Method for operating a system

Abstract

The invention relates to a method for operating a system, for example a roll stand for processing a product in a working process. In a first method step a), the method provides that vibrations at a system are detected in the form of a first temporal vibration signal, in order to subsequently transform same into an amplitude spectrum in the frequency domain in step b). Within the frequency domain, risk regions are predefined in order to check whether individual peaks of the amplitude spectrum extend at least partially into the risk regions (step c)). If they do, the magnitude of the risk for operation of the system is evaluated according to method step d), in particular insofar as the risk is based on a component of the system which is represented by the peak extending into the risk region. At least one countermeasure is proposed and implemented to change or maintain this risk, steps e) and f).

Description

[0001] Methods for operating a plant

[0002] The invention relates to a method for operating a system, for example a rolling mill, for processing a product in a work process. Furthermore, the invention relates to a computer program product corresponding to the method and to a rolling mill.

[0003] The method aims to analyze the vibration behavior of the plant or at least one component of the plant and then subsequently operate the plant in a vibration-optimized and / or output-optimized manner. Specifically, vibration problems of the "third octave" and "fifth octave" categories, i.e., especially chatter vibrations, are to be reduced without the need for additional expensive vibration damping components.

[0004] The inventive method and computer program product is applicable to a large number of different systems:

[0005] For example, it is applicable to single- or multi-stand cold or hot rolling mills for rolling sheets or strips of steel or aluminum, etc. The focus of vibration monitoring can be placed, for instance, on roller bearings or drives. Vibration monitoring can prevent damage to these components or to the products being manufactured.

[0006] Furthermore, continuous casting plants, blast furnaces, hardening furnaces, and / or coating plants are suitable for applying the method according to the invention. Continuous casting plants produce a casting strand from a liquid metal melt, from which steel slabs, billets, or ingots are later produced. The focus of vibration monitoring in continuous casting plants is, for example, on casting rollers or drives. In the case of continuous casting plants, vibration monitoring and the extensive avoidance of vibrations serve, for example, to prevent cracks or defects in the aforementioned casting products.

[0007] Page 1. Blast furnaces are used to produce pig iron. In the case of blast furnaces, the focus of vibration monitoring can be on fans or pumps. Vibration monitoring and the extensive avoidance of vibrations in blast furnaces serve to improve the quality of the pig iron produced and the productivity of the blast furnace, e.g., through improved control of the air supply.

[0008] Hardening furnaces are used for the heat treatment of metal products, and especially hardened steel parts. In this case, the focus of vibration monitoring can be on components such as the fans or pumps of the hardening furnaces, whereby the subsequent, largely eliminated vibrations lead to a more uniform temperature distribution within the furnace and ultimately to improved quality of the hardened products.

[0009] Strip processing plants, in particular coating plants, are used for surface coating, especially of metal parts, and for the production of, for example, galvanized sheets or coated strips. In these plants, the vibration analysis according to the invention and the extensive avoidance of vibrations can prevent coating defects and thus improve the quality of the produced sheets and strips.

[0010] Numerous methods for vibration detection, prediction, and avoidance in industrial plants are known in the prior art. The following table cites several patent applications as examples, highlighting the respective disadvantages of the inventions or solutions known from these patent applications.

[0011] Page 2

[0012] German patent application DE 10 2022 210 596 A1 discloses a method for analyzing the vibration behavior of a system and a corresponding computer program. The system consists of at least one

[0013] Page 3 describes a first and a second rolling stand, which are coupled to each other via a strip clamped between both stands. To better analyze the vibration behavior of individual rolling stands, it is known to first sensorily detect their vibrations as a temporal vibration signal and then transform this temporal vibration signal into an amplitude spectrum in the frequency domain. The amplitude of the peaks in the amplitude spectrum is then evaluated to determine whether it lies above or below a predetermined amplitude threshold. If so, an undesired chatter event is detected. The known method described here, as mentioned, concerns a system of two coupled rolling stands. It is therefore limited to such a system.

