Thermo-insulated pipe and method of manufacturing

Abstract

A thermo-insulated pipe (1) comprising at least one inner tubular body (2) which extends around an axis of longitudinal extension (X) so as to delimit a through-flow conduit (4) for a fluid; at least one thermal barrier layer (6) predominantly or substantially completely surrounding the inner tubular body (2) and comprising or consisting of solidified expanded polymer foam (34) containing a cell gas; wherein the thermal barrier layer (6) has an undulating profile comprising alternating ridges (12) and depressions (14) in the longitudinal direction; an outer tubular body (10) enclosing the thermal barrier layer (6); and at least one metal gas-barrier layer (16) which - radially with respect to the axis of longitudinal extension (X) - is arranged on the outside of the thermal barrier layer (6) and on the inside the outer tubular body (10); wherein said metal gas-barrier layer (16) is wound around the thermal barrier layer (6) so as to cover said undulating profile.

Description

[0001] Thermo-insulated pipe and method of manufacturing

[0002] DESCRIPTION

[0003] Field of the invention

[0004] The invention concerns the sector of pipes for transporting heated or cooled fluids, preferably for transporting heat-transfer fluids.

[0005] Prior art

[0006] Polymer foams with a solid condensed phase and closed cells are very widespread, for example in the sector of heat insulation in the building industry and refrigeration industry. In fact, closed-call foams are very effective heat insulants owing to the expansion agents used for foaming. Said expansion agents have a low heat conductivity and remain trapped in the gaseous phase inside the closed cells. These gases are known as “cell gases”.

[0007] However, the heat insulation properties and the dimensional stability of closedcell foams deteriorate significantly over time, mainly because of the diffusion - outside of the foam - of the low heat conductivity expansion agent and because of the diffusion inwards of air constituents with a higher heat conductivity. Generally, the air spreads within the foam much more rapidly than the expansion agents which are commonly used. Consequently, the short and medium-term ageing of the polymer foams is due to the diffusion internally of the air constituents, while the long-term ageing depends on the depletion of the expansion agents in the foam.

[0008] The possibility of limiting the diffusion of the gases in the closed-cell foams of flexible corrugated pipes for transporting heated or cooled fluids has hitherto never been attempted, owing to the irregular and complex form of these pipes.

[0009] US 3 615 977 A, DE 36 16 774 A1 and WO 2021 / 094937 A1 belong to the prior art.

[0010] The Applicant, after long and in-depth R&D investigation work, has developed a flexible thermo-insulated pipe and manufacturing method which are able to provide a suitable response to the existing limitations, drawbacks and problems.

[0011] In particular, the inventors of the present invention have devised a metal gasbarrier layer which, being wound around the thermal barrier layer so as to cover the undulating profile of the thermal barrier layer, offers several advantages: on the one hand it is able to adapt well to the shape of the undulating profile; on the other hand it is able to cover a greater volume and a greater external area of the thermal barrier layer compared to pipe windings located in radially more inward positions. According to a further advantage, as a result of the configuration characterized by windings, the metal gas-barrier layer tends not to offer resistance and tear, remaining substantially integral, following the inevitable folding and straightening of the flexible pipe according to the present invention during the laying processes.

[0012] The present invention therefore relates to a flexible thermo-insulated pipe having the characteristic features as defined in the attached claims.

[0013] The present invention also relates to a method of manufacturing a flexible thermo-insulated pipe having the characteristic features as defined in the attached claims.

[0014] Summary of the invention

[0015] The object of the invention is to overcome the aforementioned drawbacks of the prior art. The aforementioned objects are achieved by means of a flexible thermo-insulated pipe according to claim 1 and by means of a manufacturing method according to claim 11.

