INSULATION STRUCTURE FOR A LIQUID PIPE

Description

[0001] The present invention relates to a thermally and acoustically insulating structure for fluid conduit.

[0002] The invention relates to the field of thermal and acoustic insulation of pipes in buildings, or of pipes used in an industrial setting.

[0003] A pipe insulation structure is generally made of an insulating material, such as rock wool or glass wool. The flexibility of this type of material makes it easy to wrap it around the pipe to be insulated, and provides thermal and / or acoustic insulation once the insulating structure is in place.

[0004] This insulating structure is held around the pipe by adhesive material.

[0005] Fluids at varying temperatures, with a temperature difference that can be significant, can circulate in the heart of some of these pipes. Thus, the very high temperature difference leads to the use of metal pipes that can withstand very high or very low temperatures over time, and the mechanical constraints that these temperature differences impose. Such a pipe therefore requires thermal insulation with an insulating structure as mentioned previously. This insulating structure is wrapped around the pipe and creates direct contact between the external face of the pipe and the insulating material of the insulating structure, and this over the entire circumference of the pipe.

[0006] The technical problem arising from this type of installation is that it is common to see condensation phenomena appear on the surface of the pipe, the temperature of the fluids circulating in the pipe being able to vary extremely. The water produced following this condensation is then absorbed by the insulating material of the insulating structure, and the humidity generated causes premature corrosion of the metal pipe. This corrosion is amplified by the fact that the thermally insulating structure of the prior art behaves like a sponge which constantly keeps the external face of the pipe in a humid environment, and thus promotes corrosion over fairly long periods.

[0007] Another technical problem arising from the prior art is the acoustic insulation of the pipe. Indeed, when the insulating structure is in direct contact with the pipe, the solid transmission, that is to say the transmission of sounds produced by the fluid against the pipe through the material of the insulating structure, is then maximum. The acoustic insulation of the pipe is therefore highly dependent on the properties of the insulating structure used.

[0008] Solutions exist in the prior art, most of which relate to the field of chimney flues. These are flues equipped with a structure made of insulating material comprising spacers. These spacers are the only parts of the structure to be in direct contact with the chimney flue, thus creating a gap between the flue and the internal wall of the structure where air can circulate.

[0009] However, this solution is not entirely satisfactory. In fact, the protrusions are made of the same material as the insulating structure, i.e. rock wool or glass wool, and are therefore compressible. This therefore leads to irreversible compression of the protrusions over time, which leads to a new point of contact between the pipe and the insulating structure and which, in the long term, therefore solves neither the problem of corrosion caused by condensation, nor the problem of acoustic insulation of the pipe, the latter being in direct contact with the insulating structure.

[0010] Furthermore, these solutions are suitable for chimney flues, where only hot gases circulate. There is no passage of cold liquids or gases, and therefore no condensation phenomenon. This technical solution of the prior art therefore does not specifically concern one of the technical problems envisaged and does not claim to resolve it.

[0011] Document DE1875813U discloses an insulating sheath.

[0012] On the other hand, the present invention makes it possible to solve the technical problem of corrosion of metal pipes due to condensation, while insulating the pipe thermally and acoustically.

[0013] The invention consists of a cylindrical thermally and acoustically insulating structure configured to cover a conduit for transporting a fluid capable of being brought to variable temperatures, according to claim 1. The insulating structure comprises an inner wall and an outer wall, said insulating structure comprising at least one protrusion which emerges from its inner wall so as to generate an air space between the inner wall and the conduit, characterized in that the inner wall of the insulating structure which at least partially delimits the protrusion is denser than the outer wall of the insulating structure. The densification of the protrusion originating from the inner wall ensures resistance to deformation of the protrusion.

[0014] The resistance to deformation is increased by the densification of the protrusion. The protrusion thus allows the preservation of the air space between the pipe and the insulating structure for a given period, for example from one to four years from the installation of the insulating structure around the pipe.

[0015] In this document, the term insulating structure will be used to refer to this part providing thermal and acoustic insulation. The cylindrical shape of the insulating structure ensures the covering of the pipe and therefore its insulation. In order to envelop the pipe in its entirety, the insulating structure has a diameter, in which the internal wall is mainly located, greater than the diameter of the pipe.

