“Axial expansion compensating piping component, and installation implementing it”

Abstract

The invention relates to a piping component (1) for a circuit (81, 82) for circulating fluid (8) at high temperature, in particular liquid metal or molten salt, in particular liquid sodium at 550°C. This component comprises two inner (12) and outer (11) sleeves inserted into each other defining between them a static, non-circulating space (100), communicating with the circulating fluid (8) but thermally distant. These sleeves are connected to each other by an axially deformable bellows (13) to compensate for axial expansion of the piping (81, 82) of said circuit. This outer sleeve (11) has, in the sagittal plane, radially extreme points (111, 112) which receive purge connections and are all outside the bellows (13).The bellows can be emptied by gravity: the purge is thus more complete, with better evacuation of the allogenic residues present in the heat transfer fluid. Preferably, the compensation bellows (13) is concentric and internal to the external sleeve (11), receiving the pressure on its "external" surface. Figure for the abstract: Fig.2.

Description

Title of the invention: “Axial expansion compensating piping component, and installation implementing it”

[0001] The present invention relates to a piping component for compensating for axial expansions within a high-temperature fluid circulation circuit, of the axially deformable bellows type.

[0002] It further relates to an installation for circulating fluid within a piping circuit, in particular metallic, in particular operating at an ambient temperature below 50°C, provided for a fluid circulating at a temperature above 400°C, in particular above 450°C or even above 500°C and for example 550°C, in which said circuit comprises one or more compensating components. State of the art

[0003] In areas where a fluid at high temperature is circulated in pipes, in particular metal pipes, expansions occur between the cold state at room temperature (where the circuit is not in operation) and the operating state at high temperature.

[0004] Such fields include, for example, technologies where a molten metal or salt is circulated as a heat transfer fluid, particularly in certain power plants. But it can also involve other fields such as those using liquid aluminum for hot-dip coating or injection molding. In such fields, the circulating fluid reaches temperatures of up to 550°C for liquid sodium, or even 600°C or more in certain projects, while the minimum temperature is of the order of 20°C when the circuit is at room temperature during a prolonged stoppage of circulation.

[0005] To avoid leaks or damage to the circuit, it is often necessary to compensate for axial expansion in one way or another. The usual method is to absorb these length variations by bending the bent components. If necessary, for example for long lengths, a compensation lyre can be inserted. But these solutions take up a lot of space, and such bending is sometimes impossible or insufficient when the pipe wall is very thick or the pipe has a large diameter.

[0006] For these reasons, it has been proposed to use piping components providing compensation by axial displacement by means of an axially deformable bellows. However, this type of bellows must be subject to specific dimensioning to justify its mechanical strength under operating conditions in order to take into account takes into account the damaging deformations that occur at high temperatures, to guarantee the resistance of materials to pressure and fatigue, as well as their stability during finishing.

[0007] In order to limit the effects of high temperatures, it has been proposed to provide active cooling by circulation of cold fluid around the deformation zones, but this would lead to unacceptable risks in the event of failure of the cooling system.

[0008] Various passive configurations have been proposed, which consist of implementing thermal insulation of the bellows relative to the piping and using the ambient environment to passively cool the bellows. This may involve arranging the bellows in a position where the fluid it contains is sufficiently far from the circulating fluid (heat source) to be able to remain at a temperature lower than that of the circulating fluid, preferably below the finishing temperature of the material(s) of the bellows, for example below 400°C, and for example of the order of 300°C in document GB1242986, here illustrated in [Fig.l].

[0009] In this configuration, as proposed in document GB1242986, the interior of the pipe 10, 20 is placed in communication by an annular circulation space 40 with a static space 42 which receives the fluid but does not participate in its circulation. This static space is cylindrical and surrounds the circulation pipe 10 from which it is separated by a thickness of insulation 14, while being cooled by the ambient atmosphere, in particular by means of cooling fins 24. In its part remote from the circulation space 40, the static space 42 is surrounded by a bellows 30 with annular waves, which deforms axially when one of the pipes 10 moves longitudinally relative to the other 20. In its peripheral part, this insulating sleeve 14 includes heating wires 15 to heat the liquid blade during heating.The bellows is cooled by the external atmosphere, and the heat flow which reaches it by conduction from the circulation space 40 is previously cooled by the fins 24.