[0016] In the present invention the flexible thermo-insulated pipe 1 comprises:

[0017] - at least one inner tubular body 2 which extends around an axis of longitudinal extension X so as to delimit a through-flow conduit 4 for a fluid;

[0018] - at least one thermal barrier layer 6 predominantly or substantially completely surrounding the inner tubular body 2 and comprising or consisting of a solidified expanded polymer foam 34 containing a cell gas; wherein the thermal barrier layer 6 has an undulating profile comprising alternating ridges 12 and depressions 14 in the longitudinal direction;

[0019] - an outer tubular body 10 enclosing the thermal barrier layer 6;

[0020] - at least one metal gas-barrier layer 16 which - radially with respect to the axis of longitudinal extension X - is arranged on the outside of the thermal barrier layer 6 and on the inside of the outer tubular body 10; wherein said metal gas-barrier layer 16 is wound, preferably in helical spirals, around the thermal barrier layer 6 so as to cover (for example partially, mainly or completely) said undulating profile.

[0021] The term “flexible” In this description refers to a flexibility of the thermoinsulated pipe 1 which is sufficient to allow winding thereof onto a storage reel. The diameters of these storage reels are standard and known in the sector.

[0022] The expression “wound” means that the metal gas-barrier layer is turned several times around the thermal barrier layer so as to cover the undulating profile. Correspondingly, “winding” is the operation of turning the metal gasbarrier layer several times around the thermal barrier layer so as to cover partially, mainly or completely the undulating profile.

[0023] The axis of longitudinal extension X defines an axial direction along or parallel to said axis X and defines a radial direction in a plane orthogonal to said axis X. Therefore, unless otherwise specified, the expressions “axial”, “longitudinal” and “radial” will always be in relation to the axis of longitudinal extension X. The axis of longitudinal extension X is preferably a substantially central axis, with respect to which the at least one inner tubular body 2, the thermal barrier layer 6, the metal gas-barrier layer 16 and the outer tubular body 10 are arranged substantially coaxially.

[0024] In the present description, the expressions “inner” and “outer” will be used in a merely relative sense. For this reason, the so-called “outer” tubular body is situated radially on the outside of the so-called “inner” tubular body. As a result the outer tubular body could also be arranged inside a further layer or tubular body, located radially on the outside of the outer tubular body.

[0025] The present invention relates, moreover, to a method of manufacturing a flexible thermo-insulated pipe 1 , preferably a flexible thermo-insulated pipe according to any one of the embodiments described here, Therefore, the manufacturing method could comprise any step or feature deducible from the description - in terms of structure - of the flexible thermo-insulated pipe.

[0026] This method comprises the following steps:

[0027] (I) feeding at least one inner tubular body 2 which extends around an axis of longitudinal extension X;

[0028] (II) covering a part of the inner tubular body 2 with a polymer film shaped in the form of a tube 32;

[0029] (III) introducing an expandable polymer foam 34 into a space between the at least one inner tubular body 2 and said tube-shaped polymer film 32;

[0030] (IV) introducing the at least one inner tubular body 23 and the tube-shaped polymer film 32 into a moulding unit 32 comprising pairs of half-moulds 38 integral with a movement M (for example translation) of the inner tubular body 2 and the tube-shaped polymer film 32 in the moulding unit 36;

[0031] (V) pressing the tube-shaped polymer film 32 by means of the expanding polymer foam 34 onto inner surfaces of the closed half-moulds 38 so as to form a thermal barrier layer 6 which has an undulating profile comprising alternating ridges 12 and depressions 14 in the longitudinal direction, where the thermal barrier layer 6 comprises or consists of the at least partially solidified expanded polymer foam containing a cell gas.

[0032] (VI) winding, preferably in helical spirals, at least one metal gas-barrier layer 16 around the thermal barrier layer 6 so as to cover said undulating profile;

[0033] (VII) forming, preferably extruding and solidifying, an outer tubular body 10 on an outer surface of the metal gas-barrier layer 16, wherein said outer tubular body 10 encloses the thermal barrier layer 6.

[0034] The invention has the advantages which are listed below.

[0035] Advantageously, the metal gas-barrier layer in the flexible thermo-insulated pipe according to the present invention restricts at least partly (and, preferably, substantially prevents) escaping of the cell gases from the polymer foam and the penetration into said foam of the gases outside the pipe (for example vapour and / or atmospheric air).