[0016] The inner wall of the insulating structure has at least one protrusion ensuring, on the one hand, contact between the insulating structure and the pipe, and on the other hand, the creation of a space between the inner wall of the insulating structure and the outer face of the pipe. In other words, it is not the entire inner wall of the insulating structure that is directly in contact with the pipe, the only points of contact between the two elements being the protrusion(s) that emerge from the inner wall of the insulating structure.

[0017] The outer wall is the part of the insulating structure furthest radially from the pipe that the invention proposes to insulate. The density comparison between the inner wall and the outer wall can be carried out according to an identical thickness of these walls.

[0018] The insulating structure is manufactured in particular by hot pressing around a mandrel, thus allowing the creation and densification of the protrusion from the internal wall. For example, the material composing the insulating structure can be pressed onto the mandrel, the latter having a particular shape or comprising counterforms corresponding to the desired shapes of the insulating structure. In order to obtain the densification of the internal wall and the protrusion, the mandrel is heated for example by means of a resistance beam placed on the mandrel and / or by means of microwaves. Heating the mandrel therefore makes it possible to densify the internal wall at the protrusion, by consolidating the material composing the insulating structure so as to form a layer where said material and the glue are melted and compressed by passing through the pressing machine equipped with the heated mandrel.By densification of the material, it is meant that the material undergoes hardening following its pressing against the hot mandrel, the protrusion being able to be pressed into its counterform according to the manufacturing process explained in more detail later.

[0019] Thus, the pressing is carried out in such a way that only the inner wall at least partially delimiting the protrusion is densified. In other words, a portion of the inner wall radially located between the protrusions may be devoid of material densification. Nevertheless and alternatively, such a portion may be densified in a manner identical or similar to the protrusion in a manner similar to that described previously. The densification ensures resistance to deformation of the protrusion, possibly of the inner wall located between two protrusions, thus allowing the preservation of the air space between the pipe and the insulating structure, circumferentially on either side of the protrusion. If there are at least two protrusions on the inner wall of the insulating structure, each of these protrusions is densified as envisaged by the invention.By densification of the outgrowth, it is meant that only the wall of the outgrowth, i.e. the material directly in contact with the mandrel during pressing, is densified, a core of the outgrowth remaining flexible despite such a manufacturing process. Maintaining a certain flexibility of the core of the outgrowth allows for better acoustic insulation.

[0020] The densification of the inner wall layer can, for example, be demonstrated using a bulk density test according to EN 1602. The measurement of the density according to this standard consists of measuring the materials to be tested to deduce their volume by calculation, then weighing these same materials to deduce the mass. The density of each of these materials is thus obtained by calculating the ratio between the weighed mass and the calculated volume. Once the density value is obtained, all that remains is to calculate the ratio between this value and that of the density of water to obtain the density of the material. The higher the density value, the denser the material. Two measurements are carried out: one measurement at the inner wall at least partially delimiting the protrusion, and one measurement on the outer wall of the insulating structure, i.e. an area of ​​the insulating structure not showing any material densification.

[0021] After testing the two measured areas, the invention is recognizable when the density of the internal wall at least partially delimiting the protrusion is higher than the density of any other portion of the insulating structure, in particular its external wall. Such a test can be carried out at any time once the insulating structure has been manufactured, advantageously before the latter is installed around the pipe.

[0022] The air space thus formed by the insulating structure guarantees better resistance of the pipe to corrosion. The fluid circulating in the pipe has variable temperatures over time.

[0023] The air space, along with the densification of the material, alleviates the problem of condensation, thus preventing the absorption of moisture by the insulation material. The air space can also be swept by air circulation, further reducing the formation of condensation on the external face of the pipe.

[0024] The air gap also ensures better sound insulation of the pipe. Indeed, it has been shown that by forming such an air gap, the solid-borne transmission through the insulating structure is reduced compared to an insulating structure in direct contact with the pipe. To confirm this, a sound insulation test was carried out according to ISO 15665. Following this test, it appeared that the insertion loss of sounds coming from the pipe is generally higher when the air gap is created between the pipe and the insulating structure than when they are in direct contact with each other, despite the test on a plurality of insulating structures with different characteristics. This increase in insertion loss characterizes better sound insulation. The results of the sound insulation test are presented in more detail below.

