WO2008001238A2

WO2008001238A2 - Sensor element for the diagnostic of a multilayer structure.

Info

Publication number: WO2008001238A2
Application number: PCT/IB2007/051970
Authority: WO
Inventors: Giuliano Balbi; Giacomo Manenti
Original assignee: New Componit S.R.L.; Suntech S.R.L.
Priority date: 2006-05-26
Filing date: 2007-05-24
Publication date: 2008-01-03
Also published as: ITBG20060025A1; WO2008001238A3

Abstract

The present invention relates to a sensor element for the diagnosis of a multilayer structure (2) subject to an action of physical deterioration. The sensor element (1) comprises essentially a substrate made of insulating material (10), for example polyimide, on which a circuit (15) is applied. This circuit (15) is made of conductive material, for example a conductive ink, suitable to be crossed by an electric signal and to be connected to signalling means. The present invention also relates to a multilayer structure (2) for a fabric joint comprising said sensor element (1).

Description

SENSOR ELEMENT FOR THE DIAGNOSTICS OF A MULTILAYER STRUCTURE

DESCRIPTION

The present invention relates to a sensor element for the diagnostic of a multilayer structure subject to an action of physical deterioration. The invention also relates to a multilayer structure for a fabric joint comprising said diagnostic sensor.

As is known, in many industrial plants widespread use is made of expansion compensators provided in the ducts or channels subject to thermal expansion, vibration, torsion and misalignment. The various types of compensators include fabric compensators, also called fabric joints, which are extensively applied, for example, in thermoelectric power plants, discharge channels of gas turbines or industrial furnaces, in the chemical and petrochemical industry, in paper mills, foundries, cement works and in various other industrial contexts. The traditional fabric joints comprise a multilayer structure which is usually characterised by a high chemical inertia and a high resistance to corrosion vis-a-vis the fluids that run inside the ducts connected by the joint. At the same time this multilayer structure is impermeable to fluids so as to prevent their leakage to the outside. To achieve these aims, the structure in question comprises one or more inner layers made of wire mesh and/or fibreglass and one or more outer layers made of polymer, for example PTFE. In particular the inner layers make the structure of the joint resistant to corrosion, while the outer layers ensure impermeability to fluids.

Despite their physical conformation, the aggressive action of the fluids, usually at high temperature, causes inevitable deterioration of the structure of the fabric joint in the long term until it affects operation of the joint. The sudden rupture of the structure constitutes a considerable technical drawback as it necessarily entails stoppage of the plant for replacement of the joint. A non-scheduled interruption involves a significant loss in economic terms since the resulting work that has to be carried out is certainly not part of the routine maintenance programme.

These considerations highlight the need for devices that permit preventive diagnostic of the state of deterioration of the structure so as to programme replacement or repair of the structure during routine maintenance.

Therefore the main aim of the present invention is to provide a sensor element for the diagnostic of a multilayer structure subject to an action of physical deterioration. In the context of this aim one object of the present invention is to provide a sensor element that signals the state of deterioration of a multilayer structure to permit programming of the repair or replacement of the structure. A further object of the present invention is to provide a sensor element made of a reduced number of components that can be easily assembled via known industrial processes at low cost.

A further object of the present invention is to provide a sensor element that is highly dependable and easy to produce at competitive costs.

This aim, in addition to said and further relative objects that will be illustrated below, is achieved by a sensor element for the diagnosis of a multilayer structure subject to an action of physical deterioration, characterised in that it comprises a substrate made of insulating material on which a circuit is applied, made of conductive material. Said circuit being suitable to be crossed by an electric signal and to be connected to signalling means.

The sensor element according to the invention is operatively located inside the multilayer structure so as to be sensitive to the effects of the deterioration action on the structure. Said action causes a variation in the electric signal which is appropriately amplified by the signalling means to inform the operators of the state of deterioration of the structure and, if necessary, the extent of said deterioration.

As is obvious from the indications provided, the sensor element has an extremely simple structure which can be produced via low cost production processes. The information provided by the sensor element allows the operators to programme the operations for repair or replacement of the joint together with the routine maintenance operations with obvious advantages in terms of overall running costs.

