GLASSWORKS KILN MONITORED BY ELECTRICAL REFLECTOMETRY

Abstract

Glass furnace comprising a device for monitoring, by time-domain or frequency-domain electrical reflectometry, the state of a part of the furnace (30), said device comprising an array of wire electromagnetic waveguides (12), extending parallel to the hot face (37) and at a distance adapted so that in operation said waveguide is at a temperature greater than 500°C and less than 1300°C, and comprising a plurality of discontinuities, called "basic discontinuities" (24), - randomly distributed at least along the measurement part of the waveguide, and - capable of generating echoes having an amplitude greater than 0.5%, preferably greater than 1% and less than 30% of the amplitude of the background echo reflected by the output end of the waveguide, called "basic secondary echoes",or consisting of microreliefs or reliefs resulting from irregular segmentation of a dielectric material interposed between the first and second electrical conductors, or from local variations in the distance between the first and second electrical conductors or the distance between the first and / or second electrical conductors on the one hand, and a dielectric material of a support, or from variations in the structure and / or composition of the environment around the first and second electrical conductors or between the first and second electrical conductors, the number of basic discontinuities, per meter of waveguide measurement section, being greater than 10. No abbreviated figure,

Description

Title of the invention: GLASSWORK FURNACE MONITORED BY ELECTRICAL REFLECTION TOMETRY technical field

[0001] The present invention relates to a glass furnace equipped with a device for monitoring the condition of a part of such a furnace, in particular the condition of the refractory lining of the furnace enclosure.

[0002] It also relates to a method for manufacturing such a furnace and a method for monitoring the condition of the refractory lining of such a furnace. State of the art

[0003] Many glass products are manufactured by melting and refining a vitrifiable mixture of raw materials comprising compounds such as oxides, carbonates, sulfates, and nitrates. These two steps are carried out in furnaces whose main constituents are refractory materials capable of withstanding the thermal and mechanical stresses encountered in these furnaces, and in particular the high temperatures. Glass furnaces thus generally include a very large number of refractory materials, arranged in different locations according to their properties. For each part of the furnace, the material chosen is the one that does not cause defects rendering the glass unusable (which would reduce production yields) and that is sufficiently durable to ensure a satisfactory furnace lifespan.

[0004] Fig. 1 schematically represents half a cross-section of a glass furnace 10. In particular, a tank 11, a metal structure 13 and a superstructure 16 are distinguished. The tank 11, intended to contain the molten glass, has a vertical side wall 22 and a base 4L. The side wall 22 is conventionally made up of lateral tank blocks which extend over the entire height of the tank, up to an upper edge 29.

[0005] The superstructure 16 conventionally comprises, at its base, an intermediate layer 17 by which it rests on the metal structure, a lateral wall 26 resting on the intermediate layer 17, and a vault 28 also formed of refractory blocks.

[0006] The heating system, not shown, including for example burners, is generally located in the side wall 26. The metal structure 13, typically made of cast iron, surrounds the side wall 22 of the tank externally. It supports the weight of the superstructure 16.

[0007] The tank 11 and the superstructure 16 are the parts of the furnace that define the enclosure in which the glass is melted. They define a hot face 37 in contact with the molten glass or with its gaseous environment.

[0008] With all parts of the oven having a hot face, they are generically referred to as the "target".

[0009] The tank 11 and the superstructure 16 conventionally comprise several layers, namely - a first refractory layer of dense blocks, preferably with a porosity of less than 10%, preferably less than 5%, defining the hot face in contact with the glass or its gaseous environment; - a second layer, or "back layer", made of a different material than the first layer, and more porous.

[0010] The back layer may include a first refractory underlayer, called a "barrier layer", intended to stop glass infiltration or to condense glass vapor, and / or a second refractory underlayer or "insulating layer", preferably comprising a porous refractory material, in order to achieve a suitable thermal profile in service.

[0011] The barrier layer is preferably a layer of unshaped refractory material, in particular concrete or rammed earth. Typically, more than 90% of the grains by number have a size (largest dimension) of 5 mm or less to obtain a satisfactory surface finish, and its chemical composition is such that the Al₂O₃ mass content is at least 40%. The chemical composition can be adapted according to the type of glass to ensure sufficient resistance to molten glass.

[0012] The insulating layer typically consists of an unshaped, silico-aluminous insulating refractory material and / or refractory bricks or blocks. The thermal conductivity measured at 1000°C of the insulating refractory material is less than 7 W / mK, preferably less than 5 W / mK, and preferably less than or equal to 3 W / mK. Preferably, the insulating refractory material has a porosity greater than 15%, preferably greater than 20%, and more preferably greater than 30%. The porosity and thickness of the insulating layer are adapted according to the desired thermal profile.

[0013] Conventionally, the dense blocks of the first layer are made of a material resistant to contact with glass at temperatures exceeding 600°C, or even exceeding 1000°C, or even 1200°C. They can be composed, for more than 90% of their mass, of one or more oxides selected from the group consisting of ZrO2, Al2O3, SiO2, Cr2O3, Y2O3, and CeO2. Preferably, they comprise more than 90% ZrO2, Al2O3, and SiO2.

[0014] In operation, the furnace enclosure is subjected to extreme conditions, and in particular to a corrosive and abrasive environment that causes progressive wear. In areas in contact with molten glass, in particular, the state of wear cannot be visually assessed. To measure the remaining thickness of a refractory block, That is, the distance between its hot side and its cold side, opposite the hot side. A hook is therefore conventionally used at the waterline. This method has the disadvantage of requiring partial disassembly and reassembly of the oven and of providing only a single measurement.

[0015] More recently, WO2015147827 mentions a device that sends waves, and in particular radar waves, through the block. The reflected waves are analyzed when possible. In practice, this procedure is time-consuming to implement and does not allow for real-time monitoring.

[0016] WO2020025493 discloses an optical waveguide comprising a Bragg grating in order to measure the residual thickness of a glass furnace floor. The present inventors tested the use of optical fibers and unexpectedly observed the appearance of crystallization which was detrimental to the accuracy of the measurements and the mechanical resistance of the optical fibers.

[0017] A device for measuring the residual thickness of a blast furnace lining is also known from JPH11264706A or JP3395886B2. This device is highly invasive, increases the risk of contaminating the molten glass, and significantly increases the risk of breaching the first layer.

[0018] There is therefore a need for a robust, easy-to-implement solution that allows for continuous, real-time evaluation of the condition of the enclosure of a glass furnace, at every point, with good spatial resolution, without weakening the lining of the enclosure, and without increasing the risk of contamination of the molten glass bath.

[0019] One object of the invention is to meet, at least partially, this need. Summary of the invention

[0020] According to the invention, this goal is achieved by means of a glass furnace comprising: - a glass melting chamber with a hot face exposed towards the inside of the chamber; - a monitoring device, using time-domain or frequency-domain electrical reflectometry, to track the state of a part of the furnace, preferably a part of said enclosure, referred to as the "target", said device comprising: - an array of at least one wire waveguide, preferably a plurality of wire electromagnetic waveguides, each waveguide comprising, between an input end and an output end, first and second electrical conductors, preferably metallic, electrically insulated from each other, preferably by a dielectric material, a measurement portion of the waveguide comprising a plurality of impedance discontinuities and extending parallel to the hot face and to a depth (distance behind said hot face relative to the inside of the enclosure) greater than 10 cm, preferably greater than 15 cm, greater than 20 cm, and preferably less than 200 cm, preferably less than 100 cm, - an interrogator electrically connected to the input end and configured to inject an interrogation signal through said input end, receive a response signal reflected by said waveguide in response to said injection, analyze the response signal and transmit a message on the state of the target based on said analysis.

[0021] The inventors discovered that this waveguide arrangement relative to the target offers an excellent compromise between limited attenuation of the response signal and high robustness. The waveguide array also makes it possible to track a target of any size, and in particular the oven floor.

[0022] The target preferably comprises an assembly of refractory blocks defining the hot face of the side wall, the vault or the floor of the furnace, preferably of the floor and / or the vault.

[0023] According to a first principal embodiment, said impedance discontinuities include "basic discontinuities": - which, particularly when the length of the measurement section is less than 10 meters, are capable of generating, in response to the injection of the interrogation signal, echoes with an amplitude greater than 0.5%, preferably greater than 1% and less than 30% of the amplitude of the background echo reflected by the output end of the waveguide, known as "basic secondary echoes", and / or - consist of:

[0024] - reliefs resulting from a texturization of the outer surface of the waveguide and / or of a dielectric material interposed between the first and second electrical conductors and / or of at least one of the first and second electrical conductors, and / or - reliefs resulting from an irregular segmentation of said dielectric material, preferably by means of tabs in a dielectric material, the tabs preferably having a length of less than 10 cm, preferably less than 5 cm, preferably less than 3 cm, more preferably less than 2 cm and / or greater than 0.5 cm, and / or - local variations in the distance between the first and second electrical conductors, and / or - variations in the distance between the first electrical conductor and / or the second electrical conductor, on the one hand, and a dielectric material of a support, preferably a ceramic matrix composite; and / or - variations in the structure and / or composition of the environment around or between the first and second electrical conductors, preferably variations in the structure and / or composition position of a dielectric material of a support, preferably in a ceramic matrix composite, preferably by the random dispersion of particles and / or fibers in a dielectric material within the support, and in particular within the matrix of the ceramic matrix composite, or between the first and second electrical conductors.

[0025] Remarkably, the inventors discovered that the analysis of basic secondary echoes by electrical reflectometry TDR (Time Domain Reflectometry) or FDR (Frequency Domain Reflectometry) allows for real-time and continuous monitoring of the target's state over a long period, accurately and reliably.

[0026] Preferably, the basic discontinuities are randomly distributed at least along the measurement portion of the waveguide, or even along the entire length of the waveguide. Advantageously, the random distribution avoids interference resonance phenomena.

[0027] Preferably, the basic discontinuities are: - reliefs resulting from texturizing the outer surface of the waveguide and / or a dielectric material interposed between the first and second electrical conductors and / or at least one of the first and second electrical conductors, for example by abrasion and / or chemical attack, and / or - reliefs resulting from an irregular segmentation of said dielectric material, preferably by means of notches (for example in the form of beads or cylinders preferably with a circular base) in a dielectric material, the notches preferably having a length of less than 10 cm, preferably less than 5 cm, preferably less than 3 cm, more preferably less than 2 cm and / or greater than 0.5 cm, and / or - local variations in the distance between the first and second electrical conductors.

[0028] The conductors can be sandwiched between two textiles in a ceramic matrix composite or fixed to the surface of a ceramic matrix composite textile, a dielectric material, for example in the form of a regular pattern, preferably extending over a surface of one or more of said textiles. The dielectric material can, for example, result from the deposition of a slip and then hardening of the slip.

[0029] In one embodiment, the aforementioned sandwiches have a thickness greater than 5 mm, greater than 8 mm, greater than 10 mm and / or less than 50 mm.

[0030] In one embodiment, a textile, preferably each of the aforementioned textiles has a thickness greater than 0.5 mm, greater than 1 mm, and / or less than 10 mm, less than 5 mm or less than 2 mm.

[0031] Preferably, the basic discontinuities generated by texturing generate more than 80% of said basic secondary echoes.

[0032] The lug(s) are preferably arranged less than 1 mm from the first and / or second electrical conductor, preferably in contact with the first and / or second electrical conductor.

