System for detecting the presence of a foreign body in a flowable medium and corresponding method

Description

[0001] The invention relates to a system for detecting the presence of a foreign body in a flowing medium in a pipeline. Furthermore, the invention relates to a method for detecting the presence of a foreign body in a medium in a pipeline using a corresponding system.

[0002] In the process industry, flowable media are conveyed through pipelines. In areas with particularly stringent hygiene requirements, such as the food processing industry, it is desirable to detect foreign bodies as early and reliably as possible, for example, before or during filling into a container. The term foreign body encompasses all solid materials that are fundamentally undesirable in the medium for safety and / or quality assurance reasons. These include, for example, broken glass, fish bones, bone fragments, plastic and rubber pieces, gravel / stone, etc., but also unwanted solid particles in an otherwise liquid to viscous, pasty medium.

[0003] EP 18 53 900 A1 describes a system and method for detecting the presence of foreign bodies in a medium. Both microwaves and ultrasonic waves are emitted into the medium as transmission signals, each from a dedicated transmission unit. Based on an evaluation of received signals, the occurrence of changes in the medium, in particular the presence of a foreign body, is determined. However, the solution presented in EP 18 53 900 A1 does not provide a way to distinguish a foreign body from a gas bubble. This is particularly challenging when the gas bubble and the foreign body are essentially the same size. In contrast to foreign bodies, gas bubbles represent a harmless change in the medium.

[0004] Application US 2019 / 257 868 A1 discloses a system for detecting the presence of a foreign body in a pipeline by determining the permittivity of the medium. Application US 5 793 216 A discloses a pipeline with a compression section used to generate a stratified multiphase flow to detect the flow of each phase.

[0005] The object of the invention is therefore to provide a possibility to safely and reliably detect a foreign body in a medium flowing in a pipeline and, in particular, to distinguish it from a gas bubble.

[0006] The problem is solved by a system for detecting the presence of a foreign body in a flowing medium in a pipeline and a method for detecting the presence of a foreign body in a medium in a pipeline. Regarding the system, the problem is solved by a system for detecting the presence of a foreign body in a flowing medium in a pipeline, comprising: a pipeline with -- a pipeline inlet section and -- a compression section adjoining the pipeline inlet section in a foreseeable flow direction, in which compression section the cross-sectional area of the pipeline is compressed in a compression direction perpendicular to the flow direction, in comparison to the cross-sectional area of the pipeline in the pipeline inlet section, wherein the area dimension of the cross-sectional area of the pipeline in the compression section substantially corresponds to the area dimension of the cross-sectional area of the pipeline in the pipeline inlet section;a first transmitting / receiving unit in the line inlet section, which is configured to introduce transmitting signals into a medium flowing in the line inlet section and to receive receiving signals; a second transmitting / receiving unit in the compression section, which is configured to introduce transmitting signals into a medium flowing in the compression section and to receive receiving signals; and at least one higher-level unit; which is configured to determine an average permittivity of the medium in the line inlet section and the compression section from the respective received signals and to determine the presence of a foreign body in the medium based on at least one comparison of the average permittivity in the compression section with the average permittivity in the line inlet section.

[0007] The pipeline is therefore designed in such a way that the shape of the cross-sectional area in the pipeline inlet section differs from the shape of the cross-sectional area in the compression section, while maintaining the same area dimension.

[0008] When flows from the pipe inlet section into the compression section, an object in the medium, namely a gas bubble or a foreign body, experiences a pressure difference.

[0009] If the object is a (usually incompressible) foreign body, it is not compressed. This changes the relative proportion of the foreign body along a path in the cross-sectional area. For example, it increases in the direction of compression. This changes the average permittivity at the transition from the pipe inlet section to the compression section. In other words, the permittivity along a path within the cross-sectional area of the compression section differs from the average permittivity along a parallel path within the cross-sectional area of the pipe inlet section.

[0010] If, however, the object is a compressible gas bubble, the gas bubble is compressed in the compression section. However, due to the constant surface area of the compression section and the pipe inlet section, the relative proportion of the gas bubble along the path in the cross-sectional area remains constant. As a result, the average permittivity along a path within the cross-sectional area of the compression section corresponds to the average permittivity along the corresponding parallel path within the cross-sectional area of the pipe inlet section.

[0011] In one embodiment of the system, the pipeline comprises a line outlet section adjoining the compression section in the intended flow direction, wherein the cross-sectional area of the line outlet section substantially corresponds to the cross-sectional area of the pipeline in the line inlet section, wherein the system comprises a third transmitting / receiving unit in the line outlet section, which is configured to introduce transmitted signals into a medium flowing in the line outlet section and to receive received signals, and wherein the higher-level unit is configured to determine an average permittivity of the medium in the line outlet section from the received signals.

