阅读说明：本技术 热电偶套管中的振动检测 (Vibration detection in thermowell ) 是由 劳伦·迈克尔·安格斯塔德 杰森·哈洛德·鲁德 于 2014-03-14 设计创作，主要内容包括：一种传感器系统包括过程换能器、无动力振动传感器和过程变送器。所述过程换能器设置在热电偶套管内并且配置用于产生第一传感器信号。所述无动力振动传感器配置用于产生反映所述热电偶套管的振动的第二传感器信号。所述过程变送器配置用于接收、处理和发送所述第一和第二传感器信号。(A sensor system includes a process transducer, an unpowered vibration sensor, and a process transmitter. The process transducer is disposed within the thermowell and is configured to generate a first sensor signal. The unpowered vibration sensor is configured to generate a second sensor signal reflecting a vibration of the thermowell. The process transmitter is configured to receive, process and transmit the first and second sensor signals.)

1. A sensor system, comprising:

a process transducer disposed within the thermowell and configured to generate a first sensor signal;

an unpowered vibration sensor comprising a vibration energy harvester and signal conditioning electronics, the vibration energy harvester configured to generate an alternating current from vibrations proximate the thermowell, the signal conditioning electronics configured to generate a second sensor signal from the alternating current that reflects vibrations of the thermowell, wherein the second sensor signal provides a measure of proximity between a frequency of vibration of the thermowell and a resonant frequency of the thermowell; and

a process transmitter configured to receive, process and transmit the first and second sensor signals.

2. The sensor system of claim 1, wherein the process transducer is configured to sense a parameter of a process fluid, and wherein the first sensor signal reflects the parameter of the process fluid.

3. The sensor system of claim 2 wherein the process transducer is a temperature sensor and the first sensor signal is a temperature signal.

4. The sensor system of claim 2, wherein impingement of the process fluid on the thermowell causes vibration of the thermowell.

5. The sensor system of claim 1 wherein the vibration energy harvester and the thermowell have the same resonant frequency.

6. The sensor system of claim 1 wherein the second sensor signal is a processed output voltage amplitude of the vibration energy harvester.

7. The sensor system of claim 1, wherein the signal conditioning electronics comprise a rectifier, a smoothing filter, and a voltage divider.

8. The sensor system of claim 1, further comprising a control or monitoring system to which the process transmitter transmits the first and second sensor signals.

9. The sensor system of claim 8, wherein the process transmitter or the control or monitoring system flags an alarm condition based on the second sensor signal.

10. The sensor system of claim 9, wherein the process transmitter or the control or monitoring system flags the alarm condition in response to the second sensor signal rising or remaining above a threshold value.

11. A process system for monitoring a process fluid, the process system comprising:

a thermowell extending into the process fluid;

a process transducer housed in said thermowell and configured to generate a process signal reflective of a characteristic of said process fluid;

an unpowered vibration sensor located proximate to the thermowell and configured to generate a vibration signal reflecting vibrations proximate to the thermowell, wherein the unpowered vibration sensor comprises:

a vibrational energy harvester configured to generate an alternating current in accordance with vibrations proximate to the thermowell; and

signal conditioning electronics configured to generate an output signal based on the alternating current,

wherein the output signal provides a measure of proximity between a vibration frequency of the thermowell and a resonant frequency of the thermowell; and

a process transmitter configured to receive and process the process signal and the vibration signal.

12. The process system of claim 11, wherein the process transducer is a temperature sensor and the property of the process fluid is a temperature in the process fluid or a temperature change in the process fluid.

13. The process system of claim 11, wherein the process transmitter is configured to flag an alarm condition if the vibration signal rises or remains above a threshold value.

14. The process system of claim 11, wherein the signal conditioning electronics include a full wave rectifier to convert the alternating current to a direct current.

15. The process system of claim 11, wherein the signal conditioning electronics include a capacitor to smooth transient signals.

16. The process system of claim 11, wherein the signal conditioning electronics include a voltage divider comprised of a plurality of resistors to scale the output signal.

17. The process system according to claim 11 wherein the vibration energy harvester is tuned to share the same resonant frequency as the thermowell.

