JP6785894B2 - Improved spool body for vibrating densitometer - Google Patents

Description

The present invention relates to a vibration type densitometer, and more particularly to a spool body of the vibration type densitometer.

Densitometers are generally known in the art and can be used to measure the density of fluids. The fluid may include a liquid, a gas, a liquid having suspended particulates and / or a gas taken in, or a combination thereof.

The vibrating densitometer can include vibrating members such as cylinders that are exposed to the test fluid. An example of a vibrating densitometer has a cantilevered cylindrical conduit with an inlet end connected to an outlet pipeline or other structure and the outlet end being vibration-free. The conduit is vibrated and the resonant frequency is measured. As is generally known in the art, the density of the fluid under test is determined by measuring the resonant frequency of the conduit in the presence of the fluid. According to a well-known principle, the resonant frequency of the conduit varies as opposed to the density of the fluid in contact with the conduit.

FIG. 1 shows a prior art densitometer. Conventional densitometers include a cylindrical vibrating member that is at least partially located within the housing. The housing or vibrating member may include a flange or other member for operably connecting the densitometer to a pipeline or similar fluid transfer device to prevent fluid leakage. In the example shown, the vibrating member is cantilevered to the housing at the inlet end. The opposite end vibrates freely. The vibrating member includes a plurality of fluid openings that allow fluid to enter the densitometer and flow between the housing and the vibrating member. Therefore, the fluid comes into contact with the inner and outer surfaces of the vibrating member. This is especially useful if the fluid under test contains a gas, because a larger surface area is exposed to the gas. In another example, the opening is provided in the housing and the opening of the vibrating member is not required.

The vibrating member is vibrated at or near its natural frequency (ie, resonance frequency). As described above, the density of the fluid can be determined by measuring the resonance frequency of the vibrating member in the presence of the fluid.
The driver and vibration sensor are located on the spool body inside or outside the cylinder. The driver receives a drive signal from the meter electronic device and vibrates the vibrating member at or near the resonance frequency. The vibration sensor detects the vibration of the vibrating member and transmits the vibration information to the meter electronic device for processing. The meter electronics determine the resonant frequency of the vibrating member / test fluid and generate a density measurement from the measured resonant frequency.

The resonant frequency must be very stable in order to obtain an accurate density measurement. Unfortunately, vibrating densitometers often experience a series of V-shaped dips in response to sensors operating over a range of gas pressures. This is shown in the graph of FIG. The spool body with the cylinder has a cantilever mode that is excited during the normal operation of the densitometer, but the frequencies that excite this cantilever mode do not match between the spool bodies. An important design criterion for gas density cylinders is the separation of vibration mode shapes, which allows the vibration mode shapes to be easily and accurately distinguished. However, the cantilever mode of the spool body can appear unpredictably between 1100-1700 Hz, which is within the expected measurement range of a typical vibrating densitometer, affecting the accuracy of the measurement. It should be noted that. Frequency fluctuations are assumed to be due to inconsistencies associated with the potting material around the spool body, as the potting process is inaccurate and prone to void formation. FIG. 3 shows a potting gap in the spool body of the prior art.

As a result, prior art vibration densitometers can generate resonance frequency values that incorporate an unpredictable spool body cantilever mode, which can lead to errors in density measurements.

Therefore, there is a need to remove the cantilever mode of the spool body from the range of the natural frequency of the vibrating member. There is a need for a spool body that maintains a small footprint that matches the Scherrer equation of the densitometer while exhibiting increasing or decreasing natural frequencies. There is also a need for a spool body in which it is difficult to form a gap for potting. The present invention solves these and other needs and advances in the art are achieved.

Summary A spool body suitable for use with a vibrating densitometer is provided. The spool body comprises a core, a plurality of spines extending away from the core, and at least one channel defined by the plurality of spines.
A method of forming a vibrating densitometer is provided. This method comprises a step of providing a vibrating tube portion having a predetermined natural frequency range and a step of forming a spool body having a cantilever mode including a frequency range outside the predetermined natural frequency range of the vibrating tube portion. Including.

