Liner for magnetic flowmeter flow tube assembly

Abstract

A flow tube liner 160 for a flow tube assembly 120 of a magnetic flow meter 102 includes a cylindrical wall 166. The cylindrical wall 166 includes an electrically insulating inner layer 170 and a metallic outer layer 172. The outer layer 172 is bonded to an outer surface 174 of the inner layer 170.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to magnetic flow meters, and more particularly, to flow tube liners for use with magnetic flow meters. [Background technology]

[0002] Precise and accurate flow control is important for a wide range of fluid processing applications including, for example, bulk fluid handling, food and beverage preparation, chemical and pharmaceutical, water and air distribution, hydrocarbon extraction and processing, environmental control, and a variety of manufacturing technologies that utilize thermoplastics, films, adhesives, resins, and other fluid materials. The flow measurement technology used in each specific application depends on the fluids involved and the associated process pressures, temperatures, and flow rates.

[0003] Exemplary flow measurement techniques include turbine devices that measure flow as a function of mechanical rotation, pitot sensors and differential pressure devices that measure flow as a function of the Bernoulli effect or pressure drop across a flow restriction, vortex and Coriolis devices that measure flow as a function of vibration effects, and mass flow meters that measure flow as a function of thermal conductivity. Magnetic flow meters are distinguished from these technologies by characterizing flow based on Faraday's law, which relies on electromagnetic interactions rather than mechanical or thermodynamic effects. In particular, magnetic flow meters rely on the electrical conductivity of the process fluid and the electromotive force (EMF) induced when the fluid flows through a region of a magnetic field.

[0004] A conventional magnetic flowmeter includes a sensor section, a transmitter section, and a flowtube assembly. The fluid flow to be measured travels through the tubing section of the flowtube assembly. A pair of electrodes are positioned in contact with the flow. The electrodes extend through a non-conductive polymer liner that electrically insulates the fluid from the tubing section and prevents the fluid from forming a short circuit between the electrodes and the tubing section.

[0005] The transmitter section includes a current generator that drives a current through a coil in the sensor section to generate a magnetic field across the piping section and the flow. The magnetic field induces an EMF or potential difference (voltage) across the flow that is proportional to the velocity of the flow. The magnetic flowmeter measures the voltage difference using electrodes and determines the flow rate of the flow based on the measured voltage difference.

[0006] Over time, fluid can permeate the liner and cause a short circuit between the electrode and the piping section, which would render the magnetic flowmeter inoperable.

[0007] Additionally, vacuum events can occur where a vacuum forms inside the pipe section and the liner. Such vacuum events can cause the liner to pull away from the inner wall of the pipe section. This can cause the liner to permanently deform and result in loss of the seal between the fluid flow and the pipe section. Such events can therefore render the magnetic flowmeter inoperable.

[0008] Permeation of gases entrained in the process fluid can create a pressurized space between the piping section and the liner. During a depressurization event, this pressurized space will expand, causing permanent deformation of the liner. Such an event can also render magnetic flow meters inoperable. Summary of the Invention

[0009] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure are directed to a flow tube liner for a flow tube assembly of a magnetic flow meter, a flow tube assembly including the flow tube liner, and a method. One embodiment of the flow tube liner includes a cylindrical wall having an electrically insulating inner layer and a metallic outer layer bonded to an outer surface of the inner layer.

[0010] One embodiment of a flow tube assembly includes a pipe section, a coil, and a flow tube liner. The coil is configured to receive a coil current and generate a magnetic field across the pipe section, the magnetic field inducing an electromotive force (EMF) in a fluid flow through the interior of the pipe section. The flow tube liner includes a cylindrical wall contained within the pipe section, the cylindrical wall including an electrically insulating inner layer and a metallic outer layer bonded to an outer surface of the inner layer.

