Improvements in temperature measurement systems

Abstract

A thermowell includes a process mount and a cylindrical member. The process mount is configured to be mounted to the process intruder. The cylindrical member is configured to be exposed to a process fluid and includes a plurality of apertures extending in the cylindrical member. Each aperture is configured to receive a separate temperature sensor assembly. A redundant process fluid temperature measurement system is also provided.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a continuation application filed under 35 U.S.C. 111(a) and claims the benefit of International Application No. PCT / IB2023 / 061630 filed on November 17, 2023, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present application relates to improvements in temperature measurement systems. Background Art

[0004] Process industries use process variable transmitters to monitor process variables related to substances such as solids, slurries, liquids, steam and gases in chemical, pulp, petroleum, pharmaceutical, food and other fluid process plants. Process variables include pressure, temperature, flow, level, turbidity, density, concentration, chemical composition and other characteristics.

[0005] Temperature transmitters provide an output related to the temperature of the process fluid. The temperature transmitter output can be transmitted to a control room through a process control loop, or the output can be transmitted to another process device to monitor and control the process.

[0006] Some temperature transmitters are used with thermowells that are mounted to a pipe flange or process intrusion and are configured to receive a temperature sensor assembly or probe. Although the temperature sensor assembly is placed in thermal communication with the process fluid, it is otherwise protected from direct contact with the process fluid. The thermowell is positioned within the process fluid to ensure adequate thermal contact between the process fluid and the temperature sensor assembly disposed within the thermowell. Thermowells are typically designed with a relatively sturdy metal structure so that the thermowell can withstand many challenges presented by process fluids. These challenges can include: physical challenges, such as process fluids flowing through the thermowell at a relatively high rate; thermal challenges, such as extremely high temperatures; pressure challenges, such as process fluids being transported or stored at high pressures; and chemical challenges, such as those presented by corrosive process fluids.

[0007] Thermowells can present challenges to process installation. Typically, each thermowell requires a process intrusion where the thermowell is mounted to and extends into a process vessel, such as a tank or pipe. The process intrusion itself must be carefully designed and controlled so that the process fluid does not leak from the vessel at the intrusion point.

[0008] Many process industry operations require continuous measurement and control of multiple process parameters. These parameters may vary from process to process. However, temperature is often an important parameter for many processes. Accurate, continuous, and redundant temperature measurements are important for operator / operational safety, product quality, and process efficiency. In order to provide uninterrupted temperature measurement, redundancy may be required for certain applications. This redundancy is often provided in the form of multiple process intrusions, thermowells, or even temperature transmitters. Therefore, while process measurement redundancy can be achieved when needed, it is at a considerable cost. In addition, multiple process intrusions increase the risk of process fluid leaks. Summary of the invention

[0009] A thermowell includes a process mount and a cylindrical member. The process mount is configured to be mounted to a process intrusion. The cylindrical member is configured to be exposed to a process fluid and includes a plurality of holes extending therein. Each hole is configured to receive a separate temperature sensor assembly. A redundant process fluid temperature measurement system is also provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram of a triple redundant temperature measurement system according to the prior art.

[0011] Figure 2 is a schematic diagram of a triple redundant process temperature sensing system according to an embodiment of the present invention.

[0012] Figure 3 is a block diagram of an improved process temperature measurement system according to an embodiment of the present invention.

[0013] Figure 4 is a schematic cross-sectional view of an improved thermowell according to an embodiment of the present invention.

[0014] Figure 5 is a schematic cross-sectional view of a triple redundant temperature sensor thermowell assembly according to an embodiment of the present invention.

[0015] Figure 6A-6F Various top views of a cylindrical member configured to receive a plurality of temperature sensor assemblies in a thermowell are shown according to embodiments described herein.

[0016] Fig. 7A is a schematic diagram of an improved terminal block according to an embodiment of the present invention.

[0017] Figure 7B-Figure 7E Various design alignments between a thermowell cylindrical member and a bore for receiving a temperature sensor assembly according to embodiments described herein are shown.

