Method for carrying out a cleaning operation

Abstract

The invention relates to a method for carrying out a cleaning operation for cleaning the interior of a container (10), within the scope of which a cleaning fluid is sprayed in a periodically repeated jet pattern against the inner wall of the container (10) by means of a jet cleaner, which is introduced into the interior of the container (10) and has a nozzle head rotating about a main axis of rotation, with distance measurement values (Dn) being detected by means of an optical distance meter (30) and being output to a control unit. The invention is distinguished in that, to monitor the cleaning operation, the optical distance meter (30) is statically directed into the interior of the container (10), and the distance measurement values (Dn) are continuously detected during the spraying operation and output to the control unit, which continuously calculates monitoring values from them by averaging and compares them with a stored reference value.

Description

[0001] Procedure for carrying out a cleaning process

[0002] Description

[0003] Field of the invention

[0004] The invention relates to a method for carrying out a cleaning process for cleaning the interior of a container, in the course of which a cleaning fluid is sprayed in a periodically repeated jet pattern against the inner wall of the container by means of a jet cleaner introduced into the interior of the container and having a nozzle head rotating about a main axis of rotation, wherein distance measurement values ​​are recorded by means of an optical distance meter and output to a control unit.

[0005] State of the art

[0006] Such a method is known from WO 2019 / 241261 A1.

[0007] The internal cleaning of containers, such as tanks, using so-called jet cleaners has long been known to those skilled in the art. A distinction is made between so-called surge cleaners and so-called targeted jet cleaners, both of which will be summarized here under the term jet cleaner. In both cases, a nozzle head connected to a cleaning fluid supply via fluid lines is introduced into the interior of the container to be cleaned. This can be done temporarily, specifically for the purpose of cleaning; alternatively, variants with a nozzle head permanently mounted inside the container are also known. The nozzle head is designed to spray cleaning fluid from the supply in a jet against the inner wall of the container, rotating during the process to reach as many wall areas as possible. The corresponding rotation drive can be motor-driven or caused by the recoil of the sprayed fluid.A surge cleaner is typically used to spray a jet, also known as a surge, with a comparatively large volume flow rate under comparatively low pressure. The rotation of the nozzle head is typically one-dimensional, i.e. around a fixed axis of rotation. The resulting jet pattern is comparatively simple; coverage of the entire inner wall surface is achieved by a correspondingly wide jet profile. A targeted jet cleaner, on the other hand, typically produces a high-pressure jet with a lower volume flow rate. The nozzle head rotates around several axes of rotation simultaneously and reaches the inner wall by directing a jet with a comparatively narrow jet profile in a complex jet pattern. In any case, the jet pattern is periodic, i.e. one that repeats at regular intervals.The period from the start of one beam pattern to the start of the next beam pattern is referred to here as the period of the beam pattern.

[0008] From the aforementioned generic document WO 2019 / 241261 A1, a surge cleaner is known whose rotatable nozzle head is mounted on a rail arrangement that can be inserted into the container interior and is also linearly movable. Due to the linear mobility of the nozzle head within the container interior, the entire surface of the container's inner wall can be reliably reached, even in very long containers, such as railway tank cars. In order to be able to specifically control the linear movement of the nozzle head, the previously known nozzle head is equipped with a laser-based distance meter, by means of which the current relative position of the nozzle head to other objects in the container, in particular to the container's inner wall, can be determined. Furthermore, the aforementioned document also describes the use of the distance meter to locate contamination detected by other means, for example, by an additional image sensor on the nozzle head.

[0009] WO 2018 / 218120 A1 discloses a jet cleaner whose nozzle head is also equipped with a laser-based sensor. However, this is a dirt thickness sensor that optically detects the thickness of a dirt layer on the inner container wall to be removed during the cleaning process. Similarly, the nozzle head of the jet cleaner disclosed in EP 9 950 159 A1 is equipped with a camera and a light source to optically check the success of a completed cleaning or the need for future cleaning, in particular based on a specific luminescence signal of the expected contamination.