18. The process system of claim 11, wherein the unpowered vibration sensor at least partially powers the process transmitter.

19. The process system of claim 11, further comprising a control or monitoring system in communication with the process transmitter to receive process and vibration measurements based on the process signal and the vibration signal, respectively.

20. The process system of claim 11, wherein the unpowered vibration sensor is secured to a rigid connection extending from the process transducer to the process transmitter.

21. The process system of claim 11, wherein the thermowell extends through a process line carrying the process fluid.

Technical Field

The present invention relates generally to process sensor systems and, more particularly, to thermowell sensor housings for fluid sensors in industrial process monitoring systems.

Background

Industrial process transmitter and sensor assemblies are used to sense various characteristics of process fluids flowing through conduits or contained within vessels and to transmit information related to those process characteristics to control, monitoring and/or safety systems remotely located from the process measurement locations. Each process transmitter may be coupled to one or more sensor and/or actuator (activator) assemblies. The sensor assembly may sense a number of process parameters including pressure, temperature, pH, or flow rate. Process transmitters are typically sensor assemblies electrically connected via sensor wires for transmitting current or voltage based analog sensor output signals that reflect (reflecting) at least one such process parameter. Each transmitter reads these sensor output signals and converts them into a measurement of the process parameter. Finally, the transmitter sends the information to the control system.

Sensor assemblies for sensing process fluid temperature and temperature changes typically include at least one temperature sensor enclosed in a thermowell extending into the fluid flow. Thermowells are designed to be in physical contact with a process fluid and shield the temperature sensor from physical damage (e.g., impact, corrosion, etc.) caused by direct contact with the fluid, while effectively conducting heat between the fluid and the temperature sensor. Thermowell reliability is critical in process monitoring because a thermowell that has been broken or damaged can allow leakage of hazardous process fluids and expose delicate and/or expensive sensors to the process fluids. Severe thermowell damage can cause thermowell detachment (detach), which can cause further damage to downstream equipment.

Vibration is a major cause of damage to the thermowell and enclosed temperature sensor, and achieving vibration damping and prevention is critical to the continued operation of the sensor assembly in the process fluid. The impingement (impingement) of the process flow on the thermowell causes turbulence (turbulences) in the process fluid via vortices. This turbulence has a structure consisting ofCharacteristic wake-up frequency f determined by multiple factors_wThe factors include the geometry of the thermowell and the conditions and flow rate of the process fluid. When the wake-up frequency f_wApproaching the natural resonant frequency f of the thermowell_rAt the same time, eddy currents can cause detrimental thermowell vibration. Therefore, the expected wake-up frequency f is often utilized_wThermowell design to avoid f_w＝f_rA resonance condition. However, during the thermowell's life cycle, changes in process conditions can cause f_wAnd/or f_rIncreases the likelihood of a resonance condition.

Disclosure of Invention

The present invention relates to a sensor system including a process transducer, an unpowered vibration sensor, and a process transmitter. The process transducer is disposed within the thermowell and is configured to generate a first sensor signal. The unpowered vibration sensor is configured to generate a second sensor signal reflecting a vibration of the thermowell. The process transmitter is configured to receive, process and transmit the first and second sensor signals.

Drawings

FIG. 1 is a simplified diagram of a process monitoring or control system according to the present invention.

FIG. 2 is a circuit diagram of an energy harvesting vibration transducer for use in the process monitoring and control system of FIG. 1.

FIG. 3 is a plot of voltage versus frequency illustrating the effect of vibration at the resonant frequency of the energy harvesting vibration sensor of FIG. 2.

Detailed Description

FIG. 1 is a simplified cross-sectional view of one embodiment of a process system 10 (a system for monitoring and/or energizing an industrial fluid process). In the depicted embodiment, process system 10 includes process transmitter 12, process piping 14 (with flanged connection 16), thermowell 18, process transducer 20, extension 22, vibration sensor 24, and control or monitoring system 26.