[0025] According to a feature of the invention, the insulating structure may comprise at least two protrusions. Having more than one protrusion on the insulating structure makes it possible to center the insulating structure around the pipe, and thus to have an air space at the level of the entire circumference of the pipe, of course with the exception of the areas of direct contact between the protrusions and the pipe. Advantageously, the insulating structure comprises at least three protrusions, in order to ensure optimal and balanced positioning of the insulating structure around the pipe.

[0026] According to a characteristic of the invention, a thickness of the internal wall measured at the level of the protrusion is between 0.1 mm and 5 mm. This thickness is that where the density of the internal wall at the level of the protrusion is greater than a density of the external wall at the level of its thickness. The thickness of the internal wall is likely to vary according to the measured zone, but remains between 0.1 mm and 5 mm. Such a thickness of the internal wall can be found at the level of the entire internal wall or only at the level of the protrusions, in all or part of these protrusions.

[0027] According to a characteristic of the invention, the density of the external wall of the insulating structure is of a relative value between 40% and 70% of the value of the density of the internal wall of the insulating structure at the level of the protrusion. This relative difference in density value between the internal wall at the level of the protrusions and the external wall was measured according to the EN 1602 standard as presented previously.

[0028] The insulating material that makes up the insulating structure is mineral wool. Mineral wool can, for example, be glass wool or rock wool. Glass wool provides thermal and acoustic insulation suitable for fluid pipes that can reach extreme temperatures. Rock wool is an insulating material with the characteristic of offering better resistance to moisture than glass wool. Both materials offer substantially similar thermal and acoustic insulation. Therefore, if the pipe is located in an area where there is a lot of moisture, it is more advisable to use rock wool. Otherwise, glass wool may be preferred.

[0029] The protrusion emerging from the inner wall is curved in the direction of the axis of revolution of the cylinder formed by the insulating structure. The protrusion of the inner wall of the insulating structure is rounded, i.e. devoid of sharp angles. Such a characteristic makes it possible to limit the contact between the insulating structure and the pipe to a contact line formed by a free end of the protrusion.

[0030] The protrusion is curved in the direction of the axis of revolution of the cylinder formed by the insulating structure, that is to say in the direction of the pipe when the insulating structure is placed around it. According to other embodiments, the protrusion may take other particular shapes, for example a polygonal shape.

[0031] The protrusion may extend longitudinally along the entire length of the insulating structure or may have discontinuities depending on the counter-shapes of the mandrel. Thus, when pressing the insulating structure, the protrusion is formed and densified in a continuous linear manner, in a discontinuous linear manner, or in a punctual manner, the essential thing being that the air space formed during the installation of the insulating structure around the pipe is present over all or part of the length of the latter. In the longitudinal plane, the protrusion then has the overall shape of a half-cylinder.

[0032] The protrusion may extend along a straight line. In such a case, this line is parallel to the axis of revolution of the insulating structure.

[0033] Alternatively, the outgrowth may follow a curve that wraps around the axis of revolution of the insulating structure. The outgrowth then extends in a helical manner.

[0034] The insulating structure may comprise a plurality of protrusions that emerge from the inner wall, the protrusions being distributed angularly in a regular manner. The protrusions are present punctually circumferentially around the inner wall of the insulating structure, for example at equal angular sectors from each other. The portions of the inner wall of the insulating structure not having protrusions are not in contact with the outer wall of the pipe. There is therefore an empty volume between these portions and the pipe allowing the creation of the air space.

[0035] According to an advantageous form of the invention, the external wall is covered with a layer of a waterproof material. The layer of material covering the external wall ensures protection and / or sealing of the insulating structure against any heat loss or any damage from the external environment. The insulating structure is thus protected and is maintained in operating condition over the long term.

[0036] The waterproof material layer of the outer wall is, for example, a metal sheet. The metal sheet is ideally made of aluminum or an aluminum-based alloy, because aluminum has waterproof and malleable properties, even at very low thickness.

