Detection of fores in process media

Abstract

The invention relates to the detection of possible foreign matters (4), such as exfoliated flakes, metal chips or powder blocks, in a process medium (2) located in a container section (3) which is transparent to radar signals (S, R, THF) at least in some areas. To this end, a radar-based measurement signal (SHF) is transmitted from a first RF unit (11) into the process medium (2). After the measurement signal (THF) interacts with the process medium (2) and / or the foreign matter (4), the transmissive part (THF) and / or the reflective part (RHF) thereof is recorded by the corresponding radio frequency unit (11, 12, 13). The superordinate evaluation unit (14) can thus detect possible foreign matter (4) in real time on the basis of the recorded part (THF, RHF) of the transmitted measurement signal (THF).

Description

Technical Field

[0001] This invention relates to the detection of foreign matter in process media. Background Technology

[0002] In process automation technology, field devices and measurement systems are frequently used to record or influence process variables. For the direct recording of certain process variables, a single field device of the corresponding field device type is applied. In this case, the field device type is provided with sensors and measurement principles suitable for the process variables, such as fill level measuring devices, flow meters, pressure and temperature measuring devices, pH-redox potential measuring devices, and conductivity measuring devices. Such field device types accordingly directly record the fill level, flow rate, pressure, pH value, temperature, conductivity, or redox potential of the process medium as process variables.

[0003] In addition to determinable process variables, there are variables that cannot be recorded based on a single measurement principle—that is, the completion of a chemical or biological reaction.

[0004] In particular, recording such complex process variables requires the use of measurement systems that combine different types of field equipment and measurement principles: based on the correlation of the corresponding physical variables, the evaluation unit of the measurement system can then determine the complex process variables, such as, for example, the completion of a fermentation process. The most diverse range of such field equipment types and measurement systems is manufactured and sold by the Endress+Hauser Group.

[0005] In addition to monitoring actual process variables, detecting foreign matter within the process medium is becoming increasingly important. In this context, depending on the type of process plant and therefore the application area, the container sections where potential foreign matter will be detected can involve sections of closed piping, open pipelines, or tank interiors. Generally, the term "foreign matter," within the scope of this invention, means a locally defined, undesirable component in the process medium. This includes, for example, flakes detached from objects involved in the process, metal fragments or nut shell flakes in liquid or paste-like process media in the food industry, and powder lumps or hardened flakes resulting from insufficient mixing of the process medium. A further issue is that potential foreign matter can lead to a reduction in the flow rate of the process medium.

[0006] The publicly available text DE 102021133787 A1 describes a measurement system based on various field devices, and therefore a field device type. In this case, various field devices are primarily used to determine discrete process variables within a pipeline section. Besides these actual process variables, potential foreign objects are incidentally detected when various measurements from different field devices or field device types are tested for specific time correlations in a higher-level process control system. However, in most processes, such randomness does not exist, where multiple field devices, and therefore different field device types, are used within the pipeline section itself. Furthermore, due to the correlation of higher-level testing, it is difficult to detect potential foreign objects in real time based on this principle. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide the simplest possible measurement system by means of which foreign matter can be safely and as real-time as possible detected in process media.

[0008] This invention achieves this objective through a measurement system for detecting foreign matter in a process medium located within a container section, which is transparent to radar signals in at least certain areas. In this configuration, the measurement system includes the container section and a first high-frequency unit designed and arranged within the container section such that it can transmit radar-based measurement signals into the process medium in the direction of a first beam axis. In this context, the term "beam axis" means, in the context of this invention, the vector along which the strength of the measurement signal is greatest. Due to the reciprocal nature of radar antennas, the line along which the received portion of the measurement signal has the highest reception sensitivity is along this vector.

[0009] In the measurement system of the present invention, radar-based measurement signals are sent into and interact with the process medium, and the transmitted and / or reflected and / or scattered portions of the transmitted measurement signals are subsequently received. Since reflection and scattering can be indistinguishable, the following reference to the reflected portion also implies the inclusion of the scattered portion. According to the invention, depending on how high the portion or these portions are instantaneously measured, possible foreign objects are detected based on the transmitted portion and / or based on the reflected portion. An evaluation unit of the corresponding design of the measurement system is used for this. An advantage here is that, depending on the type of foreign object, the transmitted and / or reflected portions change significantly and without delay, thereby achieving real-time capability and reliable foreign object detection. Therefore, the container section in which the measurement system is arranged can be a pipeline section through which the process medium flows, because even here, despite high flow rates in a given situation, detection without delay is possible.

