Method for detecting the condition of measuring tubes of a Coriolis measuring device

Abstract

Method (100) for detecting the state of measuring tubes (11) of a Coriolis measuring device (1) set up to measure a mass flow rate or density of a medium flowing through the measuring tubes, wherein the measuring instrument (1) has two measuring tube groups (10.1, 10.2) each with at least one measuring tube (11), wherein the measuring tubes of each measuring tube group (10.1; 10.2) have the same geometric configuration, wherein the measuring tubes (11) are designed in an arc shape at least in sections, wherein each measuring tube arc (11.1) defines a measuring tube plane in a measuring tube rest state, wherein the measuring tube arcs (11.1) are deflected perpendicular to the respective measuring tube plane when oscillating, wherein the measuring tube bends (11.1) of a first measuring tube group (10.1) each have a first central radius of curvature (KR1) with respect to a respective measuring tube centerline, and wherein the measuring tube bends (11.1) of a second measuring tube group (10.2) each have a second central radius of curvature (KR2) with respect to a respective measuring tube centerline, wherein the first central radius of curvature is larger than the second central radius of curvature, wherein at least one exciter (13) generates measuring tube vibrations, and wherein at least two sensors (14) detect the measuring tube vibrations, wherein in a first procedural step (101) an electronic The measuring / operating circuit (77) determines a first measured value (M1) or a first measured value profile (MV1) of the medium density by means of the first measuring tube group (10.1) and a second measured value (M2) or a second measured value profile (MV2) of the medium density by means of the second measuring tube group (10.2), characterized by that in a second procedural step (102) the electronic The measuring / operating circuit (77) determines a quality parameter of at least the measuring tubes (11) of the second measuring tube group (10.2), which quality parameter indicates deposit formation or abrasion, and that, to determine the quality parameter, a deviation between first and second measured values ​​of the media density and / or between the first measured value profile and the second measured value profile is used as a measure for the quality parameter, where the deviation is only used as a measure for the quality parameter when a minimum flow velocity of the medium in the measuring tube (11) is reached, and wherein the minimum flow velocity is greater than 0.1 meters per second and in particular greater than 0.2 meters per second.

Description

[0001] The invention relates to a method for detecting the condition of the measuring tubes of Coriolis flowmeters designed to measure the mass flow rate or density of a medium flowing through the measuring tubes. The condition of the measuring tubes determines their vibration behavior and thus also the measurements of the mass flow rate and density of a medium flowing through them. The condition of measuring tubes can develop in various ways from an initial state. For example, abrasive media can attack the inner wall of the measuring tube, leading to a reduction in wall thickness. Media can also cause deposits to form on the inner wall of the measuring tube.

[0002] In Coriolis measuring instruments according to the state of the art, as shown, for example, in document DE102015120087A1, the condition of the measuring tube is determined by comparison with a reference measurement, for example, during calibration. To ensure an accurate determination of the condition, a multitude of different influences must be taken into account.

[0003] The object of the invention is therefore to propose a method in which the condition of a measuring tube can be determined better and more easily.

[0004] The problem is solved by a method according to independent claim 1.

[0005] In an inventive method for detecting the condition of measuring tubes of a Coriolis measuring device set up for measuring a mass flow rate or density of a medium flowing through the measuring tubes, The measuring instrument has two groups of measuring tubes, each with at least one measuring tube, wherein the measuring tubes of each measuring tube group have the same geometric design. wherein the measuring tubes are designed in an arc shape, at least in sections, wherein each measuring tube arc defines a measuring tube plane in a measuring tube rest state, wherein the measuring tube arcs are deflected perpendicular to the respective measuring tube plane when oscillating, wherein the measuring tube bends of a first measuring tube group each have a first central radius of curvature with respect to a respective measuring tube centerline, and wherein the measuring tube bends of a second measuring tube group each have a second central radius of curvature with respect to a respective measuring tube centerline, wherein the first central radius of curvature is larger than the second central radius of curvature, wherein in a first process step an electronic measuring / operating circuit determines a first measured value or a first measured value profile of a mass density of the medium by means of the first measuring tube group and a second measured value or a second measured value profile of the medium density by means of the second measuring tube group, wherein in a second process step the electronic measuring / operating circuit determines a quality parameter of at least the measuring tubes of the second pair of measuring tubes, where, to determine the quality parameter, a deviation between first and second measured values ​​of the media density and / or between the first measured value profile and the second measured value profile is used as a measure for the quality parameter.