[0037] The invention also covers a method of manufacturing a thermally and acoustically insulating structure as described above, comprising: a step of winding a section of insulating material around a mandrel having counterforms, a step of heating the material by the mandrel, a step of pressing the section of insulating material onto the mandrel by rollers.

[0038] The insulating structure is, for example, manufactured by a machine capable of processing any material with insulating characteristics, for example mineral fibers. These mineral fibers are fed into the machine in sections and are wound around the rotating mandrel, for example via a rotating shaft. The mandrel is heated to a temperature of approximately 350-400°C in order to melt the material and increase the density of a portion of material in direct contact with the mandrel. The mandrel has counterforms configured to form the protrusions of the insulating structure. While being wound around the mandrel, the section is pressed against it by means of rollers. These rollers thus make it possible to press the section against the counterforms of the mandrel in order to form the protrusions on the final product.

[0039] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which: [ fig. 1 ] is a sectional view of the insulating structure covering a pipe, according to one embodiment of the invention; [ fig. 2 ] is a perspective view of the insulating structure according to the same embodiment as the figure 1 ; [ fig. 3 ] is a representation of a manufacturing process of the insulating structure in cross-sectional view; [ fig. 4 ] is a sectional view of a first arrangement of the insulating structure around the metal pipe for the purpose of an acoustic insulation test; [ fig. 5 ] is a sectional view of a second arrangement of the insulating structure around the metal pipe for the same sound insulation test; [ fig. 6 ] is a curve of the insertion loss as a function of the sound frequency of a first model of insulating structure arranged around the pipe according to the figures 4 And 5 ; [ fig. 7 ] is a curve of the insertion loss as a function of the sound frequency of a second model of insulating structure arranged around the pipe according to the figures 4 And 5 ; [ fig. 8 ] is a curve of the insertion loss as a function of the sound frequency of a third model of insulating structure arranged around the pipe according to the figures 4 And 5 ; [ fig. 9 ] is a curve of the insertion loss as a function of the sound frequency of a fourth model of insulating structure arranged around the pipe according to the figures 4 And 5 ; [ fig. 10 ] is a curve illustrating the insertion loss as a function of the sound frequency of a fifth model of insulating structure arranged around the pipe according to the figures 4 And 5 .

[0040] There figure 1 represents a section of a metal pipe 1, for example circular in shape, shown here in dotted lines. The pipe 1 ensures the circulation of a fluid which may be of various natures, for example a liquid or a gas. The pipe 1 may be part of a system for conditioning or cooling a fluid, or any other system capable of creating a condensation phenomenon at the level of the pipe 1. In the case of a conditioning or cooling system, the fluid circulating in the pipe 1 may in particular be water or air. The pipe 1 may be installed within any container comprising a system within which a pipe ensures the circulation of a fluid which is colder than the external environment, for example a terrestrial construction such as a building or a vehicle such as a boat or an airplane.

[0041] The pipe 1 is entirely covered by an insulating structure 2, of a shape substantially identical to the shape of the pipe 1, for example of a circular shape if the pipe 1 is also of a circular shape. The pipe 1 and the insulating structure 2 are centered around an axis of revolution 7. The insulating structure 2 is sectioned and has an opening 8, arranged radially along a radius of the axis of revolution 7 and longitudinally along the length of the insulating structure 2. The latter is wound around the pipe 1, then is fixed for example by an adhesive strip, not shown in the figure 1 .

[0042] The insulating structure 2 comprises an inner wall 3 and an outer wall 4 which delimit the thickness of the insulating structure 2. The entire insulating structure 2 is composed of glass wool or rock wool, depending on the material chosen. The outer wall 4 can be covered with a thin layer of material ensuring the sealing of the insulating structure 2. The outer wall 4 is thus advantageously covered with an aluminum sheet ensuring the sealing and / or protection of the insulating structure 2 against the external environment.

[0043] The internal wall 3 of the insulating structure 2 is, in this embodiment, mainly circular, with the exception of protrusions 5, present in a regular and punctual manner in the internal volume delimited by the insulating structure 2.

