Flow meter primary containment fault detection

Abstract

A flow meter is provided that includes a sensor assembly and meter electronics configured to detect a containment failure within a flow meter case. One or more flow tubes and a drive mechanism are coupled to the one or more flow tubes and oriented to induce a drive mode in the flow tubes. A pair of pick-off sensors are coupled to the flow tubes and configured to measure a vibration response induced by the drive mechanism. At least one strain gauge is inside the case and configured to detect strain. Meter electronics are connected to and in series with the drive mechanism and the at least one strain gauge. The meter electronics are configured to measure a resistance of the strain gauge and compare the resistance to a baseline resistance. A primary containment failure is indicated when the resistance of the strain gauge differs from the baseline resistance by a predetermined amount.

Description

Technical Field

[0001] The embodiments described below relate to vibration meters, and more particularly, to improved vibration flow meters that utilize strain gauge-mediated primary containment detection.

Background Art

[0002] Vibration conduit sensors such as Coriolis mass flow meters and vibration density meters typically operate by detecting the movement of a vibration conduit that houses a flowing material. Characteristics related to the material within the conduit, such as mass flow and density, can be determined by processing measurement signals received from motion transducers associated with the conduit. The vibration modes of a vibrating material filling system are generally affected by the combined mass, stiffness, and damping characteristics of the conduit and the material contained therein.

[0003] It is well known to use vibration flow meters to measure the mass flow and other characteristics of materials flowing through pipelines. For example, vibration Coriolis flow meters are disclosed in U.S. Patent No. 4,491,025 issued to J.E. Smith et al. on January 1, 1985, and also in U.S. Patent No. 31,450 by J.E. Smith dated November 29, 1983. These flow meters have one or more fluid tubes. Each fluid tube configuration of a Coriolis mass flow meter has a set of natural vibration modes that can be simple bending, torsion, radial, transverse, or combined types. Each fluid tube is driven to resonate and vibrate in one of these natural modes. Since the vibration modes are generally affected by the combined mass, stiffness, and damping characteristics of the containing fluid tube and the material contained therein, mass, stiffness, and damping are typically determined during the initial calibration of the flow meter using well-known techniques. A common design vibrates two flow tubes in a single mode shape that can be described as the out-of-phase bending mode of those tubes. This mode is often called the "drive" mode because it is the vibration mode that the drive coil of the meter intentionally excites.

[0004] The material flows into the flow meter from a connected pipeline on the inlet side. The material then exits the flow meter through one or more fluid tubes toward a pipeline connected to the outlet side.

[0005] A driver, such as a voice coil style driver, applies a force to one or more fluid tubes. This force causes one or more fluid tubes to vibrate. When there is no material flowing through the flow meter, all points along the fluid tube vibrate in the same phase. As material begins to flow through the fluid tube, due to Coriolis acceleration, each point along the fluid tube has a different phase relative to other points along the fluid tube. The phase at the inlet side of the fluid tube lags behind the driver, and the phase at the outlet side leads the driver. Sensors are placed at two different points on the fluid tube and generate sinusoidal signals representing the motion of the fluid tube at the two points. The phase difference between the two signals received from the sensors is calculated in units of time.

[0006] The phase difference between two sensor signals is proportional to the mass flow rate of the material flowing through one or more fluid tubes. The mass flow rate of the material is determined by multiplying the phase difference by a flow rate calibration coefficient. The flow rate calibration coefficient depends on the material properties and cross-sectional properties of the fluid tube. One of the main characteristics of the fluid tube that affects the flow rate calibration coefficient is the stiffness of the fluid tube. Before the flow meter is incorporated into the pipeline, the flow rate calibration coefficient is determined by a calibration process. In the calibration process, the fluid is passed through the fluid tube at a given flow rate, and the ratio between the phase difference and the flow rate is calculated. The stiffness and damping characteristics of the fluid tube are also determined during the calibration process, as is commonly known in the art.

[0007] One advantage of the Coriolis flowmeter is that, because there are no moving parts within the vibrating fluid tube, the accuracy of the measured mass flow rate is not significantly affected by wear on the flowmeter's moving parts. The flow rate is determined by multiplying the phase difference between two points on the fluid tube by the flow rate calibration coefficient. The only input is a sinusoidal signal from a sensor indicating the vibration of two points on the fluid tube. The phase difference is calculated from the sinusoidal signal. Since the flow rate calibration coefficient is proportional to the material and cross-sectional properties of the fluid tube, the phase difference measurement and the flow rate calibration coefficient are not affected by wear on the flowmeter's moving parts.

