Method for determining a deposit property, and measurement assembly
The method uses microwave antennas to detect coating properties in piping systems by analyzing excitation and reflection signals, addressing the inefficiencies in existing detection methods and improving maintenance schedules through precise coating thickness monitoring.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ENDRESS HAUSER FLOWTEC AG
- Filing Date
- 2025-11-11
- Publication Date
- 2026-06-18
Smart Images
Figure EP2025082619_18062026_PF_FP_ABST
Abstract
Description
[0001] Method for determining a surface property and measurement setup
[0002] The invention relates to a method for determining a coating property of a variable coating in a measuring tube of a measuring arrangement for detecting a measured quantity of a medium. The invention further relates to a measuring arrangement which employs the inventive method.
[0003] Measuring tubes, as part of piping systems, are used in various industries, such as the food and beverage, chemical, and oil and gas industries, to transport fluids of various types, including liquids and gases, from one place to another. They are also used, for example, in industrial plants and facilities that carry out production processes.
[0004] During operation, the internal surfaces of a piping system are exposed to the fluid(s) flowing through it. Due to this exposure, the condition of the piping system can deteriorate over time through deposits, abrasion, or corrosion. The present invention relates to the monitoring of deposits caused by fluids that tend to adhere to the surface(s) exposed to these fluids. A layer of deposits that forms within a pipeline can impair active components (e.g., sensors) and reduce the internal diameter, thus increasing flow resistance. A continuously growing layer of deposits can eventually cause a blockage of the pipeline. As a countermeasure, pipelines are, for example, cleaned at regular intervals.Cleaning pipelines incurs costs and usually requires an interruption of the process being carried out at a site that includes the pipeline system.
[0005] Since a visual inspection of the prevailing conditions within the pipeline system is not normally possible during operation, the intervals between successive cleanings should be kept short enough to ensure safe operation of the pipeline system. Consequently, cleanings are performed relatively frequently, long before they are actually required based on the system's condition. Conversely, longer intervals between cleanings can lead to cleanings being carried out too late. This can have serious consequences for the safety and functionality of the pipeline system, which in turn can lead to harm to people and / or the environment, high additional costs, and / or extended downtime of the pipeline system.Therefore, there is a need in industry to monitor the prevailing condition within the pipeline system during its operation, for example to optimize the time intervals between successive cleanings or replacements.
[0006] In many applications, piping systems are equipped with measuring devices that measure physical and / or chemical properties of the fluid(s) and / or process parameters required to regulate and / or control a process carried out at a location encompassing the piping system. Many of these measuring devices are susceptible to impairment due to deposits, abrasion, or corrosion, which in turn can negatively affect their measuring characteristics.
[0007] It is known that dielectric properties, such as the physical quantities of permittivity and / or refractive index of a medium, as well as the loss factor of a medium in a process line, can be determined using high-frequency electromagnetic radiation with wavelengths in the microwave range. These quantities can be measured using electromagnetic radiation consisting of wave packets tuned to a specific frequency, or by a sequence of wave packets with several different frequencies. The measured quantities allow conclusions to be drawn about application-specific parameters, such as the proportion of water in a mixture of water and other non-polar or slightly polar components.
[0008] Document WO 2018 / 121927 A1, for example, describes a measuring arrangement for analyzing the properties of a flowing medium using microwaves. In addition to the microwave antennas, this arrangement features an electrically insulating lining on the inner surface of the measuring tube. This lining acts as a dielectric waveguide, allowing microwaves, at least partially, to travel from a first microwave antenna to a second. One application for such a measuring arrangement is the determination of solids content in the medium. Such applications can be impaired by the formation of deposits—for example, from solids accumulating in the medium—on the inner surface of the measuring tube and on the microwave antennas.
[0009] In this context, DE 10 2005 050 898 A1 describes a method for detecting deposits in a straight tube of a Coriolis measuring device by exciting torsional vibrations of the straight tube at least intermittently and detecting deposits based on the frequency of the torsional vibrations. DE 10 2005 050 898 A1 further discloses the use of this method of deposit detection to monitor the prevailing condition in a pipeline connected to the tube of the Coriolis measuring device according to the invention with regard to impairment caused by deposits.
