Thermowell with primary seal verification

Abstract

A thermowell assembly is provided for measuring a temperature of a process fluid. The thermowell assembly includes an elongate thermowell body configured to be mounted to a process vessel and extend into a process fluid contained in the process vessel. The elongate bore extends along a length of the elongate thermowell body from a proximal end of the elongate thermowell body proximate a wall of the process vessel to a sealed distal end of the elongate thermowell body located in the process fluid. The side bore extends from an exterior of the thermowell assembly to the elongated bore. The side aperture is located outside the process vessel. The verification valve includes an inlet external to the thermowell assembly coupled to the side bore and further includes an outlet. The verification valve allows an operator to verify the presence of the process fluid in the elongated bore by opening the verification valve and observing the process fluid at the outlet of the verification valve.

Description

[0001] This application is a divisional application of a patent application (filing date November 26, 2018, application number 201811423425.8, invention name “Thermocouple sleeve with primary seal verification”). Technical Field

[0002] The present invention relates to a system for measuring process variables and industrial processes. More particularly, the present invention relates to measuring process temperature using a thermowell extending into a process fluid. Background Art

[0003] Industrial processes are used to produce and manufacture commodities such as oil, chemicals, and paper. In such industrial processes, it is often necessary to measure a process variable, such as the temperature of the process fluid, and use this information to control or otherwise monitor the process. One technique for measuring process temperature is through the use of a process variable transmitter that includes a temperature sensor. The temperature sensor is thermally coupled to the temperature to be measured using a so-called "thermowell" that extends into the process fluid. The process variable transmitter uses the temperature sensor to measure the process temperature and reports this information back to another location, such as a control room.

[0004] A thermowell is typically formed from an elongated thermowell body with a bore extending therethrough. For maintenance or diagnostic purposes, an operator may need to remove a process variable transmitter from the thermowell. It is possible that over the life of the thermowell, the wall of the thermowell may fail, and the bore of the thermowell may fill with process fluid. If the process fluid is under pressure, removing the process variable transmitter may be difficult and may result in loss of process fluid to the environment through the opening in the thermowell. Summary of the Invention

[0005] A thermowell assembly is provided for measuring the temperature of a process fluid. The thermowell assembly includes an elongated thermowell body configured to be mounted to a process vessel and extend into a process fluid contained within the process vessel. An elongated bore extends along the length of the elongated thermowell body from a proximal end of the elongated thermowell body, adjacent a wall of the process vessel, to a sealed distal end of the elongated thermowell body, located within the process fluid. A side port extends from an exterior of the thermowell to the elongated bore. The side port is located exterior of the process vessel. A verification valve includes an inlet on the exterior of the thermowell assembly coupled to the side port and further includes an outlet. The verification valve allows an operator to verify the presence of process fluid in the elongated bore by opening the verification valve and observing the process fluid at the outlet of the verification valve.

[0006] The present invention summary and abstract are provided to introduce some concepts in a simplified form, which are further described in the detailed description below. The present invention summary and abstract are not intended to identify key features or essential features of the claimed subject matter, nor are they intended to be used as an aid in determining the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a simplified diagram illustrating an industrial process having a process variable transmitter coupled to a thermowell for measuring the temperature of a process fluid.

[0008] Figure 2A is a side cross-sectional view of one example configuration of a thermowell assembly including a proof valve.

[0009] Figure 2B is a side cross-sectional view of another example configuration of a thermowell assembly including a proof valve.

[0010] Figure 2C is a side cross-sectional view of another example configuration of a thermowell assembly including a proof valve.

[0011] Figure 3A is a side cross-sectional view of a sensor assembly including a verification valve constructed according to another example.

[0012] Figure 3B Assembled with thermowell Figure 3A A side cross-sectional view of the sensor assembly.

[0013] Figure 4 is a simplified block diagram of the circuitry in a process variable transmitter. DETAILED DESCRIPTION

[0014] A thermowell assembly is provided that allows verification of the integrity of a thermowell's primary seal. This allows an operator to verify the integrity of the primary seal before accessing a sealed sensing element located in or near the proximal end of the thermowell. If the sealed sensing element is accessed without verifying the integrity of the primary seal, an uncontrolled release of process fluid could occur if the thermowell's primary seal has been compromised.

[0015] Figure 1 FIG1 is a simplified block diagram illustrating an industrial process control or monitoring system 100 including a process variable (temperature) transmitter 102. Transmitter 102 is mounted to process piping 104, which contains process fluid 106. Process piping 104 is one example of a process vessel. Another example is a container or tank containing the process fluid.