[0036] Advantageously, said at least partial restricting or substantial prevention is present in the case of the embodiments with open spiralling and, even more so, in the case of embodiments with closed spiralling. In fact, although open spiralling does not cover completely the thermal barrier layer, the possibility of the cell gases escaping from the polymer foam is in any case limited in the surface areas of the thermal barrier layer on which the metal gas-barrier layer is superimposed. Moreover, open spiralling could leave uncovered spaces which are only a few millimetres or fractions of a millimetre wide.

[0037] Advantageously, the flexible thermo-insulated pipe according to the present invention is characterized by a useful working life which is longer than that of corresponding conventional pipes, this expression being understood as meaning pipes which - for the same other features (e.g. form and material) - do not have a metal gas-barrier layer.

[0038] Advantageously, the thermal barrier layer is configured to prevent or limit the dispersion of heat through a tubular wall of the inner tubular body.

[0039] Advantageously, the winding imparts to the metal gas-barrier layer a freedom of elongation about the thermal barrier layer in the longitudinal direction, resulting in mechanical stresses being damped on this metal gas-barrier layer.

[0040] Advantageously, in the manufacturing method according to the present invention, the metal gas-barrier layer is made to adhere to the bottom of the depressions by applying a negative pressure (vacuum) and / or mechanical pressing action so that said layer has a progression which follows the undulating profile of the thermal barrier layer.

[0041] Advantageously, moreover, in the manufacturing method according to the present invention, the material of the outer tubular body which is still in the melted state is used - by applying a negative pressure - to force and fix the metal gas-barrier layer onto the bottom of the depressions, thus forming a stable undulating profile which matches the undulating profile of the thermal barrier layer.

[0042] Preferred embodiments

[0043] Preferably, the metal gas-barrier layer 16 is wound around the thermal barrier layer 6 with an angle which is incident, and not orthogonal to the axis of longitudinal extension X.

[0044] The metal of the metal gas-barrier layer 16 could be aluminium or an alloy thereof.

[0045] Preferably, the metal gas-barrier layer 16 comprises a sheet or a lamina of said metal. More preferably, the metal gas-barrier layer 16 is not a polymer layer which is metallized (for example on the surface).

[0046] Preferably, the metal gas-barrier layer 16 comprises a polymer selected from the group consisting of polyethylene (optionally with a high, medium or low density), polypropylene, polyvinylchloride, polycarbonate, polyethylene terephthalate or combinations thereof, and even more preferably polyethylene.

[0047] In accordance with a preferred embodiment, the metal gas-barrier layer 16 is in the form of tape. Preferably a direction of extension of the tape Y is incident and not orthogonal to the axis of longitudinal extension X.

[0048] In accordance with another preferred embodiment, the tape of metal gas-barrier material 16 is wound in helical spirals 18 around the axis of longitudinal extension X. In other words, said tape extends in a three-dimensional space in such a way that the spirals follow a line which is wound - for example with a constant angle - around the thermal barrier layer 6 (which is generally a cylinder) in the manner of a helix.

[0049] In accordance with one embodiment, the helical spirals 18 are arranged partially overlapping (for example: only partially overlapping) or alongside each other on the thermal barrier layer 6 with a closed spiralling.

[0050] In accordance with another embodiment, the helical spirals 18 are arranged alongside each other on the thermal barrier layer 6 with an open spiralling.

[0051] In this description a spiralling is said to be “closed” when the helical spirals are arranged overlapping or alongside each other so not to leave spaces between pairs of adjacent spirals through which the underlying thermal barrier layer 6 is visible. On the other hand, an “open” spiralling has pairs of adjacent spirals which are partially spaced from each other so as to leave spaces exposed through - or rather on - the thermal barrier layer 6 and visible through the metal gas-barrier layer 16.

[0052] By way of example, a distance between adjacent spirals in the open spiralling could be comprised from 0.05 mm to 20 mm, preferably comprised from 0.1 mm to 10 mm, and more preferably comprised from 0.15 mm to 5 mm.