[0012] In one embodiment of the system, the system, in particular the higher-level unit, is set up to - as the average permittivity in the line inlet section, a permittivity averaged over a path within the cross-sectional area of the line inlet section, and - as the average permittivity in the compression section, a permittivity averaged over a path within the cross-sectional area of the compression section, and - in particular as the average permittivity in the line outlet section, a permittivity averaged over a path within the cross-sectional area of the line outlet section, and to determine.

[0013] For example, the path runs essentially along the above-mentioned compression direction, or in a direction essentially perpendicular thereto, in which the cross-sectional area of the compression section is stretched.

[0014] Since the cross-sectional area is compressed in the compression direction, the cross-sectional area is inevitably stretched in a different direction - while maintaining the same area of the cross-sectional area of the compression section and the pipe inlet section.

[0015] Preferably, the paths within the different cross-sectional areas (i.e. that of the line inlet section and that of the compression section) are parallel to each other and in particular also the path within the cross-sectional area of the line outlet section is parallel to the first two paths.

[0016] The path along which the average permittivity is determined is defined by a transmitting unit of the transmitting / receiving unit on the one hand and a receiving unit of the transmitting / receiving unit on the other. The transmitting unit is therefore arranged opposite the receiving unit along the path to determine the average permittivity along the path.

[0017] In one embodiment of the system, the cross-sectional area in the line inlet section is circular and the cross-sectional area in the compression section is elliptical.

[0018] In one embodiment of the system, a transition section runs between the pipe inlet section and the compression section to adapt to the different shapes of the cross-sectional areas.

[0019] In particular, the same surface area (i.e. that of the line inlet section and the compression section) is preferably maintained on the transition section as well.

[0020] In one embodiment of the system, in the direction of flow, the length of the upset section and / or the pipe inlet section -- at least as large as the diameter of the respective upset section or the pipe inlet section and --- at most as large as ten times the diameter of the respective upset section or the pipe inlet section.

[0021] In one embodiment of the system, the first transmitting / receiving unit comprises at least a first electrode and a second electrode, and the second transmitting / receiving unit at least a first electrode and a second electrode.

[0022] In this case, the average permittivity can be determined from the capacitance and / or conductivity measured with the electrodes. The averaging over a path is performed along the path along which the electrodes are arranged opposite each other.

[0023] In an alternative embodiment of the system to the latter embodiment, the first transmitting / receiving unit comprises: at least a first antenna for transmitting microwaves and a second antenna for receiving microwaves, and the second transmitting / receiving unit: at least a first antenna for transmitting microwaves and a second antenna for receiving microwaves.

[0024] In this case, the average permittivity can be determined from microwave received signals that have passed through the medium, for example, based on the propagation time. These are preferably pulsed microwave transmit and receive signals. Here, too, the averaging is performed along the path along which the antennas are arranged opposite each other.

[0025] In a further development of one of the last two embodiments, for the first transmitting / receiving unit in the line inlet section and for the second transmitting / receiving unit in the compression section, the first electrode is arranged on the pipeline opposite the second electrode, in particular along the path, or the first antenna is arranged on the pipeline opposite the second antenna, in particular along the path.

[0026] In a further development of the system, the first transmitting / receiving unit and the second transmitting / receiving unit each comprise: a plurality of first electrodes and a plurality of second electrodes or a plurality of first antennas and a plurality of second antennas.

[0027] The multiple electrodes or multiple antennas each serve to divide the pipe inlet section and the compression section into sub-volumes or to divide the respective cross-sectional area of the pipe inlet section and the compression section into sub-areas. By means of the division, an object flowing in the medium in the pipeline can be assigned to one of the sub-volumes or one of the sub-areas. The multiple electrodes or multiple antennas can, in particular, be arranged and, in particular, spaced from one another in such a way that they each cover an area in which an object, in particular a foreign body, is essentially completely contained. This is possible, for example, assuming a typical, assumed size of an object, in particular a foreign body, which may be determined by the respective application and is, for example, between 0.2 cm - 3 cm.

[0028] In this case, the object, specifically the foreign body, is present only in one of the partial volumes or one of the partial areas. This minimizes the influence of interference when detecting the presence of the foreign body and improves the evaluation with the system according to the invention.

[0029] Preferably, the number of first and second electrodes or the number of first and second antennas of the first transmitting / receiving unit corresponds to the number of first electrodes and second electrodes or the number of first and second antennas of the second transmitting / receiving unit.