The process pipeline 14 carries a process stream F for an industrial process. The process line 14 may be, for example, a pipe (tube) or conduit (duct) configured to carry a fluid, such as oil slurry, viscous manufacturing material, gas, or liquid. Process line 14 includes at least one flanged connection 16 to facilitate connection of a flanged mounting device to measure at least one characteristic of process stream F, such as temperature, flow rate, pressure, or pH. In the illustrated embodiment, flanged connection 16 provides an attachment point (attachment point) for thermowell 18 and process transducer 20, and provides an aperture in the process piping through which thermowell 18 and process transducer 20 can extend into process fluid F. The process fluid F may include, for example, chemicals or particulates that damage or otherwise are detrimental to the operation of the process transducer 20.

Thermowell 18 is a protective body around process transducer 20 within process fluid F. Thermowell 18, which may be, for example, a hollow conical sheath, is secured to flanged connection 16 and disposed through flanged connection 16 into process fluid F. Thermowell 18 is formed of a material having a relatively high thermal conductivity, such as brass, steel, or copper, in order to efficiently conduct heat from process fluid F to process transducer 20. Thermowell 18 has a characteristic natural resonant frequency f determined by its geometry and structure_r。

In the depicted embodiment, process transducer 20 is a temperature sensor probe encased in thermowell 18 and is capable of generating a process signal that reflects at least one of a temperature or a change in temperature of process fluid F proximate flange connection 16. The process transducer 20 can be, for example, a thermocouple, a resistance temperature detector, or a thermistor. Thermowell 18 protects process transducer 20 from process fluid F, prevents damage and increases the life expectancy of process transducer 20. Thermowell 18 also forms a fluid seal with flanged connection 16, thereby preventing leakage of process fluid F near process transducer 20. The thermowell 18 may be bolted or clamped to the flange connection 16, for example. In some embodiments, process system 10 may include additional sealing components (gaskets, O-rings, etc.) disposed between thermowell 18 and flange connection 16 for improving a fluid seal.

Process transmitter 12 is a signal processing and/or transmitting device that receives and processes signals from process transducer 20 to produce at least one measurement of a parameter of process fluid F. Process transmitter 12 can be, for example, a logic function device configured to extract a process measurement from an electrical signal received from process transducer 20. Process transmitter 12 can also include diagnostic or fault reporting components and can include persistent memory to store measurement, control and diagnostic data related to process fluid F.

In the depicted embodiment, process transducer 20 couples to process transmitter 12 via extension 22. As depicted, extension 22 is a rigid coupling that supports process transmitter 12 and carries signal wires that connect process transmitter 12 to process transducer 20. Although process transmitter 12 is shown mounted on extension 22 in spaced relation to process transducer 20, some embodiments of process system 10 may utilize a process transmitter mounted directly to process piping 14, flanged connection 16, or process transducer 20, or remotely. Process transmitter 12 can include an internal power source and/or receive power from an external grid connection or energy harvesting device. In addition, as described in more detail below with reference to FIGS. 2 and 3, process transmitter 12 can receive supplemental power from vibration sensor 24.

Vibration sensor 24 is a vibration-voltage transducer with a tunable vibration energy harvester having a resonant frequency f with thermowell 18_rClosely matched natural resonant frequency f_s. In some embodiments, the natural resonant frequency f of the vibration sensor 24 may be tuned during manufacturing, for example, by changing the tip mass or arm length of the vibrating arm of such a vibration energy harvester_s. In other embodiments, the natural resonant frequency f of the vibration sensor 24_sMay be configurable tuned, such as at a mounting location in process system 10. Although vibration sensor 24 is described as being positioned on extension 22, alternative embodiments of process system 10 can include vibration sensor 24 positioned elsewhere, such as directly mounted to thermowell 18, process transducer 20, or process transmitter 12. Generally, vibration sensors24 are positioned proximate thermowell 18 such that eddy currents from thermowell 18 generate an output voltage from vibration sensor 24, as described below with reference to fig. 2 and 3. The magnitude of the voltage generated by the vibration sensor 24 corresponds to approximately f_wTo f_s. Because of the natural resonant frequency f_sAnd f_rClosely matching, the magnitude of the voltage output of the vibration sensor 24 constitutes the sensor signal, approximating f_wReflected as the resonance condition of thermowell 18. Extension 22 can, for example, carry a signal wire that transmits this sensor signal from vibration sensor 24 to process transmitter 12.