[0010] The current state of the art presents a problem in that a certain critical coating thickness is necessary to apply known methods for determining coating thickness. Conversely, this means that it is not possible to detect a coating with a variable thickness less than the critical thickness, or that a certain amount of time is required before a variable coating can be detected as such. This can be problematic when an application requires the detection of a coating with a small variable thickness, or when a coating is in the process of forming, for example, to initiate maintenance and / or cleaning of the measuring instrument and / or pipe system.
[0011] It is therefore an object of the invention to provide a reliable method for the early detection of a prevailing condition within a piping system, in particular a property of a changing coating, during the operation of the piping system. This object is achieved by the invention through a method according to independent claim 1.
[0012] The inventive method for determining a property of a variable coating in a measuring tube comprises at least the following method steps: emitting an excitation signal by means of a first microwave antenna, wherein the excitation signal comprises a sequence of radio frequency signals; receiving a transmission signal emanating from the excitation signal by means of a second microwave antenna; receiving a reflection signal emanating from the excitation signal by means of the first microwave antenna; determining a first test quantity based on the received transmission signal; determining a second test quantity based on the received reflection signal; determining the property of the variable coating based on the first test quantity and based on the second test quantity.
[0013] The method according to the invention has the advantage that a forming deposit can be detected early and reliably based on the test parameters.
[0014] In a further development of the method according to the invention, it comprises the following additional process steps: emitting a further excitation signal using the second microwave antenna, wherein the further excitation signal comprises a sequence of high-frequency signals; receiving a further reflection signal emanating from the further excitation signal using the second microwave antenna and / or a further transmission signal using the first microwave antenna; determining at least one further test parameter based on the received further reflection signal and / or the received further transmission signal; determining the property of the variable coating based on the first test parameter, based on the second test parameter and based on the at least one further test parameter.This further training has the advantage that determining the property of the variable coating based on the first test parameter, the second test parameter and at least one further test parameter enables a more reliable result, for example by evaluating mean values.
[0015] In a further development of the inventive method, this includes the
[0016] Excitation signal with multiple signal components; wherein a first signal component has a first component frequency; wherein a second signal component has a second component frequency; wherein the first component frequency is not equal to the second component frequency.
[0017] The advantage of this advanced training is that a single excitation signal with signal components of different frequencies can be used to determine test parameters of different media, avoiding the need to set a media-specific frequency range.
[0018] In a further development of the method according to the invention, the property is a coating thickness of the variable coating and / or a size that depends on the coating thickness.
[0019] In a further development of the method according to the invention, the first test parameter comprises a phase difference between the excitation signal and the received transmission signal and / or a signal propagation time and / or a permittivity and / or a refractive index.
[0020] In a further development of the method according to the invention, the second test parameter comprises an amplitude ratio of the reflection signal relative to the excitation signal and / or a permittivity and / or a refractive index.
[0021] In a further development of the method according to the invention, the property of the variable coating is a mathematical function of the first test parameter and the second test parameter.
[0022] The advantage lies in the fact that the different effects of a forming variable coating on the reflection and transmission of an excitation signal contain information about the coating's properties, such as its variable thickness. Furthermore, the advantage is that the difference in permittivities between a transmission signal and a reflection signal is unambiguously dependent on the coating thickness of the variable coating.
[0023] In a further development of the method according to the invention, the function comprises calculating the difference between the test parameters. In a further development of the method according to the invention, a coating index is created based on the property of the variable coating; wherein the coating index depends on, in particular a function, and preferably a difference, between the first test parameter and the second test parameter; wherein the coating index indicates the coating thickness of the variable coating.
[0024] This further training has the advantage that a coating index can be determined, which coating index includes, for example, instructions, whereby the instructions include cleaning of the measuring tube and / or the sensor and / or maintenance of a pipe system and / or a measuring system.
[0025] In a further development of the inventive method, a rate of change of a property of the variable coating is determined on the basis of a rate of change over time of the coating index.
[0026] This training has the advantage that the rate of change of the coating index over time provides information about the rate of change of the variable coating, whereby an increase in the rate of change of the coating index provides indications, these indications including cleaning of the measuring tube and / or the sensor and / or maintenance of a pipe system and / or a measuring system.
[0027] In a further development of the method according to the invention, the coating index includes a measurement error of the measured quantity to be recorded.
[0028] This advanced training has the advantage that a measurement error due to a changing surface is mapped to a measured quantity that has been recorded or is to be recorded.
[0029] In a further development of the method according to the invention, the excitation signal comprises an electromagnetic wave with a frequency of at least 0.1 GHz.
