermal insulation 8 in the external annular space 7 at the junction of the two sections,Butt the external tubes 4 of each of the sections to the ends of the external tubes 4 of the sections, so that they are joined and form a single tube surrounding the internal tube 2,Weld the joined ends of the external tubes 4 of each of the sections.,

[0111] Advantageously, the thermal insulating layer 8 of the external annular space 7, due to its resistance, makes it possible to maintain the necessary space between the intermediate 3 and external 4 tubes of each of the sections during the step of welding the intermediate 3 tubes together and the tubes 4 together.

[0112] Another object of the invention relates to a method of assembling the end of a section of pipe 1 and a connector 20, 21 of a pipe 1, said connector comprising: three tubes arranged one inside the other 2, 3, 4: an internal tube 2 made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 an intermediate tube 3 made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 an outer tube 4 made of carbon steel, stainless steel, or an austenitic alloy comprising from 22 to 27% by weight of manganese, said three tubes arranged one inside the other 2, 3, 4 defining an internal annular space (6) between said inner tube 2 and said intermediate tube 3 and an external annular space 7 between said intermediate tube 3 and said outer tube 4,

[0113] the external annular space 7 comprising a microporous thermal insulator 8 based on silica, connecting pieces 9 connecting said three tubes arranged one inside the other (2, 3, 4) two by two, located in the external 7 and internal 6 annular spaces, provided with at least one orifice so as to allow the circulation of gas in the annular spaces 6, 7, said pieces being made of an alloy with an expansion coefficient less than or equal to 2.10 -6 mm -1 .K -1 , stainless steel, Inconel ®, or an austenitic alloy comprising from 22 to 27% by weight of manganese, in the case of connecting pieces 9 connecting tubes made of materials with different thermal coefficients, tubular transition pieces are positioned between the connecting pieces 9 and at least one of the two tubes, said transition pieces being made of a material with a thermal coefficient intermediate to that of the connecting piece (9) and the tube on which it is positioned, at the level of the connecting piece 9 connecting said external tube 4 and said intermediate tube 3: an external overlayer 10 of microporous thermal insulation 8 based on silica, surrounded by an external connecting tube 11 made of carbon steel, stainless steel, or austenitic alloy comprising from 22 to 27% by weight of manganese, said external connecting tube 11 being welded at its ends to the external tube 4 of the fitting,ora layer of thermal insulation 8 at the right of said connecting piece 9 is located in the inner annular 6, the method comprising the following steps:Providing an end of pipe section 1 comprising three tubes arranged one inside the other 2, 3, 4:an inner tube 2 made of a material with a thermal expansion coefficient less than or equal to 2.10, -6 mm -1 .K -1 ,an intermediate tube 3 made of a material with a coefficient of thermal expansion less than or equal to 2.10 -6 mm -1 .K -1 ,an outer tube 4 made of carbon steel, stainless steel, or an austenitic alloy comprising from 22 to 27% by weight of manganese, said three tubes arranged one inside the other 2, 3, 4 defining an internal annular space (6) between said inner tube 2 and said intermediate tube 3 and an external annular space 7 between said intermediate tube 3 and said outer tube 4,

[0114] the outer annular space 7 comprising a microporous silica-based thermal insulator 8, the inner annular space 6 not comprising any insulating material,Provide the pipe fitting 20,21 1, the inner 2, intermediate 3 and outer 4 tubes of which are of a diameter adapted, respectively, to the extension of the inner 2, intermediate 3 and outer 4 tubes of the end of the pipe section 1,Weld the end of the inner tube 2 of the end of the pipe section 1 with the end of the inner tube 2 of the pipe fitting 20,21 1,In a space between the intermediate tube 3 of the pipe fitting 20,21 1 and the intermediate tube 3 of the end of a pipe section 1, insert two intermediate half-shells made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 mm -1 .K -1and weld them each on the one hand to the end of the intermediate tube 3 of the connection 20,21 of pipe 1 and on the other hand to the intermediate tube 3 of the end of the pipe section 1, then weld the half-shells together,In the external annular space 7, fill a space between the thermal insulation layer 8 of the end of the pipe section 1 and the thermal insulation layer 8 of the connection 20,21 of pipe 1, by adding a layer of insulation 8 in continuity with said thermal insulation layer 8 of the end of the pipe section 1 and thermal insulation layer 8 of the connection 20,21 of pipe 1,In a space between the external tube 4 of the connection 20,21 and the external tube 4 of the pipe section 1, insert two external half-shells made of a carbon steel, a stainless steel, or an austenitic alloy comprising 22 to 27% by weight of manganese and weld them each on the one hand to the end of the external tube 4 of the connection 20,21 for pipe 1 and on the other hand to the external tube 4 of the end of the pipe section 1, then weld the half-shells together.,