[0008] A typical Coriolis mass flowmeter includes one or more transducers (or pick-off sensors), which are typically used to measure the vibration response of one or more flow conduits and are typically positioned upstream and downstream of the driver. The pick-off sensors are connected to electronic equipment. The equipment receives signals from the two pick-off sensors and processes the signals to derive, among other things, a mass flow measurement.

[0009] Leaky flow conduits and manifolds are potential points of failure in flow meter systems. Automatic detection of such leaks is desirable for troubleshooting systems that are not functioning according to specifications. However, leaks may not be immediately apparent when they occur inside the flow meter case.

[0010] Leak detection systems can offer significant advantages for critical applications. Direct alarms to the system allow for a rapid response to prevent further harm to the environment, installation site, and / or the process itself.

[0011] Historically, such systems utilize pressure transmitters within the flow meter case to detect such problems. Such systems have several drawbacks. Installation is generally complex. Case temperature fluctuations can cause detectable pressure fluctuations that cause the sensor to falsely report leaks. Regulatory approval is more costly and time-consuming once such systems are installed. Integrating them into standard flow meter transmitters, and their ability to power the pressure transmitters while reading the Coriolis signal, is logistically challenging and generally prohibitively expensive.

[0012] The embodiments described below overcome these and other problems and achieve technological advancements. The embodiments described below provide a flow meter that uses strain gauges to detect primary containment faults. Installation is simple, reliable, and less expensive than alternative methods, as existing wiring is utilized. [Overview of the Initiative]

[0013] According to one embodiment, a flow meter is provided that includes a sensor assembly and meter electronics configured to detect a containment fault within a flow meter case. The flow meter comprises one or more flow tubes and a drive mechanism coupled to one or more flow tubes and directed to induce drive-mode vibrations in one or more flow tubes. A pair of pick-off sensors are coupled to one or more flow tubes and configured to measure the vibration response of the flow tubes induced by the drive mechanism. At least one strain gauge configured to detect strain is located inside the case. The meter electronics is connected to the drive mechanism and the at least one strain gauge, and the drive mechanism and the at least one strain gauge are connected in series. The meter electronics is configured to measure the resistance of the strain gauge and to compare the resistance of the strain gauge to a baseline resistance, and the meter electronics is configured to indicate a primary containment fault when the resistance of the strain gauge differs from the baseline resistance by a predetermined amount.

[0014] According to one embodiment, a method is provided for detecting a containment fault in the case of a flow meter having a sensor assembly and meter electronic equipment. The method includes the steps of: using a drive mechanism to vibrate at least one of one or more flow tubes in drive-mode vibration; and using a pair of pick-off sensors to measure the vibration response of the flow tube induced by the drive mechanism. At least one strain gauge is provided inside the case. The drive mechanism and the at least one strain gauge are connected to the meter electronic equipment, and the drive mechanism and the at least one strain gauge are connected in series. The resistance of the strain gauge is measured and compared to the baseline resistance. A containment fault is indicated when the resistance of the strain gauge differs from the baseline resistance by a predetermined amount.

[0015] [Pattern] According to one embodiment, the flow meter includes a sensor assembly and meter electronics configured to detect a containment fault within the flow meter case. The flow meter comprises one or more flow tubes and a drive mechanism coupled to one or more flow tubes and directed to induce drive-mode vibrations in one or more flow tubes. A pair of pick-off sensors are coupled to one or more flow tubes and configured to measure the vibration response of the flow tubes induced by the drive mechanism. At least one strain gauge configured to detect strain is located inside the case. The meter electronics is connected to the drive mechanism and the at least one strain gauge, and the drive mechanism and the at least one strain gauge are connected in series. The meter electronics is configured to measure the resistance of the strain gauge and to compare the resistance of the strain gauge to a baseline resistance, and the meter electronics is configured to indicate a primary containment fault if the resistance of the strain gauge differs from the baseline resistance by a predetermined amount.

[0016] Preferably, the meter electronics are configured to trigger an alarm when the resistance of the strain gauge differs from the baseline resistance by a predetermined amount.