[0018] Fig. 8A and Figure 8Bis a schematic top view showing an improved housing according to an embodiment of the present invention.

[0019] Fig. 9 is a schematic diagram of logic for measuring multiple process fluid temperature values ​​using multiple temperature sensor assemblies in accordance with an embodiment of the present invention.

[0020] Fig.10 It is a logic diagram of the voting logic of the safety instrumented system. DETAILED DESCRIPTION

[0021] RTD and thermocouple are examples of temperature sensitive elements, which are widely used in industry for temperature measurement. These temperature sensitive elements are usually placed in a metal sheath to provide a temperature sensor assembly. The temperature sensor assembly is usually placed in a thermowell. The thermowell is inserted into the process fluid using a process intrusion piece created on a process device or pipeline. The thermowell usually includes a flange or threaded process connection piece fixed to the process intrusion piece. The temperature sensor assembly can be directly electrically connected to the process control system, or they can be connected through a temperature transmitter. As used herein, the temperature sensor assembly includes a temperature sensitive element (such as a thermocouple or RTD) and a metal sheath that accommodates the temperature sensor element. The temperature sensitive element is usually fixed in the metal sheath using an insulating material (such as a mineral insulating material or epoxy resin). The temperature sensor assembly is usually cylindrical in nature and is received by a cylindrical hole in the thermowell. Although direct connection requires special cables for thermocouples and multi-core (three-core or four-core) conductors for RTD, connecting through a temperature transmitter has advantages over directly connecting the temperature sensor assembly.

[0022] Each thermowell can typically house a single temperature sensor assembly. A limitation of current thermowells is that each thermowell requires a separate process intrusion on the process equipment. If the process application requires triple redundancy at the measurement level, three different process intrusions need to be created on the process equipment. Although a dual sensor option is available, in this arrangement the two sensors are packaged in a single sheath. The dual sensors can be connected to the system independently and used as two independent elements. However, due to the advantages provided by a temperature transmitter, it is preferred to connect via a temperature transmitter. Currently, temperature transmitters only provide one output signal for a dual sensor arrangement. Therefore, each process intrusion actually uses one sensor at a time, and multiple sensor assemblies and their associated thermowells are typically required depending on the redundancy requirements of the end user.

[0023] Current technology for redundant process temperature measurement has some limitations. For example, manufacturing costs increase due to the need for multiple process intrusions (one process intrusion for each thermowell). Maintenance costs will also increase. In addition, due to the distance between multiple process intrusions, it is not possible to accurately measure the temperature at the same point. In addition, an inline flow meter may require a certain length of straight obstruction - less pipe on the upstream and downstream sides. Providing a thermowell on the upstream side of the flow meter increases the length. Another limitation of current technology is that the end user may have to spend more (2x-3x) for redundant temperature measurement (the cost of multiple thermowells and temperature elements). Finally, in the example of a dual sensor, if any sensor in the dual sensor system fails, the entire temperature sensor assembly needs to be replaced because the two elements are housed in a single sheath and a single sensor cannot be replaced.

[0024] The embodiments described below generally improve the thermowell design to accommodate multiple (e.g., two, three, or more) temperature sensor assemblies instead of a single temperature sensor assembly. Another aspect of the embodiments disclosed herein is an improved terminal block design that will allow each temperature sensor assembly to be replaced individually. It is believed that the embodiments described below will save costs because redundant temperature measurement installations can be performed in a single process intrusion, and the total cost of the redundant process temperature measurement system will be lower than the cost of purchasing multiple units.

[0025] Figure 1 Schematic diagram of a triple redundant temperature measurement system according to the prior art. Figure 1 As shown, the sensor assembly housed in three thermowells 100, 102, 104 is coupled to three corresponding temperature transmitters 106, 108, and 110. Each thermowell generally includes an elongated cylindrical probe 112 that is configured to be exposed to a process fluid. As shown, each thermowell may also include a process mounting flange 114 so that the flange 114 may be mounted to an associated or corresponding flange on a process pipe. However, other types of process mounting seats (such as threaded connectors and welded connectors) may also be used with thermowells, and the embodiments described below are applicable to all such process mounting techniques.

