Vibronic measurement recorder for measuring the mass flow of a flowable medium
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- ENDRESS HAUSER FLOWTEC AG
- Filing Date
- 2024-08-20
- Publication Date
- 2026-07-01
Smart Images
Figure EP2024073292_06032025_PF_FP_ABST
Abstract
Description
[0001] Vibronic sensor for measuring the mass flow of a fluid
[0002] The present invention relates to a vibronic measuring sensor for measuring the mass flow of a flowable medium, in particular a measuring sensor with an S-shaped profile.
[0003] A generic measuring sensor comprises a line inlet section; a vibratable measuring pipe for conveying the medium, wherein the measuring pipe is bent in its rest position in a measuring pipe plane, wherein the measuring pipe has a substantially S-shaped course with a twofold rotational symmetry with respect to an axis that runs perpendicular to the measuring pipe plane; a line outlet section; at least one vibration exciter for exciting bending vibrations of the measuring pipe in a bending vibration useful mode; at least two vibration sensors for detecting vibrations of the measuring pipe; a carrier body; an inlet-side bearing body and an outlet-side bearing body; wherein the measuring pipe is firmly connected to the carrier body by means of the inlet-side bearing body and by means of the outlet-side bearing body and is delimited by the bearing bodies.The measuring pipe connects to the pipe inlet section on the inlet side and to the pipe outlet section on the outlet side, and can be connected to a pipe via the latter; the measuring pipe has two vibration nodes in the useful bending vibration mode, which is an F3 bending vibration mode, which are spaced apart from the bearing bodies. The designation F3 indicates that this bending vibration mode usually has the third-lowest natural frequency of the bending vibration modes of the measuring pipe.
[0004] Generic measuring sensors are disclosed, for example, in European patents EP 0 518 124 B1, EP 3 631 379 B1 and EP 3631 378 B1. The generic measuring sensors are designed to minimize the coupling of disruptive vibrations from the sensor's environment via its components into the measuring pipe and the dissipation of vibration energy from the measuring pipe via the sensor's components into its environment. However, further investigations of the generic measuring sensors have shown that sound waves propagating via the medium into the measuring pipe influence the vibration behavior of the latter and thus cause a zero-point error in flow measurement. It is therefore the object of the present invention to remedy this situation.
[0005] The object is achieved according to the invention by the measuring sensor according to independent patent claim 1.
[0006] The vibronic measuring sensor according to the invention for measuring the mass flow of a flowable medium comprises: a line inlet section; a vibrating measuring pipe for guiding the medium, wherein the measuring pipe is bent in its rest position in a measuring pipe plane, wherein the measuring pipe has a substantially S-shaped course with a twofold rotational symmetry with respect to an axis,which runs perpendicular to the measuring pipe plane; a pipe outlet section; at least one vibration exciter for exciting bending vibrations of the measuring pipe in a bending vibration useful mode; at least two vibration sensors for detecting vibrations of the measuring pipe; a support body; an inlet-side bearing body and an outlet-side bearing body; wherein the measuring pipe is firmly connected to the support body by means of the inlet-side bearing body and by means of the outlet-side bearing body and is delimited by the bearing bodies; wherein the measuring pipe connects to the pipe inlet section on the inlet side and to the pipe outlet section on the outlet side and can be connected to a pipe via the latter; wherein the measuring pipe has two vibration nodes in the bending vibration useful mode, which is an F3 bending vibration mode,which are spaced apart from the bearing bodies; wherein, according to the invention, the measuring sensor further comprises two damper mass bodies which are fastened to the measuring pipe, wherein the damper mass bodies each have a center of gravity which is not more than two outer diameters of the measuring pipe, for example not more than one outer diameter of the measuring pipe and in particular not more than half an outer diameter of the measuring pipe from a position at which, when the measuring pipe is filled with water, the nearest vibration node of the bending vibration useful mode is located, wherein in the case of sound coupling via the medium, this is caused by a zero-point error beat, wherein the zero-point error beat has a maximum dependent on the sound frequency, wherein the damper mass bodies (56, 58) cause the frequency-dependent maximum of the zero-point error beat to have an amplitude,which has less than 50% of the amplitude of the frequency-dependent maximum of the zero-point error beat of a reference sensor of identical construction except for the absorber masses, wherein the reference sensor has no absorber masses. The reference sensor corresponds to the prior art on which the present invention is based.
