Spray mist detection in process plants

Abstract

Measuring system for checking the functionality of at least one spray head (5) arranged in a container (3), which is designed to spray the spray mist (2) within the container (3) with a defined spray cone, comprising the following components: - a high-frequency measuring device (1), with ◯ a signal generating unit designed to generate a high-frequency signal (S HF ) to generate ◯ an antenna arrangement (11) which is aligned in the direction of the spray cone, so that the high-frequency signal (R HF2 ) can be emitted in the spray mist (2) and a reception signal (R HF1 , R HF2 ) is receivable, and ◯ an evaluation unit designed to use the received signal (R HF1 , R HF2 ) to determine a defined parameter, and to detect spray mist (2), provided that the determined parameter corresponds to a predefined reference value, - a higher-level unit (4) designed to ◯ to control or detect the switching on and off of the spray head (5), ◯ to query the detection of spray mist (2) from the high-frequency measuring device (1), and ◯ to classify the at least one spray head (5) as functional, provided that it is switched on and spray mist (2) is detected.

Description

[0001] The invention relates to spray mist detection and the testing of the functionality of spray heads in process plants.

[0002] In process automation technology, appropriate field devices are used to record relevant process parameters. To record the respective process parameters, suitable measurement principles are implemented in the corresponding field devices to record process parameters such as level, flow, pressure, temperature, pH value, redox potential, or conductivity. The Endress + Hauser Group manufactures and distributes a wide variety of field device types.

[0003] High-frequency time-of-flight measurement methods have become established for level measurement of filling materials in containers because they are robust and low-maintenance. In the context of the invention, the term "high frequency" is defined as either radar or ultrasound with frequencies between 20 kHz and 300 GHz. A further advantage of high-frequency measurement methods is their ability to measure the fill level virtually continuously. In the field of continuous level measurement, radar-based measurement methods are therefore predominantly used (in the context of this patent application, the term "radar" refers to signals or electromagnetic waves with frequencies between 0.03 GHz and 300 GHz). The pulse time-of-flight method has become established as the time-of-flight measurement method in the case of radar and ultrasound. The FMCW method (Frequency Modulated Continuous Wave) is also increasingly being used in the radar field.Time-of-flight based level measurement is described in more detail in “Radar Level Detection, Peter Devine, 2000”.

[0004] Process vessels where the fill level must be measured are often subjected to container cleaning, for example, for disinfection in the food industry. Cleaning is carried out using one or more spray heads, which are installed stationary on the side or top of the vessel to distribute the cleaning agent as a spray mist in a defined spray pattern throughout the vessel. Spray head arrangements with rotating spray heads or spray patterns are also used to ensure a wider distribution of the spray mist within the vessel. Suitable spray heads are manufactured, for example, by GEA Tuchenhagen GmbH.

[0005] A level gauge that uses dynamic echo tracking under various process conditions, including tank cleaning, is described in publication EP 3619507 B1. Publication JP 2006150243 A addresses an optical method for monitoring the cleaning systems in a tank.

[0006] Proper functioning of the spray heads is essential, especially for disinfection in food processing areas, as otherwise the contents of the container may become contaminated. Therefore, it is important that the process plant has information indicating whether the spray head(s) are functioning properly. A malfunction may occur, for example, if the spray head does not spray any mist, or if the spray head or spray cone does not rotate even though the spray head is switched on.

[0007] According to the state of the art, acoustic measuring devices are often used to monitor the proper functioning of the spray heads. These devices acoustically monitor the material flow of the liquid in the spray heads. A disadvantage, however, is that these measuring devices are often disrupted by general process noise, such as pumps, agitators, and inflow and outflow, so that the desired monitoring of the spray mist cannot be reliably ensured. Furthermore, sufficient sensitivity of these measuring devices is only guaranteed in the immediate vicinity of the spray head to be monitored. This requires the installation of at least one measuring device per spray head, which is expensive when multiple spray heads are used and often leads to space problems during installation.