[0053] In accordance with one embodiment, successive depressions 14 are spaced along the axis of longitudinal extension X with a predefined pitch P. Said pitch P is preferably comprised from 35 mm (millimetres) to 40 mm, more preferably comprised from 36 mm to 39 mm, and even more preferably substantially equal to 37.5 mm. Said predefined pitch P is preferably to be understood as being valid for pipe diameters comprised from 63 mm to 202 mm, for example comprised from 120 mm to 202 mm, optionally comprised from 63 mm to 90 mm, and / or comprised from 90 mm to 202 mm.

[0054] In accordance with another embodiment, successive depressions 14 are spaced along the axis of longitudinal extension X with a predefined pitch P. Said pitch P is preferably comprised from 25 mm (millimetres) to 40 mm, more preferably comprised from 30 mm to 37 mm, and even more preferably substantially equal to 33 mm. Said predefined pitch P is preferably to be understood as being valid for pipe diameters comprised from 63 mm to 202 mm, for example comprised from 120 mm to 202 mm, optionally comprised from 63 mm to 90 mm and / or comprised from 90 mm to 202 mm.

[0055] Preferably, the tape has a tape width comprised from 0.5 to 2 times, preferably comprised from 0.9 to 1.6 times, more preferably comprised from 1.1 to 1.4 times, the aforementioned predefined pitch P.

[0056] Preferably, the metal gas-barrier layer 16 is a multilayer in which at least one sublayer comprises a metal. For example, said multilayer has two, three, four, five, six or seven sublayers. More preferably, the metal gas-barrier layer 16 comprises or consists of the following sublayers: an inner polymer sublayer, a first adhesive sublayer, a sublayer comprising a metal, a second adhesive sublayer, an outer polymer sublayer. Even more preferably, the inner polymer sublayer and the outer polymer sublayer are made of polyethylene and / or wherein the metal sublayer is made of aluminium or an alloy thereof.

[0057] In accordance with an embodiment shown in the figures, the metal gas-barrier layer 16 is deposited on, or in contact with, an inner surface 24 of the outer tubular body 10.

[0058] Preferably, the undulating profile of the metal gas-barrier layer 16 is identical to the undulating profile of the thermal barrier layer 6 and preferably also of the outer tubular body 10. Identical undulating profiles are understood as being such when they have the same predefined pitch P, the same amplitude or depth, the same phase, and the same radii of curvature of the ridges 12 and the depressions 14.

[0059] In accordance with one embodiment, the outer tubular body 10 could be made of the same polymer as the metal gas-barrier layer 16 or of a polymer which is compatible with the polymer of the metal gas-barrier layer 16.

[0060] In the present description, the expression “compatible” is understood as meaning materials suitable for being joined or welded together without the use of adhesive or adhesion-promoting substances, for example when at least one of these polymers in the melted state is brought into contact with the other one.

[0061] The ridges 12 and the depressions 14 are preferably connected together by means of substantially straight connecting sections.

[0062] Preferably, the ridges 12 have a radius of curvature Rc and the depressions 14 have a radius of curvature RA, where a ratio RA / RC is greater than 1 , equal to 1 or less than 1. Preferably, RA I Rc is less than 0.8, more preferably comprised from 0.1 to 0.7, and even more preferably comprised from 0.2 to 0.5.

[0063] Preferably, the ridges 12 and the depressions 14 form a gentle undulation of the outer tubular body 10, equal to or less than 4.0 mm in the radial direction.

[0064] In accordance with one embodiment, a difference between a diameter De of the outer tubular body 19 at the ridges 12 and a diameter DA of the outer tubular body 10 at the depressions 14 is equal or less than 8.0 mm for diameters of said tube 1 in the range comprised from 63 mm to 202 mm, for example comprised from 120 mm to 202 mm, and optionally in the ranges comprised from 63 mm to 90 mm and / or 90 mm to 202 mm.

[0065] Preferably, said gentle undulation or said difference De - DA is comprised from 3.0 mm to 7.8 mm.

[0066] The polymer foam 34 has preferably a density comprised from 45 kg / m3to 80 kg / m3

[0067] Preferably, the polymer foam 34 is polyurethane foam or polyisocyanurate foam, more preferably polyurethane foam.

