Non-invasive temperature sensor with insulating system

Abstract

A non-invasive temperature sensor for measuring the temperature of a fluid in a pipe (2), comprising a sensor body (1), a sensing tip (12) configured to contact the surface of the pipe (2), wherein the outer contour of the sensing tip (12) defines a sensing zone (8), a shroud (3) fixed around the sensor body (1) and shaped to conform to the pipe (2) surface, the shroud (3) extending lengthwise and circumferentially along the pipe (2), a confined air chamber (4) formed between the shroud (3) and the surface of the pipe (2) due to the lengthwise and circumferential extension of the shroud (3), the confined air chamber (4) insulating the pipe (2) in an area around the sensing zone (8) from temperature influences or heat loss, a clamping system (5) holding the sensor against the pipe (2) and applying constant and uniform pressure on the shroud (3) to maintain contact between the sensing tip (12) and the pipe (2) surface.

Description

[0001] Non-invasive temperature sensor with insulating system

[0002] The invention relates to non-invasive temperature sensors and, more particularly, a sensor fixed on pipes.

[0003] Non-invasive temperature sensors are used for measuring the temperature of a flowing or static medium inside of a container, which may be a piping or a vessel. This kind of sensor does not require any interference into the container. A basic solution for non-invasive temperature sensors consists of attaching and coupling a temperature-measuring apparatus (e.g. thermocouple, RTD etc.) directly onto the external surface of the container. This arrangement may then be enveloped in insulation to minimize the impact of ambient conditions on the measurements. The insulation is usually chosen by the user, it may be a paste, a solid or a gaz. This kind of thermal insulation may generate more work or costs for the user, not always be optimal for the system, and not be durable nor repeatable. Several solutions provide and insulation of the sensor. As an example of a basic disclosure, in US 2 302 640 A1 a tubular thermometer is inserted into a member of heat insulating material with clamps to attach it onto a pipe, and the bulb of this thermometer is put in contact with the pipe’s surface. However, this thermometer assembly only discloses insulation of the thermometer, to avoid external thermal influence on the thermometer. Other inventions disclose a complete insulation of the sensor, as in EP 3633337 A1 , where the sensor is surrounded by a case which may be filled with an insulating material. The purpose of this case is to shield the sensor from the environment when measuring the temperature of the medium. Still, this solution extends more the insulation along the sensor than on the width. Other solutions provide a system surrounding the whole pipe, as in EP 3070444 A1 or DE 102021 104758 A1 , where the insulation is in a rigid structure which can also be a holding system as in the German application or a kind of housing tailored to the pipe as in the European document. The solution may still let the user choose and apply the insulation material, as in the DE 10 2021 104758 A1 where it specifies that the insulation may be a paste, an airgel, etc. Those structures applied all around a pipe with determined diameter may be expensive as it is proper to solutions with many layers and / or materials with specific technical properties, and they can make accessing the sensor for routine checks and maintenance difficult. If the insulating material is not chosen or applied properly by the user, the performance and accuracy of the sensor may be non-optimal or worsened by a poor insulation choice. Finally, there are some sensors which have built-in extrapolation algorithms to account for the gradient in the pipe wall and to remove measuring inaccuracies and optimize the measurement.

[0004] Whereas, algorithms and models may fail because of a bug, update, etc. A direct measurement excludes that factor of error.

[0005] It is an object of the invention to provide a durable, easy to manufacture, while cost- effective non-invasive temperature sensor with a durable, repeatable and flexible insulation for the pipe around the measuring point of the temperature sensor, assuring accurate measurement and adapting on large ranges of pipe dimeters.

[0006] This object is achieved by the temperature sensor according to claim 1 . Advantageous embodiments are specified in the further dependent claims.

[0007] A non-invasive temperature sensor for measuring the temperature of a fluid in a pipe, comprising a sensor body, a sensing tip configured to contact the surface of the pipe, wherein the outer contour of the sensing tip defines a sensing zone, a shroud fixed around the sensor body and shaped to conform to the pipe surface, the shroud extending lengthwise and circumferentially along the pipe, a confined air chamber formed between the shroud and the surface of the pipe due to the lengthwise and circumferential extension of the shroud, the confined air chamber insulating the pipe in an area around the sensing zone from temperature influences or heat loss, a clamping system holding the sensor against the pipe and applying constant and uniform pressure on the shroud to maintain contact between the sensing tip and the pipe surface.