[0115] The half-shells are sized to allow the joining of tubes that they are intended to connect; they are shaped like half-cylinders (or half-tubes). They allow the closing of the pipe according to the invention. In a particular embodiment, the half-shells are made of the same material as the tubes to which they are connected.

[0116] In a particular embodiment, each independently of the methods detailed above may comprise non-destructive testing of at least one weld performed therein.

Claims

Claim 1.A conduit adapted for transporting a cryogenic liquid, thermally insulated, characterized in that it comprises- three tubes arranged one inside the other (2, 3, 4):• an inner tube (2) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1,• an intermediate tube (3) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1,• an outer tube (4) made of carbon steel, stainless steel, or an austenitic alloy comprising 22 to 27% by weight of manganese, said three tubes arranged one inside the other (2, 3, 4) defining an inner annular space (6) comprised between said inner tube (2) and said intermediate tube (3) and an outer annular space (7) comprised between said intermediate tube (3) and said outer tube (4), the outer annular space (7) comprising a microporous silica-based thermal insulator (8), the inner annular space (6) not comprising any thermal insulating material,- connecting parts (9) connecting said three tubes arranged one inside the other (2, 3, 4) in pairs, located in the outer (7) and inner (6) annular spaces, and provided with at least one orifice to allow the circulation of gas in the inner (6) and outer (7) annular spaces, said parts being made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1, of stainless steel, Inconel® or an austenitic alloy comprising 22 to 27 wt% manganese,in the case of connecting parts (9) connecting tubes made of materials with different thermal coefficients, tubular transition parts positioned between the connecting parts (9) and at least one of the two tubes, said transition parts being made of a material with a thermal coefficient intermediate to that of the connecting part and the tube on which it is positioned.Claim 2.A unit (1) of conduit adapted for transporting a cryogenic liquid characterized in that it comprises:- three tubes arranged one inside the other (2, 3, 4):• an inner tube (2) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1,• an intermediate tube (3) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1,• an outer tube (4) made of carbon steel, stainless steel, or an austenitic alloy comprising 22 to 27% by weight of manganese,- said three tubes arranged one inside the other (2, 3, 4) defining an inner annular space (6) comprised between said inner tube (2) and said intermediate tube (3) and an outer annular space (7) comprised between said intermediate tube (3) and said outer tube (4),- the outer annular space (7) comprising a microporous silica-based thermal insulator (8), the inner annular space (6) not comprising any thermal insulating material,- connecting parts (9) connecting said three tubes arranged one inside the other (2, 3, 4) in pairs, located in the outer (7) and inner (6) annular spaces, and provided with at least one orifice to allow the circulation of gas in the inner (6) and outer (7) annular spaces, said parts being made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1, of stainless steel, Inconel® or an austenitic alloy comprising 22 to 27% by weight of manganese,in the case of connecting parts (9) connecting tubes made of materials with different thermal coefficients, tubular transition parts positioned between the connecting parts (9) and at least one of the two tubes, said transition parts being made of a material with a thermal coefficient intermediate to that of the connecting part and the tube on which it is positioned.Claim 3.A fitting (20) for a conduit according to claim 1 characterized in that it comprises:- three tubes arranged one inside the other (2, 3, 4):• an inner tube (2) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1• an intermediate tube (3) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1• an outer tube (4) made of carbon steel, stainless steel, or an austenitic alloy comprising 22 to 27% by weight of manganesesaid three tubes arranged one inside the other (2, 3, 4) defining an inner annular space (6) comprised between said inner tube (2) and said intermediate tube (3) and an outer annular space (7) comprised between said intermediate tube (3) and said outer tube (4),the outer annular space (7) comprising a microporous silica-based thermal insulator (8),- connecting parts (9) connecting