[0014] The invention is based on the objective of further developing a known method and computer program product for operating a plant as well as a corresponding plant in the form of a rolling mill in such a way that the disadvantages of the prior art, in particular vibration-related quality losses with regard to thickness, flatness and / or surface quality of the product to be processed, are avoided and preferably the productivity of the plant is increased at the same time.

[0015] This problem is solved by the method claimed in claim 1. Accordingly, the method serves to operate a system for processing a product in a work process, in a first pass n = 1, comprising the following steps: a) detecting vibrations at the system in the form of a first temporal vibration signal with at least one first acceleration sensor while the system is operating; b) transforming the first vibration signal in a first time interval into the frequency domain, resulting in a first amplitude spectrum for the first time interval;

[0016] Page 4 c) Define at least one risk area with at least one associated risk scale in the amplitude spectrum, check whether at least one single peak of the amplitude spectrum extends at least partially into the risk area, and interpret this – if so – as a potential risk in the operation of the plant; d) Assess the magnitude of the risk represented by the at least one peak extending into the risk area using the risk scale associated with the risk area; e) Determine at least one suitable countermeasure, in particular in the form of a suitable change to the plant settings or in the form of replacing a defective component of the plant, to change the magnitude of the risk determined in step d) in a desired way or to maintain it at the same level;and f) Outputting the identified countermeasure to a control system of the plant and / or to an operator of the plant and / or storing the countermeasure, preferably in each case with an indication of the magnitude of the risk.;

[0017] The claimed process steps a) to d) serve to analyze the vibration behavior of the plant and to determine any potential risk to its operation; in contrast, steps e) and f) serve to determine and issue a suitable countermeasure in order to change the risk during further operation of the plant - preferably depending on the operating mode of the plant - in a desired way or to maintain it at an unchanged level.

[0018] The desired change in risk can mean not only a reduction, but optionally also an increase in risk.

[0019] A "risk scale" is used to assess the risk to the operation of the plant in general. The term "risk scale" encompasses an amplitude risk scale for assessing amplitude risk and / or a frequency risk scale for assessing frequency risk to the operation of the plant or one of its components.

[0020] Page 5 Components. In this respect, amplitude risk and frequency risk are sub-cases of a general risk assessed using a general risk scale.

[0021] The claimed method according to the invention aims to provide the operator or the control system of the plant with specific recommendations or instructions for action which, in future application, aim to prevent vibration-related quality losses with regard to thickness, flatness and surface quality of the produced product and at the same time to increase the production of the plant, provided that this is easily possible from a vibration engineering point of view.

[0022] The claimed method can be applied to both existing and new systems. It is suitable for retrofitting existing systems.

[0023] The implementation of the method according to the invention generally does not require the purchase of new, additional measuring devices or vibration damping systems. Often, existing measuring technology can be used in plants, particularly rolling mills. For example, pressure transducers already present in the setting and bending cylinders or load cells can be used to detect vibrations. Similarly, existing tensile load cells can be used to detect strip tension between two rolling mills, and thickness gauges can be used to detect vibrations. Using existing components to implement the method according to the invention enables an increase in product quality and plant productivity without additional costs.

[0024] The risk that is potentially seen according to the inventive method when at least one peak in the amplitude spectrum extends into the risk area defined therein can, for example, affect the stability of the work process, the output quantity of the plant, the quality of the product produced by the plant.

[0025] Page 6 concerns the product and / or the wear and tear of components of the system in connection with the maintenance effort required for the components.

[0026] The aforementioned problem of the invention is further solved by using the countermeasures recommended according to the inventive method in the simulation of the plant or parts of the plant according to claim 22, by a computer program product according to claim 23, and by a rolling mill stand according to claim 24. The advantages of these solutions correspond to the advantages previously mentioned with regard to the claimed method.