[0007] The absorber mass bodies serve to suppress disturbing vibrations introduced into the measuring pipes, to cancel them at the location of the vibration nodes, thus to suppress them to a large extent.
[0008] In a further development of the invention, the damper mass bodies each have a principal axis of inertia that forms an angle of no more than 15°, for example, no more than 10°, and in particular no more than 5°, with the direction vector of a measuring tube guide curve in a measuring tube cross-section through the center of gravity of the damper mass body, and that runs in particular parallel to the direction vector. In one embodiment of this further development of the invention, the principal axis of inertia is in each case a maximum principal axis of inertia.
[0009] In a further development of the invention, the two absorber mass bodies each have an extension in the direction of the direction vector of the measuring tube guide curve which is not more than four, for example not more than two, measuring tube diameters.
[0010] In a further development of the invention, the centers of gravity of the absorber mass bodies are each spaced from the measuring tube guide curve by no more than one tenth of an outer radius of the measuring tube.
[0011] In a further development of the invention, the two absorber mass bodies each have a mass which is not less than eight times, in particular not less than twelve times, the mass of a section of the measuring pipe which has a length of one measuring pipe diameter.
[0012] In a further development of the invention, the two absorber mass bodies are arranged according to the twofold rotational symmetry.
[0013] In a further development of the invention, the two absorber mass bodies reduce a natural frequency of the useful bending vibration mode in an air-filled measuring tube at a pressure of 0.1 MPa and a temperature of 300 K by not more than 4%, in particular not more than 2%, compared to a comparison natural frequency of this useful bending vibration mode of the measuring tube without absorber mass bodies.
[0014] In a further development of the invention, a displacement of a position LK of the vibration node along the measuring tube guide curve by varying the density of the medium at a temperature of 300 K, a pressure of 0.1 MPa and densities between 500 kg / m 3 and 1500 kg / m 3 and in particular where da is the outer diameter of the measuring tube.
[0015] In a further development of the invention, the line inlet section and the line outlet section have substantially the same pipe cross-section as the measuring pipe, in particular the same pipe material as the measuring pipe, and are preferably manufactured in one piece with the measuring pipe.
[0016] In a further development, the measuring tube has an outer diameter of not more than 20 mm, in particular not more than 10 mm.
[0017] In a further development of the invention, the measuring tube has an outer diameter of not less than 0.5 mm, in particular not less than 1.0 mm.
[0018] In a further development, the useful bending vibration mode, which corresponds to the second symmetrical bending vibration mode, has a natural frequency of not less than 100 Hz, in particular not less than 400 Hz, when the measuring pipe is filled with water.
[0019] In a further development, the useful bending vibration mode, which corresponds to the second symmetrical bending vibration mode, has a natural frequency of no more than 1200 Hz, in particular no more than 900 Hz, when the measuring pipe is filled with water. In a further development of the invention, the support body has a support plate that runs essentially parallel to the plane of the measuring pipe.
[0020] The invention will now be explained in more detail with reference to the exemplary embodiments illustrated in the drawings. It shows:
[0021] Fig. 1 a is a plan view of an embodiment of a measuring sensor according to the invention;
[0022] Fig. 1 b is a spatial view of an absorber mass body mounted on the measuring pipe of an embodiment of a measuring sensor according to the invention;
[0023] Fig. 1 c shows a longitudinal section through an absorber mass body mounted on the measuring pipe of an embodiment of a measuring sensor according to the invention;
[0024] Fig. 1 d shows a cross-sectional view of an absorber mass body mounted on the measuring pipe of an embodiment of a measuring sensor according to the invention;
[0025] Fig. 1 e shows a cross-sectional view of an alternative damper mass body mounted on the measuring pipe of an embodiment of a measuring sensor according to the invention; and
[0026] Fig. 2 Data of zero point error beats of the zero point error due to sound coupling and associated attenuations for a sensor according to the prior art and for a sensor according to the invention.