[0044] The protrusions 5 are formed during the manufacture of the insulating structure 2 and correspond to the counterforms of a mandrel comprising, for example, counterforms making it possible to obtain the insulating structure 2 as represented in the figure 1 The protrusions 5 are therefore an integral part of the internal wall 3 due to the shape of the mandrel with which the insulating structure 2 was extruded during the manufacturing process described above.

[0045] The inner wall 3 at least partially delimits the protrusion 5. The other side of the protrusion 5 is delimited by a core 22 of the insulating structure 2. The inner wall 3 of the insulating structure forms a skin 21 which has been densified by heating during the manufacturing process of the insulating structure 2. This densified skin 21 may be located exclusively at the level of the protrusion 5, depending on the distribution of the heat exerted on the mandrel during the manufacturing of the insulating structure 2, as illustrated in the figure 1 Alternatively, this densified skin 21 can also extend over a plurality of outgrowths 5 and over the internal wall 3 located between two consecutive outgrowths 5.

[0046] In the embodiment of the figure 1 , the protrusions 5 are four in number, arranged at an angle of 90° to each other, thus forming a regular arrangement of the protrusions 5 along the internal wall 3.

[0047] In this embodiment, the protrusions 5 have an ogive shape according to a section plane of the insulating structure perpendicular to the axis of revolution of this structure.

[0048] Each rounded apex of the protrusion 5 is in direct contact with the pipe 1. Along a transverse plane, the protrusions 5 are of equal height relative to each other. In other words, the distance between the point of contact of the rounded apex of the protrusion 5 with the pipe 1 and a base of the protrusion 5 at the level of the internal wall 3 is identical regardless of the protrusion 5. The protrusions 5 thus allow the delimitation of an air space 6 between the pipe 1 and the internal wall 3, of a thickness equivalent to the height of the protrusions 5.

[0049] The assembly formed by the core 22 and the protrusions 5 is made of glass wool or rock wool depending on the choice of insulating material, just like the rest of the insulating structure 2. According to the invention, the insulating material of the insulating structure 2 at the protrusions 5, and advantageously between the protrusions, is densified following the creation of the insulating structure 2 by pressing on the mandrel. This densification is due to a particular process of heating the mandrel to a temperature of around 350-400°C by means of a bundle of heating resistors or microwaves. The densified protrusions 5 are therefore denser than the external wall 4 of the insulating structure 2 and therefore ensure that the insulating structure 2 is maintained around the pipe 1 over the long term.

[0050] There figure 2 is a perspective representation of the insulating structure 2. In this figure, several elements are represented in solid or dotted lines and correspond to different elements of the insulating structure 2.

[0051] The thinnest dotted line corresponds to the axis of revolution 7. Just as for the figure 1 , the insulating structure 2 shown on the figure 2 is circular in shape. The perspective representation therefore makes it possible to visualize the insulating structure 2 in the form of a right circular cylinder, centered around the axis of revolution 7. The two solid lines correspond to two diametrically opposite points of the external wall 4 of the insulating structure 2, delimiting the external dimensions of the insulating structure 2. The solid lines are parallel to each other, thus defining an insulating structure 2 of constant cylindrical shape in a longitudinal direction. Finally, the four strong dotted lines correspond to the protrusions 5. The embodiment of the insulating structure 2 shown in figure 2 being identical to the embodiment of the insulating structure 2 shown in figure 1 , the growths 5 are four in number, arranged at an angle of 90° to each other. The perspective representation of the figure 2 illustrates the longitudinal extension of the protrusions 5 over the entire length of the internal wall 3 of the insulating structure 2. On the figure 2 , the longitudinal extension of the protrusions 5 is continuous, but it is entirely possible to imagine a discontinuous longitudinal extension of the protrusions 5, as long as the air space 6 is maintained over the entire pipe when the insulating structure 2 is put in place there.

[0052] The protrusions 5 maintain their dimension constantly. Thus, the air space 6 is present over the entire length of the pipe 1, which therefore guarantees protection against corrosion over the entire pipe 1, air circulation between the protrusions 5, and acoustic insulation of the pipe as described below.

