Apparatus and method for identifying and correcting erroneous volume flow measurements

Abstract

The invention relates to a device (1) comprising: a pipe (10); a Coriolis mass flowmeter (20) for measuring the mass flow of a medium flowing through the pipe; wherein a first pressure sensor (31) is attached in or on an inlet side portion of the pipe and a second pressure sensor (32) is attached in or on an outlet side portion of the pipe, and / or wherein a pressure difference sensor (33) is configured to detect a pressure difference between the inlet side portion of the pipe and the outlet side portion of the pipe, wherein the pressure sensors and / or the pressure difference sensor are configured to measure the medium pressure and to determine for each determination of the pressure difference a volume flow rate of the medium through the pipe; wherein a first monitoring sensor (41) is attached in or on the inlet side portion of the pipe and a second monitoring sensor (42) is attached in or on the outlet side portion of the pipe, wherein the monitoring sensors are configured to monitor a measurement variable different from the medium pressure in order to identify a static medium state.

Description

TECHNICAL FIELD

[0001] The present invention relates to a device and a method for identifying and correcting false volume flow measurements in a Coriolis volume flowmeter. BACKGROUND

[0002] As shown for example in DE 102015120087 A1, in the case of a liquid with gas inclusions or entrained gas, a Coriolis volume flowmeter has reduced measurement accuracy. This can be compensated by measuring the pressure difference between the inlet and the outlet of the measuring tube of the Coriolis measuring device, since in the case of low flow, a better statement about the flow can be made on the basis of this pressure difference. However, it has become apparent that this pressure difference can also be unreliable. SUMMARY

[0003] It is therefore an object of the present invention to propose a device and a method for reliable volume flow measurement.

[0004] This object is achieved by the device according to the independent claim 1 and by the method according to the independent claim 4.

[0005] The device for identifying false volume flow measurements according to the invention comprises:

[0006] a pipe;

[0007] a Coriolis volume flowmeter, which comprises at least one measuring tube, which in each case has an inlet and an outlet, which is configured to measure the mass flow of a medium flowing through the pipe;

[0008] wherein for this purpose a first pressure sensor is configured in or on the inlet-side portion of the pipe and a second pressure sensor is configured in or on the outlet-side portion of the pipe,

[0009] and / or wherein the pressure difference sensor is configured to detect the pressure difference between the inlet-side portion of the pipe and the outlet-side portion of the pipe,

[0010] wherein the pressure sensor and / or the pressure difference sensor is configured to determine the flow of the medium through the pipe for each determination of the pressure difference between the inlet-side portion of the pipe and the outlet-side portion of the pipe;

[0011] wherein a first monitoring sensor is attached in or on the inlet-side portion of the pipe and a second monitoring sensor is attached in or on the outlet-side portion of the pipe,

[0012] wherein the monitoring sensors are configured to monitor a measurement variable different from the medium pressure in order to identify a static medium state.

[0013] By means of the monitoring sensor it is thus possible to monitor whether the determined pressure difference is caused by a static or quasi-static change or a moving liquid column or by a large flow rate, and if necessary to correct the volume flow measurement for each pressure difference measurement. By means of this arrangement, a reliable measurement of the flow rate is possible in the case of a flow rate at which the Coriolis volume flowmeter has a low measurement accuracy.

[0014] In an improvement, the measurement variable of the monitoring sensor is at least one of the following list:

[0015] Medium density, viscosity, sound velocity, electrical conductivity, thermal capacity, electrical capacity, physical state of the medium.

[0016] In an improvement, the electronic measurement / control circuit of the Coriolis volume flowmeter is configured to receive and process the measurement signals of the monitoring sensor, the pressure sensor and / or the pressure difference sensor and to make a statement about the flow rate of the medium,

[0017] or an external computer is configured to receive and process the measurement signals of the monitoring sensor, the pressure sensor and / or the pressure difference sensor and the volume flow measurement values of the electronic measurement / control circuit and to make a statement about the flow rate of the medium.

[0018] By measuring or monitoring at least one of the measurement variables between the inlet-side portion of the pipe and the outlet-side portion of the pipe, for example, different physical states can be determined and interpreted as an indication of a static liquid column.