[0010] A disadvantage of these methods is the lack of control over whether a cleaning process is proceeding properly or whether errors occur, for example, due to mechanical blockage of the nozzle head and / or interruption of the cleaning fluid flow. Only after the cleaning process has been completed can the result be determined using additional sensors, and the cleaning process subsequently classified as proper or improper. However, detecting errors afterward is very time-consuming.

[0011] DE 101 35 191 A1 discloses making the drain outlet of a washing machine's detergent container partially transparent, allowing light emitted by a photodiode to pass through it to a photoresistor. The signal picked up by the photoresistor depends on the turbidity of the water or the foam formation in the drain outlet. The document proposes relating the measured values ​​to the current operating state of the washing machine and comparing them with corresponding reference values ​​in order to determine possible malfunctions of the machine.

[0012] Task

[0013] It is the object of the present invention to further develop a generic method in such a way that the assessment of the cleaning process as being correct or not can be carried out while it is being carried out.

[0014] Description of the invention

[0015] This object is achieved in conjunction with the features of the preamble of claim 1 in that, for monitoring the cleaning process, the optical distance meter is statically directed into the interior of the container and the distance measurement values ​​are continuously recorded during the spraying process and output to the control unit, which continuously calculates monitoring values ​​therefrom by averaging and compares them with a stored reference value.

[0016] Preferred embodiments are the subject of the dependent claims.

[0017] The core idea of ​​the present invention lies in a special, non-intended use of an optical distance meter. This can, in particular, be a laser-based distance meter, preferably a laser-based time-of-flight detector. Such detectors are known to those skilled in the art and are available inexpensively. In the laser-based time-of-flight detector, a pulsed laser beam is generated, and the signal reflected from a distant object is detected. In particular, the times of emission and detection are recorded very precisely, so that the time difference can be used to measure the travel time of the light to the distant object and back, and from this, the distance of the distant object from the detector can be determined.

[0018] The specific functional principle of the optical distance meter is, however, of secondary importance for the present invention since, as mentioned, said detector is not used as intended within the scope of the invention, i.e., not for measuring a defined distance. Rather, the invention provides for the optical distance meter to be directed into the interior of the container in some way, but statically, i.e., unchanged during the cleaning process (and any preceding calibration step). Its detector will detect light that emanates, in particular is scattered, from cleaning fluid droplets in the volume of the container that cannot be identified in detail. During the cleaning process, the interior volume of the container is filled with a mist of cleaning fluid, which is also regularly traversed by the rotating beam. These are conditions that, in the context of a proper distance measurement, i.e.,the determination of the distance to a well-defined, distant object, would be regarded as massive disturbances that make precise distance measurement impossible. Nevertheless, the optical distance meter will generate nominal distance measurements. These will fluctuate massively due to the "disturbances" described above. Nevertheless - according to the inventors' insight - the sequence of the determined nominal distance measurements has a fixed, albeit not precisely definable, relationship to the conditions of the cleaning process. In particular, it has been found that averaging nominal distance measurements, especially over a period that is long compared to the period of the beam pattern, results in a stable value, referred to here as the monitoring value, which shows a strong dependence on whether the cleaning process is proceeding properly or not.Which concrete value is representative of a proper or improper cleaning process in the respective, specific constellation of type of cleaning process, geometry of the container, positioning and orientation of the optical distance meter, etc., varies greatly from case to case and is taken into account according to the invention by storing an individual reference value with which the determined monitoring values ​​are continuously compared. A preferred method of determining the reference value will be discussed in more detail below. In any case, according to the invention, the monitoring values ​​calculated by averaging nominal distance measurements are continuously compared with the stored reference value during the ongoing cleaning process. The result of the comparison can then be used for an automatic assessment of the cleaning process as proper or improper.These calculations and comparisons are preferably performed using software in a control unit. This can particularly preferably be a single-board microcontroller.