[0008] The sensing zone is defined by the outer contour of a sensing tip configured to contact the surface of a pipe, in a way that the sensing tip can conform to the surface of a pipe matching the shape of the pipe. A clamping system is used to hold the sensor against the pipe and to apply a uniform pressure on the shroud to maintain contact with the pipe surface and thus keeping the air in the resulting confined chamber between the shroud and the pipe. Through its flexibility the shroud is able to be fully in contact with the surface of pipes with different diameters. This combination of closed air chamber and shroud, with the dimensions defined by the shroud’s dimensions, fulfills the purpose of isolating the surface of the pipe and the sensing zone from heat loss which happens along a pipe’s walls, when a temperature is measured with a non-invasive sensor. This natural occurrence is a source of false temperature readings. Isolating a defined zone of the pipe in a defined perimeter around the sensing zone, gives the advantage of accurate readings, by minimizing this heat loss.

[0009] The temperature sensor is firmly mounted on the pipe thanks to a clamping system. This clamping system is closed on its extremities by a tightening system which can be any tightening system with adaptable tightening force, such as a screw type tightening system. The clamping system arranged around the sensor body and over the shroud is consequently applying axial constant force on the temperature sensor toward the pipe assuring a constant contact of the temperature sensor and the shroud against the pipe.

[0010] The clamping mechanism, by a particular geometry which leaves a flexure in the clamp after tightening to the pipe, provides continuous adjustment of tensioning to maintain sufficient force. This flexure takes up any loosening which happens when the sensor is subjected to changes in temperature, causing relaxation of the materials and compression set. This maintains sensor performance across a range of environmental and process conditions.

[0011] Preferably, the non-invasive temperature sensor is surrounded by a shroud extending in both circumferential directions from the sensing zone by an arc length of at least 30 degrees.

[0012] The extension of the shroud in the circumferential direction of the pipe, being equal to the arc length of a 30° section on the pipe, was determined by testing and it is an optimized angle. An arc length of an angle wider than 30° applied to the section of a chosen pipe diameter does not impact the improvement of the measurement’s accuracy nor the gradient in the pipe wall, but it would make the sensor bulkier, which may not be suitable. If the angle was less than 30° the performance of the sensor would suffer.

[0013] In another preferred embodiment the shroud covers a part of the surface of the pipe in the axial direction of the pipe, by an extension at least equal to the extension of the shroud in the circumferential direction of the pipe. This minimal surface of the pipe covered by the shroud assures a uniform insulation of the pipe all around the sensing zone in different directions.

[0014] Preferably, the portion of the shroud in contact with the pipe has a curved shape that conforms to the outer diameter of the pipe. A curved shape serves the purpose of helping to reduce the overall strain in the design, while the shroud in itself is able to conform to the pipe’s surface thanks to the flexibility of the shroud’s material.

[0015] In a preferred embodiment the shroud is made of a polymeric material. The material for the shroud is chosen to be durable to washdown and harsh environments, and is rated for high temperatures, while also being flexible. It could be for example, plastic or supported elastomer. The chosen polymer can be from the range of PFA, PEEK or PEI. The flexibility of the material allows a good adaptability of the shroud of different pipe diameters while the edge of the shroud is constantly in a fitted contact with the pipe’s surface, regardless of pipe’s diameter, which is an advantage compared to other temperature sensors. This gives an advantage of keeping the air chamber confined, thus allowing an insulation as well as sealing the system under the shroud from external exchanges, such as fluid exchanges. The durability of the material allows a robust product usable in different conditions and able to support pressurized washdowns, as well as an easy application to a pipe’s surface, in opposition to other insulation systems formed, for example, of foam or insulating material (i.e. mineral wool) directly applied on a pipe all around a sensor, and requiring destruction in order to detach the insulation or the sensor. The resistance to high temperatures allows the shroud to not get altered while being placed against a pipe with high temperature, up to 200°C.