[0011] In one embodiment of the method, a section of pipe, a coil, and a flow tube liner are provided, and the flow tube liner is inserted into the section of pipe. The coil is configured to receive a coil current and generate a magnetic field across the section of pipe, the magnetic field inducing an electromotive force (EMF) in a fluid flow passing through the interior of the section of pipe. The flow tube liner includes a cylindrical wall having an electrically insulating inner layer and a metallic outer layer bonded to an outer surface of the inner layer.

[0012] This Summary is provided to introduce some of the concepts described below in a simplified form in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended for use as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all of the shortcomings noted in the Background. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of an example industrial process measurement system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram of an example magnetic flowmeter according to an embodiment of the present disclosure. [Diagram 3] FIG. 3 is a simplified cross-sectional view of an example magnetic flowmeter according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a simplified cross-sectional view of the flow tube liner of FIG. 3 taken along line 4-4 according to an embodiment of the present disclosure. [Diagram 5]FIG. 5 is a simplified side cross-sectional view of a portion of the flow tube assembly of FIG. 3 according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a flowchart of a method according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Elements identified using the same or similar reference symbols refer to the same or similar elements. However, various embodiments of the present disclosure may be implemented in many different forms, and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0015] In the following description, specific details are given to provide a thorough understanding of the embodiments. However, it will be understood by those skilled in the art that the embodiments may be practiced without these specific details. For example, circuits, systems, networks, processes, frames, supports, connectors, motors, processors, and other components may not be shown in the drawings or in block diagram form to avoid obscuring the embodiments in unnecessary detail.

[0016] 1 is a schematic diagram of an exemplary industrial process measurement system 100 according to an embodiment of the present disclosure. System 100 can be used to process materials (e.g., process media) to convert the materials from a lower value state into higher value, useful products, such as pharmaceuticals, chemicals, paper, food, etc. For example, system 100 can be used in oil refineries that run industrial processes that can process crude oil into gasoline, fuel oil, and other petrochemical products.

[0017] The system 100 includes a magnetic flow meter 102 configured to sense a flow rate of a process fluid flow 104, such as through a piping section 106. The magnetic flow meter 102 includes a sensor section 108 and a transmitter 110. The sensor section 108 is generally configured to measure or sense the flow rate of the fluid flow 104. The transmitter 110 is generally configured to control the sensor section 108 to measure the flow rate and, optionally, transmit the measured flow rate to an external computing device 112, such as a computer control unit, which may be located remotely from the flow meter 102, such as a control room 114 of the system 100.

[0018] The transmitter 110 may communicate with an external computing device 112 via a suitable process control loop. In some embodiments, the process control loop includes a physical communication link, such as a two-wire control loop 116, or a wireless communication link. Communication between the external computing device 112 and the transmitter section may be performed via the control loop 116 according to conventional analog and / or digital communication protocols. In some embodiments, the two-wire control loop 116 includes a 4-20 milliamp control loop, and the process variable may be represented by the level of a loop current IL flowing through the two-wire control loop 116. An exemplary digital communication protocol includes modulation of a digital signal to an analog current level on the two-wire control loop 116, such as according to the HART® communication standard. Other purely digital techniques may also be used, including Foundation Fieldbus, Profibus, and Modbus communication protocols. Exemplary wireless versions of the process control loop include, for example, wireless mesh network protocols such as WirelessHART® (IEC 62591) or ISA 100.11a (IEC 62734), or other wireless communication protocols such as WiFi, LoRa, Sigfox, BLE, or any other suitable protocol.

[0019] Power may be provided to the magnetic flowmeter 102 from any suitable power source, such as an AC or DC power source. For example, the magnetic flowmeter 102 may be powered entirely by a loop current IL flowing through the control loop 116. One or more power sources may be utilized to power the process magnetic flowmeter 102, such as an internal battery or an external battery. A generator (e.g., solar panels, wind turbines, etc.) may also be used to power the magnetic flowmeter 102 and / or charge the power source used by the magnetic flowmeter 102.