Aspects In one aspect of the present invention, the vibrating member used in the vibrating densitometer includes a spool body suitable for use in the vibrating densitometer. The spool body comprises a core and a plurality of spines extending away from the core, and at least one channel is defined by the plurality of spines.

Preferably, the cantilever mode of the spool body is outside the range between about 770 Hz and 4080 Hz.
Preferably, the cantilever mode of the spool body is outside the range between about 900 Hz and 2000 Hz.
Preferably, at least one channel comprises a filter material therein.
Preferably, the material of the spool body includes a potting material.
Preferably, the potting material comprises a fiber.
Preferably, the material of the spool body comprises plastic.
Preferably, the material of the spool body comprises polyphenylene sulfide.

Preferably, a driver for vibrating the vibrating tube portion with respect to the housing and at least one vibration sensor configured to detect the vibration of the vibrating tube portion are provided.
Preferably, the vibrating tube portion is at least partially contained within the vibrating member of the vibrating densitometer.
Preferably, the plurality of spines and at least one channel are arranged circumferentially around the core.
Preferably, the plurality of spines and at least one channel are radially arranged around the longitudinal axis of the core.

In one aspect of the invention, the method of forming a vibrating densitometer is a cantilever that includes a step of providing a vibrating tube portion having a predetermined natural frequency range and a frequency range outside the predetermined natural frequency range of the vibrating tube portion. Includes a step of forming a spool body having a beam mode.

Preferably, the step of forming the spool body includes a step of forming a core, a step of forming a plurality of spines extending away from the core, and a step of forming at least one channel defined by the plurality of spines. Be prepared.
Preferably, the predetermined natural frequency range is between about 770 Hz and 4080 Hz.
Preferably, the predetermined natural frequency range is between about 900 Hz and 2000 Hz.

Preferably, the step of forming the spool body comprises placing the filter material in at least one channel.
Preferably, the material of the spool body includes a potting material.
Preferably, the potting material comprises a fiber.
Preferably, the material of the spool body comprises plastic.
Preferably, the material of the spool body comprises polyphenylene sulfide.

Preferably, the steps of forming the spool body include a step of placing a driver on the spool body configured to vibrate the vibrating tube portion and at least one vibration sensor configured to detect the vibration of the vibrating tube portion. Includes the step of placing on the spool body.

Preferably, the method of forming the vibrating densitometer comprises at least partially placing the vibrating tube portion within the vibrating member of the vibrating densitometer.
Preferably, the plurality of spines and at least one channel are arranged circumferentially around the core.
Preferably, the plurality of spines and at least one channel are radially arranged around the longitudinal axis of the core.

The same reference numerals represent the same elements on all drawings. The drawings are not always on scale.
FIG. 1 shows a prior art densitometer. FIG. 2 shows the signal response curve of a prior art densitometer, showing a dip due to at least a partial potting mismatch. FIG. 3 shows a potting gap in the spool body of the prior art. FIG. 4 shows a spool body according to an embodiment, and potting has not yet been introduced. FIG. 5 shows a cross-sectional view of the spool body according to the embodiment and has potting. FIG. 6 shows a model of the spool body according to the embodiment and shows the cantilever mode. FIG. 7 follows an embodiment FIG. 8 shows a spool body according to the present embodiment.

FIGS. 4-FIG. 8 and the following description describe to those skilled in the art how to make and use embodiments of the best mode of the invention, with particular examples. Some conventional embodiments have been simplified or omitted for the purpose of disclosing the principle of inventive step.
Those skilled in the art will understand variations within the scope of the present invention from these examples. Those skilled in the art will appreciate that the features described below are combined in various ways to form numerous variations of the invention. As a result, the invention is limited only by the claims and their equivalents, not by the particular examples described below.