[0033] Preferably, the lug(s) are threaded, in the measuring part, onto the first electrical conductor and / or onto the second electrical conductor.

[0034] In one embodiment, tabs in the form of beads and made of a dielectric material are threaded, in the measuring part, onto the first electrical conductor and / or onto the second electrical conductor, and the tabs are arranged so as to form together a segmented protective sheath extending along the entire measuring part of the waveguide.

[0035] The stop(s) are preferably spacers, or “spacers”, made of a dielectric material, arranged so as to keep the first electrical conductor away from the second electrical conductor.

[0036] In one embodiment, the lug(s) are movable relative to the first electrical conductor and / or the second electrical conductor.

[0037] Preferably, the cleat(s) are made of a thermally and electrically insulating material.

[0038] The thermally insulating material preferably has a thermal conductivity of less than 30 W / mK, less than 20 W / mK, less than 10 W / mK, or even less than 5 W / mK, at a temperature between 20°C and 1000°C.

[0039] Preferably, the cleat(s) have a melting point above 300°C, above 500°C, or above 1000°C, and preferably are made of a material chosen from mica, mica derivatives, titanium, barium, mullite, cordierite and alumina.

[0040] In one embodiment, discontinuities, preferably basic discontinuities, are created by making said measuring part integral with said support. In particular, the support may surround the measuring part, like a sheath, or sandwich the measuring part. In particular, the measuring part may be sandwiched between two textiles, preferably woven, stiffened by a ceramic matrix. The irregularities of the textiles and the matrix of such a ceramic matrix composite advantageously and unexpectedly allow the creation of basic discontinuities.

[0041] Preferably, the impedance discontinuities are separated from each other by a distance, measured along the waveguide, at least 10 times, preferably at least 15 times, preferably at least 20 times less than the reference wavelength, equal to the propagation speed of the interrogation signal, approximately 200,000 km / s for an electromagnetic wave, divided by the frequency of the highest peak of the frequency spectrum of the interrogation signal.

[0042] According to a second main embodiment, the oven further comprises one or more of the following optional features, preferably all of the following optional features: a) the measuring part of each of the waveguides of said network extends parallel to the hot face and at a distance suitable so that in service, i.e. when the furnace is in normal operation, said measuring part is at a temperature greater than 500°C, preferably greater than 600°C, preferably greater than 700°C, preferably greater than 800°C and / or less than 1300°C, preferably less than 1200°C, more preferably less than 1100°C; b) the maximum distance between two measurement parts of any two waveguides of the array is greater than 20 cm, preferably greater than 30 cm, preferably greater than 50 cm, preferably greater than 70 cm, preferably greater than 90 cm, and preferably less than 500 cm; (c) at least one, preferably each waveguide of the array is inserted into an orifice of the target, the orifice being configured to provide a thermal expansion space for the waveguide; d) the equivalent diameter of the measuring part of at least one, preferably of each waveguide of the array is greater than 1 mm and less than 50 mm, preferably less than 20 mm, preferably less than 10 mm; (e) the distance separating the first and second electrical conductors of the measuring part from at least one, preferably from each waveguide of the array, is greater than 0.3 mm, preferably greater than 0.4 mm, preferably greater than 0.5 mm and less than 30 mm, preferably less than 10 mm, preferably less than 5 mm, preferably less than 3 mm, which improves reliability and spatial resolution; f) said measuring section has a number of bends - less than 2 per meter of length of measuring part if the length of said measuring part is less than 3 meters; - less than 1 bend per meter, preferably less than 0.5 bends per meter, more preferably less than 0.1 bend per meter of measuring section, if the length of said measuring section is greater than or equal to 3 meters, which improves the integration of the waveguide while minimizing the risk of breakage of the waveguide during its installation in the furnace; the measuring part of the measuring part of a waveguide, preferably of each waveguide, preferably not having a bend; - the maximum curvature of the measuring part is such that its radius of curvature is at least 3 times, preferably at least 5 times, preferably at least 10 times, greater than the equivalent diameter of said measuring part, which reduces the mechanical stresses on the measuring part.

[0043] Preferably, the measuring part of at least one waveguide, preferably of each waveguide, is mounted to slide relative to the target and / or relative to the support.

[0044] The inventors discovered that this combination of features, resulting from research on a multitude of parameters, provides a solution adapted to the specific constraints of a glass furnace. In particular, it allows: - an installation that limits the risk of damage to the waveguides, - tracking of a large target, such as a sole, - high robustness in service; - good spatial resolution; - high reliability of the measurement; - real-time monitoring throughout the life of the furnace, without weakening the target and without increasing the risk of contamination of the molten glass bath.

[0045] According to a third principal embodiment, the first and second conductors are fixed to or integrated into a support, preferably in the form of a plate, preferably made of a ceramic matrix composite, preferably fixed by means of an interfacing layer or refractory tapes, staples or wires, or are integrated into said composite. By "integrated," it is understood that they are incorporated into the composite, for example by being warp or weft yarns of the composite textile.

[0046] Securing the conductors in or on a support helps to protect them. The support is preferably placed between the first layer and the back layer.

[0047] According to a first preferred configuration, the support comprises, preferably, a ceramic matrix composite, and the first and second conductors are integrated within the textile of the ceramic matrix composite. The conducting yarns, preferably arranged substantially parallel at a predetermined distance, may, for example, constitute part of the weft yarns. The other yarns of said textile (other than the first and second conductors) are preferably made of a dielectric material, so as to prevent any electrical contact or short circuit between said conducting yarns.

[0048] In one embodiment, the other wires in a dielectric material (or "non-conductive wires") can be modified randomly, for example by abrasion or chemical attack in order to generate random basic discontinuities.

[0049] In a complementary or alternative embodiment, the first and second conductors are modified randomly, for example by abrasion or chemical attack in order to generate random basic discontinuities.

[0050] In one embodiment, at least one of the first and second conductors is physically associated with one or more wires made of a dielectric material, for example randomly wound to generate random basic discontinuities.

[0051] In one embodiment, wires made of a dielectric material are added to the textile randomly.

[0052] In one embodiment, in order to generate random discontinuities, particularly basic discontinuities, the first and second conductors are integrated into the textile by weaving such that the distance between said conductors is variable along the conductors. Preferably, the distance between two said basic discontinuities is then less than 10 cm, preferably less than 5 cm and / or greater than 0.5 cm, preferably greater than 1 cm. Preferably, the distance between two successive points of passage of the first and second conductors over or under the base fabric, preferably the distance between two successive conduits, is less than 10 cm, preferably less than 5 cm and / or greater than 0.5 cm, preferably greater than 1 cm.

[0053] In one embodiment, in order to generate random basic discontinuities, particles and / or fibers of random size and / or random shape and / or random dimensions and / or randomly distributed spatially are placed in contact with said textile before impregnation by the matrix precursor. An irregularly textured fabric sheet can also be used as the textile.

[0054] According to a second configuration, the first and second conductors are fixed to the surface of the support and, preferably, the support comprises, preferably is made of a ceramic matrix composite.

[0055] According to one possible embodiment, the conductors, preferably the measuring portion, of at least one waveguide, preferably of each waveguide, are fixed to the substrate by means of an interfacing layer. An interfacing layer is a layer made of a material having a coefficient of thermal expansion (CTE) intermediate between that of the substrate, in particular that of the ceramic matrix of the substrate, and that of the material constituting the conductors. Preferably, the interfacing layer comprises, or is even made of, NiCrAlY.

[0056] According to another possible mode, the conductors, preferably the measuring part, of at least one waveguide, preferably of each waveguide, are attached or fixed to the support, preferably in the form of a plate, by means of refractory tapes, staples or wires.

[0057] In one embodiment, the measuring part is protected by a sheath made of a dielectric material, preferably a polymer or, even more preferably, a ceramic, said sheath surrounding the conductors, the conductors preferably being separated by a dielectric material. This sheath may be straight or curved. It may be flexible or rigid to give a shape to the measuring part, or even to the part of transmission.

[0058] In one embodiment, a support precursor, preferably consisting of a ceramic matrix composite precursor, conventionally a prepreg, is wound around the first and second conductors, at least in the measuring portion. Before or after hardening of the matrix precursor, the instrumented support precursor or the instrumented support is preferably inserted into a protective sheath, preferably ceramic.

[0059] Fixing or integrating the measuring part of a waveguide into a ceramic matrix composite is particularly advantageous, not only because the ceramic matrix composite protects the measuring part, but also because, by construction, even when the ceramic matrix composite has a woven textile, it has an irregular microstructure that generates many basic discontinuities.

[0060] According to a fourth main embodiment, the measuring part of at least one waveguide, preferably of each waveguide, is movable so that its dimensions can change under the effect of a temperature variation in operation. Preferably, the measuring part is mounted to slide relative to the target, preferably sliding in a housing, in particular an opening, provided in the target or, preferably, in the support.

[0061] Preferably, the housing provides a space for thermal expansion, preferably generated by the removal of sacrificial material around which at least part of the target or support has been formed.

[0062] Sliding can also result from the presence of a solid lubricant, preferably graphite, around the measuring part.

[0063] The lack of adhesion of the measuring part to the wall of the housing may also result from an incompatibility between the material of the target or the support defining the housing on the one hand and the measuring part on the other hand, for example from a high porosity of the material of the target defining the housing.

[0064] Sliding can also result from the insertion of the measuring part into a protective sheath, preferably non-segmented. Segmenting a protective sheath by a succession of dielectric beads along the measuring part tends to increase signal attenuation.

[0065] The invention also relates to a method for manufacturing a furnace according to the invention, said method comprising, for at least one, preferably for each waveguide of the array, the following successive steps: 1) interposition of a sacrificial material between - the measurement section of the waveguide and - the target or a precursor of the target, or a support, in particular a composite with ceramic matrix or a support precursor, then 2) after or simultaneously with the manufacture of the target or support in the case where the sacrificial material has been interposed in a precursor of the target or in a precursor of the support respectively, removal of the sacrificial material so as to create said expansion space for the measuring part.

[0066] In one embodiment, the sacrificial material is the material of a sacrificial sheath covering the measuring part, and, to interpose the sacrificial material, - the target or support is manufactured around the measuring part, preferably by casting and then sintering a precursor of the target around the measuring part, or by inserting the measuring part into a precursor of the support and then sintering the support precursor around the measuring part; - a housing is provided, in the form of a groove or a hole (or "orifice"), through or not, in the target or in a precursor of the target or in the support or in the precursor of the support, then the measuring part is inserted into the housing, then the housing is filled with an unshaped refractory product (i.e. a powder or a paste) containing a binder, preferably a hydraulic binder, preferably a cement, and capable of setting into mass by activation of the binder, preferably a refractory concrete, then the unshaped refractory product is hardened.

[0067] The target precursor may be a preform intended for sintering or a powdered mixture capable of solidifying by chemical reaction. The support precursor may be a ceramic matrix composite precursor comprising a textile and a matrix precursor impregnating the textile, or "prepreg".

[0068] The measuring portion with the sacrificial sheath can be embedded in the target or support precursor during its manufacture. Alternatively, a recess can be formed in the target or target precursor or the support or support precursor, and the measuring portion with the sacrificial sheath can be embedded in the unshaped refractory material.

