Patent Description:
Safe, accurate, and cost-effective fluid measurements are important to a wide range of industrial and scientific processes. Many of these applications require measurements using averaging pitot tube probes that are inserted into the process fluid and facilitate flow rate measurements of the process fluid, for example.

Averaging pitot tube probes are subject to a number of stress factors including flow-induced vibrations. Flow-induced vibrations typically arise as a result of vortex shedding and other turbulent wake field effects, which generate periodically alternating forces on the probe. These forces cause the averaging pitot tube probe to oscillate back and forth or vibrate, increasing mechanical stress and reducing service life for the probe.

When flow-induced vibrations occur near a natural resonant frequency of the averaging pitot tube probe, the magnitude of the forced resonant oscillations of the probe causes significant wear of the probe. Such wear can lead to early catastrophic failure of the probe particularly when combined with other stresses, such as high drag forces, corrosion, fatigue, or erosion of the structure. <CIT> discloses an averaging pitot tube with reduced coherent vortex shedding.

Embodiments of the present disclosure are generally directed to an averaging pitot tube probe assembly having an averaging pitot tube probe for use in sensing a parameter of a fluid flow in a process vessel, and a method of adjusting a resonant frequency of an averaging pitot tube probe of an industrial process sensing device. One embodiment of the averaging pitot tube probe assembly includes an averaging pitot tube probe extending through the process vessel. The probe includes a first end extending through a first opening in the process vessel, and a second end extending through a second opening in the process vessel. A fixed mount secures the first end in a fixed position relative to the process vessel. A tensioning mount includes a tensioner that is attached to the second end of the probe and is configured to adjust a tension in the probe, and thereby adjust a resonant frequency of the probe.

In one embodiment of the method, a first end of the averaging pitot tube probe extending through a first opening of the process vessel is supported in a fixed position relative to the process vessel using a fixed mount. A second end of the probe extending through a second opening of the process vessel is supported using a tensioning mount. The resonant frequency of the probe is adjusted by adjusting a tension of the probe using a tensioner of the tensioning mount.

Another embodiment of the present disclosure is directed to an averaging pitot tube probe assembly including a probe extending through a process vessel. The probe includes a first end extending through a first opening in the process vessel, and a second end extending through a second opening in the process vessel. A fixed mount secures the first end in a fixed position relative to the process vessel. A tensioning mount includes a tensioner that is attached to the second end of the probe and is configured to adjust a tension in the probe, and thereby alter a resonant frequency of the probe. An adjustment mechanism of the tensioner includes a first member having a threaded exterior surface and a second member having a threaded socket that receives the threaded exterior surface of the first member. A bias member of the tensioner is configured to flex relative to the process vessel based on the tension in the probe.

The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the Background.

Embodiments of the present disclosure are described more fully hereinafter with reference to the accompanying drawings. Elements that are identified using the same or similar reference characters refer to the same or similar elements. The various embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the particular embodiments set forth 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.

<FIG> is a simplified diagram of an exemplary industrial process measurement system <NUM>, in accordance with embodiments of the present disclosure. The system <NUM> may be used in the processing of a process fluid <NUM>, such as a liquid or a gas, to transform the process fluid <NUM> from a less valuable state into more valuable and useful products, such as petroleum, chemicals, paper, food, etc. For example, an oil refinery performs industrial processes that can process crude oil into gasoline, fuel oil, and other petrochemicals.

The system <NUM> includes an industrial process sensing or measuring device <NUM> that includes a probe assembly <NUM> having a probe <NUM> that is placed within a flow <NUM> of the process fluid <NUM> contained in a process vessel <NUM>, such as a pipe. The probe <NUM> may be configured for use in measuring or sensing a parameter of the process fluid <NUM> using one or more sensors <NUM>. The parameter of the process fluid <NUM> may be a flow rate of the fluid flow <NUM>, a temperature of the fluid <NUM>, or other process parameter. The one or more sensors <NUM> may generate one or more output signals <NUM> that indicate the sensed parameter. If necessary, the output signals <NUM> may be processed to determine desired process information. For example, a differential pressure indicated by an output signal <NUM> from a differential pressure sensor <NUM> may be processed to determine a flow rate of the fluid flow <NUM> using conventional techniques.