[0068] According to different embodiments, the inner tubular body 2 could comprise a smooth pipe (in which the tubular wall 8 of the inner tubular body 2 is externally and internally devoid of corrugations or knurling) or at least a corrugated pipe (for example made of steel). In accordance with one embodiment, the flexible thermo-insulated pipe 1 comprises at least one electric conductor 30 arranged or embedded in the thermal barrier layer 6 and extending longitudinally (namely in the axial direction). For example, said electric conductor 30 could form part of a loss detection system.

[0069] In a preferred embodiment of the manufacturing method, the step (VI) comprises winding at least one metal gas-barrier layer 16 in the form of tape in helical spirals 18 around the axis of longitudinal extension X.

[0070] Preferably, helical spirals 18 are: arranged alongside each other on the thermal barrier layer 6 with an open spiralling; or are arranged partially overlapping or alongside each other on the thermal barrier layer 6 with a closed spiralling.

[0071] In another embodiment, after step (II) and before step (III) the tube-shaped polymer film 32 is welded longitudinally.

[0072] According to a further embodiment, the manufacturing method comprises - before step (VII) - application of a negative pressure between the tube-shaped polymer film 32 and the metal gas-barrier layer 16 so that said negative pressure causes the metal gas-barrier layer 16 to adhere inside the depressions 14.

[0073] The expression “negative pressure” means a pressure less than atmospheric pressure.

[0074] According to yet another embodiment, the manufacturing method comprises - after step (VI) - mechanical pressing of the metal gas-barrier layer 16 inside the depressions 14 of the thermal barrier layer 6.

[0075] Preferably, said mechanical pressing is performed by means of a diaphragm (sealing element) arranged at the inlet of an extruder 52 used in step (VII). More preferably, said diaphragm is arranged so as to close a zone of said extruder 52 kept at a negative pressure.

[0076] In accordance with one embodiment, said diaphragm has a substantially annular shape.

[0077] An inner annular edge of said diaphragm preferably lies against an outer surface of the tube-shaped polymer film 32. More specifically, said inner annular edge forms a sliding-contact seal with said outer surface, during the movement of the latter towards the insider of the extruder 52.

[0078] Optionally, a further action of pressing or pushing the metal gas-barrier layer 16 inside the depressions 15 could be performed by a material - still fluid - of the outer tubular body 10. Said material, after solidification, acts as a means for fixing the metal gas-barrier layer 16.

[0079] The advantages of the invention will emerge even more clearly from the detailed description given below based on the attached figures provided by way of example and therefore of a non-limiting nature.

[0080] Description of the figures

[0081] Fig. 1 shows a longitudinal section through a possible embodiment of a flexible thermo-insulated pipe according to the present invention;

[0082] Fig. 2 shows a schematic representation of the method for manufacturing a flexible thermo-insulated pipe in accordance with an embodiment of the present invention.

[0083] Detailed description of the device according to a preferred embodiment

[0084] Fig. 1 shows a side view of the flexible thermo-insulated pipe 1 according to a preferred embodiment of the present invention.

[0085] The flexible thermo-insulated pipe 1 comprises, from a radially more inner position to a radially more outer position, an inner tubular body 2, a thermal barrier layer 6, a metal gas-barrier layer 16 and an outer tubular body 10, which are arranged coaxially with respect to an axis of longitudinal extension X of the inner tubular body 2. Optionally, the flexible thermo-insulated pipe 1 comprises at least one electric conductor 30 arranged or embedded in the thermal barrier layer 6 and extending in the axial direction. The inner tubular body 2 delimits a through-flow conduit 4 for a fluid, for example a heated or cooled fluid, preferably a heat-transfer fluid. In the embodiment shown, the inner tubular body 2 is a smooth body (i.e. without corrugations).

[0086] The thermal barrier layer 6 comprises or consists of a solidified expanded polymer foam 34 (preferably polyurethane foam) containing a cell gas. Said thermal barrier layer 6 has an undulating profile comprising alternating ridges 12 and depressions 14 in the longitudinal direction.

[0087] The outer tubular body 10 encloses the thermal barrier body 6 and the metal gas-barrier layer 16. Preferably, the outer tubular body 10 forms a protection for the flexible thermo-insulated pipe 1 , which is resistant to impacts and abrasion.