[0020] The transmitter 110 may be directly attached to the sensor portion 108, such as in a housing that contains the sensor portion 108, or may be located remotely (e.g., 10-1000 feet) from the sensor portion 108. If the transmitter 110 is located remotely from the sensor portion 108, electrical connections between the transmitter 110 and the sensor portion 108 may be provided by one or more connecting cables, i.e., transmission lines 118, which may be formed by cables, wires, a data bus, a control bus, or other suitable connections for electrical and data communication.

[0021] 2 is a schematic diagram of a magnetic flowmeter 102 according to an embodiment of the present disclosure. The sensor section 108 may include a flowtube assembly 120 having a piping section 122 through which the fluid flow 104 flows. The flowtube assembly 120 may also include an EMF sensor 123 having electrodes 124, such as electrodes 124A and 124B, and the flowtube assembly 120 may include one or more field coils or coil wires 126, such as coils 126A and / or 126B. The electrodes 124A and 124B and the coils 126A and 126B, respectively, may be disposed on opposite sides of the piping section 122, as shown in FIG.

[0022] Digital processor 130 may represent one or more processors that control components of magnetic flowmeter 102 to perform one or more functions described herein in response to execution of instructions, which may be stored in non-transitory, patent eligible memory. In some embodiments, digital processor 130 provides control signals to current generator 132 based on an operating setpoint of magnetic flowmeter 102 to generate a coil current IC that includes, for example, alternating direction direct current pulses (e.g., square wave current pulses) through coil 126. Other types of alternating coil currents may also be used.

[0023] In some embodiments, the current generator 132 includes a controller 140 and a power amplifier 142. The controller 140 may represent one or more processors that, in response to control signals from the digital processor 130 and / or in response to execution of instructions, which may be stored in a non-transitory patent-eligible memory represented by the controller 140, control the components of the power amplifier 142 to perform one or more functions described herein.

[0024] The controller 140 controls the power amplifier 142 to generate the coil current IC based on the setpoint level of the magnetic flowmeter 102. The controller 140 may periodically receive a current level measurement of the coil current IC from the current sampling circuit 143 as feedback to determine whether adjustment of the coil current IC is necessary to match the setpoint level of the magnetic flowmeter 102 required for accurate flow measurement. The current sampling circuit 143 may take any suitable form. For example, the current sampling circuit 143 may operate to sense a voltage associated with the coil current IC, for example at a location shown in FIG. 2, and convert the sampled voltage to a digital signal using an analog-to-digital converter to present to the controller 140, for example, as a measured current level. The controller 140 may adjust the coil current IC based on the measured current level in an attempt to match the current level of the coil current IC to a setpoint current level dictated by the operational setpoint of the magnetic flowmeter 102.

[0025] A coil current IC is supplied to the field coils 126A and / or 126B of the flow tube 120 via a suitable electrical connection, such as the transmission line 118 shown in Figures 1 and 2. This causes the coils 126A and / or 126B to generate a magnetic field that moves across the piping section 122 and changes direction at a desired excitation frequency. The process fluid flow 104 flowing through the interior 144 of the piping section 122 acts as a moving conductor that induces an EMF in the fluid according to Faraday's law of electromagnetic induction. The electrodes 124A and 124B may include electrode components that provide capacitive coupling to the conductive process fluid or direct electrical coupling to the conductive process fluid, and pick up the voltage present in the fluid flow 104. The difference in voltage at the electrodes 124A and 124B is proportional to the velocity of the fluid flow 104.

[0026] A signal processor 128 of the transmitter 110 is connected to the electrodes 124A and 124B. The flowtube assembly 120 may be electrically grounded to the piping section 122, a flange or piping section upstream or downstream of the piping section 122, or other suitable ground connection. The digital processor 130 controls the signal processor 128 to sample the voltage difference between the electrodes 124A and 124B and provide the measured voltage difference to the digital processor 130 using any suitable technique. This may involve, for example, converting an analog differential voltage signal to a digital value that is provided to the digital processor 130. The digital processor 130 may perform further signal processing of the measured differential voltage to establish a measurement of the flow rate of the process fluid flow 104. The measured flow rate may be communicated to the computing device 112 using the communication interface 134, for example, via one of the wired or wireless communication protocols described above.