[0016] In another preferred embodiment, the sensing tip is a sealed compressible tip comprising a sensing element arranged within the sensor body, a flexible heat conducting sheet arranged on a side of the temperature sensor configured to face the pipe when in use. The heat conducting sheet is thermally coupled to the sensing element and adapted to conform to the surface shape of the pipe. A compressible, thermally insulating rubber element is arranged between the sensor body and the flexible heat conducting sheet. A cylindrical element is arranged within the rubber element and the sensor body. The cylindrical element is connected to the heat conducting sheet and is surrounding the sensing element, wherein the rubber element provides a seal against the outer surface of the cylindrical element.

[0017] The sensing tip can be partially arranged in the sensor body, playing this role of compressible tip adaptable to the pipe’s surface sealing the sensor body from fluids and isolating the zone around the sensing element, in a way assuring an optimal heat transfer from the pipe to sensing element through the heat conducting sheet. The rubber element in this sensing tip has several roles as it keeps the heat conducting sheet against the pipe while acting as heat barrier keeping the heat from loss during the transfer from pipe to sensing element through the thin sheet. Placed between the sensor body and the cylindrical element, and making contact with those - especially through being in direct contact with the cylindrical element - it acts as a sealing for the sensor. Moreover, the clamping system arranged around the sensor body is consequently applying axial force on the sensing tip, the deformable rubber, and the heat conducting sheet with the sensing element, toward the pipe assuring a constant contact of the temperature sensor against the pipe.

[0018] In a preferred embodiment the sensing element is adhered to the sheet, which allows a good heat transfer and contact between the temperature sensor and the pipe.

[0019] The heat conducting sheet is preferably a metal thin sheet, such as a stainless-steel sheet. This insures a resistance of the heat conducting sheet to reaction with external environment, like corrosion.

[0020] In a preferred embodiment the cylindrical element is welded to the heat conducting sheet, and this combination is acting as a sealing for the sensing element. The purpose of this cylindrical element is also to keep the contact between the sensing element and the heat conducting sheet especially in a condition when the sensing tip and therefore the heat conducting sheet are deformed: this solves an unsolved problem observed in the field, as there is no optimal way to maintain a sensing element against a heat conducting element, without the sensing element getting loose.

[0021] The rubber element is preferably made of a high grade of raw material, such as FKM or EPDM. The chosen materials assure durability against high temperature or temperature fluctuation and caustics. Advantageously, the temperature measure and conformal contact against pipes of different diameters is optimized by the sensing tip structure, as the wide heat conducting sheet is thermally coupled to the sensing element and the heat conducting sheet deforms and adapts to the pipe’s surface under the force applied through the rubber element by the holding mechanism, meanwhile the rubber element isolating the circumference of the heat conducting sheet keeps the thermal energy from loss and allows it to be transferred to the sensing element. The rubber used in the solution and the thin sheet being durable and affordable materials, and the solution being easily manufacturable, the temperature sensor is a durable and affordable solution.

[0022] Other advantages of this invention are that, through the shroud, a durable insulation is provided with the temperature sensor, which assures repeatability by a defined surface of insulation of the pipe. This insulation fulfills the purpose of insulating the pipe and prevents from heat loss which happens through the pipe walls. The durability is assured by the type of material used for the shroud and the use of air for insulation, avoiding the use of less durable insulation materials. Chosen materials assure a flexibility of the shroud and adaptability on different pipe diameters, so as good contact between pipe surface and shroud, constantly keeping air for insulation trapped under the shroud.

[0023] The invention is explained in more detail below with reference to the drawings.

[0024] It shows schematically:

[0025] Figure 1 is a sectional view of the non-invasive sensor mounted on a pipe

[0026] Figure 2 is a sectional view of the shroud around the sensor on a pipe

[0027] Figure 3 is a 3D view of the non-invasive sensor mounted on a pipe

[0028] Figure 4 is a schematic view of heat losses around a sensing zone

[0029] Figure 5 is a schematic view of a section of the pipe

[0030] Figure 6 is a sectional view of the non-invasive sensor and sensing tip mounted on a Pipe In the following description of the preferred embodiments, identical reference signs denote identical or comparable components.