[0008] The invention is therefore based on the object of being able to monitor the function of spray heads in containers reliably and with little measuring effort.

[0009] The invention solves this problem by a measuring system for checking the functionality of at least one spray head arranged in a container, which is designed to spray the spray mist within the container with a defined spray cone, comprising the following components: - a high-frequency measuring device, with ◯ a signal generating unit designed to generate a high-frequency signal to be transmitted, ◯ an antenna arrangement which is aligned in the direction of the spray cone so that the high-frequency signal can be transmitted towards the spray mist and a reception signal can be received, and ◯ an evaluation unit designed to determine a defined parameter based on the received signal and to detect spray mist, provided that the determined parameter corresponds to a predefined reference value, - a superior unit designed to ◯ to control or detect the switching on and off of the spray head, ◯ to query the high-frequency measuring device for the detection of spray mist, and ◯ to classify at least one spray head as functional, provided it is switched on and spray mist is detected.

[0010] The invention also solves this problem by a measuring system for checking the functionality of at least one spray head arranged in a container, which is designed to spray the spray mist within the container with a defined spray cone, comprising the following components: - a high-frequency measuring device, with ◯ a signal generating unit designed to generate a high-frequency signal to be transmitted, ◯ an antenna arrangement which is aligned in the direction of the spray cone so that the high-frequency signal can be transmitted towards the spray mist and a reception signal can be received, and ◯ an evaluation unit designed to determine a defined parameter based on the received signal - a superior unit designed to ◯ to control or detect the switching on and off of the spray head, ◯ to detect spray mist, provided the parameter matches a predefined reference value, and ◯ to classify at least one spray head as functional, provided it is switched on and spray mist is detected.

[0011] Ideally, the high-frequency measuring device is arranged in such a way that the radar signal is emitted approximately orthogonally to the spray cone. Since radar- and ultrasonic-based level measuring devices generally include these required components, it is particularly synergistic to use a high-frequency-based level measuring device, which is already present and serves to determine the fill level of the filling material in the container, as the high-frequency measuring device. Within the scope of the invention, it is irrelevant whether the high-frequency signals are radar or ultrasonic signals. If the high-frequency or level measuring device is designed as a radar-based measuring device, it is again irrelevant whether the signal generation unit is designed to emit the high-frequency signal using the pulse transit time method or the FMCW method. The evaluation unit must be designed to correspond to the signal generation unit.This means that the evaluation unit must receive or process the received signal according to the pulse transit time method or using the FMCW method.

[0012] At least in the case of the pulse transit time method and the FMCW method, the received signal reproduces the amplitude curve with high temporal resolution. Accordingly, reflective objects such as the spray are reproduced in the received signal as a signal maximum, whereby the signal transit time corresponding to the signal maximum reflects the distance of the spray from the antenna arrangement. Accordingly, based on the received signal, an amplitude, in particular that of a signal maximum, can be determined as a parameter within the scope of the method according to the invention. Depending on the nature of the spray, the reflection of the radar signal by the spray can already cause a specific signal maximum at the corresponding location of the received signal. In this case, the evaluation unit can determine the amplitude of this signal maximum as a parameter from the received signal. Based on the amplitude orThe parameter can be used to detect not only the presence of any spray mist, but also, in relation to the reference value, a spray quantity of the spray mist, the unit of which is, for example, liters or cubic meters per minute.

[0013] Since radar or ultrasonic signals are diffusely reflected by spray mist depending on its composition, the amplitude of the signal maximum attributable to the reflection of the high-frequency signal from an inner wall of the container, such as the container bottom, or from a filling material, can also be determined as a characteristic value. If spray mist is in the path of the high-frequency signal, the amplitude of this signal maximum may be significantly reduced. Due to the diffuse reflection, characteristic noise can also arise in the received signal. Therefore, a corresponding noise value can be determined from the received signal as a relevant characteristic value, either alternatively or additionally.