[0027] The description includes a total of 8 figures, whereby

[0028] Figure 1 shows a flowchart of the method according to claim 1;

[0029] Figure 2 shows a first embodiment for the frequency domain with a risk area and first embodiments for a frequency risk scale and an amplitude risk scale associated with the risk area;

[0030] Figure 3 shows the frequency range and risk area from Figure 2 with a modified frequency-risk scale;

[0031] Figure 4 shows the frequency range and risk area according to Figure 2 with a modified amplitude risk scale;

[0032] Figure 4a shows the frequency range and risk area according to Fig. 2 for a peak 3 with a lower frequency;

[0033] Figure 5 shows the frequency space and risk area according to Figure 2, but with a modified distribution of peaks in the risk area and with an amplitude risk scale but without a frequency risk scale;

[0034] Page 7 Figure e shows the frequency range and risk area according to Figure 5 with a frequency-risk scale, but without an associated amplitude-risk scale; and

[0035] Figure ? shows the frequency space with two different risk areas, each of which can be assigned different risk scales;

[0036] The invention is described in detail below with reference to the figures mentioned, in the form of exemplary embodiments.

[0037] Figure 1 illustrates the inventive method for operating a plant for processing a product in a work process, initially comprising the process steps a) to f) in a first run n = 1.Accordingly, the procedure comprises the following steps: a) Detecting vibrations at the plant in the form of a first temporal vibration signal with at least one first acceleration sensor while the plant is in operation; b) Transforming the first vibration signal in a first time interval into the frequency domain, resulting in a first amplitude spectrum for the first time interval; c) Defining at least one risk zone with at least one associated risk scale in the amplitude spectrum; checking whether at least one peak of the amplitude spectrum extends at least partially into the risk zone and interpreting this – if so – as a potential risk in the operation of the plant; d) Assessing the magnitude of the risk represented by the at least one peak extending into the risk zone using the risk scale associated with the risk zone.

[0038] Page 8 e) Determine at least one suitable countermeasure, in particular in the form of a suitable change to the setting of the plant or in the form of replacing a defective component of the plant, in order to change the magnitude of the risk determined in step d) in a desired manner or to maintain it at the same level; and f) Output the determined countermeasure to a control system of the plant and / or to an operator of the plant and / or store the countermeasure.

[0039] In process step b), the amplitude spectrum is generated for the risk assessment of the plant's operation, which is carried out in the subsequent process steps. For a more precise and efficient analysis of the amplitude spectrum, its peaks can be interpolated. This can be particularly advantageous when classifying peaks as either speed-proportional or non-speed-proportional, the significance of which will be discussed further below. Interpolation allows for a more accurate determination of the peak frequencies, which is especially beneficial when the frequency spectrum has limited resolution. The peak amplitudes can also be determined more precisely, leading to a more accurate analysis and interpretation of risks.Advantageously, this method allows for a higher spectral resolution of the amplitude spectrum without the need for a larger Fast Fourier Transform over a longer time domain, thus saving computing resources.

[0040] Procedure step e) can optionally also include the identification of components for whose peaks an increased risk was identified during the risk assessment in step d). This applies in particular to the aforementioned identified peaks with a peak frequency that is proportional to known fundamental vibrations of rotating components inside or outside the system. These could be, for example, harmonic rotational frequencies or bearing failure frequencies, etc., which are generally known. If components can be assigned to these identified peaks in this way, the replacement of these typically mechanical components is recommended as a countermeasure in accordance with procedure steps e) and f).

[0041] Page 9 Components, which can improve the vibration behavior not only of this component but also of the entire system. Depending on the specific problem, the component replacement does not necessarily have to be immediate but can be scheduled for a planned system downtime. For this purpose, the component identified as potentially risky is signaled or communicated to the system operator or the system's automatic (process) control in process step f), optionally including the issuance of replacement or maintenance recommendations for this component, particularly if it is determined that the respective risk has increased with a currently processed product compared to a previously processed product.