[0030] In one embodiment of the latter further development, imaginary connecting lines run between pairs of first electrode and second electrode or between pairs of first antenna and second antenna, wherein all connecting lines are arranged parallel to one another in the respective cross-sectional area and in particular are equally spaced.

[0031] Preferably, the same distance is not only present within the respective cross-sectional area, but the distance between all connecting lines in all cross-sectional areas is essentially constant.

[0032] Therefore, for each path formed by a connecting line in the cross-sectional area of the line inlet section, there is preferably a parallel path formed by a corresponding connecting line in the cross-sectional area of the compression section. This ensures that the division into the partial areas or partial volumes occurs in the same way in the line inlet section and the compression section.

[0033] The invention also includes all the above-mentioned embodiments mutatis mutandis for the line outlet section which adjoins the compression section.

[0034] In one embodiment of the system, the system comprises a flow meter for determining the mass flow and / or the flow velocity of the medium in the pipeline.

[0035] The flow meter serves to improve the assignment of a first received signal of the first transmitting / receiving unit and a second received signal of the second transmitting / receiving unit to the same object.

[0036] With regard to the method, the object is achieved by a method for detecting the presence of a foreign body in a medium in a pipeline using a system according to the invention. The method comprises the following steps: Emitting emitted signals and receiving received signals into a medium flowing in the line inlet section. Emitting emitted signals and receiving received signals into a medium flowing in the compression section; determining an average permittivity of the medium in the line inlet section and determining an average permittivity of the medium in the compression section. Comparing the average permittivity in the compression section with the average permittivity in the line inlet section. Detecting a foreign body in the medium if the average permittivity in the compression section differs from the average permittivity in the line inlet section.

[0037] In one embodiment of the procedure, this includes the following steps: Determining an average permittivity of the medium in the line outlet section. Comparing the average permittivity in the compression section with the average permittivity in the line inlet section and the average permittivity in the line outlet section.

[0038] The pipe outlet section therefore serves as an additional control, since the average permittivity in the pipe outlet section should match the average permittivity in the pipe inlet section.

[0039] In one embodiment of the procedure, this includes the step: Detection of the presence of an object in the pipe inlet section based on a determined average permittivity of the medium, where the detection of the presence of the object occurs before the comparison of the mean permittivities.

[0040] The invention is explained in more detail with reference to the following figures, which are not to scale. Like reference numerals denote like features. For reasons of clarity or where otherwise appropriate, previously mentioned reference numerals have been omitted in the following figures.

[0041] They show: Fig. 1a : A first embodiment of a system according to the invention with a pipeline in a side view; Fig. 1b : A plan view of a cross-sectional area of the pipeline in the first embodiment of the system according to the invention. Fig. 1c : A plan view of another cross-sectional area of the pipeline in the first embodiment of the system according to the invention. Fig. 2a : A second embodiment of a system according to the invention with a pipeline in a side view; Fig. 2b : A plan view of a cross-sectional area of the pipeline in the second embodiment of the system according to the invention; Fig. 2c : A plan view of a further cross-sectional area of the pipeline in the second embodiment of the system according to the invention; Fig 3 : A schematic view of a time course of the permittivity Fig. 4a : A third embodiment of a system according to the invention with a pipeline in a side view; Fig. 4b : A plan view of a cross-sectional area of the pipeline in the third embodiment of the system according to the invention; Fig. 4c : A plan view of a further cross-sectional area of the pipeline in the third embodiment of the system according to the invention; and Fig. 1a shows a system according to the invention with a pipeline 100 through which a medium (not shown) flows in a predetermined flow direction SR. The pipeline 100 is, for example, a food-conducting pipeline, such as part of a filling system in the food processing industry. For example, the pipeline is arranged adjacent to and / or associated with a nozzle of the filling system, by means of which nozzle the medium is filled into a container. The container is then sealed and sent to the retail trade.

[0042] The pipe inlet section 1 has a cross-sectional area QE, which is circular here, for example, see also Fig. 1b The medium flows from the pipe inlet section 1 into a compression section 3 with a cross-sectional area QS. The compression section 3 is characterized by the fact that the cross-sectional area QS is compressed in a compression direction OR, which is essentially perpendicular to the flow direction SR. Therefore, the cross-sectional area QS is elliptical here, see also Fig. 1c This compression occurs while maintaining identical surface dimensions. The surface dimension A_QE of the cross-sectional area QE of the pipe inlet section 1 therefore essentially corresponds to the surface dimension A_QS of the cross-sectional area QS of the compression section 3, see. Fig. 1b und 1c , ie A_QE=A_QS In a stretching direction which is substantially perpendicular to both the flow direction SR and the compression direction OR, the cross-sectional area QS is therefore necessarily stretched.