[0019] Advantageously, for the averaging performed to calculate each monitoring value, (nominal) distance measurements are used, which are recorded within a moving time window of constant length, wherein the length of the time window is preferably greater than one period of rotation of the nozzle head around the main axis of rotation, in particular corresponding to a multiple of this rotation period. In this way, the monitoring value can be updated at intervals that are significantly shorter than the length of the moving time window. This can therefore be selected to be long without significantly slowing down the monitoring process in order to compensate for the strong fluctuations in the (nominal) distance measurements that naturally occur during a rotation period. Nevertheless, an error in the cleaning process, e.g.A mechanical blockage of the nozzle head or an interruption in the cleaning fluid supply can very quickly cause the monitoring value averaged over the time window to drift out of a predetermined tolerance range around the reference value, so that any improper progress of the cleaning process can be immediately identified and, if necessary, appropriate countermeasures can be taken. For example, if the control unit judges the cleaning process to be incorrect or no longer correct based on the comparison result, a warning signal can be issued. A time window length of at least 10 times the rotation period has proven to be particularly advantageous. Please note that with the (preferred) use of surge cleaners, the rotation period typically corresponds to the jet pattern period, since the nozzle head in this type of jet cleaner typically rotates exclusively around the main rotation axis.In jet cleaners, however, at least one additional, superimposed rotation is typically provided around a secondary rotation axis essentially perpendicular to the main rotation axis in order to generate a complex jet pattern that, if possible, scans the entire inner container wall. In such embodiments, the jet pattern period is significantly longer than the rotation period.

[0020] The optical distance meter, which, as already mentioned, is preferably one that generates an optical measuring beam to record the distance measurements, is preferably installed such that its measuring beam is directed into an area of ​​the container interior periodically traversed by the jet of cleaning fluid. In this case, the differences between the monitoring values ​​calculated by averaging the (nominal) distance measurements are particularly large in the case of a properly rotating cleaning jet and a blocked, weakened, or interrupted cleaning jet. The error can therefore be detected particularly quickly and clearly. However, such an installation of the distance meter is not mandatory for the functional principle of the invention.Even in cases where the measuring beam “only” interacts with the mist generated inside the container during the cleaning process, a proper and an improper cleaning process can be clearly distinguished from one another based on the resulting monitoring values.

[0021] Particularly preferably, the optical distance meter is fixed to the outer wall of the container and directed into the interior of the container through a fluid-tight window. Such a mounting is technically simple to implement, especially since most containers, especially tanks, used in the pharmaceutical and food industries, where the invention can be used, already have viewing or monitoring windows.

[0022] To determine the reference value, it has proven particularly advantageous if this takes place as part of the upstream calibration step, in which a cleaning process that has been independently assessed as being correct is carried out, during which the optical distance meter is directed into the interior of the container in the same way as during monitoring, and the distance measurement values ​​during the spraying process are continuously recorded in the same way as during monitoring and output to the control unit, which then calculates calibration data by averaging in the same way as it calculates the monitoring values ​​during monitoring, from which calibration data the reference value is then determined and stored. In other words, for calibration, the monitoring according to the invention of a cleaning process is essentially carried out, which is known from another source to be a correct cleaning process.This can be done, for example, through current observation using independent sensors or subsequently by checking the cleaning result. The essential difference between the calibration step and the monitoring according to the invention lies solely in the interpretation and use of the values ​​calculated by averaging. As explained, the monitoring involves the monitoring values ​​according to the invention. During the calibration step, these calculated values ​​are interpreted as calibration data, which form the basis for determining the reference value. For example, an average value from several calibration data sets recorded one after the other can be used as the reference value. However, it is essential that the apparatus setup for the calibration step is the same as for the cleaning process to be monitored.This is due to the unpredictable, although reliably reproducible, nature of the sequence of nominal distance measurements generated by the distance meter.

[0023] Advantageously, one or more tolerance values ​​are also determined and stored with the reference value. These can be used within the scope of the inventive comparison to evaluate monitoring values ​​that do not exactly match the reference value as representative of a (still) proper or (already) improper cleaning process. For example, said tolerance values ​​can be determined based on a standard deviation of the determined calibration data.