[0026] Figure 1The triple redundant system shown requires three different process intrusions to mount the three different thermowells 100, 102, 104. Each sensor assembly generally includes a housing or terminal block 116 from which wiring 118 is coupled to the electronics within the respective temperature transmitter 106, 108, 110. The electronics within each temperature transmitter generally includes measurement circuitry configured to obtain an electrical indication of a temperature sensitive element relative to the temperature sensor assembly, processing circuitry configured to calculate the process temperature based on the measured signal, and communication circuitry configured to transmit the process fluid temperature signal to a control room, as schematically indicated by reference numeral 120.

[0027] Figure 2 1 is a schematic diagram of a triple redundant process temperature sensing system according to an embodiment of the present invention. System 150 includes a single thermowell 152 configured to accommodate or mount multiple temperature sensor assemblies. As shown, thermowell 152 also includes process mounting flange 114. However, since a single thermowell is used, only a single process intrusion is required to employ triple redundant temperature sensing system 150. Figure 2 As shown, the redundant sensors housed in a single thermowell 152 are coupled to a modified housing 154 that includes separate cable entries for the cables of each temperature sensor assembly. Thus, three different temperature transmitters 106, 108, and 110 can be coupled to respective temperature sensor assemblies disposed within a single thermowell 152.

[0028] Figure 3 1 is a block diagram of an improved process temperature measurement system according to an embodiment of the present invention. System 170 generally includes an electronics housing 172 that houses a controller 174, measurement circuitry 176, a power module 178, communication circuitry 180, and a terminal block 182. Figure 3 In the illustrated embodiment, the housing 172 is directly coupled to the thermowell 174. However, those skilled in the art will recognize that the housing 172 may be spaced apart from the thermowell 174 and coupled to the thermowell 174 via suitable conductors. Figure 3As shown, the thermowell 174 is mounted with a plurality of temperature sensor assemblies 184, 186. Each of the temperature sensor assemblies 184, 186 is electrically coupled to the measurement circuit 176 via the terminal block 182. The measurement circuit 176 generally includes any suitable circuit arrangement that can engage each of the temperature sensor assemblies 184, 186 to measure their temperature-sensitive electrical characteristics. The measurement circuit 176 may include one or more 'analog-to-digital' converters and suitable switching circuits, such as a multiplexer. In addition, the measurement circuit 176 may also include suitable linearization and / or amplification circuits. The measurement circuit 176 generally provides a digital indication of the electrical characteristics of the temperature sensor assemblies 184, 186 to the controller 174. In one embodiment, the controller 175 may be a microprocessor or microcontroller, or any other suitable circuit that can receive a digital indication from the measurement circuit 176 and perform one or more suitable calculations to provide a process fluid temperature output.

[0029] The communication circuit 180 is coupled to the controller 174 and allows the temperature measurement system 170 to transmit the process fluid temperature output via the process communication loop using a process communication loop protocol. Suitable examples of process communication loop protocols include 4-20mA protocol, FOUNDATION TM Fieldbus protocols and WirelessHART (IEC63591).

[0030] The temperature measurement system 170 also includes a power supply module 178 that provides power to all components of the system as indicated by arrow 188. or FOUNDATION TM In embodiments where a wired process communication loop is used (e.g., a fieldbus process communication segment), the power module 178 may include appropriate circuitry to condition the power received from the loop to operate the various components of the system 170. Thus, in such wired process communication loop embodiments, the power module 178 may provide appropriate power conditioning to allow the entire device to be powered by the loop to which it is coupled. In other embodiments, when wireless process communication is used, the power module 178 may include a power source (such as a battery) and appropriate conditioning circuitry.

[0031] Figure 4is a schematic cross-sectional view of an improved thermowell according to an embodiment of the present invention. Thermowell 200 is generally configured to accommodate multiple temperature sensor assemblies 202, 204 therein. Suitable thermowells can be used or otherwise modified according to the various embodiments described herein to accommodate multiple temperature sensor assemblies. For example, a bar stock thermowell with a flange process connection can be used for this purpose. Two or three holes or holes with a diameter sufficient to accommodate a 3mm or 6mm outer diameter temperature sensor assembly can be made in the thermowell as needed. Although the various descriptions and examples set forth below will provide certain dimensions, these are provided for illustrative purposes only and are not intended to limit the embodiments described herein.