As described above, the vibrating member for the densitometer changes its natural frequency according to the density of the fluid measured by the densitometer. In the case of a typical gas densitometer, the operating frequency range of the vibrating member is, for example, between, but not limited to, about 900 Hz and 2000 Hz.
Conventional spool bodies exhibit cantilever modes within this range and can cause errors when trying to measure fluid density.

4 and 5 show the spool body 100 according to the embodiment. For clarity, FIG. 4 is shown with no potting attached. The spool body 100 moves the cantilever mode away from the operating mode of the vibrating member, thereby improving the accuracy of the densitometer to which the vibrating member is attached. In the embodiment, the cantilever mode is shifted to a frequency higher than the operating range of the vibrating member so that there is no conflicting mode. In another embodiment, the cantilever mode is shifted to a frequency lower than the operating range of the vibrating member so that there is no conflicting mode. The spool body 100 exhibits other modes in addition to the cantilever mode, the other modes being higher than the cantilever mode, and in the embodiment the cantilever mode is shifted to a frequency lower than the operating range of the vibrating member. The best next mode of the spool body is higher than the operating range of the vibrating member.

ここで、
ｆは周波数、κは剛性、ｍは質量である。 As an example, as shown in equation (1), it is well known that the frequency depends on the mass and stiffness of the object.

here,
f is frequency, κ is rigidity, and m is mass.

This is merely an example of the application of the equation and is not limiting the embodiment as other equations are possible. However, the relationship expressed by equation (1) is that in order to increase the natural frequency of the spool body 100, its mass must be reduced, its rigidity must be increased, or both. Indicates that it must be done. The provided embodiment reduces the mass of the spool body 100 by using less potting 102. In the embodiment, the mass of the spool body 100 is reduced by using a relatively low density potting 102. It is possible to reduce the mass of the components embedded in the potting 102, but note that the mass of these components is relatively large compared to the mass of the potting and only relatively small effects are possible. Should be. Therefore, in one embodiment, the rigidity of the spool body 100 is increased in order to increase the cantilever mode frequency. In a related embodiment, the rigidity of the spool body 100 is reduced in order to reduce the cantilever mode frequency. Note that the stiffness of the spool body can be adjusted by adjusting the mass of the spool body 100, so changes in frequency based on changes in mass or mass allocation can be partially offset by changes in stiffness. Should be.

An example of the equation used to define the stiffness (κ) of the cantilever mode of the spool body 100 is illustrated in equation (2).
κ = 3EI / L ³ (2)
Here, E is the elastic modulus of the material, I is the moment of inertia of the object, and L is the length.

This is merely an example of the application of the equation and is not limiting the embodiment as other equations are possible. Adjusting the length of the spool body 100 is a relatively cumbersome variable to change because it is related to the length of the vibrating member, the cavity in which the spool body 100 resides, and the configuration of any drive circuit. However, in one embodiment, the length of the spool body 100 is
Shortened or lengthened to achieve the desired frequency response.

By adjusting the moment of inertia, it is possible in the embodiment that all modes of the spool body 100 remain outside the operating frequency range of the sensor. In this way, the ratio of κ / m (see, eg, equation (1)) puts all bending, radial and breath modes out of the operating range of the sensor, which is generally between about 900Hz and 2000Hz. Be adjusted. In one embodiment, the operating range is between about 500 Hz and 2500 Hz. These are examples of frequency ranges and differ for other cylindrical materials or shapes.

The elastic modulus and / or moment of inertia is adjusted in the embodiment. Moment of inertia (I)
Is almost ideal already in a circular cross section and can be expressed as in equation (3).
I = πr ^4/4 (3)
Here, r is the radius of the spool body.

This is merely an example of the use of equations, and other equations are conceivable and do not limit embodiments. Changing the moment of inertia is related to increasing or decreasing the radius of the potting 102. According to the experiments performed, the moment of inertia must be increased by about 112% in order to move the cantilever mode high enough to move out of normal operating range, which is the case in some embodiments. It interferes with the vibrating member in connection with the increase in the radius of the potting portion to an impractical level. However, in some embodiments, the radius of the potting portion increases to adjust the moment of inertia.