[0030] In this further development of the method, electromagnetic signals in a frequency range of 1 to 10 GHz, in particular from 1.8 to 3 GHz, are used, which reduces their absorption rate in water and water-containing mixtures.
[0031] In a further development of the method according to the invention, the excitation signal comprises an electromagnetic wave with a frequency of no more than 100 GHz. The method according to the invention further comprises the following steps: Determining a transformed test quantity based on a transformed, in particular an integral-transformed, transmission signal, wherein the transformed test quantity comprises at least two components, a first component describing at least a partial propagation of the transmission signal in the medium, and a second component describing at least a partial propagation of the transmission signal in the variable coating; Determining the first test quantity based on the first component of the transformed test quantity.
[0032] This embodiment of the method offers the advantage that, based on the transformed test parameter, the test parameter of the transmission signal can be limited to the portion of the transmitted excitation signal whose propagation essentially occurs through the medium. Furthermore, it offers the advantage that a maximum amplitude value of the reflection signal and / or the transmission signal can be determined, particularly by means of a polynomial fit, to determine a test parameter, especially a permittivity.
[0033] In a further development of the method according to the invention, it further comprises the following step: transforming the transmission signal into a time period, in particular by means of an integral transformation and preferably by means of an inverse Fourier transformation.
[0034] The advantage of this advanced training is that the measuring device can perform this transformation itself using suitable hardware and programming.
[0035] The measuring arrangement according to the invention for detecting a measured quantity of a medium comprises: A measuring tube; A first microwave antenna and a second microwave antenna, wherein the first microwave antenna is arranged in a first receptacle of the measuring tube and wherein the second microwave antenna is arranged in a second receptacle of the measuring tube; A measuring and operating circuit, wherein the measuring and operating circuit is configured to carry out a method according to the invention.
[0036] The invention is further explained with reference to the following images. It shows:
[0037] Fig. 1 shows an embodiment of a measuring arrangement according to the invention; Fig. 2 shows an embodiment of an antenna of the measuring arrangement according to the invention;
[0038] Fig. 3 shows an example of time profiles of the test parameters and the coating index; Fig. 4 shows an example of a transformed test parameter.
[0039] The embodiment of a measuring arrangement according to the invention, shown in Fig. 1, comprises the first receptacle AM1 arranged in the measuring tube MR, in which the first microwave antenna MA1 is arranged. Also arranged in the measuring tube MR is the second receptacle AM2, in which the second microwave antenna MA2 is arranged. The measuring tube MR carries a medium ME and, in this example, has a variable coating VB with a variable coating thickness BD. In this embodiment, the first receptacle AM1 is arranged opposite the second receptacle AM2 and in the same cross-section of the measuring tube MR, so that a transmission signal TS sent by the first microwave antenna MA1 propagates through the tube cross-section and is received by the second microwave antenna MA2.In this example, the second microwave antenna MA2 is configured to transmit another excitation signal ES', which propagates through the pipe cross-section as a further transmission signal TS' and is received by the first microwave antenna MA1. The first microwave antenna MA1 and the second microwave antenna MA2 are connected to a measurement and operating circuit MB, which is configured to determine a test parameter P1 based on the transmission signal TS and a further test parameter PT based on the additional transmission signal TS'. Calculating the coating thickness BD based on all test parameters P1, P2, and PT is advantageous because it is more reliable than calculating it solely based on the first and second test parameters P1 and P2.
[0040] Figure 2 shows an embodiment of an antenna in a measuring arrangement according to the invention. The antenna corresponds, for example, to the first microwave antenna MA1 and is arranged in the first recess AM1 in the measuring tube MR. The first recess AM1 is, for example, formed by a bore through which a waveguide of the first microwave antenna MA1 extends. An excitation signal ES is fed into the waveguide of the first microwave antenna MA1 by the measuring and operating circuit MB. This excitation signal (ES) is reflected at a transition from the first microwave antenna MA1 to the medium ME and / or to the variable coating VB, forming a reflection signal RS. The reflection signal RS is received by the first microwave antenna MA1 and transmitted to the measuring and operating circuit MB, which is configured to determine a second test parameter P2 based on the reflection signal.A non-reflected portion of the excitation signal ES penetrates the medium ME and traverses it as the transmission signal TS to be received by the second microwave antenna MA2 (not shown here) and forwarded to the measuring and operating circuit. In one embodiment of the measuring arrangement according to the invention, the second microwave antenna MA2 (not shown here) transmits a further excitation signal ES' (not shown here), wherein the further excitation signal ES' is reflected at a transition from the second microwave antenna MA2 to the medium ME and / or to the variable coating VB, forming a further reflection signal RS'. The measuring and operating circuit is configured to determine a further second test parameter P2' based on the further reflection signal RS'.