[0069] In one embodiment, the sacrificial material is a filler material independent of the waveguide, that is to say, which, unlike a sacrificial sheath, is not initially attached to the waveguide and, to interpose the sacrificial material, - a housing is provided, in the form of a groove or a hole, through or not, in the target or in a precursor of the target or in a support or in a precursor of a support, then - the measuring part is inserted into the housing, then - the housing is filled with the filling material so as to submerge the measuring part, the quantity of filling material being adapted to allow for expansion space, then - the cavity is filled with a said unshaped refractory product, preferably refractory concrete, then - the unshaped refractory product is hardened.

[0070] In step 2), the sacrificial material is preferably removed by heat treatment, preferably by a consolidating heat treatment of the target precursor or support, preferably by sintering. The sacrificial material is preferably removed by heat during furnace quenching and / or during sintering of the unshaped refractory product or the target precursor or the support precursor at a temperature preferably between 400°C and 1200°C. Sintering can result from furnace quenching.

[0071] The sacrificial material can be eliminated by vaporization or combustion.

[0072] The sacrificial material thus leaves room for thermal expansion.

[0073] Preferably, the sacrificial material is an organic material, preferably a polymer. Upon degradation, such a sacrificial material advantageously generates residual carbon which limits the oxidation of the first and second conductors, thus allowing its use in an oxidizing atmosphere.

[0074] The manufacturing process may further include one or more of the following optional and preferred features: - step 1) and / or step 2) are carried out in situ, i.e. at the location of the oven in which the measuring part is intended to be used in the oven; - the housing is provided in the support or in a precursor of the support, but can also be provided in a back layer of the target or in a precursor of the back layer; - the sacrificial sheath of a waveguide, preferably of each waveguide, is made of a polymer, preferably a polymer not containing halogen and / or nitrogen and / or silicon, preferably a polyalkylene, preferably a polyethylene or one of its derivatives; - the filling material is a resin; - the removal of the sacrificial material is simultaneous with a hardening of the precursor of the target or of the support leading to said target or said support, respectively.

[0075] In one embodiment, step 1) comprises the following steps: - putting the network precursor into service position, i.e., arranging the measuring part(s) in the desired service position during furnace operation; - preparation of a starting charge having the desired composition for the target or support, considering only refractory oxides; - depositing the initial charge in order to flood the network precursor and obtain the precursor to the target or medium.

[0076] In one embodiment, at least one, preferably each measuring part, is protected by a protective sheath, preferably ceramic. The sacrificial sheath then covers the protective sheath.

[0077] According to a fifth main embodiment, the waveguide includes a protective sheath for the first and second electrical conductors.

[0078] The protective sheath can be rigidly attached to the conductors, provided it is segmented, or it can form a rigid sleeve housing the waveguide. The waveguide can be inserted into the sleeve after the sleeve has been placed in its service position. In particular, the sleeve can be incorporated into the target during its manufacture, for example, positioned before being embedded in the concrete that forms part of the target.

[0079] Preferably, the waveguide can move freely within the sleeve. The protective sheath can also provide an expansion space as described above.

[0080] A rigid sleeve can advantageously guide the waveguide to give it a predetermined shape, for example straight or bent, or guide it over a long length during its insertion.

[0081] Preferably, the waveguide is protected by two protective sheaths, namely a segmented protective sheath, preferably made up of several tabs placed end to end, and a rigid protective sheath serving as a housing for the waveguide. The segmented protective sheath can, for example, be made by stringing together a multitude of beads.

[0082] The invention also relates to a method for manufacturing a glass furnace according to the invention, said method comprising, for at least one waveguide of the array, preferably for each waveguide of the array, the following steps: A) preparation of a precursor of a ceramic matrix composite comprising a ceramic matrix precursor, preferably in the form of a plate, and integration of the measurement part of the waveguide in or on the ceramic matrix composite precursor so as to obtain an instrumented support precursor; B) hardening and / or baking, preferably sintering, of said instrumented support precursor, preferably during the oven temperature rise, so as to obtain said instrumented support by consolidation of the ceramic matrix precursor, preferably in the form of an instrumented plate; C) installation of the instrumented support if step C) is subsequent to step B) or installation of the instrumented support precursor if step C) is prior to step B), preferably between a back layer defining the hot face and a furnace heating system, preferably substantially parallel to said hot face. Preferably, step A) includes the following steps: a) preparation of the ceramic matrix precursor in the form of a slip comprising ceramic particles and / or ceramic particle precursors, the material of said ceramic particles having a dielectric constant or relative electrical permittivity with respect to vacuum at 25°C and atmospheric pressure, preferably measured at 1 MHz, greater than 3 and / or less than 30, preferably less than 15; b) independently of step a), fixing or integrating the first and second electrical conductors of said measuring part into a textile, preferably in the form of one or more fabrics or sheets of yarn, preferably ceramic yarns, the material of said textile having a dielectric constant or relative electrical permittivity with respect to vacuum at 25°C and atmospheric pressure, preferably measured at 1 MHz, greater than 3 and / or less than 30, preferably less than 15; c) impregnation of the textile by the said slip.

[0083] Before or preferably after step B), a connector is installed suitable for electrically connecting said conductors to an interrogator.

[0084] In one embodiment, the measuring part, or even the transmission part, is protected by said sheath, before fixing or integration into the support.

[0085] In one embodiment, in step B), the baking is such that the temperature of the instrumented support precursor is between 400 and 1200°C.

[0086] In a particular embodiment, step B) is carried out, prior to step C), in an oven or furnace, preferably in air and preferably under a controlled atmosphere.

[0087] In one embodiment, in step C), an instrumented support precursor is installed on or in a target precursor, and in step B), the instrumented support precursor is simultaneously consolidated by transforming the ceramic matrix precursor into a ceramic matrix and the target precursor is simultaneously consolidated to transform it into said target.

[0088] In one embodiment, in step C), the instrumented support or the precursor of the instrumented support, preferably in the form of a plate, is arranged between - said measuring part and - the target or a precursor of the target.

[0089] Of course, the characteristics of the different main aspects can be combined. They are preferably combined.

[0090] Regardless of the main embodiment, the waveguide array of a glass furnace according to the invention may further comprise one or more of the following optional and preferred features: - the waveguide network extends at least partially, preferably completely, within - of a refractory rear layer extending behind a first layer made up of an assembly of refractory blocks defining the hot face of the target or - of a refractory sub-layer of said rear layer; - the measurement part of a waveguide, preferably of each waveguide, extends into said back layer or into a sublayer of said back layer, preferably behind the barrier sublayer; - said underlayer is an insulating underlayer in contact with the cold face of the target, intended to define the thermal profile of the coating, or preferably, a barrier underlayer, intended to neutralize the molten glass in the event of a breach of the furnace, and in particular of the furnace floor; - preferably, when the target is the sole, the measurement part of a waveguide, preferably of each waveguide, extends between the barrier sublayer and the insulating sublayer; - the measurement part of a waveguide of the array, preferably of each waveguide of the array, extends into a housing, preferably in the form of an orifice, provided in the target and defining a thermal expansion space for said waveguide; - the thermal expansion space is adapted so that in service, the measuring part of the waveguide is not compressed by the target under the effect of dimensional changes of the target and of said measuring part resulting from temperature variations; - preferably, the ratio of the equivalent diameter of the housing to the equivalent diameter of the measuring part is greater than 1.05, preferably greater than 1.10, preferably greater than 1.20, and / or less than 3.00, preferably less than 2.50; - said housing is an orifice, the diameter of the orifice being less than the thickness of said layer or sub-layer in which said measuring part is placed; - the diameter of said orifice is less than 70%, or even less than 50%, of the thickness of said layer or sub-layer; - the measurement portion of a waveguide, preferably of each waveguide, excluding bends, extends at least partially, preferably completely parallel to the measurement portion of another waveguide; - the measuring part of at least one waveguide, preferably of each waveguide of the array, is free of bends; - the maximum distance between the measurement parts of any two waveguides is less than 200 cm; - Measurement sections of the waveguides together form an extending sheet along a curved or flat surface, preferably flat; - the measuring parts of said tablecloth are separated from each other by a distance greater than 1 cm, greater than 5 cm, greater than 10 cm, greater than 20 cm, and / or less than 100 cm, less than 80 cm, or less than 50 cm; - said parts of the water table extend parallel to each other or cross without touching; - the oven comprises more than 1, more than 2, preferably more than 3, preferably more than 5 said layers, said layers being preferably parallel to each other, preferably parallel to the hot face, and preferably regularly spaced in a direction perpendicular to the hot face, the distance between two successive layers being preferably less than 10 cm, 5 cm, or 2 cm, which advantageously allows for the evaluation of heat fluxes through the target; - at least one measuring section, preferably more than half of the measuring sections of the network extend in a direction perpendicular to the direction of flow of the molten glass in service; - the radius of curvature of the measuring part of a waveguide, preferably of each waveguide of the array, is at every point at least 3 times, preferably at least 5 times, preferably at least 10 times, greater than the equivalent diameter of said measuring part; - the waveguide, preferably each waveguide of the array opens onto a cold face of the target, opposite the hot face, or onto a lateral face of the target (especially when the target is the oven floor) that is colder than said hot face.

[0091] A person skilled in the art knows how to determine the dimensions of a housing for a measuring part in order to provide adequate space for thermal expansion. For example, for a floor slab, they will take into account the thermal gradient in the slab, the coefficient of thermal expansion of the slabs and the measuring part, as well as their dimensions.

[0092] The housing is also dimensioned so that the target and the waveguide can expand independently of each other, and in particular so that an elongation or a contraction of the target does not cause stress on the waveguide, and vice versa.

[0093] Regardless of the main embodiment, a waveguide, preferably each waveguide in the array, may further include one or more of the following optional and preferred features: - the waveguide satisfies the Rayleigh scattering condition, which facilitates the localization of regions that have reflected the basic secondary echoes; - the length of the measuring part and / or the waveguide is greater than 1 meter, preferably greater than 2 meters, preferably greater than 3 meters, or even greater than 10 meters and / or less than 30 meters, preferably less than 20 meters; - the length of the transmission part is preferably greater than 0.1 m and / or less than 5 meters, or even less than 2 meters; - the first and second electrical conductors are parallel, which provides robustness, efficiency and reduced cost; - the first and second electrical conductors are coaxial, which limits the bulk and reinforces the stability of the inter-conductor distance, the dielectric material holding the two coaxial conductors in position; - the first and second electrical conductors are straight, which facilitates integration into the target; the equivalent diameter of said first and second conductor is greater than 0.4 mm, greater than 0.5 mm, preferably greater than 1 mm and / or less than 50 mm, preferably less than 20 mm, preferably less than 10 mm, preferably less than 5 mm, which makes it possible to improve the quality of the signal (low attenuation) while reducing the risk of weakening or breaking the target; - the first and second electrical conductors are separated from each other by a dielectric material belonging to the target, for example an electrically insulating layer; - the first and second electrical conductors preferably comprise a refractory metal or metal alloy, for example Silver usable up to 800°C, for example Inconel (for example alloys 625 and 690), usable up to 1100°C, Kanthal of the FeCr type, for example KANTHAL APM, usable up to 1425°C or a noble metal, preferably chosen from Platinum, Tungsten, Gold, Palladium, Rhodium, Ruthenium, Iridium, or an alloy of these elements, the Platinum being able to be doped, preferably by 0.001% to 5% of zirconium, hafnium, calcium, magnesium or yttrium oxide; - a dielectric material comprising, preferably made of an oxide of at least one element chosen from Al, Zr, Mg, Ca, Ti and Si, separates said first and second conductors; - the material constituting the first and second electrical conductors has an electrical resistivity of less than 10 micro-ohm.m in the temperature range of the environment of the measuring part in service, preferably between 20°C and 1000°C; - the dielectric material separating the first and second conductors has a dielectric constant or relative electrical permittivity with respect to vacuum at 25 °C and atmospheric pressure, preferably measured at 1 MHz, greater than 3 and / or less than 30, preferably less than 15; - the dielectric material comprises an oxide of at least one element chosen from Al, Zr, Mg, Ca, Ti and Si; - at least a fraction of the measuring part, preferably at least in a region of the part of the waveguide that exits the target, is protected by a protective part, for example in the form of a tube or a perforated or grooved brick, preferably a protective sheath, preferably ceramic, partially, preferably completely surrounding said measuring part; - said protective sheath is made of an oxide material of at least one element chosen from Al, Zr, Mg, Ca, Ti and Si; - the waveguide is connected to an interrogator at each of its two ends; - the waveguide opens onto a cold face of the target, opposite the hot face, or onto a lateral face of the target that is colder than said hot face; - the first and second conductors are fixed to a plate-shaped support, preferably made of a ceramic matrix composite, preferably by means of an interfacing layer or refractory tapes, staples or wires or are integrated into said composite.