[0024] As explained above, the present invention can be used in conjunction with both jet cleaners and surge cleaners. However, it has proven particularly advantageous for the latter, as the very short jet pattern period allows for rapid detection of cleaning errors.

[0025] Further details and advantages of the invention will become apparent from the following specific description and drawings.

[0026] Brief description of the drawings

[0027] They show:

[0028] Figure 1: a schematic sectional view of a tank during a cleaning process according to the invention and

[0029] Figure 2: exemplary representations of nominal distance values ​​as they could arise during a proper cleaning process (partial figure a) or during various improper cleaning processes (partial figures b, c).

[0030] Detailed description of preferred embodiments

[0031] The same reference symbols in the figures indicate the same or analogous elements.

[0032] Figure 1 shows a highly schematic sectional view through a container 10, in particular a tank, such as is used, for example, in the pharmaceutical or food industry, during a cleaning process according to the invention. The container 10 has a main support 12, through which the rod 22 of a surge cleaner 20 is introduced into the interior of the container 10. The rod 22 is connected, in a manner not shown, to a supply of cleaning fluid, from which the cleaning fluid can be pumped to a nozzle head 24 arranged at the end of the rod 22. The rod 22 thus serves both to position the nozzle head 24 and to supply cleaning fluid. At the outlet of the nozzle head 22, a jet 26 of cleaning fluid is produced, which, in the illustrated surge cleaner 20, has a high volume flow and a very wide jet profile.As indicated by the rotation arrow 28, the nozzle head 24 rotates during the cleaning process so that the inner wall of the container 10 is sprayed all around with the cleaning fluid.

[0033] A window 14 is arranged in the wall of the container 10, through which an optical distance meter 30 "looks" into the interior of the container 10. This means that a measuring beam 32 emitted by the distance meter 30, in particular a laser beam, extends through the window 14 into the interior of the container 10. When the surge cleaner 20 is switched off, the measuring beam 32 is reflected by the wall of the container 10 at a point opposite the window 14 and returned to the distance meter 30. If, as preferably provided, the optical distance meter 30 is a time-of-flight detector that emits a pulsed measuring beam 32, the distance between the distance meter 30 and the targeted position on the container wall can be deduced from the time difference between the emission and the detection of a measuring beam pulse. However, this is not possible when the surge cleaner 20 is in operation.In this case, the entire interior of the container 10 is filled with a mist of cleaning fluid. Furthermore, in the illustrated configuration, the beam 26 of cleaning fluid periodically crosses the line of sight of the distance meter 30. Instead of a clear reflection signal from the opposite container wall, the detector of the distance meter 30 instead receives scattered light from unpredictable locations, as indicated by the scatter arrows 36.

[0034] Despite such conditions unsuitable for distance measurement, the distance meter 30 will continuously measure time intervals between the emission and detection of pulses and calculate nominal distance values ​​therefrom, to which, however, no defined distances within the apparatus structure can be assigned. Nevertheless, the resulting signal can be used according to the invention to assess whether the cleaning process is proper or improper. Figure 2 shows purely as an example possible time sequences (t) of nominal distance values ​​Dn that can occur with different qualities of a cleaning process. Figure 2a shows a possible example of a sequence of nominal distance values ​​Dn that may occur during a proper cleaning process according to the structure of Figure 1. A periodic basic structure can be seen that corresponds to the rotation of the nozzle head 24.In addition, one can see a strong noise which results from the scattering of the measuring beam 32 in the cleaning fluid mist.

[0035] Figure 2b shows a sequence of nominal distance measurements Dn that can occur during a mechanical blockage of the nozzle head 24. Here, the basic periodic structure of the data sequence is eliminated. Only the noise resulting from scattering remains.

[0036] Figure 2c shows a sequence of nominal distance measurement values ​​Dn, such as could occur if the cleaning fluid flow is interrupted while the nozzle head 24 continues to rotate. This does not occur in the embodiment shown in Figure 1, but in an embodiment in which the nozzle head 24 itself periodically crosses the measuring beam. The resulting nominal distance measurement values ​​are actual distance measurement values ​​that alternately represent the distance between the nozzle head 24 and the inner wall of the container 10 and the distance meter 30.