[0017] Preferably, at least one strain gauge is coupled to the flow meter case.

[0018] Preferably, at least one strain gauge is connected to one or more flow tubes.

[0019] Preferably, at least one strain gauge is coupled to the brace bar.

[0020] Preferably, signals from one or more strain gauges are superimposed on other signals carried by a series circuit of the drive mechanism.

[0021] Preferably, the drive mechanism series circuit includes a Wheatstone bridge. According to one aspect, a method is provided for detecting a containment failure within a case of a flow meter having a sensor assembly and meter electronics. The method includes vibrating at least one of one or more flow tubes in a drive mode vibration using a drive mechanism, and measuring a vibration response of the flow tube induced by the drive mechanism using a pair of pickoff sensors. At least one strain gauge is provided inside the case. The drive mechanism and the at least one strain gauge are connected to the meter electronics, and the drive mechanism and the at least one strain gauge are connected in series. The resistance of the strain gauge is measured and compared to a baseline resistance. A containment failure is indicated if the resistance of the strain gauge differs from the baseline resistance by a predetermined amount.

[0022] Preferably, the method includes triggering an alarm if the resistance of the strain gauge differs from the baseline resistance by a predetermined amount.

[0023] Preferably, the method includes coupling the at least one strain gauge to the flow meter case.

[0024] Preferably, the method includes coupling the at least one strain gauge to one or more of the flow tubes.

[0025] Preferably, the method includes coupling the at least one strain gauge to a brace bar.

[0026] Preferably, the method includes superimposing a signal from the one or more strain gauges on other signals carried by the drive mechanism series circuit.

[0027] Preferably, the method includes providing a Wheatstone bridge within the drive mechanism series circuit.

Brief Description of the Drawings

[0028] The same reference numbers represent the same elements in all the drawings. The drawings are not necessarily to scale. [Figure 1] Shows a prior art flow meter. [Figure 2] Shows an embodiment of a flow meter. [Figure 3] Shows an embodiment of a flow meter. [Figure 4] Shows an embodiment of a flow meter. [Figure 5] Shows an embodiment of a flow meter. [Figure 6] It is a diagram of the meter electronic device.

Mode for Carrying Out the Invention

[0029] Figures 1 to 6 and the following description show specific examples for teaching those skilled in the art how to create and use the best mode of a flow meter and related methods and embodiments. For the purpose of teaching the principles of the present invention, some conventional aspects are simplified or omitted. Those skilled in the art can understand the variations from these examples that fall within the scope of this specification. As will be understood by those skilled in the art, the features described below can be combined in various ways to form multiple variations of the invention. As a result, the present invention is not limited to the specific examples described below, but is limited only by the claims and their equivalents.

[0030] Figure 1 shows a conventional flow meter 5, which can be any vibration meter, such as a Coriolis flow meter. The flow meter 5 comprises a sensor assembly 10 and meter electronics 20. The sensor assembly 10 responds to the mass flow rate and density of a process material. The meter electronics 20 is connected to the sensor assembly 10 via leads 100 and provides density, mass flow rate, and temperature information, as well as other information not relevant to the present invention, via a path 26. The sensor assembly 10 includes a pair of manifolds 150 and 150', flanges 103 and 103' having flange necks 110 and 110', a pair of parallel flow tubes 130 (first flow tube) and 130' (second flow tube), a driver mechanism 180, a temperature sensor 190 such as a resistance temperature detector (RTD), and a pair of pickoffs 170L and 170R such as a magnet / coil pickoff, strain gauge, optical sensor, or any other pickoff sensor known in the art. Each of the flow tubes 130 and 130' has inlet legs 131 and 131' and outlet legs 134 and 134' that converge toward the flow tube mounting blocks 120 and 120', respectively. Each of the flow tubes 130 and 130' bends at at least one symmetrical position along their length and is essentially parallel throughout their entire length. The brace bars 140 and 140' serve to define the axes W and W' from which each of the flow tubes' vibrates.

[0031] The side legs 131, 131' and 134, 134' of the flow tubes 130, 130' are fixedly mounted to the flow tube mounting blocks 120 and 120', which in turn are fixedly mounted to the manifolds 150 and 150'. This provides a continuous closed material path through the sensor assembly 10.