[0010] It remains, however, desirable to improve this type of component, in particular in terms of reliability, lifetime and ease of implementation and maintenance, in particular in the context of use with a liquid metal.

[0011] An aim of the invention is to overcome in whole or in part the disadvantages of the state of the art, and in particular to improve the performance of simplicity of manufacture, flexibility of adaptation to constraints, but also of reliability, lifespan, and ease of maintenance. Presentation of the invention

[0012] The invention provides a piping component for a circulation circuit of fluid intended to vary between a minimum temperature and a maximum temperature, comprising: - a circulation space intended to be crossed by said circulation of fluid between a first inlet and a second inlet, - an internal sleeve and an external sleeve inserted into each other to define between them a so-called static space which is not crossed by said fluid circulation and is thermally distant from said circulation space, thus allowing said static space to have a temperature lower than that of the fluid circulating in said circuit when the temperature of the circulating fluid is higher than the ambient temperature, which internal and external sleeves: • are each connected in a sealed manner with one of said first and second inlets, so as to allow passage of said fluid between said static space and said circulation space, in at least one region called the connection region, and • are connected to each other in a sealed manner by at least one axially deformable bellows, called a compensation bellows, which is arranged to accept an axial elastic deformation making it possible to compensate for a variation in the axial difference between the first inlet and the second inlet, one with respect to the other, caused by an axial expansion of the piping of said circulation circuit when the temperature of the circulating fluid varies between said minimum temperature and said maximum temperature.

[0013] According to the invention, said external sleeve has a shape in which, along at least one plane which is sagittal to it, the radially extreme points of its internal wall are all located outside the parts of said bellows provided to absorb the elastic deformation producing said expansion compensation, so that said radially extreme points form all of the low points and / or high points of said static space when said component is installed with said sleeves in an axially horizontal position.

[0014] This outer sleeve has, by way of examples, a substantially cylindrical shape with a radial bulge or flare, or slightly conical or biconical, or any shape widening radially continuously towards one or more radially extreme points.

[0015] Preferably, the radially extreme point(s) of the outer sleeve each comprise a fluid connection arranged to be able to connect thereto: a liquid drain tapping in a low point, and / or a gas purge tapping in a high point.

[0016] Typically, the compensation bellows is arranged inside the outer sleeve, and in particular concentrically with the inner sleeve or itself forming said inner sleeve.

[0017] Although the cooling of the bellows may be, in an equal context in terms of materials and exchange surfaces, less than that permitted by the external bellows of the prior art, and / or more complex to install or monitor or repair, this arrangement in the invention makes it possible to guarantee that no retention space remains in the compensator.

[0018] In fact, all the low points of the bellows in contact with the liquid, that is to say the bottom of the waves of the upper part of the bellows, can empty by gravity by following the periphery of the bellows to the waves of the lower part of the bellows, which empty by gravity to the low point of the inner wall of the external sleeve, where one or more tapping points of the purge circuit can be installed without compromising the solidity of the bellows.

[0019] The invention thus makes it possible to obtain a more complete purge of the liquid, in particular at the level of the compensator, and therefore a better evacuation of all the chemical compounds and allogenic residues included in and transported by the heat transfer fluid; which are a factor of corrosion of the walls and / or of reduction of performance of the fluid if they accumulate there, in particular in a concentrated form in small retention spaces. In the case of pipes conveying liquid sodium, the presence of stagnant zones also constitutes a risk during maintenance operations for the safety of the installation due to the reactivity of sodium with water and air. As can be understood, this type of retention and accumulation is thus avoided, which existed for example in the bottom of the lower waves of the bellows of the prior art document of [Fig.l].Furthermore, in the case of liquids presenting risks of interactions during maintenance, such as sodium, the component can be inerted by ensuring that it no longer contains (or contains less) potentially reactive liquid.

