CORIOLIS MASS FLOW METER AND NODE ELEMENT

Description

[0001] The invention is based on a Coriolis mass flowmeter with at least one measuring tube, with at least one vibration generator and at least two vibration sensors and with at least two node elements, wherein the at least one vibration generator excites the measuring tube to vibrate during operation, wherein the at least two node elements define the vibration region and wherein at least one node element has at least one stiffening element. Furthermore, the invention relates to a node element for use in a Coriolis mass flowmeter with at least one measuring tube, with at least one vibration generator and at least two vibration sensors, wherein the at least one vibration generator excites the measuring tube to vibrate during operation, wherein the vibration region is defined by at least two node elements and wherein the node element has at least one stiffening element.

[0002] To determine the flow rate through a measuring tube, Coriolis mass flowmeters have a vibration generator that causes the measuring tube to oscillate (excitation mode). The flowing medium causes the tube to form a Coriolis mode, which typically corresponds to the first harmonic of the excitation mode. Vibration sensors are mounted on the inlet and outlet sides of the measuring tube to record the vibration of the measuring tube. By determining the phase shift of the Coriolis mode vibrations measured by the vibration sensors, the flow rate of the medium through the measuring tube can be determined.

[0003] It is known from the prior art to arrange node plates or node rings on the inlet and outlet sides of the measuring tube to define the vibration range. These node plates or node rings fix the measuring tube, thereby defining vibration nodes at the ends. Within the scope of the present invention, the node element can also be designed as a node ring or a node plate.

[0004] In addition to exciting the desired Coriolis mode, the measuring tube is also subjected to spurious vibrations deviating from the Coriolis mode, both by excitation from the oscillator and by external sources of interference. It is known to provide stiffening elements that specifically influence the frequency and amplitude of the spurious vibrations to suppress or separate such spurious vibrations.

[0005] For example, the document DE 10 2005 003 161 A1 discloses a Coriolis mass flowmeter with two measuring tubes and with a connecting device connecting the measuring tubes, wherein the connecting device is designed such that its flexural rigidity for bends in the common plane of the measuring tubes is greater than its torsional rigidity for torsional vibrations about the connecting line between the two measuring tubes.

[0006] The publication DE 10 2015 003 365 A1 relates to a Coriolis mass flowmeter with two measuring tubes, wherein the measuring tubes are connected to each other by a junction plate, and wherein the junction plate has an asymmetric stiffening element to increase zero-point stability. Specifically, the stiffening element serves to stabilize the relative position of the first and second measuring tubes in the region of their straight sections.

[0007] Document DE 10 2006 034 274 A1 also discloses a Coriolis mass flowmeter with two measuring tubes connected to each other via a connecting device. The connecting device comprises a stiffening plate attached to both measuring tubes and arranged parallel to the common plane of the measuring tubes, and a stiffening fin is provided on the stiffening plate. This ensures that the flexural rigidity of the connecting device for bends in the common plane of the measuring tubes, in which the excitation vibrations of the measuring tubes generally also occur, is greater than the torsional rigidity of the connecting device for torsional vibrations.

[0008] In addition, the document WO 00 / 47956 discloses a Coriolis mass flowmeter with a measuring tube, wherein a node ring is arranged on the inlet and outlet sides of the measuring tube and wherein each node ring has lateral stiffening elements so that the frequency of undesired lateral vibrations is changed in order to separate the different vibration modes.

[0009] Furthermore, US 2015 / 0330821 A1 discloses a Coriolis mass flowmeter comprising two measuring tubes coupled to each other via support struts. These support struts can be connected to lateral insulation struts.

[0010] From the document US 2011 / 247433 A1, a Coriolis mass flowmeter is known, wherein a gusset plate is provided to suppress unwanted parasitic vibrations, which extends along the curvature of the bent measuring tubes.

[0011] The document EP 0 685 712 A1 describes a Coriolis mass flowmeter with two measuring tubes, wherein two node elements are arranged on each measuring tube and wherein two stiffening elements are arranged on each node element, wherein each stiffening element is designed as a flat web.

[0012] Based on this prior art, the object of the present invention is to provide a Coriolis mass flowmeter that ensures particularly effective separation of unwanted parasitic vibrations in the measuring tube. Furthermore, the object of the invention is to provide a corresponding node element.

[0013] According to a first teaching of the present invention, the above-stated object is achieved by a Coriolis mass flowmeter mentioned at the outset in that the at least one node element is designed and arranged such that the stiffening element increases the stiffness of the measuring tube with respect to oscillations orthogonal to the excitation mode and to the Coriolis mode, so that during operation the oscillation frequency of the oscillation orthogonal to the excitation mode and to the Coriolis mode is higher than the oscillation frequency of the excitation mode, preferably higher than the frequency of the Coriolis mode.