In one embodiment, by reducing the cross section of the spool body 100, the cantilever mode is reduced and the moment of inertia is reduced accordingly. However, reducing the cross section reduces the mass, thus canceling most of the frequency changes resulting from changes in the moment of inertia. In one embodiment, as described in FIGS. 4 and 5, the spool body 100 is formed such that the plurality of spines 104 extend away from the core 106, although a lower moment of inertia is obtained. The required mass is maintained. In particular, the addition of the spine 104 reduces the bending moment of inertia by accepting the characteristics of the thinnest cross section of the core 106, while maintaining the material of the spine 104 keeps the mass relatively high. The plurality of spines 104 effectively define a series of channels 108. In one embodiment, the potting 102 can be placed within the channel 108, but the channel may not have potting. A separate base 101 exists or does not exist. In one embodiment, the channel 108 and spine 104 are arranged circumferentially around the spool body 100. In another embodiment shown in FIG. 8, the channel 108 and spine 104 are arranged radially around the longitudinal axis of the core 106 of the spool body 100.

The shape of the spool body 100 is not limited to the round cross section as shown. In the embodiment
Rectangle, ellipse, polygon, square, triangle, leaflet, dogbone and other cross-sectional shapes are also possible.

As mentioned above, the elastic modulus of the potting 102 is also adjusted in the embodiment. In one embodiment, the elastic modulus of the spool body 100 is increased by using a potting 102 having a relatively high elastic modulus. In one embodiment, the injected plastic is used in place of the potting 102, as the plastic generally has a higher modulus of elasticity than typical potting. In one embodiment, the elastic modulus of the spool body 100 is increased by forming the spool body with a material having a relatively high elastic modulus. By using injection molding, it is possible to use a material that is not generally used as a potting material. In one embodiment, fiber reinforced plastic is used instead of the conventional potting material or spool body 100 material. In one embodiment, polyphenylene sulfide, such as Ryton ™, is used instead of the conventional potting material. Polyphenylene sulfide can be used advantageously in high temperature applications and corrosive environments. Fibers can be added to make a composite material to reinforce the material that makes up the spool body 100. Possible fibers are made from, for example, glass, carbon aramid, boron, alumina, silicon carbide, quartz, other fibers known in the art, and combinations thereof, and are not limited thereto.

Injection molding is also very unlikely to create voids often found in current spool bodies (see Figure 3). In addition to affecting the movement of the spool body, voids can expose the electronics to potentially corrosive measuring fluids. Voids also lead to costly drop (defect) rates during manufacturing, increasing the average cost of the finished assembly, while also limiting production. Polyphenylene sulfide can replace potting, but polyphenylene sulfide can also be used to configure the spool body 100.

FIG. 6 shows an exemplary finite element analysis model of the spool body 100 according to an embodiment, specifically showing a cantilever mode lowered to about 770 Hz, where the next mode does not appear until 4080 Hz. These modes are outside the operating range of most vibrating members and therefore do not interfere with most density measurements.

FIG. 7 shows a vibrating densitometer 200 according to an embodiment. The vibrating member 202 of the indicated embodiment includes a base 204 and a long vibrating tube portion 206 fixed to the base 204. The vibrating member 202 is substantially hollow and includes an inlet end 208 and an outlet end 210. The base 204 is located at the inlet end 208 of the vibrating member 202. The inlet end 208 is connected to the housing 212 or other element of the vibrating densitometer 200. The fluid flowing into or passing through the vibrating member 202 can enter at the inlet end 208 and exit at the outlet end 210. It will be appreciated that in embodiments, the inlet end 208 may be configured to be an exit and the outlet end 210 may be configured to be an inlet.