[0088] The metal gas-barrier layer 16 is arranged radially on the outside of the thermal barrier layer 6 and on the inside of the outer tubular body 10 (with respect a direction radial to the axis of longitudinal extension X).

[0089] The metal gas-barrier layer 16 is wound around the thermal barrier layer 6 so as to cover the undulating profile, preferably with a closed spiralling.

[0090] Fig. 2 shows a schematic representation of the method for manufacturing a flexible thermo-insulated pipe.

[0091] At least one inner tubular body 2 is fed from a first supply reel 40 by means of a pair of feeder rollers 42.

[0092] A part of the inner tubular body 2 is covered with a polymer film fed in a flat (extended) form from a second supply reel 44. The polymer film is then shaped in the form of a tube 32 around the inner tubular body 2 and welded in the longitudinal direction. A space (cavity) is thus formed between the inner tubular body 2 and the tube-shaped polymer film.

[0093] An expandable polymer foam 34 - indicated schematically by an arrow - is introduced into this space (cavity) after the inner tubular body 2 and the tubeshaped polymer film 32 have been introduced into a moulding unit 36. The moulding unit 36 comprises pairs of half-moulds 38 integral with a movement M (for example translation) of the inner tubular body 2 and the tube-shaped polymer film 32 in the moulding unit 36.

[0094] Each pair of half-moulds 38 is movable between a closed position (for example in the central part of the moulding unit 36) and an open position (for example at the ends of the moulding unit 36): in the closed position inner surfaces of the pairs of half-moulds 38 together circumscribe a space for forming the expanded polymer foam 34; in the open position the pair of half-moulds 38 are separate from each other. Each half-mould 38 of the pair is moved between said positions by an independent movement system 46 along a closed-loop path.

[0095] At the outlet of the moulding unit 36, the thermal barrier layer 6 has an undulating profile comprising alternating ridges 12 and depressions 14 and the expanded polymer foam 34 is at least partially solidified. Said undulating profile is delimited externally by the tube-shaped polymer film 32.

[0096] Thereafter, at least one metal gas-barrier layer 16 is wound around the thermal barrier layer 6 so as to cover the undulating profile.

[0097] During said winding operation, the metal gas-barrier layer 16 is preferably rotated around the axis of longitudinal extension X. Said feature is not shown in Fig. 2 where, for simpler illustration, the metal gas-barrier layer 16 is shown as being fed from a third supply reel 48, but without showing the system for moving said reel around the thermal barrier layer 6.

[0098] During winding, the metal gas-barrier layer 16 is preferably wound around the thermal barrier layer 6 with an angle which is incident, and not orthogonal to the axis of longitudinal extension X.

[0099] Preferably, at least one metal gas-barrier layer 16 in the form of tape is wound in helical spirals 18 around the axis of longitudinal extension X, with an open or closed spiralling.

[0100] After winding of the metal gas-barrier layer 16, the manufacturing method could comprise mechanical pressing of the metal gas-barrier layer 16 inside the depressions 14 of the thermal barrier layer 6.

[0101] Said mechanical pressing action may be exerted by a diaphragm which is arranged at the inlet of an extruder 52 used in the subsequent step (VII) for forming an outer tubular body 10. The extruder 52 comprises, in fact, a zone kept at a negative pressure in which extrusion of the - still fluid - material of the outer tubular body 10 takes place. Said zone kept at a negative pressure is partially closed by the diaphragm.

[0102] Before step (VII), the manufacturing method comprises application of a pressure lower than atmospheric pressure (negative pressure) which, by removing air in the space situated between the tube-shaped polymer film 32 and the metal gas-barrier layer 16, causes the metal gas-barrier layer 16 to adhere to the metal gas-barrier layer 16 inside the depressions 14.

[0103] In a downstream forming unit 50, preferably comprising the extruder 52, an outer tubular body 10 is formed (preferably extruded and solidified) on an outer surface of the metal gas-barrier layer 16 so that the outer tubular body 10 encloses the thermal barrier layer 6.