said three tubes arranged one inside the other (2, 3, 4) in pairs, located in the outer (7) and inner (6) annular spaces, provided with at least one orifice so as to allow the circulation of gas in the annular spaces (6, 7), said parts being made of an alloy with a coefficient of expansion less than or equal to 2.10-6 m.m-1.K-1, of stainless steel, of Inconel®, or of an austenitic alloy comprising from 22 to 27 wt% of manganese),in the case of connecting parts (9) connecting tubes made of materials with different thermal coefficients, tubular transition parts are positioned between the connecting parts (9) and at least one of the two tubes, said transition parts being made of a material with a thermal coefficient intermediate to that of the connecting part (9) and the tube on which it is positioned,- at the connecting part (9) connecting said outer tube (4) and said intermediate tube (3), an outer additional layer (10) of microporous silica-based thermal insulation (8), surrounded by an outer connecting tube (11) of carbon steel, stainless steel, or austenitic alloy comprising 22 to 27 % by weight of manganese, said outer connecting tube (11) being welded at its ends to the outer tube (4) of the fitting.Claim 4.The fitting (21) for a conduit according to claim 1 characterized in that it comprises:- three tubes arranged one inside the other (2, 3, 4):• an inner tube (2) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1• an intermediate tube (3) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1• an outer tube (4) made of carbon steel, stainless steel, or an austenitic alloy comprising 22 to 27% by weight of manganesesaid three tubes arranged one inside the other (2, 3, 4) defining an inner annular space (6) comprised between said inner tube (2) and said intermediate tube (3) and an outer annular space (7) comprised between said intermediate tube (3) and said outer tube (4),the outer annular space (7) comprising a microporous silica-based thermal insulator (8),- connecting parts (9) connecting said three tubes arranged one inside the other (2, 3, 4) in pairs, located in the outer (7) and inner (6) annular spaces, provided with at least one orifice so as to allow the circulation of gas in the annular spaces (6, 7), said parts being made of an alloy with a coefficient of expansion less thanor equal to 2.10-6 m.m-1.K-1, of stainless steel, of Inconel®, or of an austenitic alloy comprising from 22 to 27 wt% of manganese,in the case of connecting parts (9) connecting tubes made of materials with different thermal coefficients, tubular transition parts are positioned between the connecting parts (9) and at least one of the two tubes, said transition parts being made of a material with a thermal coefficient intermediate to that of the connecting part (9) and the tube on which it is positioned,- at the connecting part (9) connecting said outer tube (4) and said intermediate tube (3), a thermal insulation layer (8) opposite said connecting part (9) is located in the inner annular space (6).Claim 5.An end-piece unit (30) for a conduit according to claim 1, the end-piece unit (30) characterized in that it comprises:- a first part (12) for closing the outer annular space (7) welded on one side to an outer tube (4) and on the other side to an intermediate tube (3), said part comprising an end of the intermediate tube adapted to constitute an extension to the intermediate tube (3) of the conduit, and an end of the outer tube adapted to constitute an extension to the outer tube (4) of the conduit, said part being made of an alloy with a coefficient of expansion less than or equal to 2.10-6 m.m-1.K-1, of stainless steel, of Inconel®, or of an austenitic alloy comprising 22 to 27% by weight of manganese,- a second part (12) for closing the inner annular space (6) welded on one side to one end of the extension of the intermediate tube (3) of the part for closing the outer annular space (7) and on the other side to the inner tube (2), said inner tube (2) comprising an end adapted to constitute an extension to the inner tube (2) of the conduit, said part being made of an alloy with a coefficient of expansion less than or equal to 2.10-6 m.m-1.K-1, of stainless steel, of Inconel®, or of an austenitic alloy comprising from 22 to 27 wt% of manganese,- in the outer annular space (7), a layer of microporous silica-based thermal insulation (8),- connecting parts (9) connecting said three tubes arranged one inside the other (2, 3, 4) in pairs, located in the outer (7) and inner (6) annular spaces, and provided with at least one orifice to allow the circulation of gas in the inner (6) and outer (7) annular spaces, said