[0027] 3 is a simplified cross-sectional view of an example of a magnetic flowmeter 102 according to an embodiment of the present disclosure. In some embodiments, the magnetic flowmeter 102 includes a transmitter housing 150, which can include circuitry forming a signal processor 128, a digital processor 130, a communication interface 134, a controller 140, a power amplifier 142, and / or other components. A magnetics compartment 152 surrounds the piping section 122 of the flow tube assembly 120 and can include one or more field coils 126, electrodes 124, and / or other components. As described above, the field coils 126 can be positioned opposite each other on the outside of the piping section 122 (e.g., above and below the piping section 122).

[0028] The flow tube liner 160 of the flow tube assembly 120 formed according to one or more embodiments described herein seals the tubing section 122 from the interior 144 through which the fluid flow 104 flows. The electrodes 124 can extend through tunnels 162 in the tubing section 122 while being electrically insulated from the tubing section 122. The electrodes may also extend through openings 164 in the liner 160 into the interior 144 and contact the fluid flow 104. The openings 164 may be located on opposing sides of the liner 160, as shown by openings 164A and 164B in FIG. 2. The liner 160 may include additional openings 164 as needed to accommodate additional electrodes 124, such as, for example, reference electrodes. The liner 160 provides a seal with the electrodes 124 at the openings 164 to prevent fluid ingress into the tubing section 122.

[0029] Embodiments of flow tube liner 160 provide improved protection over conventional flow tube liners against ingress of process fluid into pipe section 122, and therefore improved protection against shorts between fluid flow 104, pipe section 122, and electrodes 124A and / or 124B that would render magnetic flow meter 102 inoperable. Additionally, embodiments of flow tube liner 160 provide improved protection over conventional flow tube liners against collapse of liner 160 due to the formation of a vacuum within interior 144 of pipe section 122.

[0030] Figures 4 and 5 are, respectively, a cross-sectional view of the flow tube liner 160 of Figure 3 taken along line 4-4 and a side cross-sectional view of a portion of the liner 160 of Figure 3, according to an embodiment of the present disclosure. The illustrated features are not drawn to scale.

[0031] In some embodiments, the flow tube liner 160 includes a multi-layer cylindrical wall 166. The cylindrical wall includes a non-conductive or electrically insulating inner layer 170 and a metallic outer layer 172. The electrically insulating inner layer generally surrounds an interior corresponding to the interior 144 of the pipe section and engages the fluid flow 104, as shown in FIG. 4, while the metallic outer layer is bonded to an outer surface 174 of the inner layer 170. The outer layer 172 may be bonded directly to the outer surface 174 of the inner layer 170, or the outer layer 172 may be bonded to the outer surface 174 of the inner layer 170 via one or more intermediate layers (not shown). In some embodiments, the metallic outer layer is electrically conductive.

[0032] In one embodiment, the inner layer 170 includes a polymer. The polymer can form substantially the entirety (e.g., greater than 90% by volume or weight) of the inner layer 170. Examples of polymers include fluoropolymers, perfluoroalkoxyalkanes (PFA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), polyetheretherketone (PEEK), polycarbonate, polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), polycarbonate / acrylonitrile butadiene styrene (PC / ABS), polyetherimide (PEI), acrylic, nylon, cross-linked polyethylene (PEX), and polyoxymethylene (POM). In one embodiment, the inner layer 170 does not include a highly crystalline fluoropolymer.

[0033] In one embodiment, the outer layer 172 includes a metal. The metal may form a substantial entirety (e.g., greater than 90% by volume or weight) of the outer layer 172. Examples of metals include aluminum, stainless steel, gold, copper, titanium, chromium, tantalum, vanadium, nickel, metal oxides, and the like.