Further characteristics and advantages of the invention will become clearer from the description of preferred but not exclusive embodiments of the sensor element according to the invention, illustrated by way of non-limiting example in the accompanying drawings in which: figure 1 is a schematic view of a sensor element according to the present invention;

- figure 2 is a schematic view of a first embodiment of a multilayer structure comprising a sensor element according to the present invention;

- figure 3 is a schematic view of a second embodiment of a multilayer structure comprising a sensor element according to the present invention;

- figures 4 and 5 are schematic views of a fabric joint having a multilayer structure provided with at least one sensor element according to the present invention.

With reference to the cited figures, the sensor element 1 according to the present invention is used for the diagnosis of a multilayer structure 2 subject to an action of physical deterioration. In the description, reference will be made to use of the sensor element 1 in a multilayer structure 2 of a fabric joint 3, but it is understood that the sensor element 1 can be applied in any other conceptually equivalent situation or in the event of a diagnosis element being required to define the state of physical deterioration of a multilayer containment structure. It should furthermore be underlined that the expression "action of physical deterioration" refers to all those actions of corrosion, deterioration or disaggregation that occur in the multilayer structure 2 due to chemical-physical aggression of the fluids contained by the structure.

The sensor element 1 according to the invention comprises a substrate made of insulating material 10 on which a circuit is applied made of conductive material 15 which will be crossed by an electric control signal. The circuit made of conductive material will be electrically connected to signalling means 16 which have the purpose of amplifying and signalling any variations in the electric signal characteristic of the state of deterioration reached by the multilayer structure 2 to which the sensor element 1 is applied. To better understand operation of the sensor element 1 , it is possible to consider figure 2 which is relative to a multilayer structure 2 subject to an action of physical deterioration. The sensor element 1 is positioned inside the structure 2 in a pre-set position so as to be sensitive to the effects of the action of physical deterioration. In other words the sensor element is positioned like a layer of the structure, thus constituting a "sensor layer". Over time, the action of physical deterioration deteriorates the structure 2, wearing and/or perforating the inner layers (indicated in figure 2 by references 7A, 7B and 7C) until it causes physical alterations of the circuit made of conductive material 15 applied on the substrate made of insulating material 10. Said physical alterations can consist, for example, in physical breakage of the circuit due to perforation of the substrate 10. Said breakage of the circuit obviously causes a variation in the electric control signal which, once processed by the signalling means 16, translates into information for the operator on the state of progress of the damage in the structure 2 with respect to the pre-set position in which the sensor element 1 is located. As indicated below, the conductive material can be metallic or non-metallic. In the same way the substrate 10 can be made of insulating materials of different type, for example those traditionally used in the manufacture of fabric joints. These materials comprise, for example, vitreous-based fabrics (for example fibreglass or silica fibre fabrics), Teflon glass fabrics, needle felt, fluorinated polymer (for example PTFE used in the multilayer structures of fabric joints for production of the outer containment layers indicated in figure 2 by references 8 A and 8B). According to a further preferred embodiment, the substrate 10 is formed of a polyimide film.

On this subject, for the purposes of the invention, the polymer marketed by the company Du

Pont under the commercial brand KAPTON® has proved to be particularly suitable. In the field of films made of insulating material, the use of polyesters has also proved to be suitable, including the one marketed by Du Pont under the commercial brand MYLAR®.

In another possible embodiment, the insulating substrate 10 can consist of a laminate formed by a polymer film coupled with a film made of another insulating material. A possible structure of a laminate can comprise a polyester film coupled with a film of organic/inorganic paper. Alternatively the laminate could comprise, for example, a polyester film coupled with non-woven fabric.

The above are only some examples of insulating materials that can be used for the substrate

10. The substrate 10 can be made of all the insulating materials suitable for the application of the present invention.

In the case of the fabric joints 3, for example, excellent performance of the sensor element 1 has been obtained by using, for the substrate 10, polymer films, the sublimation temperature of which is near that of the gases that cross the ducts interlocked by the fabric joint 3. After perforating the innermost layers of the structure, the gases at high temperature come into contact with the film of insulating material 10 causing sublimation thereof or causing the immediate physical alteration of the circuit made of conductive material 15 applied to the film.

