METHOD FOR CALCULATING A QUALITY OF A MEASURING TUBE OF A CORIOLIS MEASURING DEVICE AND SUCH A MEASURING DEVICE

Abstract

The present disclosure relates to a method for calculating a quality pertaining to at least one measuring tube of a Coriolis measuring device for measuring a density or a mass flow of a medium flowing through the measuring tube, wherein a determination regarding a state of the measuring tube can be made by determining various vibration properties.

Claims

1-14. (canceled)

15. A method for calculating a quality relating to at least one measuring tube of a Coriolis measuring device configured for measuring a density or a mass flow rate of a medium flowing therethrough, wherein the Coriolis measuring device comprises: a vibration system including at least one measuring tube configured to conduct the medium therethrough; at least one exciter configured to excite measuring tube vibrations in the at least one measuring tube; at least two vibration sensors configured to detect the measuring tube vibrations, wherein the at least one exciter and/or the at least two vibration sensors each include at least one magnet device, including a permanent magnet and one coil device; a support member configured to support the at least one measuring tube; an electronic measurement/control circuit configured to operate the at least one exciter, to generate measured values of the density and/or mass flow rate of the medium, and to perform operations of the method; and an electronics housing in which the electronic measurement/control circuit is disposed, the method comprising the following steps: relating at least one excitation input variable of the at least one exciter to at least one output variable of at least one vibration sensor; determining a current vibration property of the vibration system based on a vibration model of the at least one measuring tube and the relationship of the at least one excitation input variable to at least one output variable; determining a standard vibration property of the at least one measuring tube under standard conditions from the current vibration property of the vibration system, wherein at least one of the following variables is used in at least one of the method steps: a non-linear contribution of at least one of the following temperatures: medium temperature, support member temperature and housing temperature; a medium pressure; at least one accumulated time over which at least one of the magnet devices is exposed to a temperature above a respective threshold temperature; and a medium viscosity.

16. The method of claim 15, wherein a first set of temperature coefficients or a second set of temperature coefficients is used when using at least one of the medium temperature, the support member temperature and/or the housing temperature, wherein the first set of temperature coefficients is used when the medium temperature is higher than a limit temperature, wherein the second set of temperature coefficients is used when the medium temperature is lower than the limit temperature.

17. The method of claim 15, wherein at least one of the following variables is additionally used to determine the standard vibration property: at least one of the following temperatures: medium temperature, support member temperature, housing temperature, exciter temperature and vibration sensor temperature; and a medium density and/or a square of the medium density.

18. The method of claim 15, wherein the at least one accumulated time includes a first accumulated time, measured with respect to a first threshold temperature, and a second accumulated time, measured with respect to a second threshold temperature, and wherein the first accumulated time and the second accumulated time are used to calculate the standard vibration property.

19. The method of claim 15, wherein the at least one accumulated time is an argument of a non-linear, monotonic degressive function, wherein the degressive function is a logarithm function, a root function or an exponential function.

20. The method of claim 15, wherein at least one of the medium temperature, the support member temperature, and/or the housing temperature are each determined by at least one temperature sensor adapted and arranged accordingly.

21. The method of claim 16, wherein moduli of elasticity of the at least one measuring tube, the support member or a housing wall of the electronics housing are used to determine the temperature coefficients of the first set of temperature coefficients or the second set of temperature coefficients.

22. The method of claim 15, wherein the non-linear contribution is, a quadratic, logarithmic, potential or exponential contribution.

23. The method of claim 15, further comprising: comparing the standard vibration property with a reference vibration property, which reference vibration property is determined by a factory calibration or an operating calibration under standard conditions.

24. The method of claim 15, further comprising: observing a temporal development of the standard vibration property; and outputting a warning message when: the standard vibration property has a minimum deviation from the reference vibration property; and/or a value of a rate of change of the standard vibration property exceeds a minimum value.