[0034] In some embodiments, the outer layer 172 may be formed on the inner layer 170 by any suitable means. For example, the outer layer 172 may be formed on the inner layer 170 by a vacuum deposition process, arc or flame spraying, electroless plating, electrolytic plating, or other suitable process. Thus, the bond between the inner layer and the outer layer may include a mechanical bond and / or a chemical bond.

[0035] The outer layer 172 acts as a barrier to liquid and vapor intrusion through the inner layer 170. Thus, unlike conventional flow tube liners that must use a relatively thick cylindrical wall (e.g., up to 0.5 inches thick) to reduce liquid and vapor intrusion, the flow tube liner 160 can use relatively thin polymer layers to form the inner layer 170 and the thin outer layer 172 while reducing or eliminating liquid and vapor intrusion through the liner 160. For example, the thickness 176 (FIG. 5) of the inner layer 170 may be about 0.2 inches, while the thickness 178 of the outer layer 172 may be about 30 Å to 500 Å, resulting in a total thickness of the cylindrical wall 166 of about 0.2 inches.

[0036] Each of the openings 164 in the liner 160 extends through the inner layer 170 and the outer layer 172. Each of the electrodes 124 is insulated from the outer layer 172 by either a housing for the electrode 124 or by an insulating sleeve that surrounds the electrode 124 contained within the opening 164.

[0037] Additional embodiments are directed to a flowtube assembly 120 or magnetic flowmeter 102 including a flowtube liner 160 formed according to one or more embodiments described herein, as shown in Figure 3, and a method. Figure 6 is a flow chart of a method according to an embodiment of the present disclosure.

[0038] At 180 of the method, a flow tube assembly 120 is provided. In one embodiment, the flow tube assembly 120 includes a piping section 122 and one or more coils 126 configured to receive a coil current IC and generate a magnetic field across the piping section 122 that induces an EMF in the fluid flow 104 through the piping section 122, as shown, for example, in FIG.

[0039] At 182 of the method, a flow tube liner 160 formed according to one or more embodiments described herein is provided. In one embodiment, the flow tube liner 160 includes a cylindrical wall 166 with an electrically insulating inner layer 170 and a metallic outer layer 172. The liner 160 is inserted at 184 into the interior 144 of the pipe section 122. In some embodiments, the outer diameter of the flow tube liner 160 matches the inner diameter of the pipe section 122 such that the liner 160 provides an interference fit with the pipe section 122 and generally maintains its position within the pipe section 122 once inserted. In some embodiments, an outer surface 186 of the flow tube liner 160 is bonded to an inner surface 188 of the pipe section 122.

[0040] In one embodiment, the outer layer 172 is bonded to the outer surface 174 of the electrically insulating inner layer 170, as shown in Figures 4 and 5. The outer surface of the outer layer 172 is thus bonded to the inner surface of the conduit section 122, as shown in Figure 5. Any suitable technique can be used to bond the outer surface of the outer layer 172 to the inner surface of the conduit section 122, such as using a suitable adhesive.

[0041] In some embodiments, as shown in FIG. 3, the pipe section 122 includes a central axis 190, and the flow tube liner 160 is inserted into the pipe section 122 such that it is substantially concentric with the central axis 190. The flow tube liner 160 may include opposing ends 192 that extend outside the pipe section 122 when the liner 160 is initially inserted into the pipe section 122 (step 184), as shown in phantom in FIG. 3. The ends 192 of the flow tube liner 160 may then be flared using a suitable tube flaring tool such that the ends 192 extend away from the central axis 190, as shown in FIGS. 3 and 5. The flared ends may be sandwiched between a flange 194 attached to the pipe section 122 and a flange of a pipe section adjacent the pipe section 122, from which the fluid flow 104 may be received and discharged by the pipe section 122, such as the pipe section 106 shown in FIG.