In the case, for example, of the substrate consisting of a Kapton® film, when the sublimation temperature of the latter (around 410°C) is exceeded, the electrical circuit applied on the film directly detects the deterioration action and signals, via the relative signalling means 16, perforation of the insulating substrate 10 of the sensor element 1.

The response times of the latter are determined by the dielectric constant of the material used for construction of the insulating substrate 10. Therefore, by increasing or reducing the thickness of the substrate 10, the material being equal, it is possible to select different response times for the sensor element 1. Analogously, the thickness of the substrate 10 being equal, the response times can be varied by varying the nature of the insulating material or the dielectric constant of the substrate.

If, for example, we require a sensor with relatively long response times with respect to those that can be obtained with Kapton® film, the substrate 10 can be made of PTFE for example or alternatively of a layer of fibreglass-based fabric with dielectric constant superior to that of the Kapton®. The conductive material used for the electric circuit can be a metallic material, for example the traditional copper, or a non-metallic material, especially if polyimide films are used as insulating substrates.

The use of metallic conductive materials is combined preferably with substrates 10 produced with the materials described above already used for the manufacture of fabric joints (vitreous- based fabrics, Teflon glass fabrics, fluorinated polymers). In particular the conductive circuit 15 can consist, for example, of a lamina made of aluminium, copper or other metal applied on the insulating substrate 10. Alternatively the circuits 15 applied on the substrate 10 can be made of one or more conductor wires applied so as to define a circuit for the control signal. In a further possible embodiment the circuit can also be formed of a wire mesh, for example made of stainless steel, such as the reinforcement mesh normally used to contain the layers of padding in a fabric joint.

As mentioned above, if a polyimide film is used as insulating substrate 10, for the electric circuit 15 the use of conductive pastes or inks, preferably graphite-based, has proved particularly suitable; these are already used in the electronics sector (in particular in the production of printed circuits) such as, for example, those sold by Coates Leurilleux S.p.A. under the name "PCT" and/or the inks sold by the same company under the name "XZ250". Application of the conductive material on the insulating film 10 can be advantageously performed according to the methods described in the patent application PCT/EP03/05743. It is understood that the possibility of coupling a circuit made of conductive material with the insulating substrate in the form of a film or the possibility of coupling a circuit made of non- conductive material with a substrate thicker than a film (or in the form of a laminate) falls within the scope of the present invention.

According to a further embodiment of the invention, the variation in the electric signal is advantageously exploited also to define the extent of the structural damage in addition to the position thereof. In other words, the variation in the electric signal identifies, for example, not only the layer or layers of the structure that have been perforated but also the extent of said perforation. If for example a lamina of conductive material (aluminium, copper or other material) is applied to the insulating substrate 10, it is possible to diagnose the entity of the laceration on the conductive sheet via the known Ohm's law. The metallic sheet has an ohmic value established by its physical characteristics (dimensions and resistivity of the metal used). As a result of the damage to the metallic sheet, due to the action of deterioration, said ohmic value is altered. A rapid analysis of the variation in the signal allows to establish, for example, the extent of the perforation which, by varying the signal passage section, affects said ohmic value. Further analyses of the signal can advantageously lead to the establishment of other interesting parameters characteristic of the deterioration action such as, for example, internal temperature of the gases, speed of progress of the deterioration etc.

The present invention also relates to a multilayer structure 2 which is characterised in that it comprises at least one sensor element 1 according to the present invention. On this subject, figures 2 and 3 illustrate possible embodiments of said structures in order to highlight the advantages relative to use of the sensor element 1. It should be underlined furthermore that due to its simple construction configuration, the sensor element 1 according to the invention can be applied to any multilayer structure already known, above all in the field of fabric joints for industrial plants.