[0020] It will be noted that the bellows of the invention, when it is part of the inner surface of the static space, that is to say the side facing the piping, receives the pressure on the outer surface, that is to say it works "under external pressure", that is to say on the convex side of its circumference. Now it turns out that, for the same bellows, the fact of working under external pressure allows it better resistance, instantaneous and over time, to fatigue, than when it works under "internal pressure" as is the case in the configuration of the prior art of document GB1242986A.

[0021] Furthermore, the expansion of the pipes then leads to a stress on this bellows in traction, which also proves to be more favorable (in any case combined with the external pressure) than when it works in axial compression as is the case in the configuration of the prior art of document GB1242986A.

[0022] This configuration of the invention thus makes it possible to avoid certain modes of instability encountered in the case of bellows working under internal pressure and subjected to axial compression.

[0023] Typically, in the component of the invention, the inner and outer sleeves are arranged to radially surround the first and second inlets and / or the piping to which they are connected.

[0024] Preferably, the part of the static space which is in contact with the inner wall of the compensation bellows, called the compensation space, communicates with the circulation space via a so-called intermediate space which is axially elongated relative to the inner and outer sleeves and thermally distant from said circulation space, thus creating a "thermal brake" in an axial direction for a thermal flow established within the fluid between the circulation space and said compensation space, in particular in the form of a static liquid blade surrounding the inner sleeve and thermally distant from the circulation space.

[0025] According to an optional characteristic, the internal sleeve is surrounded, inside the static space, by a thermally insulating sleeve which covers the connection region and extends towards the compensation bellows, thus delimiting an elongated and thin liquid blade forming a thermal brake between the connection region and the compensation bellows, independently of the radial gap existing between the internal sleeve and the external sleeve.

[0026] According to another particular feature, which may or may not be combined with the preceding optional characteristics, the component comprises at least two compensation bellows, in particular arranged inside the same external sleeve, the compensation spaces of which are part of the same static space and are arranged on either side of the connection region of said static space.

[0027] According to another aspect, the invention proposes an installation for circulating fluid within a piping circuit, in particular metallic, in particular operating at an ambient temperature below 50°C, provided for a fluid circulating at a temperature above 400°C, in particular above 450°C or even 500°C, in particular below 600°C and for example around 550°C.

[0028] According to this aspect, said circuit comprises one or more piping components as disclosed herein, which is implemented to provide compensation for all or part of the axial expansion of the piping of said circuit.

[0029] According to optional features of this installation, intended to be combined together in different ways: • the compensating component (1, T, 1", T") is mounted so that the expansion of the pipes (81, 82) of the circuit tends to compress axially when their temperature rises the bellows (13, 13') of said component compensator; • the circulating fluid is or includes a liquid salt or a liquid metal, in particular is or includes liquid sodium; and / or • such an installation in which the circulating fluid is or includes liquid sodium; and / or • such an installation in which the fluid is used as a heat transfer fluid.

[0030] Various embodiments of the invention are provided, integrating according to all of their possible combinations the different optional characteristics set out here. Brief description of the drawings

[0031] Other features and advantages of the invention will emerge from the detailed description of a non-limiting embodiment, and from the appended drawings in which:

[0032] [Fig-1]: [Fig.l] is an axial and vertical sectional diagram of a component with bellows fitting according to the state of the art, taken from the illustrative figure of document GB1242986A;

[0033] [Fig.2]: [Fig.2] illustrates a first example of an embodiment of the invention, by a diagram in axial and vertical section of a compensation component with an offset bellows mounted inside an external sleeve which is substantially cylindrical and coaxial with the piping;