[0014] If the measuring system is designed to repeatedly determine the parameter over a plurality of measuring cycles, it is also conceivable within the scope of the invention to determine any periodicity with which the parameter periodically changes within the measuring cycles. This can be used in particular with rotating spray heads or rotating spray cones, as this allows the correct rotation or its periodicity to be checked. In this case, with an appropriate design, the higher-level unit can classify at least one spray head as functional, provided the higher-level unit determines a defined periodicity with which the parameter periodically changes within the measuring cycles, and provided the spray head is verifiably switched on.

[0015] In the context of the invention, the term "unit" is understood to mean any separate arrangement or encapsulation of those electronic circuits that are intended for a specific application, e.g. for high-frequency signal processing or as an interface. Depending on the application, the corresponding unit can therefore comprise corresponding analog circuits for generating or processing corresponding analog signals. However, the module can also comprise digital circuits, such as FPGAs, microcontrollers or storage media in conjunction with corresponding programs. The program is designed to carry out the required method steps or apply the necessary computing operations. In this context, different electronic circuits of the unit within the meaning of the invention can potentially also access a common physical memory or be operated using the same physical digital circuit.It is not relevant whether different electronic circuits within the unit are arranged on a common circuit board or on several connected circuit boards.

[0016] The invention is explained in more detail using the following figure. It shows: Fig. 1: A radar-based level gauge for checking the functionality of a spray head in a container.

[0017] To understand the invention, Fig. 1 shows a container 3 of an industrial processing plant. Depending on the application, the container 3 can be up to more than 100 m high. The conditions in the container 3 depend on the application and the type of filling material: In applications in the food industry, for example, fermentation processes must be monitored, with the filling material being pumped out of the container 3 after the fermentation process. A radar-based level gauge 1 is arranged at a container opening on the top to monitor the fill level during filling and pumping, among other things. For this purpose, the level gauge 1 transmits radar signals S via an antenna arrangement 11 according to the pulse transit time or FMCW method, depending on the measuring method implemented. HF vertically downwards and receives corresponding RHF reception signals after reflection from the liquid or the bottom of the container.

[0018] In order to clean the interior of the container 3 before refilling or the start of the subsequent fermentation process, a spray head 5 is arranged at a side container opening. When switched on, the spray head 5 sprays, for example, a cleaning or disinfectant with a defined spray pattern. In contrast to the simplified representation in Fig. 1 it is usual for a plurality of spray heads 5 to be arranged distributed in the container 3 so that the corresponding spray cones fill the area around the container 3 as completely as possible.

[0019] Typically, the level gauge 1 and the spray head 5 are each connected to a higher-level unit 4, such as a local process control system or a decentralized server system, via a separate interface, such as "4-20 mA," "PROFIBUS," "HART," or "Ethernet." The measured level value can be transmitted via this interface, for example, to control inflows or outflows of the container 3 if necessary. However, other information about the general operating status of the level gauge 1 can also be communicated. The higher-level unit 4 can also, for example, switch the spray head 5 on and off via the interface.

[0020] According to the invention, the higher-level unit 4, the level measuring device 1 and the spray head 5 form a common measuring system through the interfaces, by means of which the correct function of the spray head 5 can be checked. This has the advantage that no separate measuring device needs to be installed to test the spray head 5, but that the functionality is checked using the level measuring device 1. In contrast to the Fig. 1, it is also conceivable within the scope of the invention to use a separate high-frequency measuring device instead of the level measuring device 1, which is equipped analogously to the level measuring device 1 with a corresponding signal generation unit, antenna arrangement and evaluation unit in order to generate the radar signal S HF to generate or transmit, and to use the received signal R HF1 , R HF2 to determine corresponding parameters.