[0053] There figure 3 presents a method for manufacturing the insulating structure 2. This figure schematically shows a machine 30 capable of processing mineral fibers, for example glass wool or rock wool, so as to form products such as the insulating structure 2. The manufacturing method shown in the figure 3 allows the insulating structure 2 to be manufactured as shown in the previous figures.

[0054] The machine 30 comprises a mandrel 31 and rollers 34. The mandrel 31 is capable of being driven in rotation in a direction 37, for example by means of a rotary shaft not shown in the figure. The machine 30 also comprises an arrival of a section 35 of mineral fibers along a direction 36, for example by means of a conveyor, not shown in the figure. The section 35 of mineral fibers is advantageously of small thickness in order to be able to obtain products which can vary in terms of thickness. Although this is not visible in the figure, it is obvious that the section 35 of mineral fibers and the mandrel 31 have a substantial longitudinal dimension, in order to create an insulating structure 2 of substantially cylindrical shape and of a longitudinal dimension suitable for being arranged around a pipe.

[0055] When it arrives in the machine 30, the section 35 is wound around the mandrel 31 by rotating the latter in the direction 37. The mandrel 31 comprises counterforms 32, shown here in the form of recesses, corresponding to the protrusions of the insulating structure 2. These counterforms 32 can for example be machined directly in the mandrel 31. The counterforms 32 extend longitudinally along the mandrel 31. When the section 35 is wound around the mandrel 31, the counterforms 32 are filled by the layers of the section 35, thanks to the combination of the rotation of the mandrel 31 and the pressure exerted by the rollers 34.

[0056] The rollers 34 have shapes that match the external wall of the insulating structure 2, and exert pressure on it, pressure allowing the counterforms 32 to be filled, but also to smooth the section 35 to avoid the appearance of manufacturing defects, for example folds.

[0057] At the start of the manufacturing process, the rollers 34 are almost in contact with the mandrel 31. Subsequently, the more the section 35 is wound around the mandrel 31, the more the thickness of the insulating structure 2 increases, and therefore the more the rollers 34 move away from the mandrel 31 while maintaining a certain pressure ensuring their functions. The machine 30 can thus create an insulating structure 2 of a variable thickness depending on the insulation requirement, and corresponding to the number of times the section 35 is wound around the mandrel 31.

[0058] While being rotated, the mandrel 31 is heated to 350-400°C by means, for example, of electrical resistors 33 located within the structure of the mandrel 31, at the counterforms 32. It is these electrical resistors 33 which, by their heating function, ensure the densification of the internal wall of the insulating structure 2 at the level of the protrusions. Furthermore, it is the proximity between the electrical resistors 33 and the counterforms 32 which causes the densification of the internal wall of the insulating structure 2 which at least partially delimits the protrusions, thus forming the densified skin. The heating process by means of the resistors 33 is in no way limiting, the internal wall being able to be heated by microwaves oriented in the direction of the protrusions, for example.

[0059] THE figures 4 And 5are schematic cross-sectional representations of two arrangements of the insulating structure 2 around the pipe 1 for the purpose of an acoustic insulation test. The same acoustic insulation test is carried out on four different models of the insulating structure 2, each according to the two arrangements shown in figure 4 And 5 .

[0060] There figure 4 presents a first arrangement for the sound insulation test. In this first arrangement, the insulating structure 2 is wrapped around the pipe 1 so that the vast majority of the internal wall 3 of the insulating structure 2 is in direct contact with the pipe 1. The four models of the insulating structure 2 used for the sound insulation test therefore all have a dimension suitable for being wrapped around the pipe 1. The insulating structure 2 is then held around the pipe 1, for example, using adhesive material.

[0061] There figure 5 presents a second arrangement for the sound insulation test. This second arrangement corresponds to the insulating structure 2 according to the invention and therefore comprises several protrusions 5 at the level of the internal wall 3 of the insulating structure 2.

[0062] On the figure 5 , and unlike the figure 1 , the protrusions 5 are three in number, distributed equilaterally along the internal wall 3, and therefore ensure the formation of the air space 6. Just as for the first arrangement, the insulating structure 2 is then held on the pipe 1 by adhesive material.