parts being made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1, of stainless steel, Inconel® or an austenitic alloy comprising 22 to 27% by weight of manganese,in the case of connecting parts (9) connecting tubes made of materials with different thermal coefficients, tubular transition parts positioned between the connecting parts (9) and at least one of the two tubes, said transition parts being made of a material with a thermal coefficient intermediate to that of the connecting part and the tube on which it is positioned.Claim 6.An elbow unit for a conduit according to claim 1, the elbow conduit unit comprising:- three tubes arranged one inside the other (2, 3, 4):• an inner tube (2) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1,• an intermediate tube (3) made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1,• an outer tube (4) made of carbon steel, stainless steel, or an austenitic alloy comprising 22 to 27% by weight of manganese,- said three tubes arranged one inside the other (2, 3, 4) defining an inner annular space (6) comprised between said inner tube (2) and said intermediate tube (3) and an outer annular space (7) comprised between said intermediate tube (3) and said outer tube (4),- the outer annular space (7) comprising a microporous silica-based thermal insulator (8),- said tubes arranged one inside the other (2, 3, 4) having a curvature at an angle comprised between 30° and 90°- connecting parts (9) connecting said three tubes arranged one inside the other (2, 3, 4) in pairs, located in the outer (7) and inner (6) annular spaces, and provided with at least one orifice to allow the circulation of gas in the inner (6) and outer (7) annular spaces, said parts being made of a material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1, of stainless steel, Inconel® or an austenitic alloy comprising 22 to 27% by weight of manganese,in the case of connecting parts (9) connecting tubes made of materials with different thermal coefficients, tubular transition parts positioned between the connecting parts (9) and at least one of the two tubes, said transition parts being made of a material with a thermal coefficient intermediate to that of the connecting part and the tube on which it is positioned.Claim 7.The conduit according to claim 1, the conduit unit (1) according to claim 2, the fitting (20,21) according to claim 3 or 4, or the end-piece unit (30) according to claim 5, wherein the material with a coefficient of thermal expansion less than or equal to 2.10-6 m.m-1.K-1 constituting the inner tube and / or the intermediate tube is an ironnickel alloy comprising 34.0% to 38.0% nickel, preferably 35.0% to 37.0% nickel, or even 35.5% to 36.5% nickel.Claim 8.The conduit according to any one of claims 1 or 7, or the fitting (20,21) according to any one of claims 3 or 4, or the end-piece unit (30) according to claim 5, wherein, respectively, the connecting parts (9) or closing parts (12) are made of an iron-nickel alloy comprising 34.0% to 38.0% nickel, preferably 35.0% to 37.0% nickel, or even 35.5% to 36.5% nickel.Claim 9.The conduit according to claim 1, characterized in that it comprises a segment of at least 10 m, preferably of at least 50 m, preferably of at least 100 m, preferably of at least 1 km, preferably of at least 5 km, preferably of at least 10 km, or even preferably of at least 15 km in which the outer 7 and inner 6 annular spaces do not contain a fitting (20,21) according to claim 3 or 4.Claim 10. The conduit according to claim 1, characterized in that when it comprises an elbow conduit unit according to claim 6, a fitting (20,21) of a conduit (1) according to claim 3 or 4 is placed upstream and / or downstream of said elbow conduit unit.Claim 11. The conduit according to claim 1 characterized in that the microporous thermal insulation (8) has a density comprised between 40 kg.m-3 and 250 kg.m-3, between 70 kg.m-3 and 190 kg.m-3, preferably between 100 kg.m-3 and 160 kg.m-3.Claim 12. The conduit according to claim 1 wherein a gas is circulated in the inner annular space (6), said gas having, at the circulation pressure in the inner annular space, a liquefaction temperature lower than that of the cryogenic liquid transported in the conduit (1).Claim 13. The conduit according to claim 12, at one end of which is coupled at least one means for analyzing the gas circulating in the inner annular space (6).Claim 14. The conduit according to any one of the preceding claims wherein the pressure in the outer annular space (7), at ambient temperature, before the conduit is cooled, is less than or equal to 10 mbar.

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