In some embodiments, the system <NUM> includes a transmitter <NUM> that includes the sensors <NUM> and is configured to process the output signals <NUM> as necessary to generate process information (e.g., temperature, flow rate, etc.) relating to the fluid flow <NUM>, and communicate the process information over a suitable wired or wireless communication link. The transmitter <NUM> may be configured to transmit the parameter information to a control unit <NUM> (e.g., computing device), which may be remotely located from the transmitter <NUM> in a control room <NUM>, for example, as shown in <FIG>. The control unit <NUM> may be communicatively coupled to the transmitter <NUM> over a suitable physical communication link, such as a two-wire control loop <NUM>, or a wireless communication link. Communications between the control unit <NUM> and the transmitter <NUM> may be performed over the control loop <NUM> in accordance with conventional analog and/or digital communication protocols.

A controller <NUM> may represent multiple controllers of the system <NUM>, such as controllers of the device <NUM>, the transmitter <NUM>, and the control unit <NUM>, for example. The controller <NUM> includes one or more processors (i.e., microprocessor, central processing unit, etc.) that perform one or more functions described herein in response to the execution of instructions, which may be stored locally in non-transitory computer readable media or memory <NUM>. The memory <NUM> may represent memory of the control unit <NUM>, memory of the transmitter <NUM>, and/or memory of the device <NUM>. Any suitable patent subject matter eligible computer readable media or memory may be utilized for the memory <NUM> including, for example, hard disks, CD-ROMs, optical storage devices, or magnetic storage devices. Such computer readable media or memory do not include transitory waves or signals.

The controller <NUM> may also represent other conventional circuitry of the transmitter <NUM>, the device <NUM> and the control unit <NUM>, such as data processing components, data communications components, and/or other components, for example.

The process assembly <NUM> supports the probe <NUM> such that it is exposed to the process fluid flow <NUM> traveling through the process vessel <NUM>. As mentioned above, the probe <NUM> may represent different types of probes that are used in process parameter sensing or measuring operations performed by the device <NUM>. In some embodiments, the device <NUM> is in the form of a flow rate measurement device, and the probe <NUM> is inserted in the fluid flow <NUM> to perform a flow rate measurement.

The probe <NUM> is an averaging pitot tube probe that is used for flow rate measurements. The pitot tube form of the probe <NUM> may be used to sense an upstream (or "stagnation") pressure of the fluid flow <NUM>, and a downstream (including "static" or "suction") pressure to produce a differential pressure value that is related to the flow rate of the fluid <NUM> impacting the averaging pitot tube probe <NUM>. The averaging pitot tube probe <NUM> may include pressure ports leading to fluid plenums in the pitot tube probe and impulse lines may be used to transmit the fluid pressures from the plenums to one of the sensors <NUM>, which may be in the form of a differential pressure sensor, in accordance with conventional averaging pitot tube probes. An output <NUM> from the sensor <NUM> indicating the sensed differential pressure may be used to calculate a flow rate of the fluid <NUM>. For example, the output signal <NUM> indicating the sensed differential pressure may be processed using conventional techniques to determine the velocity of the fluid flow <NUM>, such as by the controller <NUM>. Exemplary averaging pitot tube probes include those used in the Annubar® Flowmeter Series manufactured by Rosemount® Inc. , such as the 3051SFA series.

<FIG> is a simplified cross-sectional view of an exemplary averaging pitot tube probe assembly <NUM> taken generally along line <NUM>-<NUM> of <FIG>, <FIG> is a simplified side view of an exemplary averaging pitot tube probe assembly <NUM>, and <FIG> is a simplified side cross-sectional view of the probe assembly <NUM> of <FIG> taken generally along line <NUM>-<NUM> of <FIG>, in accordance with embodiments of the present disclosure.

As discussed above, the placement of the averaging pitot tube probe <NUM> within the fluid flow <NUM> (<FIG>) subjects the probe <NUM> to flow-induced oscillation forces corresponding to the wake frequency at which vortices are shed by the probe <NUM>. The wake frequency is a function of the fluid velocity (V), the width (d) of the probe <NUM>, and the Strouhal number (s), in accordance with the following equation:<MAT>.