Process transmitter 12 communicates with a control or monitoring system 26 (a central processing, data archiving and/or monitoring system at a control or monitoring station) that monitors a plurality of process transmitters 12. Process transmitter 12 transmits process measurements to control or monitoring system 26, including temperature measurements obtained from process transducer 20 and vibration measurements obtained from vibration sensor 24. These process measurements can be, for example, digitized copies (counters) of the raw voltage and/or current signals from process transducer 20 and vibration sensor 24 produced by process transmitter 12. Although process system 10 illustrates only a single process transmitter 12 coupled to control or monitoring system 26, some embodiments of process system 10 can include multiple process transmitters 12 sharing a common control or monitoring system 26. Similarly, while process transmitters are described as being attached to only one vibration sensor 24 and one process transducer 20, alternative embodiments of process system 10 can include multiple transducers and/or vibration collectors that communicate with a single process transmitter 12. FIG. 1 illustrates a wired connection between process transmitter 12 and control or monitoring system 26. More generally, however, process transmitter 12 can communicate with control or monitoring system 26 via a multi-wire cable, optical cable, or wireless connection. In some embodiments, process transmitter 12 can communicate with control or monitoring system 26 via a wireless connection operating over the WirelessHART protocol or a similar transmit/receive protocol. In addition to the process and vibration measurements, process transmitter 12 can provide diagnostic or log information and fault alarms to control or monitoring system 26. Similarly, control or monitoring system 26 can issue data, reset or calibration requests, or other instructions to process transmitter 12.

Process line 14 carries process fluid F through thermowell 18 which encloses and does not make direct contact with process fluid F, while making indirect thermal contact with process transducer 20. As process fluid F passes around thermowell 18, impingement of thermowell 18 on process fluid F causes turbulent flow downstream of thermowell 18. This eddy current generation has a characteristic wake-up frequency f as described above_wOf the fluid flow. By matching thermowell 20 to 18) and the resonant frequency of vibration sensor 24, process system 10 allows vibration sensor 24 to produce a measurement of the resonance between turbulent process fluid F and thermowell 20, thereby enabling process transmitter 12 and/or control or monitoring system 26 to identify when thermowell 20 experiences or is in close proximity to correspond to F_w＝f_r＝f_sPotentially damaging resonance conditions. In this manner, process system 10 is able to detect a fault in thermowell 20 before thermowell 20 completely fails.

FIG. 2 is a schematic diagram of vibration sensor 24, which includes a vibration energy harvester 100 (with signal voltage V)_s) Rectifier 102 (with diode D)₁、D₂、D₃And D₄) A smoothing filter 104 (with a capacitor C), a voltage divider (with a resistor R)₁And R₂) And an output terminal 108 (having an output voltage V)_out). In general, any unpowered device whose output is proportional to vibration may be substituted for vibration energy harvester 100. As described above with reference to fig. 2, vibration energy harvester 100 is selected or tuned such that the resonant frequency f of vibration energy harvester 100_sResonant frequency f with thermowell 18_rAnd (4) closely matching. The resonant frequency f may be calculated or empirically tested, for example, according to ASME PTC19.3TW or similar industry standards_r. As is well known in the art, for example, by varying the vibration probe within the vibration energy harvester 100The tip mass or arm length to accomplish tuning. Vibration energy harvester 100 generates an Alternating Current (AC) having a period and amplitude corresponding to the mechanical vibrations at vibration sensor 26. The vibration collector 100 is used to have a signal voltage V_sThe ac voltage source of (2). Rectifier 102, smoothing filter 104 and voltage divider 106 together form signal conditioning electronics to regulate the voltage according to signal voltage V_SGenerating an output voltage V_out. Rectifier 102 for signal voltage V_sRectified to produce a Direct Current (DC) signal. Rectifier 102 is depicted as having four diodes D₁、D₂、D₃And D₄The full wave four bridge rectifier of (1). Although the described embodiment is simple and cost effective, other types of rectifiers, including half-wave rectifiers and transistor full-wave rectifiers, may be equivalently used. Some embodiments of the vibration sensor 24 may avoid the rectifier 102 and instead quickly sample the AC signal generated by the energy harvester 100. The smoothing filter 104 removes transients from the dc output of the rectifier 102. In the depicted embodiment, the smoothing filter 104 includes a single capacitor C connected to ground. The resulting smoothed dc signal is scaled by voltage divider 106 to produce a normalized output voltage signal V at output terminal 108_out. This output voltage signal V_outFor example, can be digitized by process transmitter 12 (see fig. 1, discussed above) to produce a digital measurement of the resonance near thermowell 18, or can be processed in an analog manner. In some alternative embodiments, V_outOr V_sCan be coupled with the process sensor signal from transducer 20 to allow the combined signal to be received and digitally decoupled at a single terminal of process transmitter 12.