[0006] When determining the density of a medium, one or more physical quantities can be used, such as the natural frequency of the measuring tube, the temperature of the medium or measuring tube, the medium pressure, or the medium viscosity.

[0007] The difference between the first radius of curvature and the second radius of curvature causes different accelerations of the medium perpendicular to the center line of the measuring tube in different measuring tubes at the same flow velocity due to different centrifugal forces, which, for example, leads to greater abrasion of the measuring tubes in the second measuring tube group than in the measuring tubes of the first measuring tube group in the case of abrasive media.

[0008] This leads to increasingly divergent density measurements due to changing vibration characteristics of the measuring tubes with increasing abrasion.

[0009] Similarly, with media that form deposits, increased deposit formation can occur in measuring tubes of the first measuring tube group, leading to an apparent increase in the measuring tube mass and thus to changes in the vibration characteristics of the measuring tubes of the first measuring tube group. Deposit formation in measuring tubes of the second measuring tube group is suppressed due to stronger media turbulence, or existing deposits are washed away.

[0010] In one embodiment of the method, the ratio of the first radius of curvature to the second radius of curvature is greater than 1.1 and in particular greater than 1.2 and preferably greater than 1.3 and / or less than 3 and in particular less than 2.5 and preferably less than 2.

[0011] By setting a ratio in such a range, it can be ensured, on the one hand, that abrasion or deposit formation develops measurably differently in measuring tubes of different measuring tube groups, thus enabling a measure of the measuring tube condition, and on the other hand, that excessive impairment of measuring tubes is avoided, thus enabling the continuous operation of a Coriolis measuring device.

[0012] In one configuration, the quality parameter indicates deposit formation or abrasion.

[0013] If it is known that a medium does not form deposits, the quality parameter can supplement a measuring tube condition determination by comparison with a measuring tube reference condition. If a medium can contribute to both abrasion and deposit formation, the measuring tube condition determination can differentiate between deposit formation and abrasion by comparison with the measuring tube reference condition.

[0014] In one implementation, only a quasi-static portion of the deviation is used as a measure for the quality parameter.

[0015] The average density of a medium in a measuring tube can fluctuate significantly over short timescales. This is because, for example, gas bubbles or solid particles carried by a liquid can lead to local variations in the average density of the medium. Such fluctuations are not due to a change in the state of the measuring tube itself. Changes in the state of measuring tubes occur over timescales of days or weeks, depending on usage and the medium.

[0016] Considering the quasi-static component means that a frequency analysis, for example using Fourier analysis, is performed to examine deviations in measured value series or profiles of measured media densities for measuring tubes from different groups of measuring tubes, and then only the static contribution is taken into account. Alternatively, one can wait for stable flow conditions without significant fluctuations, which can be identified, for example, by a measurement signal where signal fluctuations remain below a defined threshold for a defined duration. A resonance frequency or the excitation current of an excitation coil used to generate measuring tube oscillations can be used as the measurement signal.

[0017] According to the invention, the deviation between first and second measured values ​​of the media density, or between the first measured value profile and the second measured value profile, is only used as a measure for the quality parameter when a minimum flow velocity of the medium in the measuring tube is reached, wherein the minimum flow velocity is greater than 0.1 meters per second, and in particular greater than 0.2 meters per second.

[0018] In one embodiment, a comparison of a current measuring tube condition with a measuring tube reference condition is carried out, whereby measured values ​​for a measuring tube stiffness of the measuring tubes of different measuring tube groups are determined via this comparison, whereby a distinction is made between abrasion and deposit formation using the measured values ​​of the measuring tube stiffnesses with regard to the quality parameter, or whereby the quality parameter is used for a redundant determination of the measuring tube condition in the case of non-depositing media.

[0019] In one embodiment, the measuring tubes each have an inlet curvature and an outlet curvature, wherein the inlet curvature radii of different measuring tubes are the same, and wherein the outlet curvature radii of different measuring tubes are the same.

[0020] In this way, the same impairment due to abrasion or deposit formation occurs at both the inlet and outlet curves.

[0021] In one embodiment, the inlet curvature radius and outlet curvature radius of each measuring tube are the same.

[0022] In one embodiment, each measuring tube group has one measuring tube each. or wherein each group of measuring tubes has two measuring tubes, the measuring tubes oscillating against each other.