[0010] Within the scope of this invention, optionally, only one of the two portions is measured, i.e., the transmitted or reflected portion of the transmitted measurement signal. In the simplest case, this is implemented by arranging a reflector opposite to the first beam axis of the first high-frequency unit in the container section. In this case, the first high-frequency unit is then configured such that it can also receive the transmitted portion after reflecting the transmitted measurement signal on the reflector. This can be accomplished, for example, using a transmit / receive splitter or a directional coupler. As an alternative to the reflector for recording the transmitted portion, an option is to supplementarily provide a second high-frequency unit to receive the transmitted portion of the transmitted measurement signal from the direction of the second beam axis. For this purpose, the second high-frequency receiving unit is preferably arranged completely opposite to the first high-frequency unit in the container section. That is, the angle between the first beam axis and the second beam axis is between 165° and 195°.

[0011] To detect the reflected portion of the transmitted measurement signal, the measurement system can include a third high-frequency unit that receives this portion from the direction of the third beam axis. For this purpose, such a third high-frequency unit is preferably arranged relative to the first high-frequency unit such that the first beam axis and the third beam axis intersect at an angle not greater than 90°, particularly about 45°.

[0012] Regarding evaluation, the measurement system of the present invention, and particularly its evaluation unit, is capable of detecting potential foreign objects in the simplest case by comparing a recorded portion with a corresponding reference value: when the transmitted portion is lower than a first reference value, or when the reflected portion exceeds a second reference value, this situation is evaluated as a foreign object being detected. In this case, the reference value represents the transmitted or reflected portion received by the corresponding high-frequency unit in a known process medium and without foreign objects.

[0013] The frequency at which the high-frequency unit transmits and receives radar signals in segments depends on the type of process medium and the anticipated foreign matter. In principle, the total radar spectrum provides frequencies between 0.1 GHz and 500 GHz. In cases where the liquid process medium has a dielectric constant between 1 and 10, frequencies between 0.5 GHz and 10 GHz are particularly advantageous. Furthermore, for improved input and output coupling, it is advantageous to arrange a dielectric matching structure between the high-frequency unit and the container segment, with a dielectric constant between that of the process medium and the high-frequency unit.

[0014] Within the scope of this invention, the measurement signal does not need to have a constant frequency. Depending on the application, such as a process medium, it is an option for the first high-frequency unit to transmit a time-modulated measurement signal, such as in the case of frequency-modulated continuous-wave radar, for example, which has a sawtooth frequency variation. Alternatively, it is an option to construct the measurement system, and thus the high-frequency unit, such that the radar signal is transmitted and received sequentially or periodically, alternatingly and in segments, having two or more frequencies distinct from each other. In this case, the evaluation unit is able to detect potential foreign objects at each frequency based on the transmission and / or reflection portions. It is advantageous here that the foreign object is recorded, which is difficult to detect using only transmission and / or reflection measurements within certain radar frequency ranges. Another option in this regard is to transmit broadband noise as the radar signal.

[0015] To further enhance the resolution of foreign object detection, the measurement system of the present invention can also be extended by adding a fourth high-frequency unit, which is similar to the first high-frequency unit in that it transmits radar-based measurement signals into the process medium; however, in the direction of the fourth beam axis, the fourth beam axis extends at an angle unequal to that of the first beam axis. In this way, at least the potential for reflection or scattering on foreign objects is increased, which in turn leads to higher resolution.

[0016] When the measurement system detects both the transmitted and reflected portions of the sent measurement signal, the evaluation unit can weight the transmitted and reflected portions, and then add or subtract the weighted portions to detect potential foreign objects based on the sum or difference of the weighted portions. In this case, the weights depend on the type of process medium and the installation of the high-frequency unit.

[0017] In principle, the term "unit" in the context of this invention means any electronic circuit or hardware suitably designed for the intended application. Thus, it can be an analog circuit for generating or processing corresponding analog signals, as needed. However, it can also be a digital circuit, such as an FPGA or a storage medium that works in conjunction with a program. In this case, the program is designed to perform corresponding method steps, or computer operations required to apply the relevant unit. In particular, the evaluation unit can therefore also be, for example, a central process control or distributed server in a process plant.