At a critical fluid velocity, this frequency overlaps with the resonant frequency of the probe <NUM>, which is the natural frequency of the mechanical structure, a destructive vibration may be created that can lead to high-magnitude oscillations of the probe <NUM>, which can lead to a structural failure. Conventional solutions to probe vibrations involve increasing the strength of the probe <NUM> by thickening the walls of the probe <NUM>, or adding specialized structures to the probe <NUM>. These solutions increase manufacturing costs and expand the probe's size and weight. Additional costs may include a decrease in sensitivity.

Embodiments of the present disclosure relate to techniques for addressing flow-induced oscillation forces on an averaging pitot tube probe <NUM> through probe resonant frequency adjustment. Specifically, embodiments of the present disclosure facilitate an adjustment to the resonant frequency of the probe <NUM> to a frequency that is outside the anticipated wake frequency that the probe <NUM> is likely to be subjected to in a given application, to thereby avoid the most destructive flow-induced oscillation forces at the resonant frequency of the probe <NUM>. As a result, the robustness of the probe <NUM> may be increased relative to conventional probes while mitigating manufacturing costs and probe weight, in addition to facilitating other benefits.

In some embodiments of the averaging pitot tube probe assembly <NUM>, the probe <NUM> extends through the process vessel <NUM> along a longitudinal axis <NUM>, and opposing ends <NUM> and <NUM> of the probe <NUM> extend through openings <NUM> and <NUM> in a section of the process vessel <NUM>, as shown in <FIG>. The end <NUM> of the probe <NUM> is supported by a fixed mount <NUM>, and the end <NUM> is supported by a tensioning mount <NUM>. The fixed mount <NUM> generally fixes the position of the probe end <NUM> relative to the process vessel <NUM>, and may comprise a suitable conventional mount. The tensioning mount <NUM> includes a tensioner <NUM> that is attached to the probe end <NUM> and is configured to adjust the tension in the probe <NUM>, which is represented by arrow <NUM> and is oriented along the axis <NUM>.

The resonant frequency of the probe is generally related to the tension <NUM> of the probe by the following equation:
<MAT>
where C is the modal constant of the structure, g is gravitational acceleration, E is the modulus of elasticity of the material forming the structure, IL is the moment of inertia of the structure, w is the unit weight of the structure, L is the length of the structure between the supported ends <NUM> and <NUM>, and FTension is the tension <NUM> of the probe <NUM>, such as that applied using the tensioning mount <NUM>. As a result, the resonant frequency of the probe <NUM> may be adjusted by adjusting the tension <NUM> of the probe <NUM> using the tensioner <NUM>, such as to a value that is higher or lower than the anticipated wake frequency.

When the outer diameter OD of the process vessel is relatively small, the resonant frequency of the probe <NUM> may be increased by shortening the length L<NUM> between the support of the probe end <NUM> and the process vessel <NUM>, and the length L<NUM> between the support of the probe end <NUM> and the process vessel <NUM>, which are shown in <FIG>. This can be achieved by using a shorter fixed mount <NUM> and/or a shorter tensioning mount <NUM> (e.g., shorter weld mounts), for example.

The fixed and tension mounts <NUM> and <NUM> may each form a seal around the corresponding openings <NUM> and <NUM> in the process vessel <NUM>, as indicated in <FIG>. In some embodiments, the fixed and tensioning mounts <NUM> and <NUM> may each include a mount <NUM> that forms a seal at the corresponding pipe openings <NUM> and <NUM>, such as a conventional weld-o-let or weld mount, for example. The fixed and tensioning mounts <NUM> and <NUM> may also include suitable structures, such as flanges <NUM>, which may be integral with, or welded to the mounts <NUM>, for forming a seal or connecting to other industrial process components, such as a transmitter module, for example.

The fixed mount <NUM> may include an interior cavity <NUM> that receives the probe end <NUM>, as shown in <FIG> and <FIG>. <FIG> is an exploded isometric view of an exemplary probe assembly <NUM> in which the fixed mount end <NUM> of the averaging pitot tube probe <NUM> is coupled to a process transmitter <NUM>. In some embodiments, a socket <NUM> of the mount <NUM> receives a compatible cylinder <NUM> that is attached to the end <NUM> of the probe <NUM>. A suitable seal may be formed between the flange <NUM> of the mount <NUM> and a flange <NUM> attached to the cylinder <NUM> to prevent process fluid leaks. The probe end <NUM> may also include a flange for coupling to a manifold <NUM>. Pressures from locations within the averaging pitot tube probe <NUM> may be routed through the end <NUM> and the manifold <NUM> to sensors <NUM> (e.g., differential pressure sensor) located in a sensor housing <NUM>, which is attached to the transmitter <NUM>. The transmitter <NUM> may receive the output signals <NUM> (<FIG>) from the sensors <NUM>, process the signals <NUM> to obtain desired process information (e.g., flow rate), and communicate the process information to the control unit <NUM>, for example.