[0094] Regardless of the main embodiment, the interrogator may further include one or more of the following optional and preferred features: - the interrogator is configured to determine, based on the analysis of the response signals, a temperature, a wear level and / or a wear rate of the target; - the interrogator is configured to predict the occurrence of a breakthrough or infiltration of the target by molten glass, or of sudden movement or degradation of the coating; - the oven preferably includes at least one thermocouple located less than 10 cm from a waveguide, preferably from any waveguide, for example in an area of ​​the oven at a temperature between 500°C and 1500°C when the oven is in operation, in order to calibrate said waveguide for indirect temperature measurement.

[0095] The invention also relates to a method for monitoring the condition of a target in a glass furnace according to the invention, said method comprising the following steps: a. manufacture of a glass furnace according to the invention; b. for each waveguide, command of the interrogator to which the waveguide is connected, so that it injects an interrogation signal through the input end of said waveguide; c. analysis of the response signal so as to determine information relating to the state of the target in the region of the measurement part of said waveguide.

[0096] According to a particular mode, the information relating to the state of the target is the residual thickness of refractory material or a temperature at one or more points of the target. Brief description of the figures

[0097] Other features and advantages of the invention will become apparent upon reading the detailed description that follows and upon examination of the accompanying drawing in which: - [Fig.l] [Fig.l] represents a schematic half cross-section of a glass furnace; - [Fig.2] [Fig.2] schematically represents an example of a tracking device according to the invention, in a service position; - [Fig.3] [Fig.3] illustrates different possible embodiments for a waveguide incorporating beads; - [Fig.4] [Fig.4] illustrates, top view, a floor of a glass furnace according to the invention; - [Fig.5] [Fig.5] illustrates, in cross-section, the conventional structure of a glass furnace floor; - [Fig.6] [Fig.6] illustrates, in cross-section, a floor of a glass furnace according to the invention, in a first, preferred embodiment; - [Fig.7] [Fig.7] illustrates, in cross-section, a floor of a glass furnace according to the invention, in a second embodiment; - [Fig.8] [Fig.8] illustrates a network of waveguides in a glass furnace vault according to the invention, in cross-section, in a preferred embodiment; - [Fig.9] [Fig.9] represents an example of a response signal; - [Fig. 10] [Fig. 10] illustrates a support plate incorporating a measuring part according to an embodiment of the invention; - [Fig. 11] [Fig. 11] illustrates a support in the form of a plate, incorporating a measuring part according to another embodiment of the invention.

[0098] In the various figures, identical references are used to designate identical or analogous organs. Definitions

[0099] The term "target" refers to a refractory part of the furnace equipped with a tracking device. The target is preferably an element of the furnace lining or a so-called first layer (viewed from inside the furnace), conventionally obtained by assembling blocks, for example, a side wall of a vessel, a vault, or a hearth. The first refractory layer is conventionally made of a molten material or a dense sintered material in order to withstand the temperature as well as corrosion from the molten glass and / or its vapors.

[0100] The "hot face" is the face of a target that is exposed to a space in the furnace containing, in operation, molten glass or intended to contain molten glass. The hot face may be in contact, or intended to be in contact, with molten glass and / or with the gaseous environment extending above the molten glass. The hot face is thus the face of the target that is subjected or intended to be subjected to highest temperatures. All the hot faces of the blocks on the side wall of the glass melting tank can also, by extension, be referred to as the "hot face." The upper surface of the hearth can also be referred to as the "hot face." The adjective "hot" is used for clarity.

[0101] Conventionally, the "thickness" of a target is its dimension measured along a direction perpendicular to its hot face, or the "depth" direction. For example, for a tank side block in contact with molten glass, the thickness is measured along a substantially horizontal direction directed towards the molten glass bath. For a base, the thickness is measured along a vertical direction.

[0102] Two objects have "substantially the same composition" when at least 80%, preferably at least 90%, of their components are identical.

[0103] Concrete is conventionally composed of a collection of coarse grains, having a size greater than 50 µm, typically between 50 µm and 25 mm, bound together by a matrix, said matrix ensuring a substantially continuous structure between the coarse grains. The matrix is ​​made up of "matrix particles" having a size less than or equal to 50 µm.

[0104] Activation is the process of setting fresh concrete. It typically results from moistening a particulate mixture containing a hydraulic binder with water or another liquid, preferably by adding more than 3% water by mass. To be shaped, the fresh concrete is preferably poured, vibro-cast if the mixture is not self-casting, or even sprayed.

[0105] By "hydraulic binder" is meant a binder which, upon activation, generates hydraulic setting and hardening, generally at room temperature. Cement is a hydraulic binder. Aluminous cement is an example of cement. Calcium aluminate cement is an example of aluminous cement.

[0106] A refractory "rammed earth" is a refractory mixture containing a chemical and / or ceramic and / or organic binder, conventionally shaped, after possible wetting, by tamping, compaction, or raking, either by hand or with appropriate mechanical means. Preferably, the particulate mixture is not moistened ("dry" application) or is moistened with less than 3% water (by mass percentage).

[0107] The "support" is a part added to the target and on or in which the measuring portion of one or more waveguides is disposed. The support physically protects the measuring portion, preferably creates basic discontinuities, and preferably allows the measuring portion to slide, particularly under the effect of temperature.

[0108] The support or support precursor is sometimes referred to as "instrumented" when it carries the measuring part of at least one waveguide.

[0109] A plate typically has two substantially parallel large faces, the thickness between the two large faces being typically less than 1 / 2, or even less than 1 / 3, or even less than 1 / 5, or even less than 1 / 10, or even less than 1 / 100 of the width of the large faces. A plate may be flat or curved. The shape of a plate-shaped support is preferably adapted to conform to the shape of the target to which it is intended to be attached.

[0110] The term “Ceramic Matrix Composite,” or “CMC,” conventionally refers to a product composed of fibers and / or yarns bonded together by a ceramic matrix, preferably representing at least 30% of the CMC by volume. The fibers and / or yarns are chosen according to the environment in which the ceramic matrix composite is to be placed, particularly with regard to temperature, corrosion, thermal cycling, expansion, and the nature of the refractory part of the furnace to be equipped.

[0111] The arrangement of the fibers and / or yarns, which constitute the reinforcement structure for the matrix, is chosen according to the desired shape of the ceramic matrix composite and the ease of attaching the waveguide. For example, a stack of woven or layered fibers is well suited for simple plates, a filament winding is well suited for plates with a geometry of revolution, and a filamentary arrangement is well suited for large, complex shapes.

[0112] A ceramic matrix composite is conventionally manufactured by heating, preferably at more than 600°C, preferably at more than 700°C, preferably by sintering.

[0113] The fibers and / or yarns are classically in the form of a textile. The CMC can then be described as a "ceramic matrix textile".

[0114] A textile can be: - an organized two-dimensional structure of fibers or threads, including a knit, a braid, a fabric, or - a random two-dimensional structure of fibers or threads, this random structure not being preferred.

[0115] A textile is distinguished in particular from a fibrous mat, in which the organization of the fibers or threads is random in the three dimensions of space.

[0116] A "fiber" is a filament whose length is greater than 5 times its equivalent diameter. The "diameter" of a fiber is the diameter of a disk with the same area as its cross-section at half its length.

[0117] A “yarn” is an assembly of fibers which, in cross-section, comprises more than 10 and preferably less than 500,000 fibers, and whose length is greater than 5 times the diameter.

[0118] By "wired" is meant "having the general shape of a wire". A cable has for example a wireframe shape. A narrow band, or "ribbon", is considered wireframe. An object having a wireframe shape preferably has a length greater than 10 times, 100 times or 1000 times or 10,000 times its width (that is, its largest dimension in a plane perpendicular to the direction of its length).

[0119] The term "waveguide" refers to a wired transmission line, separate from the target, capable of guiding an electromagnetic wave originating from a very high-frequency electrical signal in order to perform a measurement by time-domain or frequency-domain electrical reflectometry. A waveguide typically comprises at least two electrically insulated conductors extending along the length of the waveguide. The interrogation signal is typically a change in the electrical potential difference between these conductors. The interrogation signal is injected at the input end of the waveguide and then propagates as an electromagnetic wave. A change in electrical impedance causes partial reflection of this wave. The reflected response signal is also a change in the time-domain potential difference between the conductors.

[0120] The part of a response signal that is returned is called an "echo": - by a discontinuity (secondary echo), - through the input end of the waveguide, at the point where the waveguide connects to the interrogator (emission echo), or - by the output end of the waveguide (background echo 4 - see [Fig.9]).

[0121] A secondary echo is thus a response of a discontinuity to the interrogation signal. According to the amplitude of the secondary echoes, we distinguish between "noise" secondary echoes 5, "basic" secondary echoes 6 and "clear" secondary echoes 7 ([Fig.9]).

[0122] Secondary noise echoes are secondary echoes that have an amplitude less than or equal to 1% of the background echo amplitude and greater than 0.1% of the background echo amplitude. They are classically generated by "noise" discontinuities resulting from imperfections in the waveguide, generated in particular during the manufacturing of the waveguide.

[0123] Since secondary noise echoes are of low amplitude, they are attenuated very quickly. In many cases, they do not allow for precise monitoring of measurement changes, for example when the temperature increases or when the humidity is high.

[0124] Basic secondary echoes are secondary echoes generated by "basic" discontinuities generally resulting from intentional modifications to the waveguide, for example by texturing or adding cleats. When the length of the measurement section is less than 10 meters, they exhibit an amplitude greater than 0.5%, preferably greater than 1% and less than 30% of the amplitude of the background echo.

[0125] The amplitude of the basic secondary echoes may be greater than 2%, 3%, or 5%, or even 10% of the amplitude of the background echo reflected by the output end of the waveguide.

[0126] Sharp secondary echoes are secondary echoes with an amplitude greater than or equal to 30% of the background echo amplitude. They are generally isolated and generated by "sharp" discontinuities, typically resulting from a significant or abrupt change in the waveguide structure, for example, due to unintentional waveguide degradation, such as cracking. Such sharp, local discontinuities do not allow, through analysis of the sharp secondary echoes, the measurement of disturbances or changes in the environment other than at the locations of the sharp discontinuities. Therefore, they do not allow the localization of measurement variations along the entire length of the measurement area.