[0027] The measuring sensor 100 shown in Fig. 1a comprises a measuring pipe 10 with a first straight outer section 11, a second straight outer section 12 and a central straight section 13 as well as a first bent section 15 and a second bent section 16. The two straight outer sections 11, 12 are each connected to the central straight section 13 by means of one of the bent sections 15, 16. The measuring pipe 10 is delimited by two bearing bodies 21, 22 and is fastened by the latter to a rigid support plate 30. The measuring pipe 10 runs essentially in a pipe plane parallel to the support plate 30. The measuring pipe has a twofold rotational symmetry about an axis of symmetry that runs perpendicular to the pipe plane through a point C2 in the middle of the central pipe section. The measuring pipe has an inner diameter of, for example, 5 mm or less.It is made of a metal, in particular stainless steel or titanium. The metallic carrier plate 30 has a thickness of, for example, 5 mm. The carrier plate 30 has four spiral spring bearings 31, 32, 32, 33, 34, which are cut out in particular by means of a laser, and which also have twofold rotational symmetry with respect to the axis of symmetry through point C2. The carrier plate 30 is anchored to a housing plate 40 of a sensor housing by bearing bolts (not shown here) that are fixed in the center of the spring bearings. The effective stiffness of the spring bearings results from the length of the spiral cut and its width in relation to the width of the remaining material of the carrier plate 30. In the center, the spring bearings have a bore (not shown here) for receiving a bearing bolt each.Thanks to the spring bearings 31, 32, 33, 34, the support plate 30 has three degrees of freedom for translational vibration and three degrees of freedom for rotational vibration, whose natural frequencies are at least 70 Hz to avoid resonance vibrations with vibrations of up to 50 Hz, which are frequently encountered in process plants. In order not to impair the soft suspension of the support plate achieved by the spring bearings 31, 32, 33, 34, the measuring pipe can be connected to a pipeline via a sufficiently soft pipe inlet section 18 and a sufficiently soft pipe outlet section 19. The housing has a first and second housing bearing 41, 42 which are fixedly connected to the housing plate 40 and to which the line inlet section 18 and the line outlet section 19 are fixed in order to suppress transmission of vibrations of the pipeline to the measuring pipeline via the line inlet section 18 and the line outlet section 19.The translational and rotational vibration degrees of freedom of the carrier plate 30 each have natural frequencies f which are proportional to the root of a quotient of a reference value ki and an inertia term mi, i.e. fa (k / mi). 1 / 2. The line inlet section 18 and the line outlet section contribute a total of no more than 10% to the respective reference value k. In Fig. 1a, the line inlet section 18 and the line outlet section 18, 19 are shown essentially schematically. They can have reduced rigidity by means of additional pipe length and bends, whereby their contribution to the respective reference values is reduced. As further shown in Fig. 1a, the measuring sensor 100 for detecting the vibrations of the measuring pipe 10 has a first electrodynamic vibration sensor 51 and a second electrodynamic vibration sensor 52, each of which has a magnet on the measuring pipe 10 and a coil on the carrier plate 30. The two vibration sensors 51, 52 are each arranged on one of the two straight outer sections 11, 12 not more than one radius of curvature of the curved sections 15, 16 from the adjacent curved section.To excite bending vibrations, the sensor has an electrodynamic exciter 53 located at the center C2 of the twofold rotational symmetry and acting in the direction of the symmetry axis. The electrodynamic exciter 53 comprises a magnet on the measuring tube 10 and an excitation coil on the support plate 30.
[0028] The center C2 is the origin of a coordinate system for describing an advantageous aspect of a measuring sensor according to the invention. The measuring pipeline lies in an xz plane, wherein the y-axis runs parallel to angle bisectors w1, w2, which each run between a pipe axis of the straight outer sections 11, 12 and the pipe axis of the central straight section 13. The z-axis runs perpendicular to the y-axis in the pipeline plane and defines a longitudinal axis of the measuring sensor 100. If this longitudinal axis is arranged vertically, the measuring sensor can be optimally emptied. The inclination of the straight sections is then equal to half the angle between a pipe axis of the straight outer sections 11, 12 and the pipe axis of the central straight section 13. In this embodiment of the invention, this inclination is 7°.