[0018] In particular, the high-frequency unit can therefore include one or more antenna arrangements, for example, for transmitting and / or receiving measurement signals. The higher the frequency, the more suitable a planar antenna structure becomes. Depending on whether the intention is to receive or transmit, the high-frequency unit may be based, for example, on a controlled high-frequency oscillator for high-frequency generation. For signal processing of the received measurement signal portion, the corresponding high-frequency unit can perform frequency conversion from the HF region based on, for example, sampling or mixing principles. Attached Figure Description

[0019] The invention will now be explained in more detail with reference to the accompanying drawings, which are shown below: Figure 1 The present invention's measurement system for detecting potential foreign objects in pipeline sections, and Figure 2 The graph shows the transmission and reflection portions of the measurement signal of the time-periodic pattern M, based on the measurement time. Detailed Implementation

[0020] Figure 1 A pipeline section 3 with a circular cross-section through which process medium 2 flows at a controlled flow rate is shown. Pipeline section 3 is a component of a process plant, for example, for processing food. Process control is performed using a higher-level unit 14, such as, for example, a local process control system or a distributed server. For this purpose, the higher-level unit 14 is connected via a suitable interface—such as, for example, “4-20mA”, “PROFIBUS”, “HART”, or “Ethernet”—to the actuators required for this purpose—such as pumps or valves and field devices, such as flow measurement devices. In this way, the higher-level unit 14 can control the flow rate into or out of pipeline section 3 as needed to regulate the flow rate.

[0021] Additionally, Figure 1 In the example of the illustrated embodiment, the upper-level unit 14 forms a component of the measurement system 1 of the present invention, by means of which foreign matter 4 that may flow with the process medium 2 can be detected. Therefore, Figure 1 The measurement system 1 of the illustrated embodiment additionally includes three high-frequency units 11, 12, and 13, which are equidistant from each other along the pipeline section 3 relative to the flow direction. Each of the high-frequency units 11, 12, and 13 is arranged in the path of the transmitted radar signal S, radar signal R, and radar signal T. HF In this case, the transmittance in these areas can be achieved, for example, due to the corresponding transparent windows in the pipeline section 3, based on a plastic material that is appropriately resistant to the process medium 2.

[0022] Each of the three high-frequency units 11, 12, and 13 is connected by the beam axis a. S,R,T Distinguish between high-frequency measurement signals S HF Along the beam axis a S,R,T It was sent to process medium 2 and subsequently partially received. For example... Figure 1 As shown, three high-frequency units 11, 12, and 13 are arranged on pipeline section 3, offset from each other by 90°, wherein the beam axis a S,R,TExtending in the shared plane and oriented toward the shared midpoint in pipeline section 3. The first high-frequency unit 11 and the second high-frequency unit 12 are arranged completely opposite to each other on pipeline section 3 and aligned with each other, such that the first beam axis a of the first high-frequency unit 11 is aligned with the shared midpoint in pipeline section 3. S Second beam axis a T They overlap each other and therefore have an angle of 180° relative to each other.

[0023] The first high-frequency unit 11 is used to transmit the measurement signal S. HF The second high-frequency unit 12 is used to receive it. Through their orientation relative to each other, the second high-frequency unit 12 receives the measurement signal S. HF The measurement signal S transmitted through process medium 2 that is not absorbed or scattered during the process is... HF Transmission part T HF The third high-frequency unit 13 is also used for receiving. For example... Figure 1 As shown, the third beam axis a R Relative to the first beam axis a S It extends at an angle α of 90°. Therefore, the third high-frequency unit 13 does not receive the transmitted measurement signal S. HF Transmission part T HF On the contrary, for Figure 1 As shown, when the foreign object 4 is momentarily located in the process medium 2 at the plane of high-frequency units 11, 12, and 13, the third high-frequency unit 13 receives the high-frequency signal S transmitted by the foreign object 4 from the first high-frequency unit 11. HF The reflected part R HF At the same time, this naturally reduces the transmitted portion T received at the second high-frequency unit 12. HF .