[0104] Preferably, during the aforementioned application of the negative pressure inside the extruder 52, the metal gas-barrier layer 16 is pushed inside the depressions 14 also by the still fluid material of the outer tubular body 10. After said material has solidified, the metal gas-barrier layer 16 is fixed by the outer tubular body 10.

[0105] LIST OF REFERENCE NUMBERS flexible thermo-insulated pipe inner tubular body through-flow conduit thermal barrier layer tubular wall of the inner tubular body outer tubular body ridge depression metal gas-barrier layer helical spirals outer surface of the thermal barrier layer inner surface of the outer tubular body electric conductor tube-shaped polymer film polymer foam moulding unit half-moulds first supply reel feeder rollers 44 second supply reel

[0106] 46 movement system

[0107] 48 third supply reel

[0108] 50 forming unit

[0109] 52 extruder

[0110] M movement of the inner tubular body and pipe in the moulding unit

[0111] X axis of longitudinal extension

[0112] Y direction of extension of the tape

[0113] De diameter of the outer tubular body at the ridges

[0114] DA diameter of the outer tubular body at the depressions

[0115] Rc radius of curvature of the ridges

[0116] RA radius of curvature of the depressions

Claims

CLAIMS1 . A flexible thermo-insulated pipe (1 ) comprising:- at least one inner tubular body (2) which extends around an axis of longitudinal extension (X) so as to delimit a through-flow conduit (4) for a fluid;- at least one thermal barrier layer (6) predominantly or substantially completely surrounding the inner tubular body (2) and comprising or consisting of a solidified expanded polymer foam (34) containing a cell gas; wherein the thermal barrier layer (6) has an undulating profile comprising alternating ridges (12) and depressions (14) in the longitudinal direction;- an outer tubular body (10) enclosing the thermal barrier layer (6);- at least one metal gas-barrier layer (16) which - radially with respect to the axis of longitudinal extension (X) - is arranged on the outside of the thermal barrier layer (6) and on the inside of the outer tubular body (10); wherein said metal gas-barrier layer (16) is wound around the thermal barrier layer (6) so as to cover said undulating profile.

2. The flexible thermo-insulated pipe (1 ) according to the preceding claim, wherein the metal gas-barrier layer (16) is wound in helical spirals (18) around the thermal barrier layer (6).

3. The flexible thermo-insulated pipe (1 ) according to any one of the preceding claims, wherein the metal gas-barrier layer (16) is in the form of a tape, said tape being wound in helical spirals (18) around the axis of longitudinal extension (X).

4. The flexible thermo-insulated pipe (1 ) according to claim 2 or 3, wherein said helical spirals (18) are arranged partially overlapping or alongside each other on the thermal barrier layer (6) with a closed spiralling, wherein said helical spirals (18) are arranged overlapping or alongside each other so as not to leave spaces between pairs of adjacent spirals through which the underlying thermal barrier layer (6) is visible.

5. The flexible thermo-insulated pipe (1 ) according to any of claims 3 or 4,wherein successive depressions (14) are spaced along the axis of longitudinal extension (X) with a predefined pitch (P), and wherein said tape has a tape width comprised from 0.5 to 2 times, preferably comprised from 0.9 to 1 .6 times, and more preferably comprised from 1.1 to 1.4 times, said predefined pitch (P).

6. The flexible thermo-insulated pipe (1 ) according to claim 2 or 3, wherein said helical spirals (18) are arranged alongside each other on the thermal barrier layer (6) with an open spiralling, wherein pairs of adjacent helical spirals (18) are partially spaced from each other so as to leave spaces uncovered on the thermal barrier layer (6) and visible through the metal gas-barrier layer (16).

7. The flexible thermo-insulated pipe (1 ) according to claim 6, wherein a distance between adjacent spirals in the open spiralling is comprised from 0.05 mm to 20 mm, preferably comprised from 0.1 mm to 10 mm, and more preferably comprised from 0.15 mm to 5 mm.