[0043] The compression section 3 is followed in the flow direction SR by a pipe outlet section 2. Its cross-sectional area QA essentially corresponds to the cross-sectional area QE of the pipe inlet section 1. For this reason, A_QE=A_QS=A_QA.

[0044] To adapt the shape of the different cross-sectional areas QA, QS, QE, transition sections 41, 42 run between the line inlet section 1 and the compression section 3, and between the compression section 3 and the line outlet section 2. The same surface area is preferably maintained on the transition sections 41, 42.

[0045] In each of the sections 1, 3, 2, an associated transmitting / receiving unit 11, 12, 13 is provided: a first transmitting / receiving unit 11 for the line inlet section 1, a second transmitting / receiving unit 12 for the compression section 3, and a third transmitting / receiving unit 13 for the line outlet section 2. Each of the transmitting / receiving units 11, 12, 13 is designed to introduce transmitting signals into a medium flowing in the respective section 1; 3; 2 and to receive receive signals in its respective section 1; 3; 2. The receive signals are subsequently transmitted to a higher-level unit 10 and then evaluated. The line outlet section 2 is not essential to the invention and serves only as an additional check.

[0046] The higher-level unit 10 is connected to the transmit / receive units 11, 12, and 13 via a communication link (KV). The communication link (KV) can be, for example, a wired communication link, such as an analog measurement transmission link, particularly one conforming to the 4-20 mA standard, or a wired fieldbus used in automation technology, such as Foundation Fieldbus, Profibus PA, Profibus DP, HART, or CANBus. However, it can also be a communication link of a modern industrial communication network, such as an "Industrial Ethernet" fieldbus, particularly Profinet, HART-IP, or Ethernet / IP, or a communication network known from the communications sector, such as Ethernet based on the TCP / IP protocol.

[0047] In case the communication connection KV is wireless, it can be, for example, a Bluetooth, ZigBee, WLAN, GSM, LTE, UMTS communication network or even a wireless version of a fieldbus, in particular 802.15.4 based standards such as WirelessHART.

[0048] For the system according to the invention it is completely irrelevant whether it is - as in Fig. 1a shown for the sake of clarity - comprises a single higher-level unit 10, or whether it has a separate higher-level unit for each of the transmitting / receiving units 11, 12, 13, which are connected to one another via communication links KV and / or to another higher-level unit with a communication link KV.

[0049] The higher-level unit 10 is, for example, a higher-level control unit, e.g. a process control system with a computer or a programmable logic controller (PLC), or also a transmitter unit, in a remote or possibly non-remote variant.

[0050] The system further comprises a flowmeter 14, with which the flow velocity and / or the mass flow of the medium in the line inlet section 1 of the pipeline 100 can be determined. The flowmeter 14 also transmits the measured values determined by the flowmeter 14 to the higher-level unit 10 via the communication connection KV. The flowmeter 14 serves to better correlate a received signal received by the first transmitting / receiving unit 11 and a received signal received by the second transmitting / receiving unit 12 with the same object 5, namely a foreign body 51 or a gas bubble 52, based on the flow velocity and / or the mass flow.

[0051] The higher-level unit 10 determines an average permittivity epsilon_m,1; epsilon_m,3 and epsilon_m,2 for each of the sections 1, 3, 2 from the received signals and, based on a comparison of the average permittivity epsilon_m,1; epsilon_m,3 and epsilon_m,2, determines whether an object 5 present in the medium is a foreign body 51 or a gas bubble 52. In particular, the higher-level unit 10 is configured and / or the first transmitting / receiving unit 11 and second transmitting / receiving unit 12 are arranged such that the average permittivities epsilon_m,1 and epsilon_m,3 are determined along parallel paths, e.g., both along the same compression direction OR.

[0052] This is in the following Fig. 2a bis Fig. 2c in case of a gas bubble 52 and Fig. 4a bis Fig. 4c in the case of a foreign body 51. The system from the Fig 2a bis 2c and Fig 4a bis 4c essentially corresponds to the one already in the Fig. 1a bis 1c shown system and differs, as shown in more detail below, only in the differently designed transmitting / receiving units 11, 12, 13, each in the second embodiment ( Fig. 2a bis 2c ) or the third design ( Fig. 4a bis 4c ) of the system.

[0053] Fig. 2a shows, in the event that a gas bubble 52 flows from the line inlet section 1 into the compression section 3, that it is compressed or squeezed in the compression direction OR in the compression section 3, in order to then subsequently assume the previous size again in the line outlet section 2 (whose cross-sectional area QA is identical to the cross-sectional area QE of the line inlet section 1).