[0019] The method according to the application has the following steps:

[0020] Measuring the mass flow rate of a medium flowing through a pipe with a Coriolis volume flowmeter, wherein the Coriolis volume flowmeter is connected to the pipe via an inlet and an outlet,

[0021] Measuring the pressure difference of the medium between the inlet-side portion of the pipe and the outlet-side portion of the pipe,

[0022] Determining a first flow rate of the medium through the pipe on the basis of the pressure difference measurement,

[0023] characterized in that

[0024] The method has the following steps:

[0025] Measuring a medium-related measurement variable other than the medium pressure with a first monitoring sensor in or at the inlet-side portion of the pipe and a second monitoring sensor in or at the outlet-side portion of the pipe,

[0026] If the static or quasi-static medium state is determined by means of the monitoring sensor, the measurement of the flow for each pressure difference measurement is ignored.

[0027] In an improvement, the identification of the static medium state has the following steps:

[0028] A first measurement curve is generated with the first monitoring sensor and a second measurement curve is generated with the second monitoring sensor;

[0029] If a measurement value difference between the measurement values of the first measurement curve and the measurement values of the second measurement curve is greater than a first threshold value with respect to a first average value of the corresponding measurement values, the measurement value difference is interpreted as a result of the static medium state,

[0030] and / or

[0031] A second flow is determined from a cross-correlation between the first measurement curve and the second measurement curve, and if a deviation of the second flow with respect to a second average value from the first flow and the second flow is greater than a second threshold value, the deviation is interpreted as a result of the static medium state,

[0032] and / or

[0033] If a measurement value difference between the measurement values of the first measurement curve and the measurement values of the second measurement curve is constant over a time period, the measurement value difference is interpreted as a result of the static medium state.

[0034] A constant measurement value difference can be identified, for example, by a measurement value fluctuation about the average value over the time period being less than a predetermined value. Such a value can be determined, for example, from a limit of the standard deviation or from the variance. The person skilled in the art will adapt such a value to the device or method.

[0035] In an improvement, the first threshold value is, for example, at least 20% greater than the first average value and in particular at least 40% greater and preferably at least 50% greater,

[0036] and / or

[0037] wherein the second threshold value is, for example, at least 20% greater than the second average value and in particular at least 40% greater and preferably at least 50% greater.

[0038] In an improvement, the time period is greater than 2 seconds and in particular greater than 4 seconds and preferably greater than 5 seconds. BRIEF DESCRIPTION OF DRAWINGS

[0039] The application will now be described with reference to exemplary embodiments.

[0040] Figure 1 A device according to the application is shown schematically.

[0041] Figure 2 The measured value curve is shown schematically.

[0042] Figure 3 The schematic method is shown. DETAILED DESCRIPTION

[0043] Figure 1 A device 1 with a Coriolis measuring apparatus 20 with a measuring tube 21 arranged in a pipe 10 is shown according to the application. The inlet 21.1 of the measuring tube 21 is connected in the upstream portion 11 of the pipe and the outlet 21.2 is connected to the downstream portion 12 of the pipe. The Coriolis measuring apparatus can also have more than one measuring tube; the illustration chosen here is merely by way of example and not a limiting interpretation. A first pressure sensor 31 and a first monitoring sensor 41 are arranged in the inlet-side portion of the pipe 11 and a second pressure sensor 32 and a second monitoring sensor 42 are arranged in the outlet-side portion of the pipe 12. Instead of and / or in addition to the pressure sensors, a pressure difference sensor 33 can also be provided, as is shown schematically here. The positioning of the sensors 31, 32, 33, 41, 42 relative to one another is merely exemplary. For example, the sensors can also be arranged inside the pipe. The pressure sensors or the pressure difference sensor are configured to determine the pressure difference between the inlet 21.1 of the measuring tube and the outlet 21.2 of the measuring tube. If the mass flow of the medium through the pipe is so low that the Coriolis volume flowmeter operates with low reliability and measurement accuracy, a measured value of the average flow of the medium through the pipe can be determined by means of the pressure difference measurement, which can be used for a further or alternative mass volume flow measurement. As indicated schematically, the Coriolis measuring apparatus 20 can have measuring tubes with measuring tube curves in each case or even straight measuring tubes. Under certain conditions, a static or quasi-static liquid column with a liquid level can form between the inlet and the outlet of at least one measuring tube, which produces a pressure difference between the inlet 21.2 and the outlet 21.2. In this case, the flow measurement based on the pressure difference will deliver incorrect measured values. By means of the first monitoring sensor and the second monitoring sensor, it is now possible to check for the presence of a liquid column that falsifies the measured values. When such a static liquid column is identified, the measurement of the flow of each pressure difference measurement can be ignored, so that the Coriolis measuring apparatus reports zero flow.