[0032] When flanges 103 and 103', having holes 102 and 102', are connected via inlet end 104 and outlet end 104' to a process line (not shown) carrying the process material being measured, the material enters the inlet end 104 of the meter through the orifice 101 of flange 103 and is guided through manifold 150 to a flow pipe mounting block 120 having a surface 121. Within manifold 150, the material is split and routed through flow pipes 130 and 130'. Exiting flow pipes 130 and 130', the process material is recombined into a single flow within manifold 150' and then routed to outlet end 104', which is connected to a process line (not shown) by flange 103' having bolt holes 102'.

[0033] Flow tubes 130 and 130' are selected to have substantially the same mass distribution, moment of inertia, and Young's modulus around the bending axes WW and W'-W', respectively, and are appropriately mounted on flow tube mounting blocks 120 and 120'. These bending axes pass through brace bars 140 and 140'. A temperature sensor 190 is mounted on flow tube 130' to continuously measure the temperature of flow tube 130', insofar as the Young's modulus of the flow tube changes with temperature, and this change affects the calculation of flow rate and density. The voltage appearing across the ends of the temperature sensor 190 with respect to the temperature of flow tube 130', and therefore a given current passing through the flow tube, is governed by the temperature of the material passing through flow tube 130'. The temperature-dependent voltage appearing across the ends of the temperature sensor 190 is used in a well-known manner by the meter electronics 20 to compensate for changes in the elastic modulus of flow tubes 130 and 130' due to any changes in the flow tube temperature. The temperature sensor 190 is connected to the meter electronics 20 by leads 195.

[0034] Both flow tubes 130 and 130' are driven by a driver 180 in opposite directions about their respective bending axes W and W' in the so-called first phase bending mode of the flow meter. The driver 180 may comprise one of many well-known configurations, such as a magnet mounted on flow tube 130' and opposing coils mounted on flow tube 130 through which alternating current flows to vibrate both flow tubes 130 and 130'. An appropriate drive signal is applied to the driver 180 via a lead 185 by the meter electronics 20.

[0035] The meter electronics 20 receives a temperature signal on lead 195 and left and right velocity signals appearing on leads 165L and 165R, respectively. The meter electronics 20 generates a drive signal appearing on lead 185 to the driver 180, causing tubes 130 and 130' to vibrate. The meter electronics 20 processes the left and right velocity signals and the temperature signal to calculate the mass flow rate and density of the material passing through the sensor assembly 10. This information, along with other information, is applied by the meter electronics 20 to the utilization means via path 26.

[0036] For clarity, the number of conductors shown is kept to a minimum. For 26, 165L, 165R, 185, and 195, only a single line is drawn, but this single line may represent one or more conductors.

[0037] Figure 2 shows one embodiment of the flowmeter 5. Although a Coriolis flowmeter structure is described, as will be apparent to those skilled in the art, the present invention can be implemented as a vibrating tube densimeter without the additional measuring capability provided by a Coriolis mass flowmeter. Elements common to the prior art apparatus in Figure 1 share the same reference numerals. The flow tubes 130 and 130' are driven by a driver 180 in opposite directions about their respective bending axes W and W' in the so-called first phase bending mode of the flowmeter. The driver 180 may comprise one of many well-known configurations, such as a magnet mounted on the flow tube 130' and opposing coils mounted on the flow tube 130 through which an alternating current flows to vibrate both flow tubes 130 and 130'. It should be noted that the flow tubes 130 and 130' are substantially rigid, for example, made of metal, so that only limited movements, such as vibrating movements induced by the driver, are possible. An appropriate drive signal is applied to the driver 180 via a lead 185 by the meter electronics 20. A pair of pickoffs 170L and 170R are provided, such as a magnet / coil pickoff, strain gauge, optical sensor, or any other pickoff sensor known in the art.

[0038] At least one strain gauge 200 is provided. As shown in the figure, the strain gauge 200 is located on the inlet leg 131 of the first flow tube 130. The strain gauge 200 is connected in series with the driver 180, and various segments of the lead 185 are shown for further clarity.

[0039] Figure 3 shows a first strain gauge 200A located on the inlet leg 131 of the first flow pipe 130, and a further second strain gauge 200B located on the inlet leg 131' of the second flow pipe 130'. In embodiments, strain gauges may be located on both flow pipes 130, 130'. In embodiments, strain gauges may be located on both outlet legs 134, 134'. In embodiments, strain gauges may be located on any combination of at least one inlet leg 131, 131' and at least one outlet leg 134, 134'.