[0021] A malfunction of the spray head 5 can, for example, be caused by a blockage, so that the spray head 5 sprays no or a noticeably reduced amount of spray mist 2 when switched on. If the spray head 5 is designed such that it also rotates when switched on and thus periodically pivots the spray cone, a malfunction can also occur if the periodic pivoting stops. These types of malfunctions can be detected by the measuring system by the level measuring device 1 transmitting a radar signal S even during the spraying process, i.e., when the container 3 is empty of any filling material. HF According to the invention, the effect is used that the spray mist 2 in the received signal R HF can be detected by means of characteristic parameters. This can be done, for example, by the direct reflection of the radar signal R HF1 on the spray 2, or a reduced reflection of the radar signal R HF2at the bottom of the container.

[0022] In the received signal R HF This is expressed, among other things, by the amplitude of the corresponding signal maximum or by increased noise. The parameters become even more apparent when the spray head 5, as shown in Fig. 1, is arranged as orthogonally as possible to the transmit / receive direction of the level measuring device 1. Thus, the level measuring device 1 or the higher-level unit 4 can be determined based on the amplitude of the corresponding signal maximum or based on the noise level in the received signal R HF to conclude the presence of the spray mist 2. If the spray head 5 is designed to rotate, this is reflected in the received signal R HF Furthermore, the characteristic parameter changes with the corresponding temporal periodicity. To detect any periodicity, it is necessary for the level gauge 1 to receive the radar signal SHF continuously over at least the corresponding period or the corresponding measurement cycles. In connection with this, a delay time between the activation of the spray head 5 or the spray heads and the start time of the periodicity can also be recorded by the higher-level unit 4. In this case, the degree of closure of the rotating mechanism can be assigned to the delay time, so that maintenance can be initiated based on this if necessary.

[0023] The higher-level unit 4 can record one or more of these characteristic parameters by either querying the parameter(s) from the level measuring device 1 via the interface or by receiving the signal R HF from the level measuring device 1 to the higher-level unit 4 for further processing.

[0024] In order to be able to detect the presence of spray mist 5 based on the determined parameter, or to check the correct function of the spray head 5, the higher-level unit 4 must compare the respective parameter with a corresponding reference value, which is determined under known conditions. It is obvious to use the reference value or the underlying received signal R HF For example, during a calibration mode of the level gauge 1, the value can be recorded at a time when the container 3 is empty and the spray head 5 is in operation and demonstrably functioning correctly. If a subsequent comparison between the parameter recorded during regular spraying operation and the reference value shows a match, the presence of spray mist 2 can be concluded.

[0025] In order to further verify the correct functioning of the spray head 5, the higher-level unit 4 must, in addition to comparing the determined parameter with the reference value, query whether the spray head 5 is currently switched on. This information is available to the higher-level unit 4 per se, provided that it also controls the switching of the spray head 5 on and off. If the comparison matches and, provided the spray head 5 is switched on, it can be concluded according to the invention that the spray head 5 is actually functional. In the other case, i.e., if the spray head 5 is switched on but the comparison does not match, it can be concluded that the spray head 5 is malfunctioning.

[0026] The same applies to the determination of any periodicity: If the higher-level unit 4 detects a periodicity of the specified parameter and, if the spray head 5 is demonstrably switched on, it can be concluded from this according to the invention that the spray head 5 is rotating properly.

[0027] In contrast to the Fig.1, in which the measuring system monitors the function of only a single spray head 5, it is also conceivable to check the function of several spray heads 5 using the one level measuring device 1, provided their spray cones are located in the transmission / reception cone of the antenna arrangement 11. In this case too, all spray heads 5 can be considered to be functional, provided they are demonstrably switched on and the comparison of the characteristic with the reference value shows a match. In the event that the higher-level unit 4 or the level measuring device 1 does not determine a match, it can be concluded that at least one of the spray heads 5 is not functional. In order to check the function of each individual spray head 5 using a single level measuring device 1, it is of course also possible to switch the individual spray heads 5 on or off one after the other, for example during test operation.and to determine a separate characteristic value for each individual spray head, which, by comparison with a respective reference value, allows a statement to be made about the functionality of the individual spray head 5. As a result, the measuring system according to the invention requires only a few components, even in the case of multiple spray heads 5. In the event that the function of all spray heads 5 is to be individually verifiable, it is of course also conceivable to provide a separate high-frequency measuring device 1 for each individual spray head 5 or each individual spray cone. List of reference symbols 1 radar-based (level) measuring device 2 spray mist 3 containers 4 Superior unit 5 spray head 11 Antenna arrangement R HF1,2 Reception signal S HF radar signal