[0023] The invention will be described below using exemplary embodiments. Fig. 1 describes the setup of an exemplary Coriolis measuring device with an exemplary Coriolis sensor; Fig. Figure 2 shows a sketch of measuring tubes or a measuring tube arrangement suitable for carrying out the method according to the invention; Fig. 3 describes the process of a method according to the invention; Fig. Section 4 outlines exemplary measurement curves.

[0024] Fig. Figure 1 outlines the structure of an exemplary Coriolis measuring device 1 with an exemplary Coriolis sensor 2 according to the invention, wherein the Coriolis sensor comprises a vibration system with two measuring tubes 11, each with an inlet and an outlet, a support body 12 for carrying the measuring tubes, an exciter 13, and two sensors 14. The exciter is configured to excite the two measuring tubes to vibrate perpendicular to a measuring tube plane defined by the arc-shaped measuring tubes. The sensors are configured to detect the vibration imparted to the measuring tubes.The Coriolis sensor is connected to an electronics housing 80 of the Coriolis measuring device, which is configured to house an electronic measuring / operating circuit 77. This measuring / operating circuit is configured to operate the exciter and the sensors and to determine and provide flow and / or density measurements based on the vibration characteristics of the measuring tube measured by the sensors. The exciter and the sensors are connected to the electronic measuring / operating circuit by means of electrical connections 19. The electrical connections 19 can each be grouped by cable guides. The in . Fig. The measuring tubes shown in Figure 1 are exemplary and not part of the invention; they serve solely to illustrate a Coriolis measuring device. Measuring tubes suitable for carrying out the method according to the invention are shown in [reference to be added]. Fig. 2 shown. It poses no problem for the expert to understand the in Fig. 1 measuring tubes shown with the in Fig. to replace the 2 measuring tubes shown.

[0025] Fig. Figure 2 shows a side view of a measuring tube arrangement suitable for carrying out the method according to the invention, wherein the measuring tube arrangement comprises a first measuring tube group 10.1 and a second measuring tube group 10.2, each of which has a measuring tube 11. The measuring tubes each have an inlet bend 11.21 and an outlet bend 11.22 as well as a measuring tube arc 11.1 arranged centrally between the inlet and outlet bends. According to the invention, a first radius of curvature KR1 of the measuring tube arc of measuring tubes of the first measuring tube group is larger than a second radius of curvature KR2 of the measuring tube arc of measuring tubes of the second measuring tube group. This results in different centrifugal forces and thus different accelerations of the medium directed towards the outside of a respective measuring tube arc perpendicular to a respective measuring tube centerline, at the same flow velocity of a medium through the measuring tubes.

[0026] For example, with abrasive media, this leads to greater abrasion of the measuring tubes in the second group than in the first group. Due to changing vibration characteristics of the measuring tubes, this results in increasingly divergent density readings with increasing abrasion. Similarly, with deposit-forming media, increased deposit formation can occur in the measuring tubes of the first group, leading to an apparent increase or decrease in the mass of the measuring tubes and thus to changing vibration characteristics. Deposit formation in the measuring tubes of the second group is suppressed due to stronger media turbulence, or existing deposits are washed away.

[0027] Alternatively, each measuring tube group can also have more than one measuring tube. For example, a measuring tube arrangement according to the invention can also be implemented in a four-tube Coriolis measuring device, wherein each measuring tube group has two measuring tubes, which are in particular designed to oscillate against each other.

[0028] For example, the ratio of the first radius of curvature to the second radius of curvature is greater than 1.1, and in particular greater than 1.2, and preferably greater than 1.3, and / or less than 3, and in particular less than 2.5, and preferably less than 2. By setting a ratio in such a range, it can be ensured, on the one hand, that abrasion or deposit formation develops measurably differently in measuring tubes of different measuring tube groups, thus enabling a measure of the measuring tube condition, and, on the other hand, that excessive impairment of measuring tubes of the second measuring tube group is avoided, thus enabling the continuous operation of a Coriolis measuring device.

[0029] Depending on the medium and flow rate, the measuring tubes of the first group may remain essentially unaffected, while the measuring tubes of the second group experience abrasion or fouling. Alternatively, abrasion or fouling may occur in measuring tubes of both groups, but to a greater extent in those of the second group. In both cases, differing density readings or differing density reading profiles result in a degree of impairment of either measuring tubes of the second group or measuring tubes of both groups.