[0032] exist Figure 4 In the illustrated embodiment, the thermowell 200 includes a cylindrical portion 206 having a diameter of approximately 22 mm that is secured to a process mounting flange 208. In one embodiment, the cylindrical portion 206 can be welded to the process mounting flange 208. In one example, the process mounting flange 208 is a 1 inch ISO flange that includes a plurality of holes through which mounting bolts can pass to mount the thermowell to the process intrusion. Thermowell 200 also includes or is coupled to a 1 inch socket 210 that is internally threaded and configured to receive a 1 inch fitting 212. As shown in FIG. Figure 4 As shown, a 1-inch union 214 is used to couple the 1-inch union 212 to a 1-inch union 216. As shown, the 1-inch union 216 engages an internally threaded hole 218 of the housing 220, thereby coupling the housing 220 to the thermowell 200. Within the housing 220, a terminal block 222 receives individual conductors from each temperature sensor assembly 202, 204.

[0033] Figure 5 is a schematic cross-sectional view of a triple redundant temperature sensor thermowell assembly according to an embodiment of the present invention. Figure 5 The embodiments shown in Figure 4, except that the pipe 242 is arranged around the cylindrical member 252, and the cylindrical member 252 accommodates three different temperature sensor assemblies 246, 248 and 250. The assembly 240 generally includes a pipe portion 242 mounted to a process mounting flange 244. In the illustrated example, the process mounting flange 244 is a 1 inch ANSI ISO flange, however, any suitable process mounting flange may be used. The process mounting flange 244 is sealingly coupled to the pipe 242 so that when the pipe 242 is exposed to the process fluid and the flange 244 is mounted to the process, the process fluid is sealed within the process and does not leak at the process intrusion. In the illustrated example, the pipe 242 has an outer diameter of 1 inch. The system 240 includes three different temperature sensor assemblies 246, 248 and 250. In the illustrated example, each of the temperature sensor assemblies 246, 248 and 250 has an outer diameter of 3 mm, which is received within the bore of the cylindrical member 252. In addition, as shown Figure 5 As shown, the cylindrical member 252 has a suitable outer diameter (shown as 22 mm) so that it can pass through the inner diameter of the pipe 242 (shown as 28 mm). The cylindrical member 252 is preferably made of a metal suitable for immersion in a process fluid (gas, liquid, or combination). Of course, those skilled in the art will recognize that these various dimensions can be changed according to the embodiments described herein.

[0034] Figure 6A-6F Various top views of a cylindrical member configured to receive a plurality of temperature sensor assemblies in a thermowell are shown according to embodiments described herein.

[0035] Fig. 6A A cylindrical member 252 is shown having a pair of holes 260, 262, each having an inner diameter of 6.5 mm. As shown, each of the holes 260, 262 is approximately equidistant from the center of the cylindrical member 252. In this manner, each of the holes 260, 262 is spaced approximately the same distance from the outer diameter 264 of the cylindrical member 252. This arrangement helps ensure consistent measurements of the temperature sensor assembly within the holes 260, 262.

[0036] Figure 6B A cylindrical member 252 is shown with holes 266, 268 each having an inner diameter of 4 mm. These inner diameters are configured to receive a temperature sensor assembly having an outer diameter of 3 mm. Figure 6B As shown, the outer diameter of the cylindrical member 252 is approximately 22 mm.

[0037] Figure 6C2 is a top view of the cylindrical member 252, showing three temperature sensor assembly holes 270, 272 and 274, each of which has a diameter of approximately 6.5 mm and is configured to receive a temperature sensor assembly having an outer diameter of 6 mm. Figure 6C As shown, hole 272 is substantially located at the center of cylindrical member 252, and holes 270 and 274 are approximately equidistant from hole 272. Figure 6C In the example shown, the outer diameter of the cylindrical member 252 is approximately 28 mm.