In some embodiments, the tension mount <NUM> includes an interior cavity <NUM> that receives the probe end <NUM>, as shown in <FIG> and <FIG>. Additionally, the tensioner <NUM> may be contained within the interior cavity <NUM> of the tensioning mount <NUM>.

In some embodiments, the tensioner <NUM> includes an adjustment mechanism <NUM> that includes cooperating threaded members <NUM> and <NUM>, as shown in <FIG>. The member <NUM> is attached to the probe end <NUM>, and the member <NUM> extends distally along the axis <NUM> from the member <NUM> and the probe end <NUM>. One of the members <NUM> or <NUM> includes a threaded exterior surface (e.g., a screw, bolt, etc.), and the other of the members <NUM> or <NUM> includes a threaded socket (e.g., nut, bore, etc.), in which the threaded exterior surface is received. Rotation of the member <NUM> relative to the member <NUM> drives movement of the members <NUM> and <NUM> either toward or away from each other, as indicated by arrow <NUM>, thereby decreasing or increasing the tension <NUM> in the probe <NUM>. For example, the member <NUM> may comprise a threaded rod <NUM> that is attached to the probe end <NUM> and is received in a threaded socket <NUM> (e.g., nut) of the member <NUM>, as shown in <FIG>. Rotation of the nut <NUM> about the axis <NUM> can either reduce or increase the tension <NUM> in the probe <NUM>. Alternatively, the member <NUM> may include the rod <NUM> in the form of a bolt, the threaded end of which is received within a threaded socket <NUM> (phantom lines) of the member <NUM>, for example.

In some embodiments, the probe end <NUM> is not held in a fixed position relative to the process vessel <NUM>. One purpose for this is to avoid undesirable changes in the tension <NUM> in the probe <NUM> caused by thermal expansion or contraction of the probe <NUM> and the process vessel <NUM>.

In some embodiments, the tensioner includes a bias member <NUM> (<FIG>) that is connected to the probe end <NUM> and is configured to flex relative to the process vessel <NUM> in response to the tension <NUM> in the probe <NUM>. This allows the probe assembly <NUM> to accommodate thermal expansion and contraction of the probe <NUM> and the process vessel <NUM>, while substantially maintaining the desired tension <NUM> in the probe <NUM> set by the tensioner <NUM>. Thus, the bias member <NUM> allows the probe end <NUM> to move relative to the fixed end <NUM>, while maintaining the desired tension level. Accordingly, this configuration avoids the generation of potentially damaging tensile forces in the probe <NUM> that could occur if the probe end <NUM> was held in a fixed position relative to the process vessel <NUM> and the fixed end <NUM>.

The bias member <NUM> may take on any suitable form. In some embodiments, the bias member <NUM> includes a leaf spring, a star washer, a coil spring, or another suitable flexible spring-like member. In the exemplary assembly shown in <FIG>, a bias member <NUM> in the form of a leaf spring is supported within the interior cavity <NUM> of the tension mount <NUM> using any suitable technique. For example, the tension mount <NUM> may include a conical opening <NUM>, in which a disc-shaped bias member <NUM> (e.g., leaf spring) may be supported. Alternatively, the interior cavity <NUM> of the tensioning mount <NUM> may include a beveled interior diameter or shoulder for supporting the leaf spring, star washer or other bias member <NUM>. Other techniques for supporting the bias member <NUM> may also be used.

In some embodiments, the bias member <NUM> is connected to the member <NUM> of the tensioner <NUM>, such that an increase in the tension <NUM> in the probe causes the bias member <NUM> to flex toward the process vessel <NUM>. In some embodiments, the member <NUM> of the tensioner <NUM> passes through the bias member <NUM>, as shown in <FIG>.