[0037] It should be expressly pointed out that the data presented are not real data recorded within the scope of a method according to the invention, but are intended purely to illustrate the principle according to the invention.

[0038] A person skilled in the art will recognize that averaging over several periods of the circulating beam pattern in the three cases illustrated in Figure 2 results in different mean values, referred to here as monitoring values. In the theoretical case that the data noise illustrated in Figures 2a and 2b is white noise, identical mean values ​​could result in both cases. However, the inventors' experience teaches that the noise resulting from the scattering explained is not white noise, so the resulting mean values ​​or the resulting monitoring values ​​are quite distinguishable with regard to the different case constellations in Figure 2.

[0039] Those skilled in the art will understand that the term "averaging" is to be understood broadly here. An arithmetic or geometric mean can be calculated. However, any other form of combining multiple nominal distance measurements into a meaningful monitoring value is equally suitable within the scope of the invention and is intended to be included in the term.

[0040] Of course, the embodiments discussed in the specific description and shown in the figures represent only illustrative embodiments of the present invention. A person skilled in the art will be able to devise a wide range of possible variations in light of the disclosure herein. In particular, other types of optical distances may also be used.

[0041] List of reference symbols

[0042] 10 containers

[0043] 12 nozzles

[0044] 14 windows

[0045] 20 surge cleaners

[0046] 22 rods

[0047] 24 nozzle head

[0048] 26 beam

[0049] 28 Rotation arrow

[0050] 30 distance meters

[0051] 32 measuring beam

[0052] 34 Distance measuring arrow

[0053] 36 Scatter arrow Dn (nominal) distance measurement t time

Claims

Patent claims 1. Method for carrying out a cleaning process for cleaning the inside of a container (10), in the course of which a cleaning fluid is sprayed in a periodically repeated jet pattern against the inner wall of the container (10) by means of a jet cleaner introduced into the interior of the container (10) with a nozzle head (24) rotating about a main axis of rotation, wherein distance measurement values (Dn) are recorded by means of an optical distance meter (30) and output to a control unit, characterized in that for monitoring the cleaning process, the optical distance meter (30) is statically directed into the interior of the container (10) and the Distance measurement values (Dn) are continuously recorded during the spraying process and output to the control unit, which continuously calculates monitoring values by averaging and compares them with a stored reference value.

2. Method according to claim 1, characterized in that the control unit uses a result of the comparison to automatically assess the cleaning process as proper or improper.

3. Method according to one of the preceding claims, characterized in that for the averaging carried out to calculate a respective monitoring value, distance measurement values (Dn) are used which are recorded within a moving time window of constant length, the length of the time window being greater than the period of rotation of the nozzle head (24) about the main axis of rotation.

4. Method according to claim 3, characterized in that the length of the time window corresponds to at least ten times the period of rotation of the nozzle head (24) about the main axis of rotation.

5. Method according to one of the preceding claims, characterized in that the distance measuring device (30) generates an optical measuring beam (32) for detecting the distance measurement values (Dn), which is directed into a region of the container interior which is periodically crossed by the jet pattern of the cleaning fluid.

6. Method according to one of the preceding claims, characterized in that the optical distance meter (30) is fixed to the outer wall of the container (10) and is directed through a fluid-tight window (14) into the interior of the container (10).

7. Method according to one of the preceding claims, characterized in that the reference value is determined as part of a preceding calibration step in which a cleaning process is carried out which is independently assessed as being correct, during which the optical distance meter (30) is directed into the interior of the container (10) in the same way as during monitoring and the distance measurement values (Dn) are continuously recorded during the spraying process in the same way as during monitoring and output to the control unit, which uses this in the same way as it calculates the monitoring values during monitoring, to continuously calculate calibration data by averaging, from which calibration data the reference value is then determined and stored.

8. Method according to claim 7, characterized in that in addition to the reference value, one or more tolerance values are determined and stored.

9. Method according to one of the preceding claims, characterized in that the jet cleaner is a surge cleaner.

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