[0063] The acoustic test is carried out with four models of insulating structure. Each of the four models has an internal diameter of 114 mm. By internal diameter, it is understood that this corresponds to the length between two points on the internal wall of the insulating structure diametrically opposite each other when the insulating structure is placed around the pipe. All four models have the same internal diameter since they are all placed around the same pipe to carry out the acoustic insulation test.

[0064] A first model A has an insulating material thickness of 30mm and a linear weight of 1.0 kilograms per meter of length + / - 0.15 kilograms per meter of length. A second model B also has an insulating material thickness of 30mm and a linear weight of 1.2 kilograms per meter of length + / - 0.15 kilograms per meter of length. A third model C has an insulating material thickness of 60mm and a linear weight of 3.2 kilograms per meter of length + / - 0.2 kilograms per meter of length. Finally, a fourth model D has an insulating material thickness of 100mm and a linear weight of 4.4 kilograms per meter of length + / - 0.2 kilograms per meter of length.

[0065] Each of the insulating structure models is wound in turn around the pipe, and this according to each of the two arrangements, a first time according to the first arrangement presented in figure 4 , and a second time according to the second arrangement presented in figure 5 . There are therefore two installations per model, making eight installations in total. For each installation of the insulating structure, white noise, i.e. a noise with an identical sound level regardless of the frequency of said noise, is sent by a loudspeaker inside the metal pipe and a microphone located near the insulated pipe picks up said noise. The test is repeated according to a given frequency range. From the sound level of the frequencies picked up by the microphone and depending on the initial sound level of the sound at the speaker output, an insertion loss in decibels is calculated. The higher the insertion loss, the more effective the insulating structure provides sound insulation. The results of the sound insulation tests are presented on the figures 6 à 9 .

[0066] Each of the figures 6 à 9 shows a graph comprising two insertion loss curves as a function of sound frequency, one figure corresponding to one model of insulating structure. Each of the figures shows a curve with triangular marks corresponding to the curve of the results of the sound insulation test of the insulating structure arranged according to the first arrangement shown in figure 4 , and a curve with square marks corresponding to the curve of the results of the sound insulation test of the insulating structure arranged according to the second arrangement presented in figure 5 The sound frequency range selected for the sound insulation test presents nineteen different sound frequencies varying between 100Hz and 6300Hz.

[0067] There figure 6 is a graph showing the results of the sound insulation test of the first model A according to the two arrangements presented previously. Except for the three lowest frequencies where the insertion losses are identical or substantially identical, the insertion loss when the first model A of insulating structure is arranged according to the second arrangement is systematically higher than the insertion loss of the first model A is arranged according to the first arrangement, with an insertion loss differential of up to more than five decibels.

[0068] There figure 7 is a graph from the sound insulation test identical to the previous figure, but carried out with the second model B of insulating structure. In this graph, the insertion loss when the second model B is arranged according to the second arrangement is always higher than when the second model B is arranged according to the first arrangement, with an insertion loss differential of up to approximately eight decibels.

[0069] There figure 8 is a graph showing the results of the sound insulation test with the third model C of insulating structure. Except for the measurement at 160Hz which may seem negligible compared to the whole curve, the insertion loss of the third model C arranged according to the second arrangement is always higher. Just as for the second model B of insulating structure, an insertion loss differential for the third model C can also extend up to about eight decibels.

[0070] There figure 9 is a graph showing the results of the sound insulation test with the fourth D-model of insulating structure. The results of the fourth D-model show less biased measurements than for the previous insulating structure models, particularly for very low and very high frequencies. The overall result nevertheless remains in favor of the second arrangement where the insertion loss remains the highest for most sound frequencies, with an insertion loss differential of up to seven decibels.

[0071] Generally speaking, the insertion loss is higher when the insulating structures are arranged according to the second arrangement, that is to say with the presence of protrusions on the internal wall of the insulating structure ensuring the creation of an air space between the pipe and the insulating structure, despite the differences in characteristics between the four models of insulating structure, whether the thickness of the insulating material or the linear weight thereof. The presence of such an air space therefore reinforces the acoustic insulation of the pipe, in a manner at least partially independent of the properties of the insulating structure. Although the embodiment of the second arrangement differs from the embodiment of the invention presented through the detailed description, the insulating structure according to the invention also makes it possible to form an air space between the pipe and the insulating structure by means of the protrusions.The invention therefore has an acoustic insulation function in addition to solving the technical problem linked to the corrosion of the pipe following its condensation.