[0044] The first monitoring sensor 41 and the second monitoring sensor 42 can monitor, for example, at least one of the following measured variables of the medium: mass density, viscosity, sound velocity, electrical conductivity, thermal capacity, electrical capacity, physical state. In this way, two-phase properties of the medium in the form of a liquid column can be detected.

[0045] The electronic measurement / control circuit 22 of the Coriolis volumetric flow meter is configured to receive and process measurement signals from monitoring sensors, pressure sensors, and / or differential pressure sensors, and to provide information about the flow rate of the medium. Alternatively, an external computer 50 is configured to receive and process measurement signals from monitoring sensors, pressure sensors, and / or differential pressure sensors, as well as the measured volumetric flow rate value from the electronic measurement / control circuit, and to provide information about the flow rate of the medium. The electronic measurement / control circuit is typically housed in a housing (not shown) designed for this purpose, but this is known from the prior art and is familiar to those skilled in the art. The transmission of measurement signals and values ​​occurs, for example, via electrical connections and / or via wireless connections. For clarity, representations of such connections have been omitted, but such connections are known to those skilled in the art, who will independently configure these connections according to their own wishes.

[0046] Figure 2 A standard for checking the presence of a liquid column is described based on illustrative and exemplary first measurement curve MW1 and illustrative and exemplary second measurement curve MW2. Here, the first measurement curve corresponds to the measurement curve acquired by a first monitoring sensor, and the second measurement curve corresponds to the measurement curve acquired by a second monitoring sensor. The measurement curves can be, for example, measurements of the following variables: mass density, viscosity, sound velocity, electrical conductivity, heat capacity, and capacitance. The physical state of the medium or different phases can be inferred from these variables.

[0047] Here, the two measurement curves initially have very similar values ​​and therefore a small measurement difference MD. As a static liquid column forms, with the liquid level between the inlet and outlet of the measuring tube, the difference between the measurement curves can become larger than shown here. For example, when measuring the density of a local medium, air will give a smaller measurement than liquid. If the liquid level of the column is located between the inlet and outlet of the measuring tube, the first and second monitoring sensors will measure significantly different medium densities. If the difference between the measurements from the first and second monitoring sensors exceeds a first threshold in magnitude, this can be interpreted as the presence of a quasi-static or static liquid column, where the liquid level is between the inlet and outlet of the measuring tube, and the flow rate / mass flow rate of the medium calculated for each pressure difference can be ignored.

[0048] Another criterion for determining the presence of a quasi-static or static liquid column between the inlet and outlet of the measuring tube can be a time period Z, during which the difference between the measurements of the first and second monitoring sensors is at least constant. In this case, constant means that the fluctuation of the difference associated with time period Z, measured, for example, by standard deviation or variance, is less than a defined value. Those skilled in the art can determine such a value without problem based on physical considerations and / or professional experience.

[0049] Another criterion for determining the presence of a quasi-static or static liquid column between the inlet and outlet of the measuring tube can be checked by means of cross-correlation between the first and second measurement curves. In the case of a flowing medium, for example, when air bubbles are present in the liquid, the measurement curves can be altered in a characteristic manner with a time delay. This time delay dt can be determined by means of cross-correlation and provides a basis for determining the second flow rate.

[0050] The deviation of the second flow rate from the second average value of the first flow rate and the second flow rate, determined by measuring the pressure difference between the inlet and the outlet, can be evaluated as a result of a static medium state in which the liquid level is between the inlet and the outlet.

[0051] In the case of measurement variables other than the density of the medium, the equivalent form will be applied.

[0052] Figure 3 The process of method 100 according to the present invention is described.