[0031] Figure 1 is a sectional view of the entire temperature sensor assembly on a pipe 2. A shroud 3 is placed around a sensor body 1 which is fixed to a pipe by a clamping system 5. The clamping system is closed by a tightening system 6 providing continuously an adjustable source of compressive force. The clamping system is represented in default condition 7 to illustrate the ability of this system to bend and adapt to the pipe 2. The clamping system 5 applies a constant and uniform force on the shroud 3, maintaining it against the pipe 2. The tightening system 6 has an adjustable tightening allowing adaptation of the clamping on different pipe diameters. The sensing zone 8 is the outer contour of the sensing tip 12 and defines a zone of contact between the sensing tip 12 and the pipe 2, where the temperature measures are acquired. The shroud 3 is made in a way that a minimum distance is defined between the sensing zone 8 and an edge of the shroud 9 in the circumferential direction of the pipe 2. This minimum distance corresponds to an arc length related to an angle of 30° starting from the sensing zone 8, on both sides of it in the circumferential direction of the pipe 2.

[0032] Figure 2 represents the sensor with insulation system composed of the shroud 3 and confined air chamber 4, placed on the pipe 2. When the sensor is applied on a pipe 2, the air gets trapped under the shroud 3 for purpose of insulation of the pipe’s surface around the sensing zone 8.

[0033] Figure 3 is a side view of the assembly, presenting the sensor body 1 and the shroud 3 held against a pipe 2 by the clamping system 5 closed by the tightening system 6 which can be a bolt and screw type, or any other tightening system providing adjustable source of compressive force.

[0034] Figure 4 represents the mechanism of heat loss occurring in a pipe 2 and impacting a non-invasive temperature measurement. The temperature of a fluid is measured through the pipe’s wall in a sensing zone 8. A primary heat loss through the sensor body 10, thus the sensor body usually comprises an insulation mean. A secondary heat loss 11 occurs from the sensing zone 8 through the walls of the pipe 2, in the axis of the pipe 2. Resulting in a temperature gradient in the pipe wall, the heat loss 11 affects the accuracy of the measurements. The insulation, assured by the specific confined air chamber 4 around the sensing zone 8 applied on the pipe wall, eliminates the temperature gradient generated by the heat loss 11 through the pipe’s walls. Insulating that kind of system minimizes the temperature influences from outside of the sensing zone resulting from heat exchanges between the environment and the pipe walls.

[0035] On figure 5 is represented an example of an arc length corresponding to an angle of 30°, representing one of the extensions of the shroud 3 in the circumferential direction of the pipe 2. This arc length starts from the sensing zone 8, in this figure W represents half of this sensing zone 8 and of the width of the sensing tip 12 from the center to the edge of it, as the outer contour of the sensing tip 12 defines a sensing zone 8.

[0036] Figure 6 shows a sectional view of an exemplary embodiment of a non-invasive temperature sensor and the sensing tip. The temperature sensor comprises a sensor body 1 . Inside the body 1 is a compressible sensing tip formed by a sensing element 13, a cylindrical element 16, a rubber element 15 and a heat conducting sheet 14. The sensing element 13 is placed inside a cylindrical element 16 which is welded to a heat conducting sheet 14. The sensing element 13 is attached to the heat conducting sheet 14 in order to have an optimal heat transfer from the pipe 2 to the sensing element 13. The heat conducting sheet 14 is wider than the sensing element 13 in order to have a better heat transfer from the pipe 2, as the thermal resistance of the heat conducting sheet decreases with inversed proportionality to the heat conducting sheet surface area. The heat conducting sheet 14 is designed to adapt to a surface shape of the pipe 2 when the temperature sensor is placed on the pipe 2. The insulating rubber element 16 holds conformally the heat conducting sheet 14 against the pipe 2 surface adapting to the pipe shape thanks to the compressibility of the rubber element 15. The thermally insulating properties of the rubber element 15 allows to minimize energy loss toward the environment during the heat transfer through the heat conducting sheet 14 to the sensing element 13 and optimize the measurement. The rubber element 15 acts as a sealing for the sensor especially the sensing tip combination of rubber element 15 and cylindrical element 16 inserted into the body 1 . The sensing tip is placed against the pipe 2. Inside the pipe 2 a fluid, e.g., a coolant, which is not shown here, can flow or can be at rest. The non-invasive temperature sensor can be used to determine the temperature of the fluid. The sensing element 13 is connected to an external sensor connection 17 which could be wired or wireless, the detailed electronics in the sensor are not represented. The temperature sensor is maintained by a clamping system 5 arranged around the sensor body 1 applying constant and uniform force keeping the sensor and shroud 3 in optimal contact with the pipe 2 surface assuring a good performance in temperature measurement, thanks to the springiness of the clamping system 5 which accommodate expansion and contraction. The clamping system 5 is held on the extremities by a tightening system which can be a screw type. The purpose of a tightening is to provide an adjustable source of sufficient force to solidly hold the temperature sensor against pipes of different diameters, while the tightening force is not excessive which could damage the temperature sensor or the pipe.