The vibrating tube portion 206 includes a density sensing element. In some embodiments, the vibrating tube portion 206 is a thin metal tube. During operation, the vibrating tube portion 206 is operated to vibrate at its inherent (resonant) frequency. In one embodiment, the vibrating member 202 (and thus the vibrating tube portion 206) is configured to vibrate in one or more vibration modes. A fluid such as gas can pass over at least one of the inner surface 213 and / or the outer surface 215 of the vibrating tube portion 206 and thus contacts the exposed side of the vibrating tube portion 206. The mass of the fluid vibrates with the tube, "
Since increasing the vibrating mass lowers the natural frequency of vibration of the vibrating member, when the vibrating member 202 is vibrated in the presence of fluid, the density of the fluid is the natural or resonant vibration frequency of the vibrating member 202. Is determined by measuring.

The oscillating densitometer 200 is configured to determine the density of fluids such as gases, liquids, liquids with uptake gas, liquids with suspended particulates, and / or combinations thereof.

According to one embodiment, the vibrating densitometer 200 has a vibrating member 202 inside the housing 212.
including. The vibrating member 202 may be permanently or removablely secured to the housing 212. The fluid to be measured may be introduced into the housing 212 or may pass through the housing 212. In some embodiments, the vibrating member 202 is substantially coaxial with the housing 212. However, the vibrating member 202 does not have to correspond to the cross-sectional shape of the housing 212.

When the vibrating tube portion 206 is attached to the vibrating densitometer 200, the inlet end 208 of the vibrating member 202 is coupled to the housing 212, while the outlet end 210 vibrates freely. The vibrating tube portion 206 is not directly coupled to the housing 212 in the illustrated embodiment, but instead the base 204 is coupled to the housing 212 and the outlet end 210 vibrates freely. As a result, the vibrating tube portion 206 is attached to the housing 212 in a cantilever shape.

According to embodiments, the vibrating densitometer 200 further includes a driver 214 coupled to the spool body 100 and at least one vibration sensor 216. The driver 214 can be configured to vibrate the vibrating member 202 in one or more vibration modes. Although the driver 214 is shown arranged within the spool body 100 disposed within the vibrating member 202, in some embodiments, for example, the driver 214 is located between the housing 212 and the vibrating member 202. May be done.
Further, although the driver 214 is shown to be located close to the inlet end 208, it should be understood that the driver 214 may be located in any desired position. According to an embodiment, the driver 214 receives an electrical signal from the meter electronics 218 via a lead 220.

In the embodiments shown, at least one vibration sensor 216 is coaxially aligned with the driver 214. In other embodiments, the at least one vibration sensor 216 may be coupled to the vibration member 202 at other positions. For example, at least one vibration sensor 216 may be located outside the vibration member 202. Further, at least one vibration sensor 216 may be located outside the vibration member 202, while the driver 214 may be located inside the vibration member 202 and vice versa.

The at least one vibration sensor 216 transmits a signal to the meter electronics 218 via the lead 220. The meter electronic device 218 can process the signal received by at least one vibration sensor 216 to determine the resonance frequency of the vibrating member 202. In the presence of the fluid under test, the resonant frequency of the vibrating member 202 changes in inverse proportion to the fluid density, as is known in the art. Proportional changes can be determined, for example, during initial calibration. In the embodiments shown, the at least one vibration sensor 216 also includes a coil. The driver 214 receives a current that induces vibration in the vibrating member 202, and at least one vibration sensor 216 induces a voltage using the movement of the vibrating member 202 generated by the driver 214. Coil drivers and sensors are well known in the art and their further description is omitted for brevity. Further, it is understood that the driver 214 and at least one vibration sensor 216 are not limited to coils and include, but are not limited to, various other well-known vibration elements such as piezo electric drivers / sensors, laser sensors and the like. Should be. Therefore, this embodiment should never be limited to coils. Moreover, one of ordinary skill in the art will readily recognize that a particular arrangement of the driver 214 and at least one vibration sensor 216 can be modified while remaining within the scope of this embodiment.