25. The method of claim 15, wherein the standard vibration property is a modal stiffness.

26. The method of claim 25, wherein the vibration model includes with a degree of freedom that is applied up to a second order, wherein the vibration model includes the following component: $\frac{F_D}{X_S}=\mathrm{ah}.Math.1+\frac{s}{{\omega }_{0}Q}+\frac{s^2}{{\omega }_0^2}.Math.,$ where F.sub.D is an excitation force exerted by the at least one exciter on the at least one measuring tube and defining the excitation input variable, X.sub.S is an amplitude of the vibrations of the vibration system caused by the at least one exciter, which amplitude defines a response variable, a is a material-dependent and geometry-dependent constant of the at least one measuring tube, h is a tube wall thickness of the at least one measuring tube, ω.sub.0 is a resonance frequency of a respectively excited vibration mode, Q is a quality factor that describes a decay behavior of the vibrations of the vibration system during a single excitation, and s=i ω, where ω corresponds to an excitation frequency of the vibration system, and wherein the product of a and h is a measure of the modal stiffness of the at least one measuring tube.

27. A Coriolis measuring device for measuring a density or a mass flow rate of a medium flowing therethrough, the measuring device comprising: a vibration system including at least one measuring tube configured to conduct the medium therethrough; at least one exciter configured to excite measuring tube vibrations in the at least one measuring tube; and at least two vibration sensors configured to detect the measuring tube vibrations, wherein the at least one exciter and/or the at least two vibration sensors each include at least one magnet device, including a permanent magnet and one coil device; a support member configured to support the at least one measuring tube; an electronic measurement/control circuit configured to operate the at least one exciter, to generate measured values of the density and/or mass flow rate of the medium, and to perform operations of the method according to claim 15; and an electronics housing in which the electronic measurement/control circuit is disposed.

28. The measuring device of claim 27, further comprising at least one temperature sensor configured to measure at least one of the following temperatures: medium temperature, support member temperature, housing temperature, exciter temperature and vibration sensor temperature.

Description

[0069] The invention will now be described with reference to exemplary embodiments.

[0070] FIG. 1 describes a structure of an exemplary Coriolis measuring device with an exemplary Coriolis measuring transducer;

[0071] FIG. 2 describes the sequence of a method according to the invention;

[0072] FIG. 1 illustrates the structure of an exemplary Coriolis measuring device 10 according to the invention with an exemplary Coriolis measuring transducer according to the invention, the Coriolis measuring transducer having a vibration system with two measuring tubes 11 each having an inlet and an outlet, a support member 12 for supporting the measuring tubes, an exciter 13, and two sensors 14. The exciter is designed to excite the two measurement tubes to vibrate perpendicular to a longitudinal measurement tube plane defined by the arcuate measurement tubes. The sensors are designed to detect the vibration impressed upon the measurement tubes. Temperature sensors 17 are designed to detect temperatures of the support member, of the measuring tubes (influenced by a medium temperature), and of the support member. The sensors and the exciter can also be equipped with such temperature sensors. The Coriolis measuring transducer is connected to an electronic housing 80 of the Coriolis measuring device which is designed to house an electronic measurement/control circuit 77, which measurement/control circuit is designed to operate the exciter and the sensors and to determine and provide flow rate values and/or density values on the basis of vibration properties of the measuring tube as measured by means of the sensors. The exciter and the sensors are connected to the electronic measurement/control circuit by means of electrical connections 19. The electrical connections 19 can in each case be bundled by means of cable guides.

[0073] A Coriolis measuring instrument according to the invention is not limited to the presence of two measurement tubes. The invention can thus be implemented in a Coriolis measuring device having any number of measuring tubes, for example also in a single-tube or four-tube measuring device.

[0074] Unlike what is shown here, the measuring tubes can also be straight and, for example, designed to perform lateral or torsional vibrations.

[0075] A number of effects must be taken into account when operating such a Coriolis measuring device. An exciter efficiency accordingly influences a vibration amplitude of the measuring tube, and a sensitivity of the sensors influences an ability to convert a vibration of the measuring tube into a measurement variable, such as a measurement voltage or a measurement current. A Coriolis measuring device is often calibrated under standard conditions before start-up, for example, at a customer of a manufacturer of Coriolis measuring devices, and among other things a relationship between an excitation of measuring tube vibrations by the exciter and a detection of the measuring tube vibrations by the sensors is thus documented. The exciter efficiency as well as the sensor sensitivity are subject to influences which on the one hand can cause reversible changes but also irreversible changes in these variables.

[0076] An example of a reversible influence is an increase in an ohmic resistance of a coil device of a sensor due to an increase in the temperature of the coil device, which results in a reduced induction of an electrical voltage by a sensor magnet moved relative to the coil device. An example of a non-reversible change is an aging of the sensor magnet, for example, due to intense heating. Depending on the actual design of a sensor (there are also, for example, optical sensors) or exciter, corresponding similar effects can come to bear.