[0127] A "discontinuity" or "impedance discontinuity" is a part of the waveguide capable of reflecting a specific echo in response to an interrogation signal, preferably in the form of a small change in electrical potential. This echo is modified when the impedance of the discontinuity changes, particularly when it is subjected to a change in a property of its local environment (i.e., in the region of the discontinuity). The impedance of a discontinuity can, in particular, be modified when the shape and / or local temperature of the waveguide, and / or the nature of the local environment, i.e., around the discontinuity, is / are changed. If only one of the factors modifying the discontinuity is changed, for example, the local temperature, there is consequently a relationship between the impedance, and therefore the echo, and the value of this factor.

[0128] The discontinuity may in particular result from a local variation in the structure and / or composition of the waveguide, and in particular from one of the conductors of the waveguide and / or from a dielectric disposed between said conductors.

[0129] By “sacrificial sheath” is meant a sheath capable of decomposing, at least partially, preferably by heat treatment.

[0130] For the sake of clarity, a distinction is made between the protective sheath intended to be kept in service, and the sacrificial, or "temporary", sheath, which is used to provide thermal expansion space for the waveguide, and which is therefore intended to be eliminated.

[0131] The equivalent diameter of a waveguide or measuring part or conductor or housing is the largest of the transverse diameters of that waveguide or measuring part or conductor or housing, respectively, considering all the cross-sections (i.e., perpendicular to the length direction) along that waveguide or measuring part measurement of this conductor or this housing, respectively, a transverse diameter measured for a cross-section being the diameter of a disk having the same area as this cross-section.

[0132] When the cross-section is constant, the equivalent diameter is therefore equal to the transverse diameter regardless of the cross-section considered.

[0133] A “bend” is a region of the measuring part in which said measuring part changes direction by more than 45° over a length of less than 80 cm.

[0134] The "precursor" of an element is an object which, during the manufacture of the furnace, is transformed into that object. For example, the preform of a target is a precursor of the target, which is transformed into the target during sintering.

[0135] The term “preform” means a part shaped or prefabricated from a particulate mixture, such as, for example, concrete (conventionally by pouring and vibration) or rammed earth (conventionally by compaction), and intended to be consolidated by heat treatment, for example by sintering. The manufacturing processes for a preform are well known to those skilled in the art. Conventionally, the particles of a refractory powder are mixed with a temporary binder and the mixture is shaped as desired.

[0136] The adjectives "first" and "second" are used only for the purpose of clarity.

[0137] Unless otherwise specified, "driver" means the first or second electrical conductor of a waveguide.

[0138] “Local” or “locally” are used to describe a characteristic or action that only applies to a fraction of the waveguide, for example, a fraction with a length less than 5 cm, 1 cm, or 1 mm. A "local" variation of a property thus means that the value of that property varies within this fraction, for example, by more than 5% or more than 10%. This variation could be, for example, less than 500%.

[0139] A "ceramic material" is classically understood to mean a material that is neither metallic nor organic. In a preferred embodiment, an oxide glass and carbon (in various forms, crystalline or not) are considered to be ceramic materials.

[0140] “Contain”, “present” or “include” must be interpreted in such a way broad, not exhaustive. Detailed description

[0141] The invention uses the well-known principles of electrical time domain reflectometry or electrical frequency domain reflectometry (E-TDR or E-FDR, respectively).

[0142] Conventionally, a transmitter emits an interrogation signal, in the form of a The impulse travels through the electrically conductive medium. This sends back a reflected response signal, which is then analyzed to deduce information about the conductive medium.

[0143] In particular, a measuring part is subjected to a temperature that depends on the environment of the target, especially the molten glass or its vapors, but also on the thickness of material separating it from this environment. When this thickness decreases at a point on the target, the measuring part can modify its local response to the reception of the interrogation signal.

[0144] This local reaction allows the interrogator to be informed of a reduction in the thickness of the target, or even of a breakthrough by the molten glass in the target at that location. Monitoring device Electromagnetic waveguide

[0145] The waveguide 12 ([Fig.2]) has the shape of a transmission line, for example the general shape of a strip or cable, extending from an input end 12e to an output end 12s. It comprises: - a measuring part 14, which includes the discontinuities used for the measurement, and - a transmission part 15, which is used to connect the measuring part 14 to an interrogator 18.

[0146] The length of the waveguide, and preferably of the measuring part, is preferably greater than 1 m, preferably greater than 2 m, preferably greater than 5 m, preferably greater than 10 m, greater than 15 m, greater than 20 m, and / or less than 200 m, or even less than 100 m, preferably less than 50 m.

[0147] Preferably, a conductor, preferably each conductor, or even the waveguide - has an equivalent diameter or, - for a conductor or waveguide in the shape of a strip, has a thickness less than 10 millimeters, less than 5 mm, and / or preferably greater than 1 mm.

[0148] The waveguide comprises first and second electrical conductors, 12i and 122 respectively, for example in the form of a cable comprising one or more wires, an assembly of cables or a strip.

[0149] Each driver includes: - an input end (i.e., the input end of the waveguide) electrically connected to a respective terminal of the interrogator 18, and, - at the output end of the waveguide, a free output end.

[0150] The output ends are not electrically connected to each other, so that the conductors do not form an electrical circuit, as in a resistive measuring device, in which a direct or alternating current flows.

[0151] The conductor material is preferably a conductive metal such as Al, Cu, or steel or a metal alloy. It may also be a ceramic or a cermet. In particular, for application in a high-temperature environment, the conductors may be - in Inconel (for example alloys 625 and 690), usable up to 1100°C, - in platinum, - in Kanthal of the FeCr type, for example KANTHAL APM, usable up to 1425 °C, - made of tungsten, - in rhodium, - in ruthenium, - in palladium, - in iridium

[0152] A conductor in a metal coated with conductive refractory oxide of SnO2 or Cr2O3-MgO spinel or perovskite or metalloid or metal carbide may be suitable for very high temperatures.

[0153] Preferably, the material of the conductors is a noble metal, preferably chosen from Platinum, Gold, Palladium, Rhodium, Iridium.

[0154] The electrical resistivity of the first and second conductors is preferably less than 10 micro-ohm.m in the ambient temperature range, preferably between 20°C and 1000°C.

[0155] According to a first embodiment, each conductor is formed of a cable made up of one or more wires. The first and second conductors are non-coaxial and kept apart from each other by a dielectric insulator, preferably having an electrical resistivity greater than 10, 50, 100 or 1000 times that of the conductors.

[0156] According to a second embodiment, which is preferred, the waveguide is formed of a coaxial cable, for example of type BNC, comprising an inner wire or sleeve forming the first conductor and an outer sleeve forming the second conductor, the two sleeves being separated by an electrically insulating intermediate sleeve.

[0157] In one embodiment, said waveguide is formed of at least two linear conductors, preferably platinum wires, for example FKS platinum wires supplied by Ogussa, parallel and separated by a distance greater than 1 mm, preferably greater than 2 mm, and / or preferably less than 20 mm. Beads fractals, preferably alumina beads, are threaded onto the conductors, preferably through first and second through holes through which the first and second conductors pass.

[0158] The length of the waveguide, and preferably of the measuring part, is preferably greater than 1 m, preferably greater than 2 m, preferably greater than 3 m, or even greater than 10 m, and / or less than 30 m, or even less than 20 m.

[0159] The two conductors are preferably parallel except, possibly, in areas of discontinuity. Local deviations from parallelism may be introduced to create discontinuities, and in particular basic discontinuities. Protective sheath

[0160] The waveguide and / or each conductor can be inserted into a protective sheath, optionally segmented, in order to protect the conductors from heat and / or corrosion and / or chemical attack.

[0161] The protective sheath may be made of ceramic, in particular alumina, in particular for an environment with a temperature above 400°C.

[0162] The protective sheath is preferably made of a material having a coefficient of thermal expansion substantially identical to that of the material of the conductors.

[0163] Preferably, the thermal expansion coefficient of the waveguide, preferably at least of the measuring part, is substantially identical to that of the part of the target which receives the measuring part (+ / -20%, preferably + / -10%).

[0164] Said protective sheath can be straight or curved, and extends around the measuring part. This sheath can be useful for giving a curved shape to the measuring part, or even to the transmission part. Support

[0165] The waveguide, and in particular at least the measuring part, can also be fixed on a support 40 (see [Fig. 10] or 2), preferably in the form of a plate, itself in contact with the target 30.

[0166] The same support, in particular in the form of a plate, can support several measurement parts, or even all the measurement parts of the waveguide network.

[0167] The support is preferably at least partly made of a material consisting of yarns and / or fibers bonded together by a ceramic matrix, called a "ceramic matrix composite".

[0168] The fibers and / or yarns and the ceramic matrix will be chosen according to the environment in which the ceramic matrix composite is to be placed, in particular according to the conditions of temperature, corrosion, thermal cycling, expansion, and according to the nature of the target to be tracked.

[0169] The coefficient of thermal expansion of the ceramic matrix composite can be adjusted by the techniques well known to the person skilled in the art, in particular by adapting the composition of the ceramic matrix composite.

[0170] For example, a stack of woven or layered fibers or yarns is well suited for simple plates, a filament winding is well suited for plates with a geometry of revolution, a filament placement is well suited for complex shapes of large dimensions.

[0171] A support is particularly useful when the target belongs to or constitutes the side wall of the tank.

[0172] The arrangement of the fibers or wires is chosen according to the desired shape for the ceramic matrix composite, and the ease of attaching or inserting the conductors.

[0173] The ceramic matrix composite preferably has a compressive crush strength greater than 5 MPa, preferably greater than 10 MPa, and / or a thermal conductivity between 20°C and 500°C greater than 2.0 Wm*.K'.

[0174] Preferably, the ceramic matrix composite comprises, by mass percentage, more than 80%, more than 90%, more than 95%, or even substantially 100% of one or more of the following oxides: Al2O3, ZrO2, HfO2, Cr2O3, MgO, CaO, SiO2.

[0175] In one embodiment, the ceramic matrix composite has a chemical composition, in mass percentage on the basis of oxides, such that A12O3 + SiO2 > 80%, preferably greater than 85%, preferably greater than 90%, or even greater than 95%.

[0176] In one embodiment, the matrix comprises, preferably is made up of, more than 80%, more than 90%, more than 95%, preferably substantially 100% of its mass, one or more compound(s) chosen from the group formed by Al2O3, ZrO2, Cr2O3, MgO, CaO and SiO2.

[0177] Preferably, the volume of the fibers or yarns represents more than 25%, preferably more than 30%, preferably more than 40%, preferably more than 50%, preferably more than 60% and / or less than 70% of the volume of the CMC material, i.e., without taking its porosity into account, the remainder to 100% being constituted by the ceramic matrix binding said fibers together. The diameter of the fibers, measured at mid-length and averaged over all the fibers, is preferably between 3 and 30 micrometers, preferably between 5 and 25 micrometers.