Claims

[1] Measuring system for checking the functionality of at least one spray head (5) arranged in a container (3), which is designed to spray the spray mist (2) within the container (3) with a defined spray cone, comprising the following components: - a high-frequency measuring device (1), with ◯ a signal generating unit designed to generate a high-frequency signal (S HF ) to generate ◯ an antenna arrangement (11) which is aligned in the direction of the spray cone, so that the high-frequency signal (R HF2 ) can be emitted in the spray mist (2) and a reception signal (R HF1 , R HF2 ) is receivable, and ◯ an evaluation unit designed to use the received signal (R HF1 , R HF2 ) to determine a defined parameter, and to detect spray mist (2), provided that the determined parameter corresponds to a predefined reference value, - a higher-level unit (4) designed to ◯ to control or detect the switching on and off of the spray head (5), ◯ to query the detection of spray mist (2) from the high-frequency measuring device (1), and ◯ to classify the at least one spray head (5) as functional, provided that it is switched on and spray mist (2) is detected. [2] Measuring system for checking the functionality of at least one spray head (5) arranged in a container (3), which is designed to spray the spray mist (2) within the container (3) with a defined spray cone, comprising the following components: - a high-frequency measuring device (1), with o a signal generating unit designed to generate a radio frequency signal (S HF ) to generate ◯ an antenna arrangement (11) which is aligned in the direction of the spray cone, so that the high-frequency signal (RHF2 ) can be emitted in the spray mist (2) and a reception signal (R HF1 , R HF2 ) is receivable, and ◯ an evaluation unit designed to use the received signal (R HF1 , R HF2 ) to determine a defined parameter, - a higher-level unit (4) designed to ◯ to control or detect the switching on and off of the spray head (5), ◯ to detect spray mist (2) if the parameter corresponds to a predefined reference value, and ◯ to classify the at least one spray head (5) as functional, provided that it is switched on and spray mist (2) is detected. [3] Measuring system according to claim 1 or 2, which is designed to use the received signal (R HF1 , R HF2 ) to determine a noise or an amplitude, in particular that of a signal maximum, as a characteristic. [4] Measuring system according to claim 3, which is designed to determine the amplitude of the signal maximum which corresponds to the reflection of the high-frequency signal (R HF2 ) on an inner wall of the container (3) or on a filling material. [5] Measuring system according to claim 3, which is designed to determine the amplitude of the signal maximum which corresponds to the reflection of the high-frequency signal (R HF1 ) can be assigned to the possible spray mist (2). [6] Measuring system according to claims 1 to 5, which is designed to determine a spray quantity of the spray mist (2) on the basis of the characteristic variable. [7] Measuring system according to at least one of the preceding claims, wherein the high-frequency measuring device is designed as a radar-based measuring device, in particular as a level measuring device, wherein the signal generation unit is designed to generate the high-frequency signal (S HF) by means of the pulse transit time method or by means of the FMCW method, and wherein the evaluation unit is designed to receive the signal (R HF1 , R HF2 ) to receive and process accordingly. [8] Measuring system according to one of the preceding claims, which is designed - to determine the parameter over a number of measuring cycles, and - to determine a periodicity with which the characteristic variable changes periodically within the measuring cycles, wherein the higher-level unit (4) is designed to classify a rotation of the at least one spray head (5) as functional, provided that the spray head (5) is switched on and the periodicity with which the characteristic variable changes periodically within the measuring cycles is determined. [9] Measuring system according to one of the preceding claims, wherein the high-frequency measuring device (1) is arranged to measure the radar signal (S HF) approximately orthogonal to the spray cone.

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