[0034] [Fig.3]: [Fig.3] is a half-view from [Fig.2], obtained by axisymmetric thermal calculation and which illustrates the temperature variations within the component of [Fig.2], for a fluid circulating at 550°C in the hypothesis of a static fluid, with purely conductive heat exchange;

[0035] [Fig.4]: [Fig.4] illustrates a second exemplary embodiment of the invention, by a diagram in axial and vertical section of a compensation component with two offset bellows mounted symmetrically inside an external sleeve which is substantially cylindrical and coaxial with the piping;

[0036] [Fig.5]: [Fig.5] illustrates a third exemplary embodiment of the invention, by a diagram in axial and vertical section of a compensation component with an offset bellows mounted inside an external sleeve which is substantially cylindrical and coaxial with the piping, and including a thermally insulating intermediate sleeve;

[0037] [Fig.6]: [Fig.6] illustrates a fourth example of an embodiment of the invention, by a diagram in axial and vertical section of a compensation component with two offset bellows mounted symmetrically inside a sleeve external substantially cylindrical and coaxial with the piping, and each including a thermally insulating intermediate sleeve. Description with reference to the figures

[0038] [Fig. 2] illustrates a first exemplary embodiment of the invention. The other exemplary embodiments will only be described in their differences.

[0039] In this first exemplary embodiment, the axial expansion compensating component 1 comprises a first coaxial inlet 181 and a second coaxial inlet 182, by which the compensating component is connected in series to the circulation circuit of a heat transfer fluid, and is crossed by the circulation space 108 of this circuit. This is for example liquid sodium 8 circulating at a temperature of up to 550°C. For this, the component 1 is interposed between a first pipe 81 and a second pipe 82 of the circulation circuit of this heat transfer fluid, which are here thermally insulated by insulating sleeves 811 and 821 from the ambient atmosphere, for example the Earth's atmosphere or the interior atmosphere of a building, the temperature of which typically varies between -10°C and 40°C, and in particular between 10°C and 30°C.

[0040] The first inlet 181 extends radially outwards by a first annular blank 118 to an external sleeve 11, which is here substantially cylindrical and coaxial with the two inlets 81, 82. The second inlet 82 extends radially outwards by a second annular blank 128 to an internal sleeve 12, which is here substantially cylindrical and coaxial with the two inlets 81, 82. Between these first and second inlets 181, 182, these two annular blanks delimit a so-called connection space 101.

[0041] On the side opposite the connection space, the internal sleeve 12 is extended by a bellows 13 with axial deformation formed by a succession of annular waves. At its end opposite the connection space, the bellows 13 is connected by a third annular flank 123 to the end of the external sleeve 11, thus sealingly closing the envelope of the compensating component 1.

[0042] The bellows 13 is arranged to be able to absorb, by bending the annular waves that it comprises, the differences in longitudinal position of the first 181 and second 182 inputs relative to each other, for example in the form of a variation in the gap E812 between the first 118 and the second 128 annular flank of the connection space 101. Typically, if the component is cold-mounted, the expansion of the pipes 81, 82 of the circuit will cause a reduction in this gap E812, and therefore an axial tensioning of the bellows 13.

[0043] The circulation space 108 of the piping thus communicates with the connection space 101, with the so-called intermediate space between the two sleeves 11, 12, and with the so-called compensation space between the bellows 13 and the sleeve. external 11, which form a so-called static space 100. Although the heat transfer fluid can thus spread in this static space 100, the volume located there does not circulate during normal operation and is not heated by the liquid circulating 8 in the piping.

[0044] The static space is further thermally separated from the circulation space 108 by the annular static liquid blade of the connection space and by the cylindrical static liquid blade of the intermediate space. These static liquid blades are cooled by the external atmosphere, their length constituting a thermal brake making it possible to maintain a thermal gradient between the temperature of the circulating fluid 8 and the compensation space 103, and in particular the bellows 13.