[0030] Fig. Figure 3 outlines the process of a method 100 according to the invention, wherein in a first process step 101 the electronic measuring / operating circuit 77 (see Fig. 1) using the first measuring tube group to determine a first measured value M1 based on recorded measuring tube vibrations (see Fig. 4) or an initial measurement curve MV1 (see Fig. 4) a mass density of the medium and, using the second measuring tube group, a second measured value M2 (see Fig. 4) or a second measurement curve MV2 (see Fig. 4) the media density of the medium is determined, wherein in a second process step 102 the electronic measuring / operating circuit determines a quality parameter of at least the measuring tubes of the second pair of measuring tubes, wherein to determine the quality parameter a deviation between first measured values ​​and second measured values ​​of the media density and / or between the first measured value profile and the second measured value profile is used as a measure for the quality parameter.

[0031] Since, according to the invention, the first radius of curvature KR1 of the measuring tube bend of measuring tubes in the first measuring tube group is larger than the second radius of curvature KR2 of the measuring tube bend of measuring tubes in the second measuring tube group, a greater degree of deposit formation or abrasion occurs in measuring tubes of the second measuring tube group, and the vibration characteristics of the measuring tube are altered to varying degrees. An increasing difference in media density measurements indicates a progressive deterioration of the condition of the measuring tubes. In order to disregard short-term fluctuations in the difference caused, for example, by air bubbles, preferably only a quasi-static component of the deviation is used as a measure for the quality parameter.

[0032] According to the invention, the deviation is only used as a measure for the quality parameter when a minimum flow velocity of the medium in the measuring tube is reached, wherein the minimum flow velocity is greater than 0.1 meters per second and, in particular, greater than 0.2 meters per second. In this way, it can be ensured that the medium in the measuring tubes has a homogeneous temperature distribution.

[0033] Fig.Figure 4 outlines, in an exemplary manner, measured values ​​and measurement profiles of density measurements based on different measuring tube groups. The first measured values ​​M1, based on the first measuring tube group 10.1, exhibit a first measurement profile MV1, and the second measured values ​​M2, based on the second measuring tube group, exhibit a measurement profile M2. Upon commissioning at time t0, density measurements of a medium located in the measuring tubes initially yield identical or very similar measured values. Since the density of a medium flowing through the measuring tubes can change, the measurement profiles can fluctuate, as schematically depicted here. As abrasion or deposit formation increasingly affects the measuring tubes of the second measuring tube group over time, a growing deviation between the first and second measurement profiles can be observed.For example, a warning message can be issued if there is a minimum relative or absolute deviation between the second set of measurements and the first set of measurements. The warning message can be issued, for instance, as soon as an absolute deviation of 0.2 kilograms per cubic meter is reached.

[0034] The measurement curves shown here are idealized, as short-term fluctuations, for example those caused by air bubbles or solids carried in a liquid medium, are not shown. Such short-term fluctuations, if they occur only or frequently in measuring tubes within a group of measuring tubes, can lead to short-term deviations and are advantageously disregarded, as they are not a measure of measuring tube impairment or condition. A person skilled in the art will therefore advantageously perform, for example, a frequency analysis or frequency selection to filter out high-frequency components from a profile of deviations in density measurements or density measurement profiles from measuring tubes of different groups of measuring tubes. High-frequency components are those that cover periods of less than one week or, in particular, less than one day. Reference symbol list 1 Coriolis measuring device 2 Coriolis sensors 10 Measuring tube group 10.1 First measuring tube group 10.2 second measuring tube group 11 Measuring tube 11.1 Measuring tube bend 11.21 Inlet Curve 11.22 Outlet curvature 12 carrier bodies 13 pathogens 14 Sensor 19 electrical connections 77 electronic measuring / operating circuit 80 electronic enclosures 100 procedures 101 First procedural step 102 second procedural step M1 first measured value MV1 first measurement curve M2 second measured value MV2 second measurement curve KR1 first radius of curvature KR2 second radius of curvature