[0040] Figures 2 and 3 show strain gauges 200A and 200B on the inlet legs 131 and 131' of the flow pipes 130 and 130'. It should be noted that the strain gauges 200A and 200B may be positioned on the outlet legs 134 and 134', closer to the driver 180 than currently shown, on the brace bars 140 and 140', the transducer mount, the manifolds 150 and 150', the flow pipe mounting blocks 120 and 120', or any other part of the sensor assembly 10. Overall, the strain elements are mounted on other parts of the flow pipe and / or meter structure that will be subjected to strain when a primary containment failure occurs. The strain gauges 200A and 200B are connected in series with the driver 180, and various segments of the lead 185 are shown for further clarity.

[0041] Figure 4 shows a first strain gauge 200A installed on the inlet leg 131 and a second strain gauge 200B installed on the outlet leg 134 of the same flow conduit 131. The strain gauges 200A and 200B are connected in series with the driver 180, and the various segments of the lead 185 are shown for further clarity.

[0042] Figure 5 shows strain gauges installed in the case 198 of the flow meter 5. The electrical connections between the driver 180 and the strain gauges 200 are shown schematicly for clarity and should be noted that they generally fall within the confines of the case 198. Although only one strain gauge 200 is shown, multiple strain gauges may be mounted on the case 198, as in Figures 3 and 4. In other embodiments, the strain gauges may be mounted on both the case 198 and the flow conduit. The strain gauges 200 are connected in series with the driver 180, and various segments of the lead 185 are shown for further clarity.

[0043] As shown in the diagram, strain gauges 200A and 200B are connected in series within the driver 180 circuit. This has the advantage of allowing signals to be transmitted from these strain gauge elements to the Coriolis transmitter without requiring any changes to the number of conductors in the existing meter feedthrough design or transmitter connection. The strain elements are connected in series with each other, as well as in series with the existing drive coil circuit. By using the drive coil circuit, the pick-off coil signal, which is important for flow and density measurements performed by the meter, remains intact. In the illustrated series connection, the driver is positioned between the two strain gauges 200A and 200B. With respect to the flow of current, the driver can be considered the first element in the circuit. With respect to the flow of current, the driver can also be considered the last element in the circuit. With respect to the flow of current, the driver can also be considered the element between the strain gauges in the circuit.

[0044] In one embodiment, signals from one or more strain gauges are superimposed on other signals carried by existing driver circuit conductors. By transmitting strain gauge signals via signal conductors already present in the previous design of the existing flow meter, this embodiment can be more easily implemented and retrofitted to existing meter designs.

[0045] This unique approach allows for the creation and use of indications in diagnostics within the meter transmitter, while eliminating the need for additional signals and / or power lines via feedthroughs to power conventional pressure transmitters.

[0046] In one embodiment, an alarm and / or notification is generated when a strain signal received by the meter's electronic equipment indicates a primary containment fault. The alarm and / or notification is triggered when the change in the baseline resistance reading from the strain gauge differs by a predetermined amount. As will be understood by those skilled in the art, the baseline resistance and threshold will vary depending on the application, as there are numerous strain gauge configurations, different numbers of strain gauges, different strain gauge installation locations, different flow meter materials, configurations, and sizes.

[0047] In one embodiment, when the strain signal received by the meter electronics indicates a primary containment fault, the meter electronics automatically stops the operation of the flowmeter. The stop is triggered when the change in the baseline resistance reading from the strain gauge differs by a predetermined amount.

[0048] For clarity, the number of conductors shown in Figures 2-5 is kept to a minimum. Only single lines are depicted for 26, 165L, 165R, and 195, although these single lines may represent one or more conductors. However, conductor 185 is shown in more detail schematicly to clearly illustrate the series nature of the driver and strain gauge circuits.

[0049] The resistance changes of strain gauges 200A and 200B are caused by strain on the surface beneath them. Default strain gauge resistances can be factory-read and baselined to the transmitter. In the case of primary containment faults and pressure rise within the case, the strain gauges will measure a significant shift, which is indicated by a change in resistance. It is worth noting that the magnitude and / or sensitivity of the resistance shift is not critical; rather, all that is needed is a binary indication that the resistance has changed from the baseline.