[0072] There figure 10 is a graph showing the results of the sound insulation test as carried out previously. The mineral wool used for the test corresponds to a fifth model E, with an insulating material thickness of 30mm, like the first model A and the second model B. The fifth model E has a density of 66kg / m 3< . The fifth model E is virtually wrapped around a pipe, and is virtually traversed by several white noises at different frequencies. The two arrangements of the fifth model E are similar to the arrangements shown in figure 4 And 5 .

[0073] The acoustic test carried out here is identical to that mentioned when describing the figures 6 à 9 . The frequency range used is between 100 Hz and 4000 Hz and is applied on the fifth model E according to the first arrangement and according to the second arrangement. The insertion loss in decibels is measured for each frequency and the results are presented in figure 10 . It can be seen that the insertion loss differential is in favor of the second arrangement, with a differential ranging from 5 decibels to 15 decibels. The acoustic test is therefore also conclusive. The invention is not limited to this embodiment. It is obviously possible to choose the insulating material according to requirements. It is also possible to vary the height of the protrusions 5 according to the diameter of the insulating structure 2, or simply to create a larger air space 6, if necessary.

[0074] The number and the shape seen in section of the protrusions 5 can also vary, depending on the shape of the mandrel on which the insulating structure 2 is formed. Increasing the number of protrusions 5 ensures better stability of the insulating structure 2 around the pipe 1 but reduces the overall volume of the air space 6. The embodiments described above are thus in no way limiting; it is possible in particular to imagine variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics mentioned in this document, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

Claims

1. A cylindrical thermally and acoustically insulating structure (2) configured to cover a pipe (1) for transporting a fluid capable of being brought to variable temperatures, comprising an inner wall (3) and an outer wall (4), said insulating structure (2) comprising at least one protrusion (5) which emerges from its inner wall (3) so as to generate an air space (6) between the inner wall (3) and the pipe (1), the inner wall (3) of the insulating structure (2), which at least partially delimits the protrusion (5), being denser than the outer wall (4) of the insulating structure (2), characterized in that a densification of the protrusion (5) emanating from the inner wall (3) providing the protrusion (5) with an increased resistance to deformation and allowing conservation of said air space (6) between the pipe (1) and the insulating structure (2).

2. The insulating structure (2) as claimed in claim 1, comprising at least two protrusions (5).

3. The insulating structure (2) as claimed in either one of the preceding claims, in which a thickness of the inner wall measured at the protrusion (5) is between 0.1 mm and 5 mm.

4. The insulating structure (2) as claimed in any one of the preceding claims, in which the density of the outer wall (4) of the insulating structure (2) has a relative value of between 40% and 70% of the value of the density of the inner wall (3) of the insulating structure (2) at the protrusion (5).

5. The insulating structure (2) as claimed in any one of the preceding claims, in which the insulating material which composes it is mineral wool.

6. The insulating structure (2) as claimed in any one of the preceding claims, in which the protrusion (5) which emerges from the inner wall (3) is curved in the direction of the axis of revolution (7) of the cylinder formed by the insulating structure (2).

7. The insulating structure (2) as claimed in any one of the preceding claims, comprising a plurality of protrusions (5) which emerge from the inner wall (3), the protrusions (5) being angularly distributed in a regular manner.

8. The insulating structure (2) as claimed in any one of the preceding claims, in which the outer wall (4) is covered with a layer of leak tight material.

9. The insulating structure (2) as claimed in the preceding claim, in which the layer of leak tight material of the outer wall (4) is a metal foil.

10. A method for manufacturing a thermally and acoustically insulating structure (2) as claimed in any one of the preceding claims, comprising : - a step of winding a portion (35) of insulating material around a mandrel (31) having counter-shapes (32), - a step of heating the material by means of the mandrel (32), - a step of pressing the portion (35) of insulating material onto the mandrel (31) by means of rollers (34).