[0045] Indeed, the thermal resistance is characterized by the axial thermal conduction between the hot source (constituted by the circulation space 108) and the cold source (the ambient air). Given the ratio of the thermal conductivities between the circulating fluid 8 (in particular in the case of a metallic fluid) and the casing (in particular the external sleeve 11) associated with its possible thermal insulator 110, the heat transfer is mainly carried out by the fluid of the intermediate space 102. The thermal resistance equivalent to the axial thermal conduction can be approximated by the relation: _______*______, with Re and Ri the external radii and — k (fie2 —Ri2} A internal thermal brake, 1 the length of the fluid blade and 3. the thermal conductivity of the fluid. This thermal resistance is therefore all the higher (and therefore effective) as the ratio is close to 1, that is to say that the liquid blade is thin, and If that the length l of the fluid blade is large. In this calculation, the fluid is considered static, the heat exchange within the fluid is therefore purely conductive.

[0046] Thus, as illustrated in [Fig.3], in the case of a fluid circulating at 550°C, this thermal gradient makes it possible to obtain a temperature lowered to 400°C at the entrance to the static space, which allows the bellows 13 to remain at an even lower temperature and to improve its service life.

[0047] In a vertical axial plane, the external sleeve 11 has two and only two radially extreme points, which can be seen to be located outside the compensation bellows 13. One 111 constitutes a high point (or possibly a horizontal line of high points), and carries a tapping point 116 which can be opened or closed towards the outside, thus allowing easy gas purging of the component 1 for example when filling the circuit. The other 112 constitutes a low point (or possibly a horizontal line of low points), and carries a tapping point 117 which can be opened or closed towards the outside, thus allowing complete liquid emptying of the compensating component 1, and therefore good evacuation of the liquid used and any foreign residues it may contain.

[0048] Concerning the bellows 13, it will be noted that all the low points of the waves 131 of its upper part can empty by gravity by following the periphery of the bellows up to the waves of the lower part 132 of the bellows, which do not have any low points since they can empty by gravity up to the low point 112 of the inner wall of the external sleeve 11.

[0049] The parts constituting the sealed envelope, in particular the bellows, the external and internal sleeves and the blanks, are typically made of materials such as stainless steel (for example 316L) or its alloys, or inconel, or titanium, or an alloy including these materials, or any material known to be suitable for the temperature and pressure conditions used. Their assembly is preferably done by welding, in particular according to one or more methods known in this field and for these materials.

[0050] The insulating parts are for example made of rock wool, or of materials known to be suitable for these conditions.

[0051] For example, for a sodium-based heat transfer fluid circulation installation, in particular for a secondary circuit of a power plant, the pipes typically represent one or several hundred meters and are typically of a diameter of the order of 700 mm. The expansion compensating component then has similar dimensions for the first and second inlets, and an external sleeve with a diameter of the order of 1000 mm. Second example of embodiment

[0052] A second exemplary embodiment of the invention is illustrated in [Fig.4], in which the compensator 1' comprises a first compensating bellows 13 similar to that of the component of [Fig.2] and a second bellows 13' on a second internal sleeve 12' mounted on the side opposite the first 13, 12 with respect to the connection space 101. Inside the same external sleeve 11, this component 1' thus comprises a second intermediate space 102' and a second compensating space 103', forming a common static space 100. Preferably, for example for better mechanical behavior, the second bellows and sleeves are identical to the first and mounted symmetrically.

[0053] The two sleeves are then connected in a sealed manner with the first 181 and the second 182 inlets: the internal sleeves 12 and 12' are connected directly with the second inlet 182 and respectively the first inlet 181, while the external sleeve 11 is connected to these two inlets indirectly by means of the bellows 13, 13' and the internal sleeves 12, 12'. In a similar manner to the previous examples, these connections allow a passage of the fluid between the static space 100 and the circulation space 108 at the level of the same region connection 101.