[0054] The first transmitting / receiving unit 11 in the line inlet section 1 comprises here, see Fig. 2b , two first electrodes 61a, 62a and two second electrodes 61b, 62b. In each case, a first electrode 61a; 62a is arranged along an imaginary connecting line opposite a second electrode 61b; 62b. The connecting line thus runs, for example, from the first electrode 61a to the second electrode 61b. By means of the plurality of electrodes 61a, 61b, 62a, 62b, a division of the cross-sectional area QE of the line inlet section 1 into several partial areas is achieved, wherein the gas bubble 52 in the line inlet section 1 is located in only one of the partial areas. This is indicated by the dashed lines in Fig. 2b indicated.

[0055] The same applies to the second transmitting / receiving unit 12 in the compression section 3, see Fig. 2c This comprises two first electrodes 71a, 72a and two second electrodes 71b, 72b. The first electrode 71a is arranged along an imaginary connecting line opposite a second electrode 71b, and another first electrode 72a is arranged along an imaginary connecting line opposite a further second electrode 72b. All connecting lines are parallel to one another. Furthermore, the distance between the connecting lines of the electrodes 61a, 61b, 62a, 62b of the first transmitting / receiving unit 11 corresponds to the distance between the connecting lines of the electrodes 71a, 71b, 72a, 72b of the second transmitting / receiving unit 12, and a connecting line from the cross-sectional area QE of the line inlet section 1 is parallel to a connecting line of the compression section 3.

[0056] Via the pairs of electrodes 61a, 61b; 62a, 62b; 71a, 71b; 72a, 72b arranged opposite one another in the cross-sectional area QE, QS, an electrical capacitance and / or a conductivity present between the pairs of electrodes 61a, 61b; 62a, 62b; 71a, 71b; 72a, 72b is received as a received signal by the transmitting / receiving units 11, 12 and transmitted to the higher-level unit 10 (cf. Fig. 1a ) transmitted.

[0057] The higher-level unit 10 then determines an average permittivity epsilon_m,2 or epsilon_m,3 of the medium, respectively for the cross-sectional area QE of the line inlet section 1 and the cross-sectional area QS of the compression section 3. This is done along the path defined by the oppositely arranged pairs of electrodes 61a, 61b; 62a, 62b; 71a, 71b; 72a, 72b. The permittivity epsilon is also referred to in the art as dielectric conductivity or dielectric constant.

[0058] In one embodiment, the presence of an object 5 in the medium, namely a foreign body 51 or a gas bubble 52 in the medium flowing in the pipeline 100, is determined. This is done, for example, by evaluating a temporal profile of the average permittivity epsilon_m,1 in the pipeline inlet section 1, as in Fig. 3 shown in more detail.

[0059] The invention is particularly suitable for round objects 5, so that the pressure difference at the transition from the line inlet section 1 to the compression section 3 would cause no or essentially hardly any turbulence or rotation of the object, which would have an undesirable influence on the average permittivity epsilon_m1; epsilon_m,3 determined along the path.

[0060] Fig. 3 shows a determined mean permittivity epsilon_m,1 as a function of time, for example in the cross-sectional area QE of the pipe inlet section 1, for the case of an object 5 flowing through the pipe inlet section 1. The mean permittivity epsilon_m,1 is determined, for example, as a location-dependent function and converted into a time-dependent function based on a known and / or determined flow velocity of the medium. This can be done, for example, using the method mentioned above and in Fig. 1 The flowmeter 14 shown here is also possible. Of course, it is also possible to directly analyze a location-dependent function. The temporal progression of the mean permittivity epsilon_m,1 is stored, for example, in a storage unit associated with, or at least connected to, the higher-level unit 10.

[0061] Due to the emergence of the object 5 in the medium, the mean permittivity epsilon_m,1 decreases in a reversed peak to a local minimum over time see Fig. 3 , starting from an initial permittivity epsilon_i of the medium 1, and then subsequently increasing back to the initial permittivity epsilon_i. Fig. 3 already a time course of a spatially integrated mean value of the permittivity along the path at whose opposite ends the oppositely arranged pairs of electrodes 61a, 61b; 62a, 62b are arranged in the cross-sectional area QE of the line inlet section 1. A similar time course to that in Fig. 3 shown for the pipe inlet section 1, for the mean permittivity epsilon_m,3.