[0042] The flow tube liner 160 can include openings 164 that extend through the inner layer 170 and the outer layer 172 and are generally disposed on opposing sides of the liner 160 as described above. Additionally, the tubing section 122 can include tunnels 162 aligned with the openings 164. The method can include positioning the electrodes 124 such that each of the electrodes 124 extends through one of the tunnels 162 and one of the openings 164 into the interior 144 of the tubing section 122 and the flow tube liner 160, as shown in FIG. 2, thereby exposing the electrodes 124 to the fluid flow 104 for voltage measurements.

[0043] In operation, the outer layer 172 of the flow tube liner 160 operates to provide greater protection against liquid and vapor intrusion from the fluid flow 104 into the piping section 122 than a corresponding conventional polymeric flow tube liner. As a result, a magnetic flowmeter 102 utilizing a flow tube assembly 120 including the flow tube liner 160 is less likely to become inoperable due to a short circuit caused by liquid or vapor intrusion. Additionally, the flow tube liner 160 can be made thinner than conventional flow tube liners by using the outer layer 172 as a liquid and vapor intrusion barrier rather than a thick polymer layer as in conventional flow tube liners.

[0044] Additionally, a magnetic flowmeter 102 utilizing a flowtube assembly 120 including a flowtube liner 160 is less likely to become inoperable due to vacuum collapse of the flowtube liner 160 due to the improved structural resiliency that the metallic outer layer 172 provides to the cylindrical wall 166 of the flowtube liner 160 as compared to the single polymeric layer of conventional flowtube liners. Additionally, the outer layer 172 may be bonded to the inner surface 188 of the piping section 122, further reducing the likelihood of vacuum collapse.

[0045] Additionally, the flow tube liner 160 is less susceptible to misalignment with the pipe section 122 during installation of the magnetic flowmeter 102 compared to conventional flow tube liners. Such "misalignment" could cause the electrode 124 to contact the pipe section 122, shorting the electrode 124 or introducing a leak into the electrode 124. Either of these conditions could render the magnetic flowmeter 102 inoperable. For example, the more resilient structure of the flow tube liner 160 compared to conventional flow tube liners allows for a more secure interference fit with the pipe section 122 during installation, reducing the likelihood of the liner 160 misaligning during installation of the magnetic flowmeter 102. Additionally or alternatively, the flow tube liner 160 may be bonded to the pipe section 122, further reducing the likelihood of the liner 160 misaligning during installation of the magnetic flowmeter 102.

[0046] Although embodiments of the present disclosure have 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 present disclosure.

Claims

1. A structure of a flow tube assembly of a magnetic flow meter, comprising: A piping portion made of a conductive material; a flow tube liner comprising a cylindrical wall including an electrically insulating inner layer and an outer layer of metal bonded to an outer surface of the inner layer and bonded to an inner surface of the pipe section; Equipped with the inner layer comprises a polymer and the outer layer comprises a metal or metal oxide; the polymer is selected from the group consisting of fluoropolymer, perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), polyetheretherketone (PEEK), polycarbonate, polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), polycarbonate / acrylonitrile butadiene styrene (PC / ABS), polyetherimide (PEI), acrylic, nylon, crosslinked polyethylene (PEX), and polyoxymethylene (POM); A construction wherein said inner layer does not comprise a highly crystalline fluoropolymer.

2. The structure of claim 1, wherein the metal is selected from the group consisting of aluminum, stainless steel, gold, copper, titanium, chromium, tantalum, vanadium, nickel, and metal oxides.

3. An opening for a first electrode extends through the inner layer and the outer layer; a second electrode opening extends through the inner and outer layers on an opposite side of the cylindrical wall from the first electrode opening; The structure of claim 1.