[0024] exist Figure 1 In the illustrated embodiment, the measurement signal S, measurement signal T, and measurement signal R... HF The input and output coupling of the process medium 2 is optimized by a dielectric matching structure 110 arranged between each of the three high-frequency units 11, 12, and 13 and the container section 3. For this purpose, the material on which the matching structure 110 is based has a dielectric constant between that of the process medium 2 and that of the high-frequency units 11, 12, and 13. In this regard, the material can be, for example, suitable glass, dielectric plastic, or ceramic. Additionally, the coupling is optimized by a funnel-shaped widening towards the container section 3 and the process medium 2, such as... Figure 1 As shown.

[0025] Since each of the high-frequency units 11, 12, and 13 is connected to the higher-level evaluation unit 14 via its own interface—such as "4-20mA," "PROFIBUS," "HART," or "Ethernet"—the second high-frequency unit 12 and the third high-frequency unit 13 are able to detect a portion of the R in each case. HF T HF The values ​​are transmitted to evaluation unit 14, where they can be processed. In this case, it is not important whether the transmission occurs in analog form, so it can be, for example, as a raw signal or based on a digital protocol. Naturally, other information can be transmitted via the interface, such as parameter data for high-frequency units 11, 12, and 13, or information about their operating status.

[0026] Based on the measured transmission / reflection components R and T HF The transmission value, evaluation unit 14 can detect possible foreign matter 4 in process medium 2: if the transmission part T HF Reduce and / or reflect part R HF If this is increased, then this situation points to the instantaneous existence of foreign object 14.

[0027] The instantaneous measurements of the transmission / reflection portions R and T by the evaluation unit 14 are possible. HF To identify possible reductions or increases, the reference values ​​for generally expected transmission and reflection are coordinated with previously identified reference values. In this case, the key is only that the reference values ​​for pipeline section 3 and the type of process medium 2 are valid. In this case, for example, in the context of calibration using process medium 2 that can be proven to be free of foreign matter, it is essential to ensure that specific reference values ​​are identified.

[0028] because Figure 1 The embodiment of the measurement system 1 of the present invention shown determines the transmission portion T. HF and the reflective part R HF Therefore, in this embodiment, a portion of the R recorded is additionally tested. HF T HF The feasibility of foreign object detection is justified when the reduced transmission portion T HF It is related to the increased reflective portion R HF Simultaneous recording in this situation means that the detection of foreign object 4 can be considered feasible. Therefore, in other cases, when partial R, T HF When only one part of R and T changes, or when both parts R and T change. HF When the direction is changed, the measurement becomes infeasible, and it may be due to defects, for example, in the second high-frequency unit 12 or the third high-frequency unit 13.

[0029] Based on the foreign object detection of the present invention, given a detected foreign object 4, a suitable response can be taken within the process plant: when foreign object 4 is detected, the evaluation unit 14 can, for example, close a shut-off valve located downstream of the foreign object 4 and the high-frequency units 11, 12, 13 in the flow direction, so that the foreign object 4 is not bottled unnoticed. Alternatively, the process medium 2 can be arranged as a bypass downstream of the high-frequency units, through which the process medium is discarded. In this way, the process plant can operate with complete safety and higher efficiency.

[0030] The more frequently the measurement system 1 of the present invention checks the process medium 2 for possible foreign matter 4, the safer the monitoring of the present invention. In this case, the above-described method of the present invention can be repeated according to the following defined cycle: - Radar-based measurement signal S HF The signal is transmitted from the first high-frequency unit 11 to the process medium 2. - Transmission section T HF The measurement signal S is measured by the second high-frequency unit 12 and transmitted. HF The reflective part R HF Measured by the third high-frequency unit 13, and - Based on the transmission portion T by the superior evaluation unit 14 HF and the reflective part R HF Detect possible foreign objects 4. In this case, the period can be freely selected, for example, between one millisecond and up to one hour. In this case, only when process medium 2 is not flowing, or with... Figure 1 The example shown in the illustration contrasts with the one where, when container segment 3 is not a pipeline section but rather, for example, a storage container segment, low cycles in the hourly range are recommended. In this regard, the measurement section T... HF R HF Depending on the exact orientation of high-frequency units 11, 12, and 13 relative to each other, the type of process medium 2, and the expected foreign object 4 in evaluation unit 14, they are weighted differently under a given condition so that the weighted portion T can be used to determine the optimal value. HF R HF 4. Safely detect possible foreign objects.