[0062] In the case of a substantially water-based medium, the medium without an object has an average permittivity epsilon_i of approximately 80, whereas a foreign body 22 (depending on the material it is made of) typically has an epsilon permittivity in the range between 2 and 8. This is in similar ranges to the epsilon permittivity of a gas bubble 52, which means that distinguishing between a gas bubble 52 and a foreign body 51 is not always possible based solely on the evaluation of the temporal progression of the average permittivities epsilon_m,1 in the line inlet section 1 without further measures.

[0063] The device according to the invention and the method according to the invention solve this problem by comparing the average permittivity epsilon_m,1 in the line inlet section 1 with the average permittivity epsilon_m,3 in the compression section 3. Specifically, during the comparison, an average permittivity epsilon_m,1 is determined in the line inlet section 1 and an average permittivity epsilon_m,3 is determined in the compression section 3. The average permittivity epsilon_m is determined as the spatial mean value determinable across the oppositely arranged pairs of electrodes 61a, 61b; 62a, 62b or 71a, 71b, 72a, 72b. That is, along the path at whose opposite ends the oppositely arranged pairs of electrodes 61a,61b;62a,62b and 71a,71b,72a,72b are arranged.

[0064] By squeezing the gas bubble 52 in the compression section 3 in the compression direction OR, the average permittivity epsilon_m,3 in the compression section 3 will essentially correspond to the average permittivity epsilon_m,1 in the line inlet section 1, see Fig. 2a und 2b . The flowmeter 14 supports the better assignment of the mean permittivities epsilon_m,1; epsilon_m,3 to the same object 5 (here: gas bubble 52), and the presence of the virtual partial volumes or partial areas (by using at least two pairs of electrodes 61a, 61b, 62a, 62b, ...) further minimizes the influence of interference effects in the aforementioned comparison.

[0065] When checking whether the average permittivity epsilon_m,1 in the line inlet section 1 essentially corresponds to the average permittivity epsilon_m,3 in the compression section 3, a limit value for a tolerable deviation is stored, for example, in the higher-level unit 10 and / or the associated storage unit. The limit value depends in particular on the specific design of the system, including the design of the transmitting / receiving units 11, 12 and / or the specific compression of the compression section 3 compressed in the compression direction OR, and / or the size of the object 5. Therefore, further specification is not useful here.

[0066] The size of object 5 can be determined beforehand. For example, the width of the inverted peak from Fig. 3 the length of object 5 (ie extension of object 5 along compression direction OR) can be determined, and the height of the inverted peak from Fig. 3 the width (i.e., the extent of object 5 along the flow direction SR) is recognizable. Alternatively or additionally, the size of object 5 can also be estimated in advance, e.g., based on a user's preselection, based on knowledge of typical sizes of potential objects 5 in the medium.

[0067] If it is determined - possibly taking into account the stored limit value - that the mean permittivity epsilon_m,3 in the compression section 3 essentially corresponds to the mean permittivity epsilon_m,1 in the line inlet section 1, the higher-level unit 10 determines that the object 5 is a gas bubble 52.

[0068] This can be additionally verified by observing signals received by a third transmitting / receiving unit 13 arranged in the line outlet section 2. This unit, just like the first transmitting / receiving unit 11 and the second transmitting / receiving unit 12, also comprises several electrodes, analogous to Fig. 2b und 2c shown (not shown here).

[0069] If the presence of a gas bubble 52 is detected, the higher-level unit 10 generates a corresponding message, e.g., "Detected object 5 is identified as gas bubble 52."

[0070] The case of a foreign body 51 is in the Fig. 4a bis 4c The system essentially corresponds to the one described above in Fig 2a bis 2c shown system, the only difference being that the first transmitting / receiving unit 11 and the second transmitting / receiving unit 12 are made of Fig. 2b und 2c in Fig. 4b und Fig 4c Here, antennas 81a, 81b, 82a, 82b, 91a, 91b, 92a, 92b are used for transmitting (e.g., antennas 81a, 82a, 91a, 92a) or receiving (e.g., antennas 81b, 82b, 91b, 92b) ultrasonic waves. Preferably, these are pulsed ultrasonic waves. Just as previously described for the case of the electrodes made of Fig. 2b, 2c an average permittivity epsilon_m,1 or epsilon_m,3 can be determined based on the ultrasonic reception signals received by the receiving antennas 81b, 82b, 91b, 92b.

[0071] Since the foreign body 51 is essentially incompressible, the pressure difference at the transition from the line inlet section 1 to the compression section 3 does not cause compression of the foreign body 51, see Fig. 4a . This leads to the fact that the mean permittivity epsilon_m,3 in the compression section 3, determined (in the same manner as explained above), differs noticeably from the mean permittivity epsilon_m,1 in the line inlet section 1.

[0072] For this purpose, too, there may be a second limit value, which, if exceeded, will cause the higher-level unit 10 to display a message "Foreign body 51 is detected".