[0016] Temperature transmitter 102 includes a housing 108 coupled to a thermowell assembly 110 via a sensor adapter or assembly 111. Temperature transmitter 102 includes a temperature sensor 202, which is carried by sensor adapter 111 and thermally coupled to thermowell assembly 110. Electronics within housing 108 are coupled to temperature sensor 202 and used to measure the temperature of process fluid 106. Information related to this temperature is transmitted to a remote location 112, such as a process control room, modeled as a resistor 114 and a voltage source 116. Communication can occur via, for example, a two-wire process control loop 118, where the same two wires can be used to power temperature transmitter 102 and transmit information. An example of a two-wire process control loop is one operating according to the HART® communication standard, where current is carried on process control loop 118. The analog value of the current can be modulated by transmitter 102 to represent a process variable, such as a measured variable. Additionally, digital information may be modulated on top of the analog current levels to convey additional information to or from the process variable transmitter 102. Other types of process control loops 118 may also be used, including wireless process control loops, such as those compliant with WirelessHART® (IEC 62591).

[0017] exist Figure 1 , a thermowell assembly 110 is shown including an elongated thermowell body 120 that is mounted to a process vessel 104 using a mounting plate 122. As will be described in greater detail below, a verification valve 124 is provided for verifying that the primary seal provided by the elongated thermowell body 120 is intact.

[0018] Figure 2A 、 2B 2C are side cross-sectional views illustrating example embodiments of thermowell assembly 110, however, the present invention is not limited to these particular configurations. Figure 2A 、 2B In Figures 2 and 2C, thermowell assembly 110 includes an elongated bore 140 extending from a proximal end 142 of elongated thermowell body 120 into elongated thermowell body 120 to a sealed distal end 144. Wall 146 of elongated thermowell body 120 provides a primary seal to prevent process fluid from entering elongated bore 140. Sensor assembly 111 provides a secondary seal to prevent fluid from entering the environment in the event of a loss of containment in the primary thermowell.

[0019] like Figures 2A-2CAs shown, a side port 150 extends from the exterior of the elongated thermowell body to the elongated bore 140. The side port 150 is positioned along the length of the elongated thermowell body 120 so that it is located outside of any process vessel in which the elongated thermowell body is mounted. The verification valve 124 is sealably coupled to the side port 150 and includes an inlet 152 coupled to the side port 150. The verification valve 124 also includes an outlet 154. A valve stem 156 is provided so that the valve stem 156 can be rotated by an operator to open or close the connection between the inlet 152 and the outlet 154. Note that in Figure 2B In the configuration of FIG. 1 , the thermowell assembly 110 includes the following: Figure 1 Mounting plate 122 is shown.

[0020] Figure 3A is a side cross-sectional view of a sensor adapter 111 according to another example embodiment. Figure 3B FIG is a side cross-sectional view of the sensor adapter 111 assembled with the thermowell body 120. Figure 3A and 3B As shown, temperature sensor 202 includes wires 170 that are coupled to transmitter electronics to provide a signal related to the sensed temperature to the electronics. Sensor adapter 111 includes a threaded portion 172 that is threadedly received within a threaded portion of thermowell body 120. Temperature sensor 202 extends into elongated bore 140 of thermowell body 120. In this configuration, side port 150 is coupled to elongated bore 140 through body 176 of sensor assembly 111. Figure 3A and 3B The configuration shown in allows a conventional thermowell assembly to be retrofitted with a verification valve 124 by using a modified sensor assembly 111 .

[0021] Figure 4FIG2 is a simplified block diagram of transmitter circuitry 200 housed in transmitter housing 108. Circuitry 200 includes a temperature sensor 202, which is thermally coupled to process fluid 106 via thermowell assembly 110. The temperature sensor can be based on any technology, such as an RTD sensor, a thermistor, a thermocouple, a semiconductor-based sensor, an infrared sensor, or some other technology. Sensor 202 is an example of a sealed sensing element and can be located in or near bore 140 of thermowell body 120. The output of temperature sensor 202 is received by analog-to-digital converter 204, which provides a digital output related to the sensed temperature to microprocessor 206. Microprocessor 206 operates according to instructions stored in memory 208 and at a speed determined by clock 210. Memory 208 can also be used to store variables or other parameters as needed. Microprocessor 206 provides an output related to the sensed temperature to input / output circuitry 212. Input / output circuitry 212 provides an output related to this information on industrial process control loop 118. For example, an analog current of level 1 and controlled between 4 and 20 mA may be used to represent the sensed temperature. As discussed above, digital outputs and wireless outputs may also be used. In one configuration, power is received from loop 118 and used to partially or fully power circuit 200.