Meter electronics 218 may be connected to bus 222 or other communication link. Meter electronics 218 can transmit density measurements via bus 222. In addition, meter electronics 218 may transmit other signals, measurements or data of any method via bus 222. In addition, meter electronics 218 may receive instructions, programming, other data or instructions via bus 222.

The wall of the vibrating tube portion 206 is excited by the operation. In one embodiment, the wall of the vibrating tube section 206 is excited by a driver 214 or other excitation mechanism in radial and radial vibration modes. The wall of the vibrating tube section 206 vibrates in the corresponding radial mode, which vibrates at the resonant frequency of the elongated vibrating tube section 206 and the surrounding flowing fluid.

The provided embodiment of the spool body 100 makes it possible to separate the vibrating tube portion 206 and the resulting vibration mode by at least a predetermined frequency difference from the frequency dip of the spool body 100 due to the cantilever mode. Thus, the vibration densitometer 200 can filter, or otherwise separate or distinguish, the vibration modes picked up by at least one vibration sensor 216 from the cantilever mode interference.

When the densitometer 200 is configured, the spool body 100 is formed. In one embodiment, the spool body 100 is formed at least partially by casting. In one embodiment, the spool body 100 is at least partially formed by machining. In one embodiment, the spool body 100 is formed at least partially by electrical discharge machining. These provide non-limiting examples of potential construction techniques and do not function to limit the use of other construction techniques. The spool body 100 can be composed of metal, plastic, polymer, composite material, and a combination thereof. The spool body 100 does not have to be made of a single material
A portion made from the first material and at least other portions made from the second material can be included. In some embodiments, the potting 102 may be cast, injected, or otherwise introduced into channel 108 of the spool body 100.

The detailed description of the above embodiments is not a complete description of all embodiments considered by the inventor within the scope of the present invention. In fact, one of ordinary skill in the art is aware that certain elements of the above embodiments may be combined or removed in various ways to create further embodiments, and such additional embodiments are It is within the scope of the current description and disclosure. It will also be apparent to those skilled in the art that all or part of the above embodiments may be combined to create additional embodiments within the scope of the current description and disclosure.

Although certain embodiments are described herein for purposes of illustration, experts in the art will find that various equivalent modifications are possible within the scope of the current description.
The disclosure provided herein may apply to other vibrating members, not just the embodiments described above and shown in the accompanying drawings. Therefore, the scope of the above embodiments should be determined from the appended claims.

Claims (13)

A method of forming a vibrating densitometer,
And have a predetermined natural frequency range, comprising: providing a vibration tube portion operable to vibrate with a vibration type in densitometer,
A step of forming a spool body having a cantilever mode including a frequency range outside a predetermined natural frequency range of the vibrating tube portion, and
A step of connecting the vibrating tube portion and the spool body ,
A method comprising arranging a driver configured to vibrate a vibrating tube portion on the spool body . The steps to form the spool body are
The steps to form the core and
Steps to form multiple protrusions that extend away from the core,
The method of claim 1, comprising the step of forming at least one channel defined by a plurality of protrusions. The method of claim 1, wherein the predetermined natural frequency range is between 770 Hz and 4080 Hz. The method of claim 1, wherein the predetermined natural frequency range is between 900 Hz and 2000 Hz. The method of claim 1, wherein the step of forming the spool body comprises placing the filter material in at least one channel. The method according to claim 1, wherein the material of the spool body includes a potting material. The method of claim 6, wherein the potting material comprises a fiber. The method according to claim 1, wherein the material of the spool body includes plastic. The method according to claim 1, wherein the material of the spool body includes polyphenylene sulfide. Comprising at least one step of placing a vibration sensor on a spool body configured to sense the vibration of the vibrating tube portion The method of claim 1. The method of claim 1, comprising the step of placing the vibrating tube portion in the vibrating member of the vibrating densitometer at least partially. The method of claim 1, wherein the plurality of protrusions and at least one channel are arranged circumferentially around the core. The method of claim 1, wherein the plurality of protrusions and at least one channel are radially arranged around a longitudinal axis of the core.

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