[0054] This type of configuration allows for example to have a greater compensation capacity with a single component and therefore a single assembly in the circuit. This can be interesting for example to avoid having to use a longer bellows, which constitutes a significant constraint during manufacturing. Third example of embodiment

[0055] A third example of an embodiment of the invention is illustrated in [Fig.5]. Compared to the structure of that of [Fig.2], the component 1" of this third example has an internal sleeve 12 of a smaller diameter, allowing for example a greater gap D12 with the external sleeve 11, but also which has a simpler shape.

[0056] Around the internal sleeve 12, this component 1" further comprises a thermally insulating intermediate sleeve, which is connected to the first connection blank 118 so as to limit or even prevent liquid communication between, on the one hand, the circulation spaces 108 and connection spaces 101 and, on the other hand, the so-called external intermediate part 105 of the static space 100. The presence of this "intermediate" insulating sleeve 14 thus delimits, between the connection space 101 and the compensation space 103, an intermediate space called internal 104 radially reduced compared to the gap between the internal 12 and external 11 sleeves. This reduction thus limits the thickness of the liquid layer which circulates therein, and also thereby limits the thermal flux which circulates therein. Compared to the configuration of [Fig.2], a shape is thus obtained which imposes fewer constraints on the manufacture and / or assembly of these sleeves 11, 12 and of the compensating component 1" itself, while making possible an internal liquid blade 104 of low thickness which preserves or even improves the effectiveness of the improved thermal brake between the circulating fluid 8 and the bellows 13.

[0057] In this example, the external sleeve 11 carries optional cooling fins 1101, here welded in a longitudinal position. It will be noted that these optional fins are also provided for the other exemplary embodiments. Fourth exemplary embodiment

[0058] A fourth example of an embodiment of the invention is illustrated in [Fig.6], with a component 1'" which has, compared to that of [Fig.5], the same modifications as that of [Fig.4] compared to that of [Fig.2]: the compensation structure with insulating intermediate sleeve 14 is doubled and distributed on both sides of the connection space 101, with similar advantages.

[0059] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. Nomenclature (Fig.2 to Fig.6)

[0060] expansion compensating component

[0061] 100 static space

[0062] 101 connection region

[0063] 102, 102' intermediate space

[0064] 103 compensation space

[0065] 104 internal intermediate space, internal liquid blade

[0066] 105 external intermediate part

[0067] 108 circulation space

[0068] 11 external sleeve

[0069] 110 thermal insulation of the envelope

[0070] 1101 longitudinal cooling fins

[0071] 111, 112 radially extreme points, high and low points

[0072] 116 gas purge tapping (high point)

[0073] 117 liquid drain tapping (low point)