As illustrated, the sensor element 1 is arranged in a pre-established position inside the multilayer structure 2 so as to be located between one or more outer layers 8A and 8B made of material impermeable to fluids and one or more inner layers 7A, 7B, 7C, 7D and 7E made of material resistant to corrosion. The outer layers 8A and 8B therefore have the function of containing the fluid, while the inner ones 7A, 7B, 7C and 7E oppose the chemical-physical aggression of the fluid, preserving the functionality of the outer layers 8 A and 8B.

The function of the sensor element 1 is therefore that of constituting a "sensor layer" which signals to the operators, via the signalling means 16 outside the structure, the state of deterioration of the inner layers 7A, 7B, 7C and 7E of the structure 2 before the damage affects the outer containment layers 8 A and 8B.

In the two solutions illustrated, the fluid is contained by the presence of a layer 8A made of fluorinated polymer, preferably in PTFE, and by a layer of Teflon glass fabric which constitutes the outermost layer of the structure 2.

The resistance to corrosion is provided by at least one more internal layer of wire mesh and one or more layers of fibreglass in the form of glass fabric or needle felt.

In the solution illustrated in figure 2, for example, the innermost layer 7A of the structure 2 consists of a layer of stainless steel mesh, while a second layer 7B adjacent to the first 7A is made of glass fabric. A third layer 7C adjacent to the second consists of fibreglass needle felt while the sensor element 1 is arranged between this third layer 7C and a fourth layer 7D also consisting of fibreglass needle felt.

The multilayer structure 2 schematically illustrated in figure 3 differs from the one of figure 2 due to the presence of an inner layer 7E made of silica fabric and another silica fibre layer arranged between the innermost layer 7A made of wire mesh and the fibreglass layer 7B adjacent to the sensor element 1. This further layer increases resistance to chemical-physical aggression, allowing the structure 2 to operate in harsher conditions than that of figure 2. It is understood that the structures described are to be considered simply examples of multilayer structures 2 to which the sensor element 1 can be applied according to the present invention. In fact, due to its simple construction form, the sensor element 1 is suitable for application to a virtually indefinite number of multilayer structures 2 having different composition according to the application for which they are intended.

With reference to figures 4 and 5, the present invention also relates to a fabric joint 3 characterised in that it comprises a multilayer structure 2 to which a sensor element 1 is applied according to the above description. In these figures the sensor element 1 is shown by a broken line to further highlight its operating position within the multilayer structure 2. The signalling means 16 are obviously located in a position external to the structure 2 to interface with the operators. On this subject, in order to detect and record effectively the breakage signal generated by the sensor element, the signalling means can comprise a signal control unit which can be connected via GPS or GSM systems to an ordinary mobile phone or to another remote user interface means. Via this solution, it is possible, for example, not only to promptly identify rupture of the joint, but also to know at any time the extent of the rupture and the position thereof in the joint structure. In other words, the information provided by the signalling means can be transferred to remote stations with respect to the operating position of the fabric joint by exploiting widely used communication and transmission systems. Again with reference to figures 4 and 5, the fabric joint 3 is defined not only by the multilayer structure 2 but at times also by a pair of end flanges 50 which permit mechanical connection of the joint 3 to two ducts for the passage of a fluid. It is understood that the joint 3 can take different forms, for example distinguished by a cylindrical, square or elliptic cross section, just as the connection flanges can in certain situations be absent.

With reference in particular to figure 5, on the same multilayer structure 2 several sensor elements 1 could be arranged to increase the amount of information available to the operators. In this case the sensor elements 1 can be inserted at different levels of the structure 2, but can also be inserted at the same level at different points. In the case, for example, of a square cross section fabric joint, the elements 1 could be arranged at the same level but separate from one another so that each of them operatively controls the conditions of one side of the cross section of the joint. The use of a plurality of sensor elements 1 allows the operators to establish more accurately the evolution of the internal damage of the structure 2, thus facilitating programming of maintenance work.

The technical solutions adopted for the sensor element provide for full achievement of the pre-established aims and objects. In particular, the sensor element has an extremely simple configuration which permits use in a large number of applications. The sensor element is at the same time dependable and easy to produce via known low-cost industrial processes.