[0029] The measuring pipe 10 has a preferred symmetrical bending vibration mode with two vibration nodes between the bearing bodies 21, 22. This bending vibration mode has a higher natural frequency than the symmetrical fundamental bending vibration mode, which has no vibration nodes. However, it differs from the fundamental bending vibration mode in that the center of gravity of the measuring pipe 10 has a lower vibration amplitude for the same exciter deflection, so that less vibration energy of the bending vibration mode can be dissipated in this way. Together with the previously described mounting of the support plate 30 in the spring bearings and the associated frequency separation between the bending vibration mode and the vibration of the support plate, the measuring sensor 100 is very well protected against unwanted mechanical coupling or decoupling of vibrations via structural elements of the measuring sensor.
[0030] The measuring sensor according to the invention is further characterized in that two damper mass bodies 56, 58 are attached to the measuring pipe 10, the centers of gravity of which ideally each coincide with one of the vibration nodes of the symmetrical bending vibration useful mode. The damper mass bodies 56, 58 are of identical construction and can, for example, comprise perforated circular plates, as shown in the example of one of the damper mass bodies 58 in Fig. 1b, 1c and 1d. The damper mass bodies 56, 58 are fixed in position on the measuring pipe by joining, for example, brazing. The circular plate shape is obviously a simple shape to enable symmetrical mounting of the damper mass bodies (56, 58). However, if a more compact design is desired, other shapes of the damper mass bodies (56, 58) may be expedient, as is clear from the exemplary embodiment in Fig. 1e.The damper mass body 58' here has a rectangular basic shape, whereby the extension of the rectangle perpendicular to the plane of the measuring pipe 10' is significantly smaller than parallel to the plane of the measuring pipe 10'. In this way, the distance between the measuring pipe 10' and the support body 30' can be significantly reduced. To minimize the impact on the vibration behavior of the measuring pipe, the damper mass bodies 56, 58 are mounted such that their centers of gravity coincide with the measuring pipe guide curve at the location of the vibration node. Furthermore, the maximum principal axis of inertia of the damper mass bodies should deviate as little as possible from the direction vector of the measuring pipe guide curve at the respective vibration node.
[0031] Since the masses of the absorber mass bodies 56, 58 act at the vibration nodes of the desired bending mode, they barely influence its vibration properties. In particular, these masses cause a reduction in the natural frequency of the desired bending mode by less than 2% at most. This means that the dynamics of the density measurement are barely affected by the absorber mass bodies.
[0032] One effect of the absorber mass bodies is explained below with reference to Fig. 2. The data in Fig. 2 come from an experiment in which the measuring pipe was filled with a still liquid and excited with the natural frequency of the useful bending vibration mode, in this case the second symmetrical bending vibration mode. In this case, a flow measurement value of zero would be expected. A flow measurement value deviating from zero in this case corresponds to a zero point error N, which in a given flow situation should be minimal and, in particular, constant. In the present case, however, sound signals were coupled into the measuring pipe via the liquid. These sound signals interact with the vibration of the measuring pipe in the useful bending vibration mode in a frequency-dependent manner and cause beats that manifest themselves in particular as zero point error beats N.In the experiment, the amplitude AN of the zero-point error beats N was maximized by varying the sound frequency. The diagram shows a smoothed curve N1-max of the maximum zero-point beat for a prior-art sensor (top) and a smoothed curve N2-max of the maximum zero-point beat for a sensor according to the invention (bottom). For clarity, the curves are shifted vertically relative to each other, but apart from that, they each have the same scale. It is immediately apparent that the amplitude AN2-max of the maximum zero-point error beat N2-max of the sensor according to the invention is significantly reduced compared to the amplitude AN1-max of the maximum zero-point error beat N1-max of the prior-art sensor. Fig. 2.further shows associated damping curves D1 and D2, wherein the damping of the bending vibration useful mode has a similar beat to that of the zero point error, and wherein the amplitude of the damping D2 in the case of the measuring sensor according to the invention is considerably reduced compared to the amplitude of the damping D1 according to the prior art.