<FIG> is a flowchart illustrating an exemplary method of adjusting a resonant frequency of an averaging pitot tube probe <NUM> of an industrial process sensing or measuring device <NUM> for sensing a parameter of a process fluid flow <NUM> in a process vessel <NUM>, in accordance with embodiments of the present disclosure. In some embodiments, the averaging pitot tube probe <NUM> is a component of a probe assembly <NUM> formed in accordance with one or more embodiments described herein.

At <NUM> of the method, a first end <NUM> of the probe <NUM> is supported in a fixed position relative to the process vessel <NUM>, as shown in <FIG>. This may involve extending the end <NUM> through an opening <NUM> in the process vessel <NUM>, and securing the end <NUM> using a fixed mount <NUM>, such as described above with reference to <FIG>.

At <NUM> of the method, a second end <NUM> of the probe <NUM> is supported using a tensioning mount <NUM>, as shown in <FIG>. This may involve extending the end <NUM> through an opening <NUM> in the process vessel <NUM>, and supporting the end <NUM> using a tensioning mount <NUM>, such as described above with reference to <FIG>.

At <NUM> of the method, the resonant frequency of the probe <NUM> is adjusted using a tensioner <NUM> (<FIG>) of the tensioning mount <NUM>. Embodiments of step <NUM> include adjusting the tension <NUM> in the probe <NUM> using the tensioner as discussed above with reference to <FIG>. In some embodiments, the tension <NUM> of the probe <NUM> is increased using the tensioner <NUM>, which increases the resonant frequency of the probe <NUM>.

The adjusted resonant frequency of the averaging pitot tube probe <NUM> may be set to a value that is higher or lower than the wake frequency that is expected to form in the fluid flow <NUM> (<FIG>). Thus, the probe <NUM> may be used in the fluid flow <NUM> without being subjected to high-magnitude oscillation forces at the resonant frequency of the probe <NUM>. As a result, the operating life of the probe <NUM> in the fluid flow <NUM> is increased relative to a similarly structured probe having a resonant frequency that is close to or matches the wake frequency.

Some exemplary embodiments of the present disclosure apply the features described above using a probe <NUM> in the form of an averaging pitot tube probe <NUM> to other types of probes. In one example not covered by the claims, the probe <NUM> may take the form of a shedding bar (e.g., bluff body or a vortex generator) of a vortex flow meter. This version of the probe <NUM> splits the flow into two paths causing vortices to shed from alternate sides of the probe <NUM> at a frequency that is linearly proportional to a velocity of the fluid flow <NUM>. The one or more sensors <NUM> are used to detect this frequency, and output a corresponding signal <NUM>, which, for example, can be processed using conventional techniques to determine the flow rate of the fluid, such as by the controller <NUM>.

In yet another example not covered by the claims, the probe <NUM> may take the form of a thermowell that is used to detect a temperature of the fluid <NUM>. Here, one of the sensors <NUM> may be in the form of a temperature sensor 116T (e.g., thermocouple, resistive temperature detector, thermistor, etc.) that is housed within the thermowell, as indicated in <FIG>. The temperature sensor 116T detects the temperature of the process fluid <NUM> through the thermowell, and provides an output signal <NUM> indicating the sensed temperature. The output signal <NUM> may be processed using conventional techniques to determine a temperature of the fluid <NUM>, such as using the controller <NUM>.

Accordingly, probe assemblies <NUM> formed in accordance with embodiments of the present disclosure include a probe <NUM> in the form of an averaging pitot tube probe, and in accordance with examples not covered by the claims include a probe in the form of a vortex flow meter, and a thermowell.

Claim 1:
An averaging pitot tube probe assembly (<NUM>) for use in sensing a parameter of a fluid flow (<NUM>) in a process vessel (<NUM>), the averaging pitot tube probe assembly comprising:
an averaging pitot tube probe (<NUM>) extending through the process vessel and including a first end extending through a first opening (<NUM>) in the process vessel, and a second end extending through a second opening (<NUM>) in the process vessel;
a fixed mount (<NUM>) securing the first end in a fixed position relative to the process vessel; and
characterized by a tensioning mount (<NUM>) including a tensioner (<NUM>) attached to the second end of the probe and configured to adjust a tension in the probe and thereby alter a resonant frequency of the probe.