[0074] 118, 128 first and second connecting flanks

[0075] 12, 12' internal sleeve

[0076] 123 third end flank

[0077] 13, 13' compensation bellows

[0078] 131 vertically superior waves of the bellows

[0079] 132 vertically lower waves of the bellows

[0080] 14 thermally insulating intermediate sleeve

[0081] 181 first entry

[0082] 182 second entry

[0083] 8 circulating fluid

[0084] 81 first piping

[0085] 811 insulation of the first pipe

[0086] 82 second piping

[0087] 821 insulation of the second pipe

[0088] D12 gap between inner and outer sleeves

[0089] E812 axial deviation caused by thermal expansion of pipes

Claims

Claims

1. A piping component (1, 1', 1", 1"') for a circuit (81, 82) for circulating fluid (8) intended to vary between a minimum temperature and a maximum temperature, comprising: a circulation space (108) provided to be crossed by said circulation of fluid between a first inlet (181) and a second inlet (182); an inner sleeve (12) and an outer sleeve (13) inserted into each other to define between them a so-called static space (100) which is not crossed by said fluid circulation and is thermally distant from said circulation space (108), thus allowing said static space to have a temperature lower than that of the fluid circulating in said circuit when the temperature of the circulating fluid (8) is higher than the ambient temperature, which inner and outer sleeves: • are connected in a sealed manner with the first (181) and the second (182) inlets, in particular the external sleeve (11) with the first inlet (181) and the internal sleeve (12) with the second inlet (182, so as to allow passage of said fluid between said static space (100) and said circulation space (108) in at least one region called the connection region (101), and • are connected to each other in a sealed manner by at least one axially deformable bellows (13), called a compensation bellows, which is arranged to accept an axial elastic deformation making it possible to compensate for a variation in the axial gap (E812) between the first inlet (181) and the second inlet (182), one with respect to the other, caused by an axial expansion of the piping (81, 82) of said circulation circuit when the temperature of the circulating fluid varies between said minimum temperature and said maximum temperature; said component being characterized in that said external sleeve (11) has a shape in which, according to at least one plane which is sagittal to it, the radially extreme points (111, 112) of its internal wall are all located outside the parts of said bellows (13) provided to absorb the elastic deformation producing said expansion compensation, so that said radially extreme points (111, 112) form all of the low points and / or high points of said static space (100) when said component (1) is installed with said sleeves (11, 12) in an axially horizontal position.

2. Device according to the preceding claim, characterized in that the radially extreme point(s) (111, 112) of the external sleeve (11) each comprise a fluid connection arranged to be able to connect thereto a liquid drain connection (117) and / or a gas purge connection (116).

3. Device according to any one of the preceding claims, characterized in that the compensation bellows (13) is arranged inside the external sleeve (11), and in particular concentrically with the internal sleeve (12) or itself forming said internal sleeve, said compensation bellows thus receiving the pressure on its "external" surface.

4. Device according to any one of the preceding claims, characterized in that the inner (12) and outer (11) sleeves are arranged to radially surround the first (181, 182) and second inlets and / or the piping (81, 82) to which they are connected.

5. Device according to the preceding claim, characterized in that the part of the static space which is in contact with the inner wall of the compensation bellows (13), called the compensation space (103), communicates with the circulation space (108) via a so-called intermediate space (102) which is axially elongated relative to the inner (12) and outer (11) sleeves and thermally distant from said circulation space (108), thus providing a thermal brake in an axial direction for a heat flow established within the fluid between the circulation space (108) and said compensation space (103), in particular in the form of a substantially static liquid blade surrounding the inner sleeve and thermally distant from the circulation space.

6. Device according to the preceding claim, characterized in that the inner sleeve (12) is surrounded, inside the static space (100), by a thermally insulating sleeve (14) which covers the connection region (101) and extends towards the at least one compensation bellows (13), thus delimiting inside said insulating sleeve (14) an elongated and thin liquid blade (104) forming a thermal brake between the connection region (101) and the compensation bellows (13), independently of the radial gap (D12) existing between the inner sleeve (12) and the outer sleeve (11).

7. Device according to the preceding claim, characterized in that it comprises at least two compensation bellows (13, 13'), in particular arranged inside the same external sleeve (11), the compensation spaces (103, 103') of which form part of the same static space (100) and are arranged on either side of the connection region (101) of said static space.

8. Fluid circulation installation (8) within a piping circuit, in particular metallic, in particular operating at an ambient temperature below 50°C, intended for a fluid circulating at a temperature above 400°C, in particular above 450°C or even 500°C, in particular below 600°C and for example around 550°C, characterized in that said circuit comprises one or more compensating components (1, 1', 1", 1'") of piping according to any one of the preceding claims implemented to compensate for all or part of the axial expansion of the piping (81, 82) of said circuit.

9. Installation according to the preceding claim, characterized in that the compensating component (1, 1', 1", 1'") is mounted so that the expansion of the pipes (81, 82) of the circuit tends to axially compress the bellows (13, 13') of said compensating component when their temperature rises.

10. Installation according to the preceding claim, characterized in that the circulating fluid is or comprises a liquid salt or a liquid metal.

11. Installation according to the preceding claim, characterized in that the circulating fluid is or comprises liquid sodium.

12. Installation according to any one of the preceding claims, characterized in that the fluid is used as heat transfer fluid.

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