[0053] In method step 101, the mass flow rate of the medium flowing through the pipe 10 is measured using a Coriolis volumetric flow meter 20, wherein the Coriolis volumetric flow meter is connected to the pipe via the inlet 21.1 and outlet 21.2 of the measuring tube (21).

[0054] In method step 102, the pressure difference of the medium between the inlet side portion and the outlet side portion of the pipe is measured by means of a first pressure sensor 31, a second pressure sensor 32 and / or a differential pressure sensor 33.

[0055] In method step 103, the first flow rate of the medium passing through the pipe is measured based on the pressure difference measurement.

[0056] In method step 104, a first monitoring sensor 41 located at the inlet side of the pipe and a second monitoring sensor 42 located at the outlet side of the pipe are used to measure media-related measurement variables other than media pressure.

[0057] In method step 105, if the static or quasi-static medium state is determined by means of a monitoring sensor, the flow measurement for each pressure difference measurement is ignored.

[0058] Quasi-static means, for example, that the level of the medium or the medium has a movement speed lower than the specified minimum speed of the Coriolis measuring device or the specified minimum speed of the flow rate relative to each pressure difference measurement.

[0059] The installation of the Coriolis measuring equipment can be considered here. Whether the Coriolis measuring equipment is installed vertically or at an angle, the height difference between the pressure sensors will result in a pressure difference, which may also need to be taken into account.

[0060] The identification of the static medium state preferably includes the following steps:

[0061] A first measurement curve MW1 is generated using the first monitoring sensor 41, and a second measurement curve MW2 is generated using the second monitoring sensor 42;

[0062] If the measurement difference MD between the measured values ​​of the first and second measurement curves is greater than a first threshold relative to the first average of the corresponding measured values, then the measurement difference is interpreted as a result of the static medium state.

[0063] and / or

[0064] The second flow rate is determined from the cross-correlation between the first and second measurement curves, and if the deviation of the second flow rate relative to a second average value from the first and second flow rates is greater than a second threshold, the deviation is interpreted as a result of the static medium state.

[0065] and / or

[0066] If the difference between the measured values ​​of the first and second measured curves is constant over the time interval (Z), then the difference is interpreted as a result of the static state of the medium.

[0067] The first threshold is preferably, for example, at least 20% larger than the first average value, and particularly at least 40% larger, and preferably at least 50% larger.

[0068] and / or

[0069] The second threshold is, for example, at least 20% larger than the second average, and particularly at least 40% larger, and preferably at least 50% larger.

[0070] In this case, it is preferable that the time period Z is greater than 2 seconds, particularly greater than 4 seconds, and preferably greater than 5 seconds. This eliminates measurement differences at slow or low flow rates due to, for example, locally different media compositions.

[0071] Method steps are not required to follow a strict chronological order and can, for example, be executed at least partially concurrently. The numbering used is primarily for identifying method steps.