[0042] The recommended countermeasure can be implemented in real time during the current workflow for the product being processed. Alternatively or additionally, it can also be applied as a preset for a product to be processed subsequently.

[0043] The vibration and process information collected during the execution of the method according to the invention, as well as the recommendations for countermeasures issued according to the method of the invention, and possibly also the reactions of the operator or the system when the countermeasures are applied, are preferably stored. In this way, they can be used for future improvements to the operation of the system and to improve its safety, especially when fed into self-learning algorithms. These self-learning algorithms can, for example, define limit values ​​for the recommended countermeasures, such as a change in the process speed of the system.

[0044] In process step a), operating the plant means in particular the following alternatives: Either empty operation of the plant, in which no product is processed or manufactured; or normal operation of the plant, in which the product is processed or manufactured.

[0045] Page 10 After carrying out the procedural steps a) to f), it is recommended, according to procedural step g), to implement the previously identified and proposed countermeasures in the form of a corresponding change in the setting of the plant and to continue operating the plant with the changed setting.

[0046] It is recommended that the aforementioned procedural steps a) to g) not only be carried out once, but rather repeated once or multiple times for an n = n + 1'th time period with n = 2 to N, which follows the first time period n = 1. The nth time period with n > 2 falls either in a first period while a first product is being processed, or in a second period while a second product is being processed. With each repetition of the aforementioned procedural steps, a new n + 1'th amplitude spectrum is generated in procedural step b). This new amplitude spectrum, when processed in the subsequent procedural step d), can lead to a changed risk assessment of individual peaks, which in turn necessitates new or modified countermeasures according to procedural step f).

[0047] It is recommended to continue repeating process steps a) to g) until a predefined termination criterion is met. The termination criterion could be met, for example, when a predetermined number of repetitions have been performed or reached, or when a currently processed product has been completed.

[0048] Figure 2 illustrates an example of an amplitude spectrum with a defined risk area R1. In this example, risk area R1 is assigned two risk scales: an amplitude risk scale for assessing amplitude risk and a frequency risk scale for assessing frequency risk. It is recommended to use both risk scales, as their combined evaluation allows for a more precise definition of the operational risk. However, only the use of at least one of these risk scales is mandatory for carrying out the procedure.

[0049] Page 11 Threshold values ​​may be defined on the respective ordinate of the risk scales, the exceedance of which indicates a greater risk to the operation of the plant according to procedure step d), which necessitates a countermeasure according to procedure step e) in order to change the magnitude of the risk determined in step d) in a desired way or to maintain it at the same level.

[0050] For the amplitude risk scale plotted on the ordinate, at least one amplitude threshold can be defined for the peaks in the spectrum; for the frequency risk scale plotted on the abscissa, at least one frequency threshold can be plotted on the ordinate. Or at least one overall threshold can be defined that relates to a combination of the two risk scales, i.e., the amplitude and the frequency risk scales.

[0051] Regardless of how the magnitude of the risk was assessed in procedure step d), whether based on the amplitude risk scale, the frequency risk scale, or a combination of both, in all these cases the countermeasure according to procedure step e) can be defined depending on sub-risk areas, which are limited by one or more threshold values, and into which a peak falls with its amplitude and / or frequency. For example, two threshold values ​​can be specified, such as 0.5 and 0.8, thereby defining three sub-risk areas. For example, the countermeasure for a first sub-risk area from 0 to 0.5 could then be to increase the actual operating speed of the plant and observe the effects of this change.For a second partial risk area of ​​0.5 to 0.8, it may be recommended to maintain the current actual speed of the plant, and for a third partial risk area greater than 0.8, the countermeasure may consist of recommending a reduction in the actual speed.

[0052] Of course, other threshold values ​​for the risks can also be defined, e.g. at 0.4 and 0.7.