[0050] A Wheatstone bridge circuit may be used to amplify the signal. In one embodiment, a strain signal from the internal vibration structure of the flowmeter is input to the meter's electronic equipment and processed to detect changes in strain that may indicate internal leakage.

[0051] This unique approach allows for the creation and use of containment fault indicators in diagnostics within the meter transmitter, while eliminating the need for further signals and / or power lines via feedthroughs to power conventional pressure transmitters, thus enabling the use of existing wiring schemes.

[0052] Figure 6 shows the meter electronic equipment 20 of a flow meter 5 according to one embodiment of the present invention. The meter electronic equipment 20 includes an interface 201 and a processing system 203.

[0053] The meter electronic equipment 20 receives signals from the sensor assembly 10, such as strain gauge signals, RTD signals, driver signals, and pick-off signals, in order to obtain flow characteristics of the fluid material flowing through the sensor assembly 10. For example, the meter electronic equipment 20 can determine one or more of the following from the sensor signals: phase difference, frequency, time difference (Δt), density, mass flow rate, strain, and volumetric flow rate. Furthermore, according to the present invention, other flow characteristics can be determined.

[0054] Interface 201 receives strain gauge signals via leads used for drive signals. Any strain gauges 200A, 200B and driver 180 are connected in series. Interface 201 can perform any necessary or desired signal adjustments, such as formatting, amplification, and buffering, in any manner. Alternatively, some or all of the signal adjustments can be performed by the processing system 203. The meter electronics can apply well-established digital signal processing (DSP) techniques to convert either the dynamic resistance measurement of the circuit and / or the dynamic change in the drive current into the frequency domain.

[0055] Furthermore, interface 201 may enable communication between the meter electronic equipment 20 and an external device, for example, via a communication path 26. Interface 201 may enable any form of electronic, optical, or wireless communication.

[0056] In one embodiment, the interface 201 includes a digitizer 202, and the sensor signal includes an analog sensor signal. The digitizer 202 samples and digitizes the analog sensor signal to generate a digital sensor signal. The interface / digitizer can also perform any necessary decimation, and the digital sensor signal is decimated to reduce the amount of signal processing required and shorten processing time.

[0057] The processing system 203 performs the operation of the meter electronic equipment 20 and processes the flow rate measurements from the sensor assembly 10. The processing system 203 executes one or more processing routines, thereby processing the flow rate measurements to generate one or more flow characteristics.

[0058] The processing system 203 may comprise a general-purpose computer, a microprocessing system, logic circuits, or any other general-purpose or customized processing device. The processing system 203 may be distributed across multiple processing devices. The processing system 203 may also include any type of integrated or standalone electronic storage medium, such as the storage system 204.

[0059] In the illustrated embodiment, the processing system 203 determines the vibration mode frequency characteristics from the vibration response 220. The processing system 203 can determine at least the magnitude, phase difference, time difference, and frequency of the response 220.

[0060] The memory system 204 can store flow meter parameters and data, software routines, constant values, and variable values. In one embodiment, the memory system 204 includes routines executed by the processing system 203. In one embodiment, the memory system 204 stores a phase shift routine 212, a notification routine 213, a phase difference routine 215, a frequency routine 216, a time difference (Δt) routine 217, and a strain detection routine 218. In some embodiments, the memory system 204 stores one or more flow characteristics obtained from flow measurement values.

[0061] The strain detection routine 218 detects strain from at least one strain gauge. The resistance of at least one strain gauge is measured and subsequently compared to a baseline resistance. The baseline resistance is typically a default strain gauge resistance that is measured at the factory under controlled conditions and baselined to the transmitter. The strain detection routine 218 indicates a primary containment fault if the strain gauge resistance differs from the baseline resistance by a predetermined amount. The predetermined amount varies depending at least on the location of the strain gauge, the size and geometry of the flowmeter, and the operating conditions. The notification routine 213 may trigger an alarm and / or stop the operation of the flowmeter and / or halt the process if the strain detection routine 218 indicates a primary containment fault.

[0062] In these embodiments, a bridge circuit may be used to amplify the distortion signal. However, in other embodiments, the distortion signal is utilized without a bridge circuit.