Claims

Method (100) for detecting the state of measuring tubes (11) of a Coriolis measuring device (1) configured for measuring a mass flow rate or density of a medium flowing through the measuring tubes, wherein the measuring device (1) has two groups of measuring tubes (10.1, 10.2) each with at least one measuring tube (11), wherein the measuring tubes of each group of measuring tubes (10.1; 10.2) have the same geometric configuration, wherein the measuring tubes (11) are at least partially curved, wherein each measuring tube arc (11.1) defines a measuring tube plane in a measuring tube at rest state, wherein the measuring tube arcs (11.1) are deflected perpendicular to the respective measuring tube plane when oscillating, wherein the measuring tube arcs (11.1) of a first group of measuring tubes (10.1) each have a first central radius of curvature (KR1) with respect to a respective measuring tube centerline, and wherein the measuring tube arcs (11.1) a second measuring tube group (10.2) have a second central radius of curvature (KR2) with respect to a respective measuring tube centerline, wherein the first central radius of curvature is larger than the second central radius of curvature, wherein at least one exciter (13) generates measuring tube vibrations, and wherein at least two sensors (14) detect the measuring tube vibrations, wherein in a first process step (101) an electronic measuring / operating circuit (77) determines a first measured value (M1) or a first measured value profile (MV1) of a media density of the medium on the basis of detected measuring tube vibrations by means of the first measuring tube group (10.1) and a second measured value (M2) or a second measured value profile (MV2) of the media density of the medium by means of the second measuring tube group (10.2), characterized in that in a second process step (102) the electronic measuring / operating circuit (77) determines a quality parameter of at least the measuring tubes (11) of the second measuring tube group (10.2) determines which quality parameter indicates deposit formation or abrasion, and that to determine the quality parameter a deviation between first and second measured values ​​of the media density and / or between the first measured value profile and the second measured value profile is used as a measure for the quality parameter, wherein the deviation is only used as a measure for the quality parameter at a minimum flow velocity of the medium in the measuring tube (11), and wherein the minimum flow velocity is greater than 0.1 meters per second and in particular greater than 0.2 meters per second. Method according to claim 1, wherein the ratio of first radius of curvature (KR1) to second radius of curvature (KR2) is greater than 1.1 and in particular greater than 1.2 and preferably greater than 1.3 and / or less than 3 and in particular less than 2.5 and preferably less than 2. Method according to one of the preceding claims, wherein only a quasi-static portion of the deviation is used as a measure for the quality parameter. Method according to one of the preceding claims, wherein a comparison of a current measuring tube condition with a measuring tube reference condition is carried out, wherein measured values ​​for a measuring tube stiffness of the measuring tubes (11) of different measuring tube groups (10.1; 10.2) are determined via this comparison, wherein the measured values ​​of the measuring tube stiffnesses are used to differentiate between abrasion and deposit formation with respect to the quality parameter, or wherein the quality parameter is used for a redundant determination of the measuring tube condition in the case of non-depositing media. Method according to one of the preceding claims, wherein the measuring tubes (11) each have an inlet curvature (11.21) and each have an outlet curvature (11.22), wherein the inlet curvature radii of different measuring tubes (11) are the same, and wherein outlet curvature radii of different measuring tubes (11) are the same. Method according to the previous claim, wherein the inlet radius of curvature and the outlet radius of curvature of each measuring tube (11) are the same. Method according to one of the preceding claims, wherein each measuring tube group (10.1; 10.2) has one measuring tube (11), or wherein each measuring tube group (10.1; 10.2) has two measuring tubes (11), wherein the measuring tubes (11) oscillate against each other. A Coriolis measuring device (1) configured for implementing the method according to one of the preceding claims, comprising: a Coriolis sensor (2) with at least two measuring tubes (11), with a support body (12) for carrying the measuring tubes (11), with at least one exciter (13) for generating measuring tube vibrations, and at least two sensors (14) for detecting measuring tube vibrations; an electronic measuring / operating circuit (77) configured to operate the exciter (13) and to determine and provide flow rate and / or density measurement values ​​based on the vibration characteristics of the measuring tube (11) measured by means of the sensors (14), wherein the measuring tubes (11) are assigned to the first measuring tube group (10.1) or the second measuring tube group (10.2), wherein the measuring tube bends (11.1) of the first measuring tube group (10.1) each have a first central radius of curvature (KR1) with respect to a respective measuring tube centerline, and wherein the measuring tube bends (11.2) of the second measuring tube group (10.2) with respect to a respective measuring tube centerline each have a second central radius of curvature (KR2), wherein the first central radius of curvature (KR1) is larger than the second central radius of curvature (KR2).

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