[0178] Preferably, the support is in the form of a plate, flat or not flat, and has, between its large faces, an average thickness that is preferably constant, preferably less than 40 mm, preferably less than 32 mm, preferably less than 28 mm, preferably less than 22 mm, preferably less than 20 mm, or even less than 18 mm or 15 mm or 10 mm, and / or preferably more than 1 mm, preferably more than 2 mm, or even more than 3 mm, or more than 5 mm.

[0179] The surface area of ​​a large face of the support is preferably greater than 100 cm2, preferably greater than 200 cm2, preferably greater than 300 cm2, preferably greater than 400 cm2, and / or less than 20,000 cm2, preferably less than 15,000 cm2 or even less than 10,000 cm2.

[0180] In one embodiment, the support is in the form of a roll before being placed against the target. In another embodiment, the support is fixed to a cold face of the target and, preferably, the support has a perforated area, i.e., a region through which a plurality of openings pass in order to facilitate heat exchange with the cold face.

[0181] The target may in particular be a first layer made up of dense blocks, fused or sintered.

[0182] In one embodiment, the support is bonded to the cold side of the target. Preferably, the adhesive used to fix the waveguide to the support and / or the support to the target is chosen from mixtures of ceramic powders and binders, preferably applied in liquid form.

[0183] Preferably, the powders are alumina and / or silica and / or mullite powders. Preferably, the binders are selected from colloidal silica, sodium silicate, organic resins, organic adhesives, and mixtures thereof. The adhesive used may also be a commercial adhesive such as Unifrax's Fixwool FX adhesives.

[0184] In one embodiment, the measurement part of the waveguide is embedded within the ceramic matrix composite or the precursor of said ceramic matrix composite, preferably sandwiched between two textiles of said composite.

[0185] According to a first particular embodiment, the measuring part of the waveguide is fixed to the support by means of an interface layer. The interface layer may be, in particular if the temperature of the face of the target receiving the support, in particular the cold face, is less than or equal to 400°C, an adhesive comprising a thermosetting, thermoplastic or elastomer polymer.

[0186] In one embodiment, the measuring part of the waveguide is fixed to the support by means of refractory tapes, staples or wires.

[0187] In one embodiment, the first and second conductors of the measuring part are integrated into the yarn arrangement of the ceramic matrix composite or of the precursor of said ceramic matrix composite, for example as weft yarn, warp yarn, or knitting yarn. They extend substantially parallel to each other and at a predetermined distance. Preferably, the distance separating the conductors is greater than 0.3 mm, preferably greater than 0.4 mm, preferably greater than 0.5 mm and less than 30 mm, preferably less than 10 mm, preferably less than 5 mm, preferably less than 3 mm.

[0188] To maintain a distance between the two conductors, at least one wire, or even a plurality of wires made of a dielectric material, may be interposed between the first and second conductors of the waveguide. In one embodiment, the same support may support several measurement sections of different waveguides.

[0189] In one embodiment, the measuring part is housed in a ceramic protective sheath incorporated into the support during its manufacture, or in a channel formed in the support during or after the manufacture of said support. Separator

[0190] Regardless of the embodiment, the absence of direct electrical contact between the two conductors can be facilitated by the interposition of a dielectric insulator 25, or "separator", for example of mica, a mica derivative, titanium, barium, mullite, cordierite or alumina.

[0191] The dielectric insulator may be a single piece or consist of an assembly of several dielectric tabs. Preferably, the dielectric tabs are interposed between the conductors, the tabs preferably having the form of beads strung on at least one of the conductors, preferably on both conductors.

[0192] The cleats are described in more detail later in the description.

[0193] The predetermined distance between the two electrical conductors is preferably substantially constant.

[0194] When the first and second conductors are integrated into the textile of a ceramic matrix composite and constitute constituent yarns of the textile, for example, weft or warp yarns, the separator can be made of yarns of a dielectric material also constituting the textile. For example, if the first and second conductors are weft or warp yarns, they can be separated by one or more other weft or warp yarns, respectively, of a dielectric material (yarn 25 in [Fig. 11]). Discontinuities

[0195] The number of discontinuities, in particular basic discontinuities, per meter of waveguide measurement section is preferably greater than 10, greater than 15, greater than 20, greater than 30, greater than 40, greater than 50, and / or less than 10,000, less than 1,000, less than 500, less than 100. Advantageously, it is thus possible to evaluate the property of the environment of the measurement section substantially over its entire length, and with good accuracy.

[0196] Preferably, the distance between any two discontinuities 24, in particular between any two successive basic discontinuities along the waveguide 12, is less than 1 / 100 of the wavelength of the interrogation signal (equal to the propagation speed of the interrogation signal, approximately 200,000 km / s for an electromagnetic wave). magnetic, divided by the frequency of the highest peak in the frequency spectrum of the interrogation signal).

[0197] This distance is preferably greater than 10 mm, 15 mm or 20 mm and / or less than 100 mm or 50 mm.

[0198] The sensitivity of the information provided by the interrogator is advantageously improved.

[0199] The use of discontinuities reflecting a small variation in electrical potential avoids the need to create large discontinuities, which could significantly attenuate the interrogation signal and thus prevent tracking along the entire length of the measurement section of the waveguide. Preferably, more than 50%, preferably more than 80%, preferably more than 90% of the discontinuities reflect basic and / or noise secondary echoes, preferably basic secondary echoes.

[0200] Exploiting these small random variations in electrical potential runs counter to developments in electrical reflectometry, as these variations are considered detrimental. Preferably, discontinuities are added randomly to the waveguide.

[0201] The discontinuities are variable, that is to say, they do not all return the same echo when they receive the same interrogation signal. Preferably, the variation of the discontinuities, in particular of basic discontinuities, is random.

[0202] Discontinuities 24, in particular basic discontinuities, can be obtained by modifying the surface and / or the constituent material of one or both conductors and / or the dielectric insulator, for example by surface modification by abrasion, by chemical attack, by adding a dopant to the material, or by adding tabs.

[0203] In one embodiment, the waveguide is formed of a coaxial cable, for example of the BNC type, comprising a wire forming the first conductor and an outer sleeve forming the second conductor, the two sleeves being separated by an electrically insulating intermediate sleeve. It is possible to create discontinuities 24, in particular basic discontinuities, by modifying the surface condition of the insulating sleeve, for example by creating roughness. Another method consists of creating random discontinuities, in particular basic discontinuities, on the outer sleeve, for example by abrasion (without stopping electrical conduction within the outer sleeve).

[0204] In one embodiment, discontinuities, in particular basic discontinuities, are surface irregularities on the separator, preferably located opposite the conductors, preferably in at least one area of ​​the separator in contact with the conductors. Texturing said area advantageously allows for the generation of random discontinuities.

[0205] It is also possible to create discontinuities 24, in particular basic discontinuities, preferably random, by modifying the surface condition of the dielectric insulator 25 (texturing), for example by creating roughness, for example by abrasion.

[0206] Preferably, the texturing involves the creation of microreliefs with a height greater than 0.05 mm, preferably greater than 0.1 mm, preferably greater than 0.2 mm, preferably greater than 0.2 mm, preferably greater than 0.5 mm, or even greater than 0.8 mm, and / or less than 3 mm, less than 2 mm or less than 1 mm.

[0207] The predetermined distance between the two electrical conductors is preferably substantially constant. The two conductors are preferably parallel except, possibly, in areas of discontinuity. Local deviations from parallelism may be introduced to create discontinuities, and in particular basic discontinuities.

[0208] Preferably, to create discontinuities, dielectric stops are arranged in contact with the first and second conductors.

[0209] The dielectric stops, and in particular the beads, may have a length, measured along the length of the waveguide, greater than 10 mm, 15 mm or 20 mm and / or less than 100 mm or 50 mm.

[0210] Dielectric stops, and in particular beads, preferably have a width, that is to say a larger dimension in a plane transverse to the direction of their length, greater than 1 mm, 2 mm or 3 mm and / or less than 10 mm or 5 mm.

[0211] Figure [Fig. 3] illustrates different possible embodiments for cleats. electrical. In particular, it illustrates embodiments in which: - 23 beads are strung on one of the first and second conductors (3E) or on both the first and second conductors (3A-3D); - beads 23 are strung to form a segmented (3A, 3C-3E) or non-segmented (3B) protective sheath 27 on the first and second conductors (3A-3D), for one (3E) or for both conductors; - 23 beads of identical shape (3A, 3D) or different shape (3B, 3C, 3E) are strung together; - 23 beads having textured surfaces in the same way (3A-3C, 3E) or not (3D) are strung; - one or more of the conductors extend symmetrically with respect to the axis of each bead 23 (3A, 3B, 3C, 3D) or not (3E); - one or more of the conductors extend parallel to the axis of each bead 23 (3A-3E) or not.

[0212] The tabs also facilitate the identification of regions generating basic secondary echoes, and can therefore serve as identification marks. Random distribution of discontinuities

[0213] Preferably, the discontinuities are not regularly distributed along the waveguide. Preferably, the discontinuities, in particular basic discontinuities, are randomly distributed along the waveguide.

[0214] The random nature of the distribution or intensity of the discontinuities advantageously avoids the risk of creating an accumulation of secondary echoes of the same period, which could strongly dampen the interrogation signal.

[0215] Dielectric stops may have identical or different shapes and / or dimensions and / or be made of identical or different materials. Even if the dielectric stops appear identical, no two stops are completely identical.

[0216] Variations in the shape and composition of the cleats, particularly the beads, and variations in the positioning of the beads relative to the conductors make it possible to randomize the discontinuities they generate. It is thus possible to create basic discontinuities randomly.

[0217] To generate random discontinuities, in particular basic discontinuities, in the embodiment in which the first and second conductors of the measuring part are integrated into the yarn arrangement of a support made of a ceramic matrix composite, for example as weft yarn, warp yarn, or knitting yarn, the first and second conductors and / or other yarns made of a dielectric material (or non-conductive yarns) can be modified randomly, for example, by abrasion or chemical attack. Yarns made of a dielectric material can also or alternatively be wound randomly around the first and / or second conductor. Yarns and / or fibers and / or particles made of a dielectric material can also or alternatively be added to the textile randomly.Particles of varying size or shape, or unevenly distributed, can also be placed in contact with the textile before impregnation, either in addition to or as an alternative to the other possibilities described above. The choice of particle size or shape, texture, or fiber length allows for the creation of random discontinuities.

[0218] The conductors can also or alternatively be placed in contact with an irregularly textured fabric or a mat of randomly arranged fibers, before impregnation with a matrix precursor and then hardening to form an instrumented support. Rayleigh scattering condition

[0219] The waveguide preferably satisfies the Rayleigh scattering condition. Advantageously, the regions that have reflected the basic secondary echoes can be easily located.

[0220] Preferably, the basic discontinuities 24 are separated from each other by a distance, measured along the waveguide, at least 10 times, preferably at least 15 times, preferably at least 20 times less than the reference wavelength, equal to the propagation speed of the interrogation signal, of about 200,000 km / s for an electromagnetic wave, divided by the frequency of the highest peak of the frequency spectrum of the interrogation signal.

[0221] This distance can in particular be defined by the length of dielectric blocks, in particular beads strung on the waveguide. To generate sufficient basic secondary echoes, the length of the blocks is preferably adapted, depending on the reference frequency (inverse of the reference wavelength), so as to satisfy the Rayleigh scattering condition.