[0038] Fig.6D FIG. 2 is a top view of the cylindrical member 252, showing three temperature sensor assembly holes 276, 278 and 280. As can be seen, the arrangement of the holes 276, 278 and 280 is similar to Figure 6C However, the diameters of holes 276, 278 and 280 are smaller than Figure 6C In the example shown, holes 276, 278, and 280 have a hole diameter of approximately 4 mm and are configured to receive a temperature sensor assembly having an outer diameter dimension of 3 mm.

[0039] Fig. 6E 2 is a top view of a cylindrical member 252 having three temperature sensor assembly holes 282, 284, and 286. As shown, holes 282, 284, and 286 have a diameter of approximately 6.5 mm and are sized to slidably receive a temperature sensor assembly having an outer diameter of 6 mm. Fig. 6E As shown, each of the holes 282, 284, and 286 are spaced substantially equidistant from the center of the cylindrical member 252 and are spaced at approximately regular angular intervals (approximately 120°).

[0040] Fig. 6F FIG. 2 is a schematic top view of a cylindrical member 252 having three temperature sensor assembly holes 288, 290, and 292. The arrangement of the holes 288, 290, and 292 is similar to Fig. 6E The arrangement shown in is similar, however, the holes 288, 290 and 292 are approximately 4 mm in diameter and are configured to receive a temperature sensor assembly having an outer diameter of 3 mm.

[0041] Fig. 7A is a schematic diagram of an improved terminal block according to an embodiment of the present invention. Typically, the terminal block used in the embodiments herein is modified to facilitate independent sliding of two / three or more temperature sensor assemblies in the thermowell. This allows replacement of each temperature sensor assembly in the event of a failure. Fig. 7AAs shown, the terminal block 300 includes a plurality of holes 302, 304, the size of which is set to allow the temperature sensor assembly to slide in these holes. In addition, suitable terminals 306 are provided for each temperature sensor assembly. In addition, a plurality of screws 308 are used to install the terminal block 300 in the housing.

[0042] Figure 7B-Figure 7E It is intended to illustrate various designs of alignment between the thermowell cylindrical member 252 and the bore for receiving the temperature sensor assembly and the corresponding terminal block hole to allow the temperature sensor assembly mounted in the bore of the cylindrical member 252 to slide independently through the terminal block. Figure 7B-Figure 7E The cylindrical member 252 is shown above the terminal block 300, but this is for illustration purposes only, and in reality the cylindrical member 252 is disposed directly below the terminal block such that the aperture of the cylindrical member aligns with the aperture of the terminal block, thereby allowing individual temperature sensor assemblies to be slidably removed and replaced as needed.

[0043] Fig. 8A and Figure 8B is a schematic top view showing a modified housing according to an embodiment of the present invention. In some examples, the housing of the temperature sensor wiring is modified to allow three cable entries and for mounting a terminal block therein using screws or other means. Fig. 8A and Figure 8B As shown in each of the three different cable entries 310, 312 and 314. Furthermore, in the illustrated embodiment, the cable entries are spaced apart at an angle of approximately 120°. Furthermore, as can be seen, each cable entry 310, 312, 314 is substantially aligned with various terminals of a selected one of the three different temperature sensor assemblies. Specifically, referring to Fig. 8A , terminals 316, 318, and 320 are located close to the cable entry 312 so that the conductor 322 extending from the terminals 316, 318, and 320 through the cable entry 312 can pass directly through the cable entry without having to pass through other conductors. This simplifies the wiring and / or replacement tasks for field technicians. Note that although the various terminals shown have three terminals for each temperature sensor, this is to support three-wire RTDs. Two-wire RTDs and thermocouples only require two terminals each.