[0041] The example shown in Fig. 3 illustrates the time profiles of the first test parameter P1 and the second test parameter P2, where measurements are taken several times a day over several days to weeks. In this example, the first test parameter P1 and the second test parameter P2 are permittivities. The first test parameter specifically represents a combined permittivity of the medium ME and the variable coating VB, which are traversed by the transmission signal TS. The time profiles of the first test parameter P1 and the second test parameter P2 are constant from the start of the measurement. From a first time t1, the measured value of P1 decreases over time, and from a second time t2, the measured value of the second test parameter P2 decreases. The rate of change of the first test parameter P1 differs from the rate of change of the second test parameter P2.Calculating a coating index BI based on the difference between the measured values of the first test parameter P1 and the second test parameter P2 produces the depicted time course. The coating index BI changes over time because the underlying test parameters exhibit different rates of change. For example, the rate of change dBI / dt of the coating index BI is derived from the quotient of the change in the coating index dBI over a time interval dt. A rate of change dBI / dt of the coating index BI allows for an assessment of the change in the variable coating VB and, in particular, can indicate the need for cleaning and / or maintenance of the measuring setup.
[0042] Figure 4 shows examples of transformed test parameters PT for different coating thicknesses BD, namely 1.0 mm, 3.0 mm, and 5 mm, and a reference signal without a varying coating, H₂O. The test parameter can, for example, be a first test parameter P₁, and in particular comprise a measurement of the permittivity or refractive index of a transmission signal TS, which in this specific example comprises a multitude of signals with different frequencies. The first test parameter P₁ is transformed into a transformed space using a suitable transformation procedure, for example, a Fourier transform or an inverse Fourier transform. In this example, the first test parameter P₁ was acquired as a function of frequency and transformed using an inverse Fourier transform, which allows its mapping as a transformed test parameter PT on the time axis.The transformed signal TS exhibits a maximum for the reference signal in the time range of 0 to 4 ns at a propagation delay of approximately 2.4 ns, which also corresponds to the expected propagation delay of the transmission signal TS through water. With a variable coating VB, another maximum forms at lower propagation delays (in this specific case at approximately 0.7 ns). This maximum takes the form of a shoulder with a variable coating VB and a coating thickness BD of 1 mm, but increases with increasing coating thickness BD, so that the amplitude value at, for example, a coating thickness of 5 mm is already greater than the contribution of the transmission signal TS through the water.
[0043] The reason for the occurrence of a second maximum is an additional path formed by the changing coating VB, along which the transmission signal TS propagates with a shorter propagation time. The amplitude value for the propagation time along the shortest distance increases after the coating is present. This is due to the improved coupling of the excitation signal into the water by the coating on the front surface of the microwave antenna. In this example, the transformed test quantity PT therefore comprises a first component A1, which includes times from approximately 2 ns to at least 8 ns, and a second component A2, which includes times from approximately 0 ns to 2 ns. The first component A1 comprises the portion of the transmission signal TS whose propagation occurs predominantly through the medium ME.Since the propagation of the transmission signal TS is of different speeds in medium ME and variable coating VB, the formation of the first test parameter P1 based on the first component A1 of the transmission signal TS enables a continuous application of the method according to the invention.
[0044] Reference symbol list
[0045] VB variable coating
[0046] MR measuring tube
[0047] MA1 first microwave antenna
[0048] E Excitation signal
[0049] TS transmission signal
[0050] MA2 second microwave antenna
[0051] RS reflection signal
[0052] P1 first test parameter
[0053] P2 second test parameter
[0054] RS' further reflection signal
[0055] TS' further transmission signal
[0056] PT further test parameter
[0057] P2' further test parameter
[0058] BD coating thickness
[0059] BI coating index dT rate of change over time
[0060] PT transformed test quantity
[0061] A1 first part of the transformed test quantity
[0062] A2 second part of the transformed test quantity
[0063] ME Medium
[0064] AM1 first recording of the measuring tube
[0065] AM2 second recording of the measuring tube
[0066] MB measuring and operating circuit
Claims
Patent claims 1. Method for determining a property of a variable coating (VB) in a measuring tube (MR), comprising at least the following method steps: - Emitting an excitation signal (ES) using a first microwave antenna (MA1 ), - Receiving a transmission signal (TS) emanating from the excitation signal (ES) using a second microwave antenna (MA2); - Receiving a reflection signal (RS) emanating from the excitation signal (ES) using the first microwave antenna (MA1); - Determining a first test parameter (P1) based on the received transmission signal (TS); - Determining a second test parameter (P2) based on the received reflection signal (RS); - Determining the property of the variable coating (VB) using the first test parameter (P1) and the second test parameter (P2).