[0222] For example, for a reference wavelength of about fifteen centimeters, cleats, for example beads, less than 3 cm long, preferably less than 2 cm or 1 cm, are well suited. For example, for an interrogation signal with a frequency of 1 GHz, alumina beads less than 10 mm long and strung on platinum wires produce secondary echoes of too low an amplitude, while beads longer than 100 mm produce clear secondary echoes.

[0223] With basic discontinuities and under Rayleigh scattering conditions, it is possible to carry out precise measurements over a length greater than 1 m, preferably greater than 2 m, preferably greater than 5 m, preferably greater than 10 m, greater than 15 m, or greater than 20 m, and / or less than 500 m, for example over the entire length of the measurement part. waveguide array

[0224] Preferably, the network comprises several measurement sections, preferably parallel to each other and to the hot face of the target, such that the discontinuity density, preferably the basic discontinuity density, on the equipped surface is greater than 3, preferably greater than 10, preferably greater than 50, preferably greater than 100, preferably greater than 500, preferably greater than 800 discontinuities and / or less than 1,000,000, preferably less than 500,000, preferably less than 100,000, preferably less than 50,000, preferably less than 10,000, preferably less than 5,000, preferably less than 2,000, per m² of hot face surface. This improves the reliability of the analysis by the interrogator.

[0225] Preferably, the measuring parts form a sheet extending along a curved or flat surface, preferably flat, each waveguide being preferably connected to an interrogator of its own.

[0226] The waveguide array may comprise more than 1, more than 2, preferably more than 3, preferably more than 5 said sheets, said sheets being preferably parallel to each other and preferably regularly spaced from each other in a direction perpendicular to a surface of the assembly.

[0227] On [Fig.4], two sheets 32 and 34 have been shown, in this case to equip a sole 41.

[0228] In one embodiment, at least two waveguides intersect at different depths, the depth being measured from the hot face, perpendicular to the hot face. Since the identity of the superimposed waveguides is known, it is advantageously possible to define a temperature profile along the depth direction, and / or to evaluate the extent of a reduction in the thickness of the target, for example, the sole, at each point on the hot face below which several waveguides are superimposed. To this end, a central computer can collect the messages from the different interrogators and, knowing the spatial distribution of the waveguides, deduce a wear profile. Interrogator

[0229] The input ends of the waveguide's electrical conductors are electrically connected to the interrogator 18, or "reflectometer". The interrogator is configured to: - inject the interrogation signals by establishing a variation in the potential difference between the two conductors of the waveguide; and - analyze the reflected response signals in response to the interrogation signals.

[0230] The interrogator 18 conventionally comprises a transmitter / receiver 21 and a control module 31 ([Fig. 2]). The control module 31 conventionally comprises a processor and memory in which a computer program is loaded. Using this computer program, the processor can control the transmission of the interrogation signals and analyze the received reflected signals in order to identify the echoes returned by the discontinuities. In one embodiment, the analysis is performed by an analysis computer 39 in communication with the interrogator.

[0231] The interrogator can be, for example, a voltage generator coupled to an oscilloscope enabling the reception and analysis of reflected signals. The interrogator can be a network analyzer equipped with software such as "VNA software" for generating the interrogation signal and analyzing the reflected signal.

[0232] In a preferred embodiment, as illustrated in [Fig. 4], a first interrogator 18i is connected to the input end of a waveguide. A second interrogator 182 is connected to the output end of the waveguide.

[0233] The second interrogator therefore receives the parts of the interrogation signal injected by the first interrogator that have not been reflected by the various discontinuities of the waveguide. Preferably, the second interrogator can also send an interrogation signal. The presence of two interrogators advantageously allows, in the event of a waveguide rupture, for information to be obtained from both sides of the rupture zone. It therefore improves the robustness of the device. Analysis

[0234] The analysis performed by an interrogator is based on electrical time domain reflectometry or electrical frequency domain reflectometry (E-TDR or E-FDR, respectively), which is a conventional technique for measuring changes in the state of a medium by means of a waveguide and an interrogator.

[0235] Each interrogation signal, preferably in the form of a pulse or "Dirac" signal, is generated by establishing a variation in the potential difference between the two conductors of the waveguide. The waveguide returns a response signal, which is then analyzed to deduce information about the medium through which the pulse passes. In the presence of an impedance discontinuity, for example, a significant physicochemical variation in the medium resulting in a local impedance variation, a portion of the interrogation signal is reflected back to the interrogator, thus enabling the identification and analysis of this variation.

[0236] The interrogation signal may take the form of a periodic wave of any shape. The interrogation signal may be repeated. Preferably, the maximum amplitude of the interrogation signal is between 0.1 V and 100 V, preferably less than 10 V, preferably less than 1 V. The frequency of the highest peak in a frequency spectrum of the interrogation signal is preferably greater than 10 kHz, preferably greater than 100 kHz, preferably greater than 1 MHz, preferably greater than 100 MHz, preferably greater than 200 MHz, preferably greater than 500 MHz, preferably greater than 1 GHz, and / or less than 50 GHz, preferably less than 30 GHz, preferably less than 20 GHz, preferably less than 10 GHz, preferably less than 6 GHz, preferably less than 4 GHz.Interrogation signals can be sent in the form of signal trains preferably comprising a series of periodic signals of varying frequencies depending on the periodic signal considered.

[0237] The frequency of the interrogation signal is conventionally adapted to the length of the measurement section. The wavelength of the interrogation signal is conventionally shorter than the length of the measurement section of the waveguide. The ratio of the wavelength of the interrogation signal to the length of the measurement section of the waveguide is preferably between 0.1 and 0.9, preferably between 0.1 and 0.5, and preferably between 0.1 and 0.3.

[0238] Preferably, the length of the measuring portion of the waveguide is not a multiple of the wavelength of the interrogation signal in order to avoid resonance problems.

[0239] For example, the frequency of the interrogation signal can be 1 GHz (corresponding to a wavelength of approximately 20 cm) for a length of the measurement part of the waveguide between 10 and 15 m, for a measurement at 600°C or more.

[0240] Each interrogation signal propagates through the waveguide to the free end of the conductors. At each discontinuity, a portion of the interrogation signal, or "echo," is reflected back to the interrogator. All the reflected echoes together constitute the response signal associated with the interrogation signal, which the interrogator analyzes.

[0241] In particular, a distinction is made between the emission echo reflected by the input end of the waveguide, the background echo reflected by the output end of the waveguide, and a set of discontinuity echoes reflected by the discontinuities of the waveguide. The discontinuity echoes are of low amplitude and have various amplitudes and shapes.

[0242] The interrogator is programmed to analyze the reflected signals, and possibly compare them, so as to determine information relating to the state of the target in the region of the measuring part of the waveguide and, preferably, to transmit a message accordingly.

[0243] All the techniques for analyzing response signals used in time-domain or frequency-domain electrical reflectometry can be implemented, and in particular those described in the article “Distributed temperature sensing with unmodified coaxial cable based on random reflections in TDR signal” by Baokai Chen et al, 2019 Meas. Sci. Technol. 30 015105 or in the article “Electric time domain reflectometry distributed flow sensor” by Aurimas Dominauskas et al, in the journal Composites Part A 38(2007) 138-146.

[0244] Preferably, the message should specify: - a value for the physical state of the target, and in particular a value for the residual thickness or an average temperature and / or a value representative of the temperature variations along the measurement area; and / or - a value representing a change in said value compared to a previous situation; and / or - a localization of defects or damage affecting said physical state of the target.

[0245] The message may be sent to a central computer and / or presented to an operator, for example on a screen and / or by activating a light and / or by emitting an audible signal.

[0246] In a preferred embodiment, at least a portion of the waveguides is capable of providing, in the response signal it returns, a quantitative indication of the temperature it experiences due to target wear. As the thickness of the target component, for example, the sole, decreases, the frequency of the response signal returned by the waveguide changes. This change advantageously allows for the determination of the local temperature evolution. This makes it particularly useful to detect abnormal temperature changes in a waveguide and to intervene to repair the target, for example, by replacing the refractory coating. Target

[0247] The target 30 may be all or part of the glass furnace having a hot face, in particular the side wall of the vessel or the hearth, or a block or set of blocks belonging to the side wall of the vessel or the hearth. The target could also be, for example, a block of a feeder, a superstructure part (nose piece, arch block, etc.), a forming part (lip, etc.) or a throat block.

[0248] The target may include a back layer, for example be the side wall of the tank or the base.

[0249] The use of a waveguide advantageously allows exposure to high temperatures, for example above 100°C, above 125°C, above 200°C or above 300°C. A metal waveguide sheathed with a sacrificial polymer sheath, for example, allows tracking in an environment up to 300°C. Manufacturing or assembly

[0250] Various techniques can be used to install the waveguides, including in the rear layer of the target.

[0251] According to a preferred embodiment, at least a part, preferably the entire measuring part of each waveguide is covered with a sacrificial sheath.

[0252] Each measuring element is disposed in an orifice, for example formed in the back layer, or, for example, in a groove formed in the back layer. A starting charge of refractory mixture, preferably concrete, having substantially the same composition as that of the back layer, is deposited in the orifice or groove in order to cover the sacrificial sheath of the waveguide.

[0253] The starting charge is then hardened, and preferably sintered, preferably during the quenching of the furnace. The sacrificial sheath is removed, conventionally by heat treatment, preferably during sintering or quenching, preferably by applying a temperature between 400°C and 1200°C.

[0254] In addition to or as an alternative to the sacrificial sleeve, a sacrificial filling material, for example a resin, can be used to fill the orifice or groove.

[0255] Such a method advantageously allows close contact between the waveguide and the target, which allows good heat exchange and limits the risk of molten glass infiltration while limiting stress on the waveguide. First example: Sole

[0256] The target can be the oven floor according to the invention.

[0257] In the embodiment shown in [Fig.4], the sole has, viewed from above, a general rectangular shape.

[0258] As illustrated in [Fig. 5], it conventionally comprises, in superposition, a first layer of refractory blocks 241, in the form of slabs, in contact with the molten glass, two layers of concrete 242a and 242b and two layers of insulation 243a and 243b. The whole of these layers is delimited laterally by so-called "sidewalk" blocks 244 and rests on a foundation 245.

[0259] The arrow referenced D indicates the direction of flow of the molten glass.

[0260] The refractory blocks 241 can be of different shapes, for example rectangular parallelepiped shape.

[0261] The refractory blocks 241 are preferably made of a material resistant to contact with glass at temperatures above 600°C, or even above 1000°C, or even above 1200°C. The refractory blocks may consist, for more than 90% of their mass, of one or more oxides selected from the group consisting of ZrO2, Al2O3, SiO2, Cr2O3, Y2O3, and CeO2. They preferably comprise more than 90% ZrO2, Al2O3, and SiO2.

[0262] In one embodiment, the blocks contain more than 15% ZrO2, preferably between 26% and 95% ZrO2. Their composition is typically, for a total of more than 90%, preferably more than 95%: 26% to 40% ZrO2; 40% to 60% Al2O3; 5% to 35% SiO2. The glassy phase represents approximately 5% to 50%, preferably between 10% and 40%. Preferably, this glassy phase is a silicate phase with a mass proportion of Na2O less than 20%, preferably less than 10%, and / or a mass proportion of Al2O3 less than 30%. All percentages are conventionally expressed by mass based on the oxides. Preferably, oxides represent more than 90%, preferably more than 95%, preferably more than 98% of the mass of the refractory block.