[0044] Fig. 9 340 is a schematic diagram of logic for measuring multiple process fluid temperature values ​​using multiple temperature sensor assemblies according to an embodiment of the present invention. Logic 340 may be directly embodied in controller 174 (e.g., Figure 3340 ) or any other suitable logic device of the temperature transmitter. The analog inputs 342, 344 and 346 correspond to the measured electrical characteristics of each of the three different temperature sensor assemblies. As shown, each of the analog inputs 342, 344 and 346 is provided to the corresponding inputs 348, 350 and 352 of the logic block 354. In addition, an input selection block 356 is provided, in which the mode of the logic 340 can be selected between automatic 358 or manual 360. The logic block 354 provides an output 362, which is connected to the process variable output variable block 364 and can be adjusted based on the process variable proportional block 366. The logic 340 allows the controller to determine the process variable by sending multiple independent signals relative to the readings of the individual temperature sensor assemblies, and / or to provide a combined temperature sensor measurement based on a combination of signals using suitable voting logic, weighting or other appropriate programming techniques.

[0045] Fig.10 4 is a logic diagram of a safety interlock in a safety instrumented system. Logic 400 includes three analog input blocks 402, 404, and 406. These analog inputs are provided to corresponding inputs 408, 410, and 412 of processing logic 414. Processing logic 414 may have additional inputs based on system status, such as bypass status 416, system startup status 418, optional status 420, and num_to_trip status 422. Based on the analog inputs and one or more status inputs, processing logic 414 provides an output indicating process temperature at logic block 424. The output may be a series of signals indicating the readings of various temperature sensor components, and / or combinations thereof.

[0046] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

1. A thermocouple sleeve, comprising: a process mount configured to mount to a process intrusion; as well as A cylindrical member is configured to be exposed to a process fluid, the cylindrical member having a plurality of apertures extending therein, each aperture configured to receive a separate temperature sensor assembly.

2. The thermowell according to claim 1, wherein: The process mount includes a mounting flange coupled to the cylindrical member.

3. The thermowell of claim 1, wherein: The cylindrical member is formed of metal.

4. The thermowell of claim 1, wherein: The plurality of holes includes three different holes.

5. The thermowell of claim 1, wherein: The plurality of holes are equally spaced from a center of the cylindrical member.

6. The thermowell of claim 1, wherein: One of the plurality of holes is located at the center of the cylindrical member.

7. The thermowell of claim 1, wherein: The plurality of holes are regularly spaced apart from one another.

8. The thermowell of claim 1 further comprising a housing coupled to the thermowell, the housing having a terminal block therein.

9. The thermowell of claim 8, wherein: The terminal block includes a plurality of holes, each hole being configured to allow a temperature sensor assembly disposed in the thermowell to slide therethrough.

10. The thermowell of claim 8, wherein: The housing includes a plurality of cable entryways, each cable entryway providing a cable to a corresponding temperature sensor assembly disposed within the thermowell.

11. The thermowell of claim 1 further comprising a temperature sensor assembly disposed in each of the plurality of holes.

12. A redundant process temperature measurement system, the system comprising: Thermowells, including: a process mount configured to mount to a process intrusion; and a cylindrical member configured to be exposed to a process fluid, the cylindrical member having a plurality of holes extending therein, each hole housing a temperature sensor assembly, A plurality of temperature transmitters are each operably coupled to a respective temperature sensor assembly, each temperature transmitter being configured to provide a temperature measurement based on a measurement of an electrical characteristic of the respective temperature sensor assembly.

13. The system of claim 12, wherein: Each temperature transmitter is operably coupled to a corresponding temperature sensor assembly via a terminal block.

14. The system of claim 13, wherein: The terminal block includes a plurality of holes therethrough, each hole being configured to slidably pass through a corresponding temperature sensor assembly.

15. The system of claim 12, wherein: Each temperature sensor assembly is formed of a temperature sensitive element disposed within a metal sheath, and wherein the metal sheath is disposed within one of the plurality of holes.

16. The system of claim 12, wherein: Each temperature transmitter includes an electronics housing that houses: Measurement circuitry is operably coupled to each temperature sensor assembly.

17. The system of claim 16, wherein: The electronics housing is spaced apart from the thermowell.

18. The system of claim 12, wherein: The plurality of holes includes three holes in the cylindrical member.

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