[0073] In this way, the system or method according to the invention provides a way to identify a foreign body 51 in a medium flowing in the pipeline 100 reliably and with the exclusion of false-positive messages.

[0074] Of course, the invention is not limited to the electrodes 61a, 61b, 62a, 62b, 71a, 71b, 72a, 72b or antennas 81a, 81b, 82a, 82b, 91a, 91b, 92a, 92b explained above, but also includes other possible transmitting / receiving units 11, 12 with which the determination of an average permittivity epsilon_m,1 or epsilon_m,3 is possible.

[0075] Furthermore, the Fig. 2b und Fig. 2c or Fig. 4b und Fig. 4c The number of electrodes 61a, 61b, 62a, 62b, 71a, 71b, 72a, 72b or antennas 81a, 81b, 82a, 82b, 91a, 91b, 92a, 92b shown is not essential to the invention; it is entirely sufficient if at least two electrodes 61a, 61b or 71a, 71b (or antennas 81a, 81b or 91a, 91b) are provided in the cross-sectional area QE of the line inlet section 1 and in the cross-sectional area QS of the compression section 3. Bezugszeichen und Symbole

[0076] 100Pipeline 1Pipe inlet section 2Pipe outlet section 3Compression section 41, 42Transition sections 5Object 51Foreign body 52Gas bubble 61a, 61b, 62a, 62b,...Electrodes 71a, 71b, 72a, 72b,...Electrodes 81a, 81b, 82a, 82b,...Antennas 91a, 91b, 92a, 92b,...Antennas 10Superior unit 11First transmitting / receiving unit 12Second transmitting / receiving unit 13Third transmitting / receiving unit 14Flowmeter SR Flow direction OR Compression direction QE, QA, QS Cross-sectional area of 1, 2, 3 A_QE, A_QA, A_QS Area dimensions of the cross-sectional areas epsilon_m, 1 Average permittivity in cross-sectional area of 1 epsilon_m, 2 Average permittivity in cross-sectional area of 2 epsilon_m, 3 Average permittivity in cross-sectional area of 3 KV Communication connection

Claims

1. System for detecting the presence of a foreign body (51) in a flowable medium in a pipeline (100) comprising: - a pipeline (100) with -- a pipe inlet section (1) and -- an upsetting section (3) adjoining the pipe inlet section (1) in a predetermined flow direction (SR), in which upsetting section (3), in an upsetting direction (OR) perpendicular to the flow direction (SR), the cross-sectional area (QS) of the pipe (100) is upsetting compared to the cross-sectional area (QE) of the pipe (100) in the pipe inlet section (1), wherein the area dimension (A_QS) of the cross-sectional area (QS) of the pipeline (100) in the upsetting section (3) substantially coincides with the area dimension (A_QE) of the cross-sectional area (QE) of the pipeline (100) in the pipeline inlet section (1); - a first transmitting / receiving unit (11) in the line inlet section (1), which is arranged to introduce transmitting signals into a medium flowing in the line inlet section (1) and to receive receiving signals - a second transmitter / receiving unit (12) in the upsetting section (3), which is arranged to introduce transmitting signals into a medium flowing in the upsetting section (3) and to receive receiving signals; and - at least one superordinate unit (10), which is set up to determine an average permittivity of the medium (epsilon_m,1) in the line inlet section (1) and the compression section (3) from the respective received signals, and to determine the presence of a foreign body (51) in the medium on the basis of at least one comparison of the mean permittivity (epsilon_m,3) in the upsetting section (3) with the mean permittivity (epsilon_m,1) in the line inlet section (1).

2. System according to claim 1, wherein the pipeline (100) comprises a pipeline outlet section (2) adjoining the upsetting section (3) in the predicted flow direction (SR), and wherein the cross-sectional area (QA) of the pipe outlet section (2) substantially corresponds to the cross-sectional area (QE) of the pipe (100) in the pipe inlet section (1), wherein the system comprises a third transmitting / receiving unit (13) in the line outlet section (2), which is arranged to introduce transmitter signals into a medium flowing in the line outlet section (2) and to receive receiver signals, and wherein the superordinate unit (10) is set up to determine an average permittivity (epsilon_m,2) of the medium in the line outlet section (2) from the received signals.

3. System according to claim 1 or 2, whereby the system, in particular the superordinate unit (10), is configured to determine: - as the mean permittivity (epsilon_m,1) in the line inlet section (1), a permittivity averaged over a path within the cross-sectional area (QE) of the line inlet section (1), and - as the mean permittivity (epsilon_m,3) in the upsetting section (3) a permittivity averaged over a path within the cross-sectional area (QS) of the upsetting section (3) and - in particular as the mean permittivity (epsilon_m,2) in the line outlet section (2) a permittivity averaged over a path within the cross-sectional area (QA) of the line outlet section (2).