[0263] The concrete layers 242a and 242b are, for example, from the ERSOL range sold by the company SEFPRO. They are conventionally formed by pouring into checkerboard formwork arranged in a staggered manner in relation to the formwork of the first upper layer (closest to the glass) in order to increase thermomechanical resistance and reduce the risk of infiltration in the event of a breach of the molten glass.

[0264] The upper insulation layer 243a can be formed from a prefabricated refractory concrete veneer, classically from the ERMOLD range also supplied by SEFPRO.

[0265] The lower insulating layer 243b may be made of fibrous insulation.

[0266] According to a first configuration illustrated in [Fig. 6], waveguides 12, preferably each surrounded by a sacrificial polymer sheath (for example, PET or PE), are arranged perpendicular to the direction D of the molten glass flow. These waveguides are placed on the upper insulating layer 243a. They may optionally be fixed using a temporary adhesive that will decompose during the quenching of the furnace. The concrete forming the lower insulating layer 242b is poured over the waveguides and covers them.

[0267] The waveguides open outside the furnace through an opening made for example through the sidewalk blocks.

[0268] In one embodiment, a protective sheath 27 made of alumina surrounds, at least partially, at least one waveguide in order to protect it and facilitate its replacement.

[0269] The waveguides 12 are connected to at least one interrogator 18 electrically connected to the input end 12e of each waveguide via a transmission section 15, configured to inject an interrogation signal through said end and receive a reply signal through the waveguide in response to said injection. Said interrogator is in communication with an analysis computer 39, for example via Wi-Fi or by means of cables. The analysis computer 39 preferably has memory and software or a program configured to link the reply signals from the waveguides to a state of the target.

[0270] According to a second possible configuration illustrated by the assembly diagram in [Fig. 7], which can be combined with the previous configuration, said waveguide 12, preferably surrounded by a sacrificial polymer sheath, is positioned parallel to the direction D of the molten glass flow. It is placed on the upper insulating layer 243a. It is optionally fixed using a temporary adhesive that can decompose during the quenching of the furnace. The concrete forming layer 242b is poured over the waveguide and covers it.

[0271] Preferably, a network of waveguides is provided in the sole, preferably in the form of several parallel and / or perpendicular waveguides, for example in the form of two sets whose measuring parts are oriented at right angles, viewed from above, as in [Fig.3].

[0272] The waveguides are placed in a thermal zone of the sole at a temperature typically between 800°C and 1100°C.

[0273] In one embodiment, all the waveguides extend in the same plane. Alternatively, waveguides can be arranged at different depths in the sole. Example: Vault

[0274] The same provisions as those described above can be applied to a vault.

[0275] As illustrated in [Fig.8], the vault comprises dense blocks 241 forming the springers 241-1 and the voussoirs 241-2 of said vault 28, said blocks being generally covered with a back layer consisting of a barrier layer 242 of concrete and an insulating layer 243. According to one possible embodiment, the measuring part is preferably placed on the cold face of the dense blocks 241 in the concrete barrier layer 242. Example: Tank side wall

[0276] The same provisions as those described above may also be applied when the target is all or part of the side wall of the tank.

[0277] As illustrated in [Fig. 10], the side wall of the tank comprises dense blocks 241 in contact with the molten glass, and optionally a back layer formed of porous refractory blocks. The waveguide 12, and in particular at least the measuring portion of the waveguide, can be fixed to a plate-shaped support 40 (see [Fig. 10]) itself in contact with the blocks 241. The support is preferably at least partly made of a ceramic matrix composite, as previously described.

[0278] As is now clear, the invention provides a solution for evaluating, more precisely and in real time, the residual thickness or temperature of a target in a glass furnace.

[0279] Of course, the invention is not limited to the embodiments described and represented, which are provided for illustrative purposes only.

[0280] In particular, the target examples previously presented are not mutually exclusive.

Claims

1. Demands Glassmaking furnace comprising: - a glass melting chamber (11; 16) having a hot face (37) exposed towards the inside of the chamber; - a monitoring device, by time-domain or frequency-domain electrical reflectometry, for the state of a part of the furnace, referred to as the "target" (30), said device comprising: - an array of at least one wire waveguide, preferably of a plurality of wire electromagnetic waveguides (12), each waveguide comprising, between an input end and an output end, first and second electrical conductors (12i, 122), electrically insulated from each other, - an interrogator (18) electrically connected to the input end (12e) and configured to inject an interrogation signal through said input end, receive a response signal reflected by said waveguide in response to said injection, analyze the response signal and transmit a message on the state of the target based on said analysis, the waveguide comprising, between the input and output ends of said waveguide, a measuring portion (14) extending parallel to the hot face (37) and to a depth greater than 10 cm, the measuring portion (14) comprising a plurality of discontinuities, referred to as "basic discontinuities" (24), randomly distributed at least along the measuring portion of the waveguide, the number of basic discontinuities per meter of measuring portion of the waveguide being greater than 10, the basic discontinuities: - being capable of generating, in response to the injection of the interrogation signal, echoes having an amplitude greater than 0.5%, preferably greater than 1%, and less than 30% of the amplitude of the background echo reflected by the output end of the waveguide, known as "basic secondary echoes", and / or - being constituted by - reliefs resulting from a texturization of the outer surface of the waveguide and / or of a dielectric material interposed between the first and second electrical conductors and / or of at least one of the first and second electrical conductors, and / or - reliefs resulting from an irregular segmentation of a di- material electrical interposed between the first and second electrical conductors, and / or - local variations in the distance between the first and second electrical conductors; and / or - variations in the distance between the first electrical conductor and / or the second electrical conductor on the one hand, and a dielectric material of a support, preferably in a ceramic matrix composite; and / or - variations in the structure and / or composition of the environment around the first and second electrical conductors or between the first and second electrical conductors.

2. Oven according to the immediately preceding claim, wherein the basic discontinuities are - reliefs resulting from a texturization of the outer surface of the waveguide and / or of a dielectric material interposed between the first and second electrical conductors and / or of at least one of the first and second electrical conductors, and / or - reliefs resulting from an irregular segmentation of a dielectric material interposed between the first and second electrical conductors; and / or - local variations in the distance between the first and second electrical conductors.

3. Oven according to the immediately preceding claim, comprising pegs (23) in the form of beads and made of a dielectric material are threaded, in the measuring part, onto the first electrical conductor and / or onto the second electrical conductor.

4. Oven according to the immediately preceding claim, in which the lug(s) are arranged so as to form together a segmented protective sheath (27) extending along the entire length of the measuring portion of the waveguide.

5. Oven according to any one of the preceding claims, wherein the waveguide satisfies the Rayleigh scattering condition.

6. Oven according to any one of the preceding claims, wherein: a) the measuring part of each of the waveguides of said array extends parallel to the hot face and at a distance suitable so that in service said measuring part is at a temperature above 500°C; b) the maximum distance between two measurement sections of any two waveguides of the array is greater than 20 cm; c) each waveguide of the array is inserted into an orifice of the target, the orifice being configured to provide a thermal expansion space for the waveguide; d) the equivalent diameter of the measurement section of each waveguide of the array is greater than 1 mm and less than 50 mm; e) the distance separating the first and second electrical conductors of the measurement section of each waveguide of the array is greater than 0.3 mm and less than 30 mm; f) said measurement section has a number of bends - less than 2 per meter of length of measurement section if the length of said measurement section is less than 3 meters; - less than 1 bend per meter if the length of said measurement section is greater than or equal to 3 meters.

7. Oven according to any one of the preceding claims, wherein the waveguide array extends at least partially, preferably completely, within a back layer extending behind a first layer consisting of an assembly of blocks defining the hot face of the target or in a sublayer of said back layer.

8. Oven according to any one of the preceding claims, wherein the radius of curvature of the measuring portion of each waveguide of the array is at every point at least 3 times greater than the equivalent diameter of said measuring portion.

9. Furnace according to any one of the preceding claims, wherein: - the material constituting the electrical conductors is a refractory metal or a noble metal, preferably selected from Platinum, Tungsten, Gold, Palladium, Rhodium, Ruthenium, Iridium, or an alloy of these elements, and / or - said first and second electrical conductors are separated by a dielectric material comprising an oxide of at least one element selected from Al, Zr, Mg, Ca, Ti, Si, and / or - at least a fraction of the measuring portion of each waveguide of the array is protected by a ceramic sheath surrounding said measuring portion.

10. Oven according to any one of the preceding claims, in which at least some of the measurement parts of the waveguides, apart from the bends, extend parallel to each other.

11. Oven according to any one of the preceding claims, wherein each measuring portion of a waveguide of the array extends into a housing formed in the target and defining a thermal expansion space for said waveguide, the ratio of the equivalent diameter of the housing to the equivalent diameter of the measuring portion being greater than 1.05 and less than 3, the equivalent diameter of the measuring portion or of the housing being the greater of the cross diameters of said measuring portion or of said housing, respectively, considering all the cross sections along said measuring portion or of said housing, respectively.

12. Oven according to any one of the preceding claims, wherein the first and second conductors are fixed to a support (40), preferably in the form of a plate, made of a ceramic matrix composite and within which said first and second conductors are integrated or to the surface of which said first and second conductors are fixed.

13. Furnace according to any one of the preceding claims, wherein at least a measuring portion of a waveguide extends in a direction perpendicular to the direction of flow of the molten glass.

14. A method for manufacturing a furnace according to the immediately preceding claim, said method comprising, for at least one waveguide of the array, the following successive steps: 1) interposition of a sacrificial material between the measuring part of the waveguide and the target or a precursor of the target, then 2) after or simultaneously with the fabrication of the target in the case where the sacrificial material has been interposed in a precursor of the target, removal of the sacrificial material so as to create a thermal expansion space for the measuring part.

15. A method according to the immediately preceding claim, wherein: - the sacrificial material is the material of a sacrificial sheath covering the measuring part, and, to interpose the sacrificial material, - the target is manufactured around the measuring part, or - a recess, in the form of a groove or a hole, is made in the target or in a target precursor, then the measuring part is inserted into the recess, and then the recess is filled with a an unshaped refractory product containing a binder, preferably a cement, and capable of setting in mass by activation of the binder, preferably a refractory concrete, then the unshaped refractory product is hardened; or - the sacrificial material is a filler material independent of the waveguide and, to interpose the sacrificial material, - a recess, in the form of a groove or a hole, is made in the target or in a precursor of the target, then the measuring part is inserted into the recess, then the recess is filled with the filler material so as to encase the measuring part, the quantity of filler material being adapted to allow for expansion space, then the recess is filled with an unshaped refractory product containing a binder, preferably a cement, and capable of setting in mass by activation of the binder, preferably a refractory concrete, then the unshaped refractory product is hardened.

16. A method according to any one of the two immediately preceding claims, wherein - in step 2), the sacrificial material is removed by heat during furnace quenching and / or during sintering of the unshaped refractory product or target precursor at a temperature between 400°C and 1200°C.

17. A method for monitoring the state of the target of a glass furnace according to any one of claims 1 to 13, said method comprising the following steps: a. manufacturing the glass furnace; b. for each waveguide, controlling the interrogator to which the waveguide is connected, so that it injects an interrogating signal through the input end of said waveguide; c. analyzing the response signal so as to determine information relating to the state of the target in the region of the measuring part of said waveguide.

18. A method according to the immediately preceding claim, wherein the information relating to the state of the target is a residual thickness of refractory material or a temperature at one or more points of the target.

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