8. The flexible thermo-insulated pipe (1 ) according to any one of the preceding claims, wherein the metal gas-barrier layer (16) comprises or consists of the following sublayers: an inner polymer sublayer, a first adhesive sublayer, a sublayer comprising a metal, a second adhesive sublayer, an outer polymer sublayer; preferably wherein the inner polymer sublayer and outer polymer sublayer are made of polyethylene, and wherein the metal sublayer is made of aluminium or an alloy thereof.

9. The flexible thermo-insulated pipe (1 ) according to any one of the preceding claims, wherein the metal gas-barrier layer (16) is arranged in contact with an inner surface (24) of the outer tubular body (10), and wherein the undulating profile of the metal gas-barrier layer (16) is identical to the undulating profile of the thermal barrier layer (6) and the outer tubular body (10), preferably in terms of the pitch (P), width or depth, phase and radius of curvature of the ridges (12) and depressions (14).

10. The flexible thermo-insulated pipe (1 ) according to any one of the preceding claims, wherein the ridges (12) and depressions (14) are connected to each other by means of substantially straight connecting sections, whereinthe ridges (12) have a radius of curvature (Rc), and the depressions (14) have a radius of curvature (RA), a ratio RA I Rc being greater than 1 , equal to 1 , or less than 1 , preferably less than 1 .

11. A method of manufacturing a flexible thermo-insulated pipe (1), preferably a flexible thermo-insulated pipe according to any one of the preceding claims, comprising the following steps:(I) feeding at least one inner tubular body (2) which extends around an axis of longitudinal extension (X);(II) covering a part of the inner tubular body (2) with a polymer film shaped in the form of a tube (32);(III) introducing an expandable polymer foam (34) into a space between the at least one inner tubular body (2) and said tube-shaped polymer film (32);(IV) introducing the at least one inner tubular body (2) and the tube-shaped polymer film (32) into a moulding unit (36) comprising pairs of half-moulds (38) integral with a movement (M) of the inner tubular body (2) and the tube-shaped polymer film (32) in the moulding unit (36);(V) pressing the tube-shaped polymer film (32) by means of the expanding polymer foam (34) onto inner surfaces of the closed half-moulds (38) so as to form a thermal barrier layer (6) having an undulating profile comprising alternating ridges (12) and depressions (14) in the longitudinal direction, wherein the thermal barrier layer (6) comprises or consists of the at least partially solidified expanded polymer foam (34) containing a cell gas;(VI) winding at least one metal gas-barrier layer (16) onto the thermal barrier layer (6) so as to cover said undulating profile;(VII) forming, preferably extruding and solidifying, an outer tubular body (10) on an outer surface of the metal gas-barrier layer (16), wherein said outer tubular body (10) encloses the thermal barrier layer (6).

12. The manufacturing method according to the preceding claim, wherein step (VI) comprises winding at least one metal gas-barrier layer (16) in the form of tape in helical spirals (18) around the axis of longitudinal extension (X).

13. The manufacturing method according to the preceding claim, wherein at least one metal gas-barrier layer (16) is in the form of tape, wherein said helical spirals (18) are:- arranged alongside each other on the thermal barrier layer (6) with an open spiralling in which pairs of adjacent helical spirals (18) are partially spaced from each other, so as to leave spaces uncovered on the thermal barrier layer (6) and visible through the metal gas-barrier layer (16); or- are arranged partially overlapping or alongside each other on the thermal barrier layer (6) with closing spiralling in which said helical spirals (18) are arranged overlapping or alongside each other so not to leave spaces between pairs of adjacent spirals through which the underlying thermal barrier layer (6) is visible.

14. The manufacturing method according to any one of claims 11-13, comprising - before step (VII) - application of a negative pressure between the tube-shaped polymer film (32) and the metal gas-barrier layer (16) so that said negative pressure causes the metal gas-barrier layer (16) to adhere inside the depressions (14).

15. The manufacturing method according to any one of claims 11-14, comprising - after step (VI) - mechanical pressing of the metal gas-barrier layer (16) inside the depressions (14) of the thermal barrier layer (6), wherein said mechanical pressing action is exerted by means of a diaphragm arranged at the inlet of an extruder (5) used in step (VII); preferably wherein said diaphragm is arranged so as to close a zone of said extruder (52) kept at a negative pressure.

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