2. The method according to claim 1, comprising the further method steps: - Emitting another excitation signal (ES') using the second microwave antenna (MA2); - Receiving a further reflection signal (RS') emanating from the further excitation signal (ES') using the second microwave antenna (MA2) and / or a further transmission signal (TS') using the first microwave antenna (MA1); - Determine at least one further test parameter (PT, P2') based on the received further reflection signal (RS') and / or the received further transmission signal (TS'); - Determining the property of the variable coating (VB) based on the first test parameter (P1), based on the second test parameter (P2) and based on at least one further test parameter (PT, P2').
3. Method according to one of claims 1 or 2, - wherein the excitation signal (ES) comprises several signal components; - where a first signal component has a first component frequency; - where a second signal component has a second component frequency; - where the first component frequency is not equal to the second component frequency.
4. Procedure according to one of claims 1 to 3, - where the property is a coating thickness (BD) of the variable coating (VB) and / or a quantity dependent on the coating thickness (BD).
5. Method according to any one of claims 1 to 4, - wherein the first test parameter (P1) includes a phase difference between the excitation signal (ES) and the received transmission signal (TS) and / or a signal propagation time and / or a permittivity and / or a refractive index.
6. Method according to any one of claims 1 to 5, - wherein the second test parameter (P2) comprises an amplitude ratio of the reflection signal (RS) relative to the excitation signal (ES) and / or a permittivity and / or a refractive index.
7. Method according to any one of claims 1 to 6, - where the property of the variable coating (VB) is to be described by a mathematical function of the first test parameter (P1 ) and the second test parameter (P2).
8. Method according to claim 7, - where the function includes a difference of the test parameters (P1 , P2).
9. Method according to any one of claims 1 to 8, - where a surface index (BI) is created based on the property of the variable surface (VB); - wherein the coating index (BI) depends on, in particular a function, and preferably a difference, between the first test parameter (P1 ) and the second test parameter (P2); where the coating index (BI) indicates the coating thickness (BD) of the variable coating (VB).
10. Method according to claim 9, - where a rate of change of a property of the variable coating (VB) is determined based on a rate of change over time (dBI / dt) of the coating index (BI).
11. Method according to claim 9 or 10, - where the coating index (BI) includes a measurement error of the measured quantity.
12. Method according to any one of claims 1 to 11 , - wherein the excitation signal (ES) is an electromagnetic wave with a frequency of at least 0.1 GHz.
13. Method according to any one of claims 1 to 12, - where the excitation signal (ES) is an electromagnetic wave with a frequency of no more than 100 GHz.
14. A method according to any one of claims 1 to 13, further comprising the following steps: - Determining a transformed test parameter (PT) based on a transformed, in particular an integral transform, of the transmission signal, o wherein the transformed test parameter (PT) comprises at least two components, o wherein a first component (A1 ) describes at least a partial propagation of the transmission signal (TS) in the medium (ME), o wherein a second component (A2) describes at least a partial propagation of the transmission signal (TS) in the variable coating (VB); - Determining the first test quantity (P1 ) based on the first component of the transformed test quantity (PT).
15. The method of claim 14, further comprising the following step: - Transforming the transmission signal (TS) into a time period, in particular by means of an integral transformation and preferably by means of an inverse Fourier transformation.
16. Measuring arrangement for detecting a measured quantity of a medium (ME), comprising: - A measuring tube (MR); - A first microwave antenna (MA1) and a second microwave antenna (MA2), o wherein the first microwave antenna (MA1) is in a first recording of the measuring tube (AM1 ) is arranged and o wherein the second microwave antenna (MA2) is arranged in a second receptacle of the measuring tube (AM2); - A measuring and operating circuit (MB), wherein the measuring and operating circuit (MB) is configured to perform a method according to any one of claims 1 to 15.