[0053] Page 12 Figure 2 shows three exemplary peaks P1, P2, and P3 in the amplitude spectrum. Peaks P1 and P2 clearly extend into risk area R1, while the third peak, P3, lies outside risk area R1; this would be detected during the test when performing procedure step c). Therefore, peaks P1 and P2 represent a potential risk to the operation of the plant; peak P3, however, does not.

[0054] The risk assessment, represented by the individual peaks, is derived by evaluating the peaks on the amplitude risk scale and the frequency risk scale. As can be seen in Figure 2, the amplitude risk is the same for peaks P2 and P3, while it is lower for peak P1 than for peaks P2 and P3. The frequency risk assessment shows that the frequency risk is highest for peak P2 and lower for peak P1 than for peak P2. The frequency risk for peak P3 is zero.

[0055] An analysis of both the amplitude risk scale and the frequency risk scale reveals that the overall risk for peak P2 is highest and greater than the risk for the first peak, P1. This is because both the amplitude and frequency risks for peak P2 are higher than those of the first peak. Furthermore, the overall risk of peak P2 is significantly higher than that of peak P3. This is because peak P3 does not extend into risk area R1, and therefore its frequency risk is zero. This is true even though the amplitude risk for peaks P2 and P3 is, as mentioned, the same. Finally, the overall risk of peak P1 is higher than that of peak P3 because, as stated, the latter does not extend into risk area R1.

[0056] Individual risk scales can be defined for different risk scenarios. Then, in step e), the countermeasures taken to modify the risk level determined in step d) as desired or to maintain it unchanged can be specified, depending on the respective risk scenario.

[0057] Page 13 can be selected. For example, a distinction can be made between whether the plant is operated, or is intended to be operated, with an output-optimized, quality-optimized, or maintenance-optimized approach. Output-optimized operation aims to increase the plant's output quantity, while quality-optimized operation aims to increase the quality of the product produced by the plant or to maintain it within certain tolerances. Maintenance-optimized operation can aim to keep the wear and tear of plant components low in order to minimize the maintenance effort required for these components. Thus, the countermeasures taken or proposed according to step e) can be less stringent, and consequently, the risk reduction is also less pronounced if the plant is to be operated with an output-optimized approach. Conversely, i.e.,If the plant is to be operated in a maintenance- or quality-optimized manner, it is recommended to propose and initiate more effective countermeasures so that the reduction in risk is greater.

[0058] After performing process step b), and before performing process step c), it can be checked whether at least one of the peaks of the amplitude spectrum has a peak frequency proportional to known fundamental frequencies of rotating components inside or outside the system. Such peaks should then be identified. In the subsequent execution of process steps c), d), e), and f), preferably for all peaks of the amplitude spectrum, the risk assessment according to process step d) should use a frequency risk scale that rates the frequency risk for peaks with frequencies away from the fundamental frequencies lower than for the previously identified peaks with frequencies proportional to the fundamental frequencies.

[0059] Figure 3 shows an example of this situation. Compared to the frequency-risk scale in Figure 2, the frequency-risk scale in Figure 3 is significantly more streamlined and focuses primarily on the frequency of peak P5 and its immediate surroundings. Lower and higher frequencies located further away are assigned a near-zero frequency risk by this frequency-risk scale.

[0060] Page 14 Therefore, the overall risk assessment of the individual peaks is as follows:

[0061] The overall risk of peak P5 is the highest compared to the overall risks of peaks P4 and P6, simply because their frequency risk is zero. For this reason, the risks of peaks P4 and P6 are approximately equal, although their respective amplitude spectra differ slightly; however, given the absence of frequency risk, this difference in amplitude risk is negligible. In comparison with the peaks in Figure 2, the overall risk of peaks P2 and P5 is approximately equal. The risk of peak P4 is significantly lower than the risk of peak P1 because, as mentioned, the frequency risk of peak P4 is zero. Finally, the overall risk of peaks P3 and P6 is approximately equal.