V_outAnd is not a direct measurement of the amplitude of vibration at thermowell 18. On the contrary, due to f_r≈f_sVibration energy harvester 100 will tend to cause signal voltage V at the resonant condition of thermowell 18_s(and corresponding output voltage V)_out) And max. Therefore, V of the vibration sensor 24_outProviding the frequency of vibration of thermowell 18 (consisting essentially ofAt a wake-up frequency f_wEddy current of) and thermowell resonant frequency f_rThe proximity of each other. When f is_wAway from f_rWhen, V_outIs small and there is little risk of detrimental resonance between thermowell 18 and the turbulent flow of process fluid F. When f is_wApproach f_rWhen, V_outRelatively large, corresponding to increased resonance and increased vibration in thermowell 18. Thus, V_outThe larger values of (a) correspond to potentially harmful resonance conditions of thermowell 18. This relationship is discussed in more detail below with reference to fig. 3.

As disclosed in fig. 2, the vibration sensor 24 comprises an unpowered sensor with relatively simple wiring. Because the vibration energy harvester 100 produces an alternating voltage signal that reflects the vibration amplitude of the mechanical vibrations directly from the vibration sensor 24, no supplemental voltage source is required to operate the vibration sensor 24. In some embodiments, additional power from vibration energy harvester 100 can be routed to process transmitter 12 and/or used to power a visual or audio indication indicative of a resonance condition.

FIG. 3 depicts the output voltage V_outAccording to the wake-up frequency f_wExemplary diagram of changes. As described above with reference to FIG. 2, the output voltage V_outAt f_s(the resonant frequency of vibration energy harvester 100). Tuning or selecting vibration energy harvester 100 so that f_s≈f_r. Thus, V_outAt f_w＝f_s≈f_rAt or near a maximum value corresponding to a resonance condition of thermowell 18, potentially producing harmful vibrations in thermowell 18. FIG. 3 illustrates the resonance frequency f_rRelevant resonance range Δ f_r. Resonance range Δ f_rCorresponding to a sufficient proximity of f_rAt a wake-up frequency f that causes unwanted vibrations in thermowell 18_wThe frequency band of (2). In the resonance range Deltaf_rInternally sensed vibration frequency producing output voltage V_out≥V_r(resonance threshold voltage). Process transmitter 12 and/or control or monitoring system 26 can, for example, flag thermowell 18 for useAt the alternative or when V_out>V_rGiving an alarm, especially if V_out>V_rFor a longer period of time. Can be based on machine tolerances, f_sTo f_rTuning accuracy of (1) and (f)_rSelection of the resonant threshold voltage V_r. In alternative embodiments, process transmitter 12 and/or control or monitoring system 26 can be kept out of contact with any resonant threshold voltage V_rRecording the output voltage V in the case of comparison_out。

The vibration sensor 24 provides a compact and inexpensive means for detecting a potentially harmful resonance condition of the thermowell 18 prior to component failure. The thermowells can be coded and/or have a matching resonant frequency (f) with respect thereto for ease of distribution and installation_s≈f_r) Is sold together, allowing the end user to select a vibration sensor 24 suitable for each thermowell 18, rather than individually tuning the vibration sensor 24. The vibration sensor 24 does not draw (draw) external power and therefore does not require power from the process converter 18 or a separate power source. In some embodiments, vibration sensor 24 can power process transmitter 12 in place of a power source, in addition to or in place of power from other sources.

While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.