[0037] References:

[0038] 1 Sensor body

[0039] 2 Pipe

[0040] 3 Shroud

[0041] 4 Confined air chamber

[0042] 5 Clamping system

[0043] 6 Tightening system

[0044] 7 Clamping system in default condition

[0045] 8 Sensing zone

[0046] 9 Edge of the shroud

[0047] 10 heat loss through the sensor body

[0048] 11 heat loss through the pipe

[0049] 12 Sensing tip

[0050] 13 sensing element

[0051] 14 heat conducting sheet

[0052] 15 rubber element

[0053] 16 cylindrical element

Claims

Claims:1 . A non-invasive temperature sensor for measuring the temperature of a fluid in a pipe (2), comprising- a sensor body (1 );- a sensing tip (12) configured to contact the surface of the pipe (2), wherein the outer contour of the sensing tip (12) defines a sensing zone (8);- a shroud (3) fixed around the sensor body (1 ) and shaped to conform to the pipe (2) surface, the shroud (3) extending lengthwise and circumferentially along the pipe (2);- a confined air chamber (4) formed between the shroud (3) and the surface of the pipe (2) due to the lengthwise and circumferential extension of the shroud (3), the confined air chamber (4) insulating the pipe (2) in an area around the sensing zone (8) from temperature influences or heat loss;- a clamping system (5) holding the sensor against the pipe (2) and applying constant and uniform pressure on the shroud (3) to maintain contact between the sensing tip (12) and the pipe (2) surface.

2. The non-invasive temperature sensor according to claim 1 , wherein the shroud (3) extends in both circumferential directions from the sensing zone (8) by an arc length of at least 30 degrees.

3. The non-invasive temperature sensor according to claim 1 or 2, wherein the shroud (3) covers a part of the surface of the pipe (2) in the axial direction of the pipe (2), by an extension at least equal to the extension of the shroud (3) in the circumferential direction of the pipe (2).

4. The non-invasive temperature sensor according to any preceding claim, wherein the portion of the shroud (3) in contact with the pipe (2) has a curved shape that conforms to the outer diameter of the pipe (2).

5. The non-invasive temperature sensor according to any preceding claim, wherein the shroud (3) is made of a polymeric material selected from the group of PFA, PEEK or PEI.

6. The non-invasive temperature sensor according to any preceding claim, wherein the sensing tip (12) comprises:- a sensing element (13) arranged within the sensor body (1 );- a flexible heat conducting sheet (14) arranged on a side of the temperature sensor configured to face the pipe (2) when in use, the heat conducting sheet (14) being thermally coupled to the sensing element (13) and adapted to conform to the surface shape of the pipe (2);- a compressible, thermally insulating rubber element (15) arranged between the sensor body (1 ) and the flexible heat conducting sheet (14); and- a cylindrical element (16) arranged within the rubber element (15) and the sensor body (1 ), the cylindrical element (16) being connected to the heat conducting sheet (14) and surrounding the sensing element (13), wherein the rubber element (15) provides a seal against the outer surface of the cylindrical element (16).

7. The non-invasive temperature sensor according to claim 6, wherein the sensing element (13) is adhered to the heat conducting sheet (14).

8. The non-invasive temperature sensor according to claim 6 or 7, wherein the cylindrical element (16) is welded to the heat conducting sheet (14).

9. The non-invasive temperature sensor according to any claim 6 to 8, wherein the heat conducting sheet (14) is made from stainless steel.

10. The non-invasive temperature sensor according to any claim 6 to 9, wherein rubber element (15) is made from high graded raw material.

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