[0062] As an alternative to the test procedure just described for peaks whose peak frequency is proportional to known fundamental frequencies, the procedure for peaks whose peak frequency is not proportional to known fundamental frequencies can provide the following steps for implementation according to procedure step b):

[0063] - Check whether at least one of the peaks of the amplitude spectrum has a peak frequency that is not proportional to known fundamental frequencies of rotating components inside or outside the plant;

[0064] - Identifying peaks that are not proportional to known fundamental frequencies of rotating components inside or outside the plant; and

[0065] - Performing steps c), d), e) and f) for the peaks thus identified, using an amplitude risk scale for the risk assessment according to step d) which rates the amplitude risk for the identified peaks as lower than another amplitude risk scale which rates the amplitude risk, e.g., for peaks with a peak frequency proportional to known fundamental oscillations of other rotating components.

[0066] Page 15, Figure 4 illustrates a correspondingly modified amplitude risk scale. In this case, peaks P4 and P6 could each exhibit a peak frequency that is not proportional to known fundamental frequencies of rotating components inside or outside the system.

[0067] For the peaks P4, P5 and P6 shown in Figure 4, the following relationship of risks also results in comparison to P1, P2 and P3 according to Figure 2:

[0068] risk

[0069] P5 » P4 P5 « P2

[0070] P5 » P6 P4 < P1

[0071] P4 > P6 P6 ~ P3

[0072] Figure 4a shows a modified configuration where, compared to Figure 2, peak P3 has a significantly lower frequency and therefore just barely falls within the risk range. The following then applies to the risks:

[0073] P2 > P1 P2 > P3 P3 > P1

[0074] Figure 5 shows an example where the risk area R1 from Fig. 4a is assigned only an amplitude risk scale, but not a frequency risk scale. Furthermore, the peaks from Fig. 4a, previously P1, P2, and P3, have been renamed P4, P5, and P6. Assessing risks solely based on the amplitude risk scale carries the risk of misinterpretation. Specifically, evaluating only the amplitude risks in Figure 5 would indicate that the risk for peak P5 is significantly higher than for peak P4. Simultaneously, evaluating the amplitude risk would suggest that the risks of peaks P5 and P6 are approximately equal, while the amplitude risk of peak P6 is higher than that of peak P4.

[0075] Page 16, Figure 6 shows an example of considering only a frequency risk scale for assessing the risk to the plant. Such a sole consideration is also not recommended because—compared to a combined consideration of the amplitude and frequency risk scales—it would again lead to incorrect results. For example, if only the frequency risk were considered, the risk for peak P5 would be greater than for peak P4, the frequency risk for peak P5 would be greater than for peak P6, and the frequency risks for peaks P4 and P6 would be approximately the same.

[0076] However, any individual risk assessment, whether based solely on the amplitude risk scale or solely on the frequency risk scale, is misleading or even in fact incorrect compared to a combined consideration of both risk scales. Only such a joint or simultaneous consideration of both risk scales leads to a realistic and reliable assessment of the overall risk.

[0077] Then, for example, it would become apparent that the overall risk of peak P5 is significantly greater than the overall risk of peak P6 because the frequency risk of peak P5 is significantly greater than the frequency risk of peak P6, even though the pure amplitude risks of the two peaks are the same. Similarly, it would become apparent that the overall risk of peak P6 is greater than the overall risk of peak P4 because the amplitude risk of peak P6 is greater than the amplitude risk of peak P4, even though their frequency risks are approximately the same.

[0078] Figure 7 illustrates, by way of example, the arrangement of several risk areas within the frequency space, here the risk areas R1 and R2.

[0079] For each of these risk areas, individual amplitude and / or frequency scales can be specified, as illustrated above with reference to Figures 2 to 6.

[0080] Individual thresholds for defining countermeasures can also be defined for each of the risk areas R1 and R2, as explained above.