[0014] According to the invention, it was recognized that the integration of a stiffening element into the node element is particularly advantageous, so that oscillations orthogonal to the excitation mode and to the developing Coriolis mode, i.e. in particular vertical oscillations, can be distinguished from the excitation mode by their oscillation frequency. In detail, the oscillation range for the oscillations in the plane of the stiffening element(s) is reduced by the at least one locally acting stiffening element. In this way, disturbing vibrations can be taken into account or filtered out during the recording and / or evaluation of the detected vibration of the measuring tube, so that the measuring accuracy of the Coriolis mass flowmeter can be increased. Additional components for suppressing disturbing vibrations can be avoided in this way.

[0015] According to a preferred embodiment, at least one second stiffening element is provided, wherein the second stiffening element is arranged on the at least one node element, preferably opposite the first stiffening element. The suppression of unwanted vertical vibrations is particularly effective according to this embodiment. The second stiffening element can be identical to the first stiffening element or can have a different shape and / or a different material.

[0016] A further advantageous embodiment of the Coriolis mass flowmeter is characterized in that the at least one stiffening element rests on the circumference of the measuring tube with a support surface. This embodiment has the advantage that the direct and preferably large-area contact of the stiffening element with the measuring tube makes the stiffness of the measuring tube particularly high with respect to vibrations orthogonal to the excitation vibration.

[0017] According to one embodiment, the at least one stiffening element covers less than 40%, preferably less than 30%, particularly preferably less than 20%, of the measuring tube circumference. According to one embodiment, the stiffening element covers less than 10% of the measuring tube circumference.

[0018] Particularly preferably, the extension of the stiffening element perpendicular to the measuring tube is, at least in some sections, greater than the extension of the stiffening element in the circumferential direction of the measuring tube. According to a further embodiment, the extension of the stiffening element perpendicular to the measuring tube is, at least in some sections, approximately as large as the extension of the stiffening element in the circumferential direction of the measuring tube.

[0019] According to the invention, the at least one stiffening element comprises at least two separate and / or separately acting components. These components can be connected to one another or arranged separately on the measuring tube. Particularly preferably, each component exerts a separate moment of area on the measuring tube. In this way, the stiffness of the measuring tube with respect to the disturbing vibrations to be suppressed can be further increased particularly effectively.

[0020] Particularly preferably, the extension of at least one component of the stiffening element perpendicular to the measuring tube is greater than the extension of this component in the circumferential direction of the measuring tube. The resulting increase in the area moment increases the stiffness of the measuring tube with respect to disturbing vibrations, which affects the frequency of the disturbing vibrations.

[0021] According to a further advantageous embodiment of the Coriolis mass flowmeter, the longitudinal extension of at least one component of the stiffening element runs parallel to the longitudinal axis of the measuring tube. The extension of the at least one component in the measuring tube direction is therefore greater than in the other directions. In this way, the contact area of the at least one component with the stiffening element is particularly large.

[0022] According to the invention, the at least two components are designed as at least two stiffening ribs, wherein the at least two stiffening ribs preferably rest on the measuring tube with their narrow edges. This configuration is particularly advantageous with regard to increasing the local stiffness of the measuring tube.

[0023] Further according to the invention, the at least two stiffening ribs are arranged parallel to each other such that the edges facing the measuring tube are arranged on a circular arc on the measuring tube.

[0024] Furthermore, it is particularly advantageous if the longitudinal extension of the at least two stiffening ribs is aligned parallel to the longitudinal axis of the measuring tube.

[0025] Particularly preferably, the individual components of the stiffening element are connected by at least one, preferably circular-arc-shaped, connecting surface, preferably by the support surface. According to one embodiment, the at least one connecting surface is arranged on the side of the stiffening element facing the measuring tube and / or on the side of the stiffening element facing away from the measuring tube. According to a next embodiment, two connecting surfaces are provided, with one connecting surface being arranged on the side of the stiffening element facing the measuring tube and one connecting surface being arranged on the side of the stiffening element facing away from the measuring tube.

[0026] According to a further embodiment, the at least one stiffening element is formed integrally with the node element. Within the context of the present invention, "integral" means that the node element and the stiffening element are manufactured from a single workpiece and are not subsequently joined together.

[0027] According to a particularly preferred embodiment, the at least one node element with the at least one stiffening element is applied directly to the measuring tube using a generative process. Alternatively, the at least one node element with the at least one stiffening element can also be manufactured using a conventional process and subsequently connected to the measuring tube.