[0077] An adapted method for operating the Coriolis measuring device is thus necessary for accurate measurements of mass flow and/or density and for monitoring of aging or condition.

[0078] FIG. 2 describes the sequence of an exemplary method according to the invention for calculating a quality relating to at least one measuring tube 11.1 of a Coriolis measuring device.

[0079] In a first method step 101, at least one excitation input variable AEG of the at least one exciter is related to at least one output variable AG of at least one sensor, and

[0080] in a second method step 102, a current vibration property ASE of the at least one measuring tube is determined on the basis of a vibration model of the measuring tube and the relationship.

[0081] In a third method step 103, a standard vibration property SSE of the measuring tube under standard conditions is determined from the current vibration property of the measuring tube.

[0082] In at least one of the method steps, at least one of the following variables is used:

[0083] a non-linear contribution of at least one of the following temperatures: medium temperature, support member temperature, housing temperature;

[0084] a medium pressure;

[0085] at least one accumulated time over which the magnet device is exposed to a temperature above a respective threshold temperature;

[0086] a medium viscosity.

[0087] By determining the standard vibration property according to the invention, it is possible to determine the standard vibration property of a measuring tube much more accurately, since subtle interfering influences are now corrected.

[0088] As shown in FIG. 2, the method can have further method steps.

[0089] The method shown here thus comprises the following method steps:

[0090] comparing the standard vibration property with a reference vibration property in a fourth method step 104, which reference vibration property RSE is determined, for example, by a factory calibration or an operating calibration under standard conditions.

[0091] observing a temporal development of the standard vibration property in a fifth method step 105,

[0092] outputting a warning message in a sixth method step 106 if:

[0093] the standard vibration property SSE has a minimum deviation from the reference vibration property RSE,

[0094] and/or a value of a rate of change of the standard vibration property exceeds a minimum value.

[0095] In this way, the customer of a manufacturer of such Coriolis measuring devices and/or the manufacturer can be notified of a lack of reliability or a poor measuring tube condition of measuring tubes of the Coriolis measuring device, for example due to abrasion or coating formation, and timely replacement or cleaning can be ensured.

[0096] A standard vibration property SSE can thus be represented in an abstract manner, for example by the following equation:

SSE=ASE*K_temp*K_density*K_pressure*K_aging*K_visc,

wherein constant, linear and non-linear influences can be used in the correction terms K as described above. The person skilled in the art is able to quantify these influences in a Coriolis measuring device and to determine corresponding coefficients for these influences.

[0097] The correction term K_temp can, for example, be defined as follows:

[0098] K_temp=C1+K1*T_med+K2*(T_med)^2 with T_med as medium temperature, C1 as a constant, K1 a first coefficient and K2 a second coefficient. The same applies to the correction terms with respect to the support member temperature or the housing temperature. The non-linear term here is quadratic, by way of example, but can have any other desired form of non-linearity and can thus be, for example, a logarithmic, potential, or exponential contribution.

[0099] In a similar manner, the correction terms can be formulated with their own coefficients with regard to the variables of density, pressure, viscosity and aging of the permanent magnets. With the aging of the permanent magnets, a logarithm or a root function or an exponential function can be used as degressive function for the purpose of describing the aging, for example, wherein the at least one accumulated time over which the magnet device is exposed to a temperature above a respective threshold temperature is included in the function as an argument in each case. An example of a description of the aging with a function having an exponential function is the following term: C2−K3*exp(−x*K4+K5) with x as a variable for the accumulated time, C2 as a constant and K3 to K5 as coefficients.

[0100] The description of a relationship between SSE and ASE presented here is to be interpreted purely as an example and not limiting.

LIST OF REFERENCE SIGNS

[0101] 10 Coriolis measuring device

[0102] 11 Vibration system

[0103] 11.1 Measuring tube

[0104] 12 Support member

[0105] 13 Exciter

[0106] 14 Sensor

[0107] 15 Magnet device

[0108] 16 Coil device

[0109] 17 Temperature sensor

[0110] 19 Electrical connection

[0111] 77 Electronic measurement/control circuit

[0112] 80 Electronics housing

[0113] 100 Method

[0114] 101-106 Method steps

[0115] AEG Excitation input variable

[0116] AG Output variable

[0117] ASE Current vibration property

[0118] SSE Standard vibration property

[0119] RSE Reference vibration property