Claims
Patent claims 1. A vibronic measuring sensor (100) for measuring the mass flow of a flowable medium, comprising: a line inlet section (18); a vibratable measuring pipe (10) for guiding the medium, wherein the measuring pipe (10) is bent in its rest position in a measuring pipe plane, wherein the measuring pipe (10) has a substantially S-shaped profile with a twofold rotational symmetry with respect to an axis that runs perpendicular to the measuring pipe plane; a line outlet section (19); at least one vibration exciter (53) for exciting bending vibrations of the measuring pipe (10) in a bending vibration useful mode; at least two vibration sensors for detecting vibrations of the measuring pipe; a support body (30); an inlet-side bearing body (21) and an outlet-side bearing body (22);wherein the measuring pipe (10) is firmly connected to the support body (30) by means of the inlet-side bearing body (21) and by means of the outlet-side bearing body (22) and is delimited by the bearing bodies; wherein the measuring pipe (10) connects to the pipe inlet section (18) on the inlet side and to the pipe outlet section (19) on the outlet side and can be connected to a pipe via the latter; wherein the measuring pipe (10) has two vibration nodes in the useful bending vibration mode, which is an F3 bending vibration mode, which vibration nodes are spaced apart from the bearing bodies; characterized in that; the measuring sensor further comprises two damper mass bodies (56, 58) which are fastened to the measuring pipe (10), wherein the damper mass bodies (56, 58) each have a center of gravity which is not more than two outer diameters of the measuring pipe, for example not more than one outer diameter of the measuring pipe (10) and in particular not more than half an outer diameter of the measuring pipe (10) away from a position at which the nearest oscillation node of the bending oscillation useful mode is located when the measuring pipe is filled with water, wherein in the case of sound coupling via the medium, this is caused by a zero-point error beat, wherein the zero-point error beat has a maximum dependent on the sound frequency, wherein the damper mass bodies (56, 58) cause the frequency-dependent maximum of the zero-point error beat to have an amplitude,which has less than 50% of the amplitude of the frequency-dependent maximum of the zero-point error beat of a reference measuring sensor of the same construction except for the absorber mass bodies, whereby the reference measuring sensor has no absorber mass bodies.
2. Vibronic measuring sensor (100) according to claim 1, wherein the absorber mass bodies each have a main axis of inertia which encloses an angle of not more than 15°, for example not more than 10° and in particular not more than 5°, with the direction vector of a measuring tube guide curve in a measuring tube cross-section through the center of gravity of the absorber mass body, and in particular runs parallel to the direction vector.
3. Vibronic measuring sensor (100) according to claim 2, wherein the two absorber mass bodies each have an extension in the direction of the direction vector of the measuring tube guide curve which is not more than four, for example not more than two, measuring tube diameters.
4. Vibronic measuring sensor (100) according to one of claims 2 to 3, wherein the centers of gravity of the absorber mass bodies are each spaced from the measuring tube guide curve by no more than one tenth of an outer radius of the measuring tube.
5. Vibronic measuring sensor (100) according to one of claims 2 to 4, wherein the principal axis of inertia is a maximum principal axis of inertia.
6. Vibronic measuring sensor (100) according to one of the preceding claims, wherein the two absorber mass bodies each have a mass which is not less than eight times, in particular not less than twelve times, the mass of a section of the measuring pipe (10) which has a length of one measuring pipe diameter.
7. Vibronic measuring sensor (100) according to one of the preceding claims, wherein the two absorber mass bodies are arranged according to the twofold rotational symmetry.
8. Vibronic measuring sensor (100) according to one of the preceding claims, wherein the two absorber mass bodies reduce a natural frequency of the useful bending vibration mode in an air-filled measuring tube at a pressure of 0.1 MPa and a temperature of 300 K by not more than 4%, in particular not more than 2%, compared to a comparison natural frequency of this useful bending vibration mode of the measuring tube line (10) without absorber mass bodies.
9. Vibronic measuring sensor (100) according to one of the preceding claims, wherein for a displacement of a position LK of the vibration node along the measuring tube guide curve due to a variation of the density of the medium under reference conditions: in particular where d a is the outer diameter of the measuring tube.
10. Vibronic measuring sensor (100) according to one of the preceding claims, wherein the line inlet section and the line outlet section have substantially the same pipe cross-section as the measuring pipe, in particular the same pipe material as the measuring pipe, and are preferably manufactured in one piece with the measuring pipe (10).
11. Vibronic measuring sensor (100) according to one of the preceding claims, wherein the carrier body has a carrier plate which runs substantially parallel to the measuring pipe plane.