[0031] Furthermore, in contrast to periodic measurements, the inspection process of medium 2 is almost uninterrupted, thus providing real-time detection of foreign matter 4 is also an option. For this purpose, the above method is continuously performed. That is, high-frequency units 11, 12, and 13 continuously transmit and receive, and the transmission portion T... HF and the reflective part R HF The value is transmitted almost continuously to the evaluation unit 14.

[0032] The portion T measured almost continuously HF R HF The value in Figure 2 The diagram is schematically shown according to time. In this case, a special case is additionally shown, where part of T... HF R HF The measurement is a superposition of periodic events. These events can involve, for example, a stirrer that periodically moves along beam axis a during operation. S,R,T At least one of them. As can be seen from the corresponding measurement curves (a) and (b), this superposition is shown in the form of a periodic repeating offset M, or more generally, in the form of a characteristic pattern M that varies over time in the plotted measurement curves (a, b). In this case, measurement curve (a) shows the measurement time period in which the foreign object 4 is absent, while the measurement time period on which measurement curve (b) is based is affected by the foreign object 4, as shown by the corresponding negative peaks in measurement curves (b) and (c). In the basic measurement scenario, the foreign object 4 is involved, which flows through pipeline section 3 in the corresponding measurement time period and thus only causes the transmission portion T. HF The pulse shape decreases, such as Figure 2 The measurement curves are shown in (b) and (c).

[0033] from Figure 2 As can be seen from the measurement curves (a) and (b), in the case of periodic superposition, due to the temporary offset M, it is impossible to detect the portion T by instantaneous means. HF R HF Pure coordination with the reference value is used to reliably detect possible foreign objects 4. Therefore, in this case within the scope of the invention, there exists a basis for the transmission portion T. HF Or the reflective part R HF The time-resolved measurement curves (a, b) are used to record the possible time-periodic pattern M. This allows for the generation of a compensated measurement curve (c), i.e., as shown... Figure 2 As shown, the curve is compensated for with respect to the time-periodic pattern M.

[0034] Therefore, Figure 2 The compensated measurement curve (c) shown can be obtained in the following way: - Thus, the periodic time span caused by periodic superposition and the associated offset value M were determined from the original measurement curve (b), and - Subtract the offset value M, which is identified over the time span, from the corresponding measurement point in the original measurement curve (b).

[0035] To detect and extract time-periodic patterns, for example, self-learning algorithms and process-specific knowledge can be used.

[0036] An advantage of this further development of foreign object detection in the present invention lies in the fact that the transmission portion T and the reflection portion R from the compensated measurement curve (c) HF The resulting values ​​can still be compared with the fixed reference values ​​as described above, so that possible foreign objects can be reliably detected despite the periodic superposition of the system.

[0037] List of reference numerals in the attached figures

[0038] 1 Measurement System

[0039] 2. Medium

[0040] 3 Container Section

[0041] 4. Foreign objects

[0042] 11 First High-Frequency Unit

[0043] 12 Second High Frequency Unit

[0044] 13 Third High-Frequency Unit

[0045] 14. Higher-level evaluation unit

[0046] 110 Dielectric Matching Structure

[0047] a S,R,T Beam axis

[0048] R F The scattered or reflected portion of the measured signal

[0049] S HF High-frequency measurement signals

[0050] T HF Transmission portion of the measurement signal

[0051] α The angle between the first beam axis and the third beam axis

Claims

1. A measurement system for detecting foreign matter (4) in a process medium (2), comprising: - Container section (3), said container section being sensitive to radar signals (S, R, T) in at least certain areas. HF (2) is transparent, wherein the process medium (2) is located in the container section (3). - A first high-frequency unit (11), the first high-frequency unit being designed and arranged at the container section (3) such that the first high-frequency unit is capable of operating on the first beam axis (a S The direction will be based on the radar measurement signal (S) HF ) is sent to the process medium (2), - A reflector, which is arranged opposite to the first beam axis (a) of the first high-frequency unit (11) at the container section (3). S On the above, wherein the first high-frequency unit (11) is designed such that the first high-frequency unit is capable of receiving the transmitted measurement signal (S). HF The transmitted portion (T) after reflection on the reflector HF ), and / or - A second high-frequency unit (12), the second high-frequency unit being designed and arranged at the container section (3) such that the second high-frequency unit can receive signals from the second beam axis (a). T The direction of the received measurement signal (S) HF The transmission portion (T) HF ), and / or - A third high-frequency unit (13), which is designed and arranged in the container section (3) such that the third high-frequency unit can be emitted from the third beam axis (a R The direction of the received measurement signal (S) HF The reflective part (R) HF ),as well as - Evaluation unit (14), the evaluation unit being designed based on the transmission portion (T) HF ) and / or based on the reflective portion (R HF (4) to detect possible foreign objects.