[0028] According to a second teaching of the present invention, the object mentioned at the outset is achieved by a node element described at the outset, in particular in the form of a node ring or a node plate, in that the node element is designed and can be arranged in operation in such a way that the stiffening element increases the stiffness of the measuring tube with respect to oscillations orthogonal to the excitation mode and the Coriolis mode, so that during operation the oscillation frequency of the oscillations orthogonal to the excitation mode and the Coriolis mode is higher than the oscillation frequency of the excitation mode, preferably higher than the frequency of the Coriolis mode, that the at least one stiffening element has at least two separate and / or separately acting components, wherein the at least two separate and / or separately acting components are designed as at least two stiffening ribs and that the at least two stiffening ribs are arranged parallel to one another such that the edges facing the measuring tube are arranged on a circular arc on the measuring tube in the assembled state.

[0029] According to a particularly preferred embodiment, the node element is designed such that it is suitable for all of the Coriolis mass flow meters described above.

[0030] In detail, there are now numerous possibilities for designing and developing the Coriolis mass flowmeter according to the invention. Reference is made to the claims subordinate to the independent patent claims as well as to the following description of preferred embodiments in conjunction with the drawings. The drawings show: Fig. 1 shows a first exemplary embodiment of a node element, Fig. 2 shows a second exemplary embodiment of a node element, Fig. 3 shows a third exemplary embodiment of a node element arranged on a measuring tube, Fig. 4 shows a fourth exemplary embodiment of a node element arranged on a measuring tube, Fig. 5 shows an example not according to the invention of a node element arranged on a measuring tube, and Fig. 6 shows a first exemplary embodiment of a Coriolis mass flowmeter according to the invention.

[0031] In Fig. 1 1 shows a first exemplary embodiment of a node element 2, which is designed as a node ring, with a stiffening element 3. In the exemplary embodiment shown, the stiffening element 3 has five stiffening ribs 4. In addition, the node ring has a second stiffening element 3, which is arranged on the node ring opposite the first stiffening element 3, wherein the second stiffening element also has five stiffening ribs 4. The individual stiffening ribs 4 of the stiffening elements 3 are aligned and arranged such that, during operation, they rest on the measuring tube 6 of a Coriolis mass flowmeter 1. The stiffening ribs 4 are aligned such that, in the connected state, their longitudinal extent runs parallel to the measuring tube axis.

[0032] Overall, the illustrated nodal ring 2 is designed such that, when connected, it enables the separation of the parasitic vibrations developing perpendicular to the excitation mode and the Coriolis mode from the oscillations of interest in the Coriolis mode. At an excitation frequency of approximately 430 Hz, the parasitic vibration developing perpendicular to the Coriolis mode can be increased by approximately 40 Hz to approximately 470 Hz.

[0033] Fig. 2 shows a second embodiment of a node ring 2 with two oppositely arranged stiffening elements 3, each having stiffening ribs 4. In contrast to the Fig. 1 In the embodiment shown, the individual stiffening ribs 4 are connected to one another by a support surface 5.

[0034] In Fig. 3 A node element 2 in the form of a node ring is arranged on a measuring tube 6. The stiffening ribs 4 rest on the measuring tube 6 in such a way that they increase the stiffness of the measuring tube 6 in the vertical plane such that the frequency of the oscillations in the vertical plane differs from the frequency of the oscillations in the horizontal plane.

[0035] Fig. 4 shows a further embodiment of a node element 2 arranged on a measuring tube 6 in the form of a node ring, wherein in the illustrated embodiment the node element 2 has a stiffening element 3, wherein the stiffening element 3 has two separate components 7. Both components 7 rest on the measuring tube 6. The components 7 are designed such that their extension perpendicular to the measuring tube 6 is greater than the extension of the respective component 7 in the circumferential direction of the measuring tube 6. In this way, the stiffness of the measuring tube 6 in the vertical direction can be particularly advantageously increased during operation.

[0036] The Fig. 5 The node element 2 shown in the form of a node ring, not according to the invention, has two stiffening elements 3, which rest with a support surface on the measuring tube 6. The two stiffening elements 3 each cover less than 20% of the measuring tube circumference.

[0037] Fig. 6 shows a first embodiment of a Coriolis mass flowmeter 1 with a measuring tube 6, with a vibration generator 8 and two vibration sensors 9 and with a control and evaluation unit 10.

[0038] In addition, two node elements 2 are arranged on the measuring tube 6, which define the vibration range of the measuring tube 6. The node elements 2 each have two stiffening elements 3, which are aligned by the arrangement of the node elements 2 in such a way that they increase the stiffness of the measuring tube 6 with respect to vibrations orthogonal to the excitation mode. Because disruptive vibrations can be effectively suppressed or filtered out, the Coriolis mass flowmeter shown exhibits particularly high measurement accuracy. Reference symbol

[0039] 1Coriolis mass flowmeter 2Node element 3Stiffening element 4Stiffening rib 5Support surface 6Measuring tube 7Stiffening element component 8Vibration generator 9Vibration sensor 10Control and evaluation unit