[0072] List of reference numerals

[0073] 1 device

[0074] 10 Pipelines

[0075] 11. Upstream section

[0076] 12 Downstream section

[0077] 20 Coriolis volumetric flow meter

[0078] 21 Measuring tube

[0079] 21.1 Entry

[0080] 21.2 Exports

[0081] 22 Electronic measurement / control circuits

[0082] 31 First pressure sensor

[0083] 32 Second pressure sensor

[0084] 33 Differential Pressure Sensor

[0085] 41 First monitoring sensor

[0086] 42 Second monitoring sensor

[0087] 50 external computers

[0088] 100 methods

[0089] Methods and steps 101–105

[0090] MW1 First Measurement Curve

[0091] MW2 Second Measurement Curve

[0092] MD measurement difference

[0093] Z time period

Claims

1. A method (100) for operating an apparatus (1) for identifying erroneous volumetric flow rate measurements, the apparatus comprising: Pipeline (10); A Coriolis volumetric flow meter (20) comprising at least one measuring tube (21) having an inlet (21.1) and an outlet (21.2) in each case, the Coriolis volumetric flow meter (20) being configured to measure the mass flow rate of a medium flowing through the pipe, the Coriolis volumetric flow meter being connected to the pipe via the inlet (21.1) and outlet (21.2) of the measuring tube (21); The first pressure sensor (31) is attached to the inlet side portion of the pipe or to the inlet side portion of the pipe, and the second pressure sensor (32) is attached to the outlet side portion of the pipe or to the outlet side portion of the pipe. And / or wherein the differential pressure sensor (33) is configured to detect the pressure difference between the inlet side portion and the outlet side portion of the pipe, Wherein, the first pressure sensor and the second pressure sensor and / or the pressure difference sensor are configured to determine the flow rate of the medium passing through the pipe by determining each pressure difference between the inlet side portion and the outlet side portion of the pipe; Furthermore, a first monitoring sensor (41) is attached to the inlet side portion (11) of the pipe or to the inlet side portion (11) of the pipe, and a second monitoring sensor (42) is attached to the outlet side portion (12) of the pipe or to the outlet side portion (12) of the pipe. The first and second monitoring sensors are configured to monitor measurement variables other than the pressure of the medium in order to identify the static state of the medium. The measurement variables of the first monitoring sensor (41) and the second monitoring sensor (42) are at least one of the following: the medium density, viscosity, sound velocity, electrical conductivity, heat capacity, electrical capacity, and physical state of the medium. The method includes: The mass flow rate of the medium flowing through the pipe (10) is measured using a Coriolis volumetric flow meter (20); The pressure difference of the medium between the inlet side portion and the outlet side portion of the pipe is measured by means of a first pressure sensor (31), a second pressure sensor (32) and / or a pressure difference sensor (33); The first flow rate of the medium passing through the pipe is determined based on the pressure difference measurement; The measurement variables related to the medium, other than the medium pressure, are measured using a first monitoring sensor (41) located in or at the inlet side of the pipe and a second monitoring sensor (42) located in or at the outlet side of the pipe. Furthermore, if the static or quasi-static medium state is determined by means of the first monitoring sensor and the second monitoring sensor, the flow rate measurement for each pressure difference measurement is ignored.

2. The method according to claim 1, in, The electronic measurement / control circuit (22) of the Coriolis volumetric flow meter is configured to receive and process measurement signals from the first monitoring sensor (41) and the second monitoring sensor (42), measurement signals from the first pressure sensor (31) and the second pressure sensor (32), and / or measurement signals from the differential pressure sensor (33), and also to provide a description of the flow rate of the medium. Alternatively, the device may include an external computer (50) configured to receive and process measurement signals from the first monitoring sensor (41) and the second monitoring sensor (42), measurement signals from the first pressure sensor (31) and the second pressure sensor (32), and / or measurement signals from the differential pressure sensor (33), as well as volumetric flow rate measurements from the electronic measurement / control circuit, and to provide a description of the flow rate of the medium.

3. The method according to claim 1 or 2, in, The identification of the static medium includes: A first measurement curve (MW1) is generated using the first monitoring sensor (41), and a second measurement curve (MW2) is generated using the second monitoring sensor (42). If the difference in measurement values ​​(MD) between the measured values ​​of the first measurement curve and the measured values ​​of the second measurement curve is greater than a first threshold relative to the first average value of the corresponding measured values, then the difference in measurement values ​​is interpreted as a result of the static medium state. and / or A second flow rate is determined from the cross-correlation between the first and second measurement curves, and if the deviation of the second flow rate relative to a second average value from the first and second flow rates is greater than a second threshold, the deviation is interpreted as a result of the static medium state. and / or If the difference between the measured values ​​of the first and second measured curves is constant over the time interval (Z), then the difference is interpreted as a result of the static state of the medium.

4. The method according to claim 3, in, The first threshold is at least 20% greater than the first average value. and / or Wherein, the second threshold is at least 20% larger than the second average value.

5. The method according to claim 4, in, The first threshold is at least 40% greater than the first average value.

6. The method according to claim 4, in, The second threshold is at least 40% larger than the second average value.

7. The method according to claim 5, in, The first threshold is at least 50% greater than the first average value.

8. The method according to claim 6, in, The second threshold is at least 50% larger than the second average value.

9. The method according to claim 3, in, The time period (Z) is greater than 2 seconds.

10. The method according to claim 3, wherein, The time period (Z) is greater than 4 seconds.

11. The method according to claim 3, wherein, The time period (Z) is greater than 5 seconds.

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