4. System according to at least one of the preceding claims, wherein the cross-sectional area (QE) in the pipe inlet section (1) is circular and the cross-sectional area (QS) in the upsetting section (3) is elliptical.

5. System according to at least one of the preceding claims, wherein a transition section (41) runs between the pipe inlet section (1) and the upsetting section (3) to adapt the different shapes of the cross-sectional areas (QE, QS).

6. System according to at least one of the preceding claims, - wherein in the direction of flow (SR) the length of the upsetting section (3) and / or the pipe inlet section (3) -- at least as large as the diameter of the respective upsetting section (3) or the pipe inlet section (1) and --- is at most as large as ten times the diameter of the respective upsetting section (3) or the pipe inlet section (1).

7. System according to at least one of the preceding claims, wherein the first transmitting / receiving unit (91) comprises: - at least a first electrode (61a) and a second electrode (61b), and wherein the second transmitting / receiving unit (92) comprises: - at least a first electrode (71a) and a second electrode (71b).

8. System according to at least one of the preceding claims 1 to 6, wherein the first transmitting / receiving unit (11) comprises: - at least a first antenna (81a) for emitting microwaves and a second antenna (81b) for receiving microwaves, and wherein the second transmitting / receiving unit (12) comprises: - at least a first antenna (91a) for emitting microwaves and a second antenna (91b) for receiving microwaves.

9. System according to at least claim 7 or 8, wherein for the first external transmitting / receiving unit (11) in the line inlet section (1) and for the second external transmitting / receiving unit (12) in the compression section (3) in each case - the first electrode (61a;71a,...) is arranged on the pipeline (100) opposite the second electrode (61b;71b,...), in particular along the path, or - the first antenna (81a;91a,...) is arranged on the pipeline (100) opposite the second antenna (91b;91b,...), in particular along the path.

10. System according to claim at least one of the preceding claims 7 to 9, wherein the first transmitting / receiving unit (11) and the second transmitting / receiving unit (12) each comprise: - several first electrodes (61a,62a,...; 71a,72a,...) and several second electrodes (61b,61b,...,71b,72b) or - several first antennas (81a,82a,...;91a,92a,...) and several second antennas (81b,82b,...;91b,92b,...).

11. System according to claim 10, wherein imaginary connecting lines extend between pairs of first electrode (61a,62a,...; 71a,72a,...) and second electrode (61b,61b,...,71b,72b) or between pairs of first antenna (81a,82a,...;91a,92a,...) and second antenna (81b,82b,...;91b,92b,...), and wherein all connecting lines in the respective cross-sectional area (QE; QS) are arranged parallel to one another and, in particular, are equally spaced.

12. System according to at least one of the preceding claims, comprising a flow meter (14) for determining the mass flow rate and / or the flow velocity of the medium in the pipeline (100).

13. Method for detecting the presence of a foreign body (51) in a medium in a pipeline (100) with a system according to at least one of the previous claims 1 to 12, comprising the steps of: - Transmitting outgoing signals and receiving incoming signals into a medium flowing in the pipe inlet section (1) - Transmitting outgoing signals and receiving incoming signals into a medium flowing in the upsetting section (3); - Determination of an average permittivity (epsilon_m,1) of the medium in the line inlet section (1) and determination of an average permittivity (epsilon_m,3 ) of the medium in the compression section (3) - Comparison of the mean permittivity (epsilon_m,3 ) in the upsetting section (3) with the mean permittivity (epsilon_m,1) in the line inlet section (1) - Detection of a foreign body (51) in the medium (3) if the mean permittivity (epsilon_m,3) in the upsetting section (3) differs from the mean permittivity (epsilon_m,1) in the line inlet section (1).

14. Method according to claim 13, comprising the steps of: - Determining an average permittivity (epsilon_m,2) of the medium in the pipe outlet section (2) - Comparison of the mean permittivity (epsilon_m,3) in the upsetting section (3) with the mean permittivity (epsilon_m,1) in the line inlet section (1) and the mean permittivity (epsilon_m,2) in the line outlet section (2)15. Method according to claim 13 or 14, comprising the step of: - Detection of the presence of an object (5) in the pipe inlet section (1) on the basis of a determined average permittivity (epsilon_m,1) of the medium, wherein the detection of the presence of the object (5) takes place before the comparison of the mean permittivities (epsilon_m,3; epsilon_m,1).