4. A flow tube assembly for use in a magnetic flowmeter for measuring a flow rate of a fluid flow, comprising: A piping portion made of a conductive material; a coil configured to receive a coil current and generate a magnetic field that induces an electromotive force (EMF) in a fluid flow across and within the section of piping; a flow tube liner including a cylindrical wall received within the pipe section, the cylindrical wall including an electrically insulating inner layer and a metallic outer layer bonded to an outer surface of the inner layer and bonded to an inner surface of the pipe section; A flow tube assembly comprising:

5. The flow tube assembly of claim 4, wherein the inner layer comprises a polymer and the outer layer comprises a metal.

6. The flow tube assembly of claim 5, wherein the polymer is selected from the group consisting of fluoropolymer, perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), polyether ether ketone (PEEK), polycarbonate, polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), polycarbonate / acrylonitrile butadiene styrene (PC / ABS), polyetherimide (PEI), acrylic, nylon, cross-linked polyethylene (PEX), and polyoxymethylene (POM).

7. The flow tube assembly of claim 6, wherein the inner layer does not contain a highly crystalline fluoropolymer.

8. The flow tube assembly of claim 5, wherein the metal is selected from the group consisting of aluminum, stainless steel, gold, copper, titanium, chromium, tantalum, vanadium, nickel, and metal oxides.

9. The flow tube assembly of claim 5, wherein an outer surface of the outer layer is bonded to an inner wall of the piping section.

10. The piping section includes a central axis, the cylindrical wall is substantially concentric with the central axis and is disposed outside the pipe section and includes opposed flared ends extending away from the central axis.

6. The flow tube assembly of claim 5.

11. An opening for a first electrode extends through the inner layer and the outer layer, and an opening for a second electrode extends through the inner layer and the outer layer on an opposite side of the cylindrical wall from the opening for the first electrode; a first electrode disposed in a first tunnel extending through the first electrode opening and the piping section, the first electrode being exposed to an interior of the piping section; a second electrode disposed in a second tunnel extending through the second electrode opening and the piping section, the second electrode being exposed to an interior of the piping section; The flow tube assembly of claim 10 comprising:

12. A flow tube assembly as claimed in claim 11; a power amplifier configured to generate a coil current; a signal processor configured to receive the voltages sensed by the first and second electrodes and generate a digital voltage signal indicative of a voltage difference between the first and second electrodes proportional to an electromotive force and a rate of fluid flow; a digital processor configured to process the digital voltage signal and establish the rate of flow of the fluid; A magnetic flow meter comprising:

13. Providing a flow tube liner including: a piping section made of an electrically conductive material; a coil configured to receive a coil current and generate a magnetic field that induces an electromotive force (EMF) in a fluid flow across and through the piping section; and a cylindrical wall contained within the piping section, the cylindrical wall including an electrically insulating inner layer and a metallic outer layer bonded to an outer surface of the inner layer; inserting the flow tube liner into the section of pipe and bonding the outer layer to an interior surface of the section of pipe; The method includes:

14. The inner layer comprises a polymer selected from the group consisting of fluoropolymer, perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), polyether ether ketone (PEEK), polycarbonate, polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), polycarbonate / acrylonitrile butadiene styrene (PC / ABS), polyetherimide (PEI), acrylic, nylon, cross-linked polyethylene (PEX), and polyoxymethylene (POM); the outer layer comprises a metal selected from the group consisting of aluminum, stainless steel, gold, copper, titanium, chromium, tantalum, vanadium, nickel, and a metal oxide; The method of claim 13.

15. The method of claim 13, further comprising bonding an outer surface of the outer layer to an inner surface of the piping section.

16. The piping section includes a central axis, the cylindrical wall of the flow tube liner is substantially concentric with the central axis and includes opposed ends extending outside the pipe section; The method of claim 13 including flaring the opposing ends of the flow tube liner to extend away from the central axis.

17. The flow tube liner includes an opening for a first electrode extending through the inner layer and the outer layer, and an opening for a second electrode extending through the inner layer and the outer layer on an opposite side of the cylindrical wall from the opening for the first electrode, disposing a first electrode in a first tunnel extending through the first electrode opening and the conduit section, exposing the first electrode to an interior of the conduit section; disposing a second electrode in a second tunnel extending through the second electrode opening and the conduit section, exposing the second electrode to an interior of the conduit section; The method of claim 13, comprising:

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