[0063] The detailed description of the embodiments described above is not an exhaustive description of all embodiments that the inventors consider to be within the scope of the invention. In fact, as will be apparent to those skilled in the art, further embodiments may be obtained by combining or excluding certain elements of the embodiments described above, and such further embodiments are included within the scope and teachings of this specification. Furthermore, as will be obvious to those skilled in the art, further embodiments may be obtained within the scope and teachings of the invention by combining the embodiments in whole or in part.

[0064] Accordingly, specific embodiments of the present invention and examples for the present invention are described herein for illustrative purposes, but as those skilled in the art will recognize, various equivalent modifications are possible within the scope of the invention. The teachings provided herein can be applied not only to the embodiments shown above and in the accompanying figures, but also to other devices and methods. Accordingly, the scope of the invention should be determined from the following claims.

Claims

1. A flow meter (5) comprising a sensor assembly (10) and meter electronics (20) configured to detect containment faults within a flow meter case (198), One or more flow tubes (130, 130') and A drive mechanism (180) is coupled to one or more of the aforementioned flow tubes (130, 130') and directed to induce drive mode vibrations in the one or more of the aforementioned flow tubes (130, 130'), A pair of pick-off sensors (170L, 170R) are coupled to one or more of the aforementioned flow tubes (130, 130') and configured to measure the vibration response of the flow tubes (130, 130') induced by the drive mechanism (180), At least one strain gauge (200) in the flow meter case (198) configured to detect strain and Equipped with, The meter electronic equipment (20) is connected to the drive mechanism (180) and the at least one strain gauge (200), and the drive mechanism (180) and the at least one strain gauge (200) are connected in series. The meter electronic equipment (20) is configured to measure the resistance of the strain gauge (200) and compare the resistance of the strain gauge (200) with a baseline resistance, and the meter electronic equipment (20) is configured to indicate a containment fault when the resistance of the strain gauge (200) differs from the baseline resistance by a predetermined amount, the flow meter (5).

2. The flow meter (5) according to claim 1, wherein the meter electronic equipment (20) is configured to trigger an alarm when the resistance of the strain gauge (200) differs from the baseline resistance by a predetermined amount.

3. The flow meter (5) according to claim 1, wherein at least one strain gauge (200) is coupled to the flow meter case (198).

4. The flow meter (5) according to claim 1, wherein at least one strain gauge (200) is coupled to one or more flow tubes (130, 130').

5. The flow meter (5) according to claim 1, wherein at least one strain gauge (200) is coupled to a brace bar (140, 140').

6. The flow meter (5) according to claim 1, wherein signals from one or more strain gauges (200) are superimposed on other signals carried by the drive mechanism and a circuit having a series connection of at least one strain gauge.

7. The flow meter (5) according to claim 1, wherein the drive mechanism and the circuit having the series connection of at least one strain gauge comprises a Wheatstone bridge.

8. A method for detecting a containment fault in the case of a flow meter having a sensor assembly and meter electronic equipment, A step of using a drive mechanism to vibrate at least one of one or more flow tubes in a drive mode vibration, A step of measuring the vibration response of one or more flow tubes induced by the drive mechanism using a pair of pick-off sensors, The steps include providing at least one strain gauge inside the case, A step of connecting the drive mechanism and the at least one strain gauge to the meter electronic equipment, wherein the drive mechanism and the at least one strain gauge are connected in series; The steps include measuring the resistance of the strain gauge, The steps include comparing the resistance of the strain gauge with the baseline resistance, The step of indicating a containment failure when the resistance of the strain gauge differs from the baseline resistance by a predetermined amount. A method that includes this.

9. The method according to claim 8, further comprising the step of triggering an alarm if the resistance of the strain gauge differs from the baseline resistance by a predetermined amount.

10. The method according to claim 8, comprising the step of coupling the at least one strain gauge to the case.

11. The method according to claim 8, comprising the step of coupling the at least one strain gauge to the one or more flow tubes.

12. The method according to claim 8, comprising the step of coupling the at least one strain gauge to a brace bar.

13. The method according to claim 8, further comprising the step of superimposing the signals from one or more strain gauges onto other signals carried by the drive mechanism and a circuit having the at least one strain gauge connected in series.

14. The method according to claim 8, further comprising the step of providing a Wheatstone bridge in a circuit having the drive mechanism and the series connection of at least one strain gauge.

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