Claims

1. Coriolis mass flowmeter (1) having at least one measuring tube (6), having at least one oscillation generator (8) and at least two oscillation sensors (9) and having at least two node elements (2), wherein the at least one oscillation generator (8) excites the measuring tube (6) to oscillation during operation, wherein the at least two node elements define the oscillation range and wherein at least one node element (2) has at least one stiffening element (3), and wherein the at least one node element (2), which has at least one stiffening element (3), is designed and arranged in such a manner that the stiffening element (3) increases the stiffness of the measuring tube (6) with respect to oscillations orthogonal to the excitation mode and to the Coriolis mode so that, during operation, the oscillation frequency of the oscillation orthogonal to the excitation mode and to the Coriolis mode is greater than the oscillation frequency of the excitation mode, preferably greater than the frequency of the Coriolis mode, characterized in that the at least one stiffening element (3) has at least two separate and / or separately acting components (7), wherein the at least two separate and / or separately acting components are designed as at least two stiffening ribs (4) and that the at least two stiffening ribs (4) are arranged parallel to each other in such a way that the edges of the stiffening ribs facing the measuring tube (6) are arranged on a circular arc on the measuring tube (6).

2. Coriolis mass flowmeter (1) according to claim 1, characterized in that at least a second stiffening element (3) is present, wherein the second stiffening element (3) is arranged, preferably opposite to the first stiffening element (3), on the node element (2).

3. Coriolis mass flowmeter (1) according to claim 1 or 2, characterized in that the at least one stiffening element (3) rests on the circumference of the measuring tube (6) with a resting surface (5).

4. Coriolis mass flowmeter (1) according to any one of claims 1 to 3, characterized in that the at least one stiffening element (3) covers less than 40%, preferably less than 30%, particularly preferably less than 20%, of the circumference of the measuring tube.

5. Coriolis mass flowmeter (1) according to any one of claims 1 to 4, characterized in that the extension of the stiffening element (3) perpendicular to the measuring tube (6) is greater, at least in sections, than the extension of the stiffening element (3) in the circumferential direction of the measuring tube (6).

6. Coriolis mass flowmeter (1) according to any one of claims 1 to 5, characterized in that the extension of at least one component (7) of the stiffening element perpendicular to the measuring tube is greater than the extension of this component in the circumferential direction of the measuring tube.

7. Coriolis mass flowmeter (1) according to any one of claims 1 to 6, characterized in that the longitudinal extension of at least one component (7) of the stiffening element (3) extends parallel to the longitudinal axis of the measuring tube (6).

8. Coriolis mass flowmeter (1) according to any one of claims 1 to 7, characterized in that the at least two components (7) are designed as at least two stiffening ribs (4), wherein the at least two stiffening ribs (4) preferably rest on the measuring tube (6) with the narrow edge.

9. Coriolis mass flowmeter (1) according to any one of claims 6 to 10, characterized in that the individual components (7) of the stiffening element (3) are connected by at least one, in particular arc-shaped, connecting surface, preferably by the resting surface (5), wherein the at least one connecting surface is arranged on the side of the stiffening element facing the measuring tube and / or on the side of the stiffening element facing away from the measuring tube.

10. Coriolis mass flowmeter (1) according to any one of claims 1 to 9, characterized in that the at least one stiffening element (3) is formed integrally with the node element (2).

11. Coriolis mass flowmeter (1) according to any one of claims 1 to 10, characterized in that the at least one node element (2) with the at least one stiffening element (3) is applied directly to the measuring tube (6) by means of a generative method.

12. Node element (2) for use in a Coriolis mass flowmeter (1) having at least one measuring tube (6), having at least one oscillation generator (8) and at least two oscillation sensors (9), wherein the at least one oscillation generator (8) excites the measuring tube (6) to oscillation during operation, wherein the at least two node elements define the oscillation range and wherein the node element (2) has at least one stiffening element (3), and wherein, during operation, the at least one node element (2) is designed and can be arranged in such a manner that the stiffening element (3) increases the stiffness of the measuring tube (6) with respect to the oscillations orthogonal to the excitation mode and to the Coriolis mode, so that, during operation, the oscillation frequency of the oscillation orthogonal to the excitation mode and to the Coriolis mode is greater than the oscillation frequency of the excitation mode, preferably greater than the frequency of the Coriolis mode, characterized in that the at least one stiffening element (3) has at least two separate and / or separately acting components (7), wherein the at least two separate and / or separately acting components are designed as at least two stiffening ribs (4) and that the at least two stiffening ribs (4) are arranged parallel to each other in such a way that, in the mounted state, the edges of the stiffening ribs facing the measuring tube (6) are arranged on a circular arc on the measuring tube (6).

13. Node element (2) according to claim 12, characterized by the features of the characterizing part of at least one claim of claims 2 to 11.