The sensor element thus conceived is subject to numerous modifications and variations, all falling within the scope of the inventive concept; furthermore all the details can be replaced by others that are technically equivalent.

In practice, any materials and contingent dimensions and forms can be used according to requirements and the state of the art.

Claims

1. Sensor element for the diagnostic of a multilayer structure (2) subject to an action of physical deterioration, characterised in that it comprises a substrate made of insulating material (10) on which a circuit (15) made of conductive material is applied, said circuit (15) being suitable to be crossed by an electric signal and to be connected to signalling means.

2. Sensor element (1) according to claim 1, characterised in that said substrate (10) is made of fluorinated polymer.

3. Sensor element (1) according to claim 1, characterised in that said substrate (10) is made of PTFE.

4. Sensor element (1) according to claim 1, characterised in that said substrate (10) consists of a polyimide film.

5. Sensor element (1) according to claim 4, characterised in that said polyimide consists of the polymer marketed under the brand KAPTON® .

6. Sensor element (1) according to claim 1, characterised in that said substrate (10) is made of polyester.

7. Sensor element (1) according to claim 1, characterised in that said substrate (10) is formed of a laminate comprising at least one film made of polyester coupled with organic or inorganic paper.

8. Sensor element (1) according to claim 1, characterised in that said substrate (10) is formed of a laminate comprising at least one film made of polyester coupled with a non- woven fabric.

9. Sensor element (1) according to claim 1, characterised in that said substrate (10) consists of a fibreglass substrate.

10. Sensor element (1) according to claim 1, characterised in that said substrate (10) consists of a Teflon glass fabric.

11. Sensor element according to one or more of the claims from 1 to 10, characterised in that said conductive material is a metallic material.

12. Sensor element (1) according to claim 11, characterised in that said circuit made of conductive material consists of a lamina made of metallic material applied on said substrate (10).

13. Sensor element (1) according to claim 11, characterised in that said circuit made of conductive material consists of a wire mesh applied on said substrate (10).

14. Sensor element (1) according to one or more of the claims from 1 to 8, characterised in that said conductive material is a non-metallic material.

15. Sensor element (1) according to claim 14, characterised in that said circuit is provided through a conductive ink applied to said substrate (1) comprising a polyimide film.

16. Sensor element (1) according to claim 15, characterised in that said conductive ink is graphite-based.

17. Multilayer structure (2) for a fabric joint characterised in that it comprises a sensor element (1) according to one or more of the claims from 1 to 16, said sensor element (1) being located in a pre-set position inside said multilayer structure (2), said circuit (15) of said sensor element (1) being connected to said signalling means (16), said signalling means signalling the state of deterioration of said structure (2) with respect to said pre-set position according to the variation of said electric signal due to said action of physical deterioration.

18. Multilayer structure (2) according to claim 17, characterised in that said sensor element (1) is positioned between one or more outer layers (8 A, 8B) made of material impermeable to fluids and one or more inner layers (7 A, 7B, 7C, 7C, 7E) made of material resistant to corrosion.

19. Multilayer structure (2) according to claim 18, characterised in that said one or more outer layers (8 A, 8B) consist of fluorinated polymer.

20. Multilayer structure (2) according to claim 19 characterised in that said one or more outer layers (8 A, 8B) are made of PTFE.

21. Multilayer structure (2) according to claim 18, characterised in that said one or more outer layers (8A, 8B) are made of Teflon glass fabric.

22. Multilayer structure (2) according to one or more of the claims from 18 to 21, characterised in that said one or more inner layers (7 A, 7B, 7C, 7C, 7E) consist of a wire mesh.

23. Multilayer structure (2) according to one or more of the claims from 18 to 21, characterised in that said one or more inner layers (7 A, 7B, 7C, 7C, 7E) consist of fibreglass.

24. Multilayer structure (2) according to one or more of the claims from 18 to 21, characterised in that said one or more inner layers (7 A, 7B, 7C, 7C, 7E) consist of silica fibres.

25. Fabric joint for the connection of ducts of industrial plants characterised in that it comprises a multilayer structure according to one or more of the claims from 17 to 24.