2. The measurement system according to claim 1, wherein, The evaluation unit (14) is designed to evaluate a portion (R) HF T HF (4) The foreign object is detected by comparing it with the corresponding reference value.

3. The measurement system according to at least one of the preceding claims, wherein, The container section (3) is the pipeline section.

4. The measurement system according to any one of the preceding claims, wherein, The third high-frequency receiving unit (13) is arranged relative to the first high-frequency unit (11) such that the first beam axis (a S ) and the third beam axis (a R They intersect at an angle (α) of no more than 90°, especially about 45°.

5. The measurement system according to any one of the preceding claims, wherein, The high-frequency units (11, 12, 13) are designed to transmit and receive radar signals (S, R, T) at frequencies between 0.3 GHz and 250 GHz. HF ).

6. The measurement system according to any one of the preceding claims, wherein, The high-frequency units (11, 12, 13) are designed for both transmitting and receiving. - At least two radar signals (S, R, T) of different frequencies HF ) and / or - Based on the frequency of time modulation, especially the sawtooth-shaped radar signal (S, R, T) HF ), and The evaluation unit (14) is designed to be based on the transmission portion and / or reflection portion (T) HF R HF )Detect possible foreign objects at each frequency (4).

7. The measurement system according to any one of the preceding claims, wherein, The third high-frequency unit (13) is arranged substantially relative to the first high-frequency unit (11) in the container section (3).

8. The measurement system according to any one of the preceding claims further comprises: - A fourth high-frequency unit, which is designed and arranged in the container section (3) such that the fourth high-frequency unit transmits the radar-based measurement signal (S) in the direction of the fourth beam axis. HF ) is sent to the process medium (2), the fourth beam axis is aligned with the first beam axis (a S ) Unequal angle extensions.

9. The measurement system according to any one of the preceding claims, wherein, The evaluation unit (14) is designed to evaluate the transmission portion (T) HF ) and the reflective portion (R) HF ) are weighted, and based on the weighted portion (T) HF R HF (4) The sum or difference of ) is used to detect possible foreign objects.

10. The measurement system according to any one of the preceding claims further includes a dielectric matching structure (110) disposed between at least one of the high-frequency units (11, 12, 123) and the container segment (3), the dielectric constant of the dielectric matching structure being between the dielectric constant of the process medium (2) and the dielectric constant of the high-frequency units (11, 12, 13).

11. A method for detecting foreign matter (4) in a process medium (2) located in a container section (3) by means of a measurement system according to at least one of the preceding claims, said container section (3) being sensitive to radar signals (S, R, T) in at least certain areas. HF Transparent, among which, The method includes the following steps: - Based on radar measurement signals (S HF ) is sent to the process medium (2), - Receive the transmitted measurement signal (S HF The transmission portion (T) HF ) and / or reflective portion (R HF ),as well as - Based on the aforementioned transmission portion (T) HF ) and / or the reflective portion (R HF (4) to detect possible foreign objects.

12. The method according to claim 11, wherein, When the transmission portion (T) HF When the value is lower than the first reference value or when the reflective portion (R) is lower than the first reference value, HF When the value exceeds the second reference value, a foreign object is detected (4).

13. The method according to claim 11 or 12, wherein, Record the transmission portion (T) HF ) and / or the reflective portion (R HF The time-resolved measurement curves (a, b) are used to determine the transmission portion (T). HF ) and / or the reflective portion (R HF Possible time-periodic patterns (M) of ) Among them, a measurement curve (c) with time-periodic pattern (M) compensation is generated, and Among them, the possible foreign objects are detected based on the compensated measurement curve (c) (4).

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