[0022] In operation, an operator can check or verify the integrity of the primary seal provided by the wall 146 of the elongated thermowell body 120 by opening the verification valve 124 using the valve stem 156. If the valve 124 is open and process fluid flows into the inlet 152, through the valve body, and out the outlet 154, the operator will know that the primary seal has been breached. The valve 124 can then be closed while the process is shut down, allowing the failed thermowell assembly 110 to be replaced. If no process fluid is observed, the primary seal can be assumed to be intact, and the transmitter housing 108 can be removed as needed.

[0023] In one example construction, Figure 4 An optional pressure sensor or pressure switch 220, shown in FIG, is disposed in or otherwise fluidly coupled to the side port 150. This can provide a signal to the transmitter electronics 200 that the primary seal has failed and be used to provide a warning. Similarly, the sensor 220 can be disposed at the outlet 154 and used to detect process fluid or pressure from within the elongated bore 140. In another example configuration, the inlet 152 can include Figures 2A-2C And an optional coating or other surface 222 shown in 3B that changes color or shape when exposed to stress due to failure of the primary seal. In this configuration, the valve can be an optional component.

[0024] 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 thermowell assembly for measuring the temperature of a process fluid, characterized in that: The thermowell assembly comprises: an elongated thermowell body configured to be mounted to a process vessel and to extend into the process fluid contained in the process vessel; a sensor assembly attached to the elongated thermowell body; an elongated bore extending from a proximal end of the elongated thermowell body adjacent a wall of the process vessel, along the length of the elongated thermowell body, to a sealed distal end of the elongated thermowell body positioned in the process fluid; a side aperture extending from an exterior of the thermowell assembly, through the sensor assembly, and to the elongated bore, the side aperture being located exterior to the process vessel; and A verification valve has an inlet external to the thermowell assembly coupled to the side port and has an outlet whereby an operator can confirm the presence of process fluid in the elongated port by opening the verification valve and observing process fluid at the outlet of the verification valve.

2. The thermowell assembly according to claim 1, wherein: The side port is coupled to the elongated hole through the body of the sensor assembly.

3. The thermowell assembly according to claim 2, wherein: The side hole has a first hole portion extending perpendicular to the body of the sensor assembly and a second hole portion extending parallel to the body of the sensor assembly.

4. The thermowell assembly according to claim 1, wherein: The side hole extends at an acute angle relative to the elongated hole.

5. The thermowell assembly according to claim 1, wherein: The side hole extends parallel to the elongated hole.

6. The thermowell assembly according to claim 1, wherein: The sensor assembly is threadably received by the elongated thermowell body.

7. The thermowell assembly according to claim 6, wherein: There is a gap between the sensor assembly and the elongated thermowell body, and the side hole is in communication with the elongated hole via the gap.

8. The thermowell assembly according to claim 1, wherein: The sensor assembly includes a temperature sensor thermally coupled to the elongated thermowell body.

9. The thermowell assembly according to claim 1, wherein: The verification valve includes a visual indicator that indicates pressure is present within the elongated bore.

10. The thermowell assembly according to claim 9, wherein: The visual indicator includes a coating on the verification valve or a surface of the verification valve.

11. The thermowell assembly according to claim 9, wherein: The visual indicator changes color or shape in response to applied pressure.

12. A temperature transmitter coupled to a thermowell assembly, characterized in that: The temperature transmitter is a thermocouple well assembly according to claim 1, and the temperature transmitter comprises: a temperature sensor coupled to the elongated thermowell body and configured to measure the temperature of the process fluid; and Transmitter electronics are configured to measure a temperature of the process fluid and provide an output related to the measured temperature.

13. The temperature transmitter according to claim 12, characterized in that: The output is provided on a process control loop.

14. The temperature transmitter according to claim 12, characterized in that: The temperature transmitter also includes a sensor coupled to the side port, the sensor configured to sense pressure in the side port, the sensor configured to provide an output to the transmitter electronics.

15. A method of identifying a failed primary seal in a thermowell assembly, characterized in that: The thermowell assembly is the thermowell assembly of claim 1, the method comprising: opening the verification valve; and Observe process fluid at the outlet of the verification valve.

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