[0081] Page 17 The recommended countermeasures for the two risk areas can be defined solely with regard to an amplitude risk scale, solely with regard to a frequency risk scale, or with regard to a combined consideration of amplitude and frequency risk scales.

[0082] As mentioned in the introduction, the method according to the invention can be applied to a wide variety of different plant types. However, its application is particularly recommended for a rolling mill stand used to process the product in the form of a rolled product. The work process then takes place in the form of a rolling process, i.e., by rolling the rolled product. A rolling mill stand typically comprises at least two work rolls, which together create a roll gap for rolling the rolled product. The rolling mill stand typically has at least one actuator for adjusting the rolling mill stand and, in particular, the roll gap, and for influencing the rolling process. Components that can cause undesirable vibration behavior of the rolling mill stand include, for example, the rolls, roll bearings, rollers, bearings, and / or gears in transmissions.

[0083] The actuator could, for example, be a speed control for the rotary-driven work rolls. In process step e), the primary countermeasure recommended is to change the speed of the work rolls and thus the throughput speed of the rolled product through the rolling stand, and / or to implement this change by appropriately adjusting the speed control setting, in order to reduce undesirable vibration behavior and the associated operational risk for the rolling stand as a system.

[0084] In the case of a rolling mill as a plant with multiple rolling stands arranged one after the other in a single direction of travel, process steps a) to f) can be carried out individually and independently of one another, at least for some of the rolling stands. However, if speed control is present as the actuator, it is then necessary to follow the recommendations for changing the speed given for the individual rolling stands.

[0085] Page 18 to coordinate their work rolls and convert this into an optimal rotational speed for the work rolls of the last rolling stand of the rolling mill. The principle of maintaining mass flow must be observed.

[0086] This is achieved by multiplying the optimal rotational speed of the work rolls of the current rolling stand by the ratio of the cross-sectional areas of the rolled product material before the current rolling stand and after the last rolling stand of the rolling mill. In this way, the material flow is kept constant.

[0087] Constant mass flow states that the product of the velocity and cross-sectional area of ​​the rolled product must be constant at all times as it passes through a rolling stand or the rolling mill. Based on this principle, the velocity of the rolled product through the i'th rolling stand can be converted to the velocity of the rolled product through the i + 1'th rolling stand using the following formula (1): with

[0088] Ai Cross-sectional area of ​​the rolled product before the i'th rolling stand

[0089] Ai+i Cross-sectional area of ​​the rolled product before the i+ 1 'th rolling stand

[0090] Vi speed of the rolled product before the i'th rolling stand;

[0091] Vi+i speed of the rolled product before the i+ 1 'th rolling stand

[0092] The necessary conversion of the speed Vi of the rolled product before the i'th rolling stand into the rotational speed ni of the work rolls of the i'th rolling stand can then be carried out simply according to the following formula (2): n, = — with di = work roll diameter (2)

[0093] Page 19 Maintaining a constant mass flow avoids, on the one hand, quality problems, e.g., regarding the thickness or surface quality of the rolled product, and / or, on the other hand, production interruptions.

[0094] To calculate the optimal rotational speed for the work rolls of the last rolling stand, formulas (1) and (2) are successively applied to the individual rolling stands of the rolling mill until i+1 refers to the last rolling stand of the rolling mill.

[0095] According to procedure step e), several countermeasures can also be proposed to reduce the risk. In particular, in the case of a rolling mill, in addition to changing the rotational speed of the work rolls via the speed control as a primary countermeasure, a secondary countermeasure can also be taken by adjusting the position of the pressure cylinders on the roll mounting blocks in the rolling mill. The pressure cylinders serve to move the work rolls, in particular, in or against the rolling direction in the rolling mill.

[0096] Alternatively or additionally, i.e. as an alternative secondary countermeasure or as a tertiary countermeasure, a specific adjustment of the rolling plan for the rolling stand or the rolling mill can also be provided, for example in the form of a change or adjustment of the thickness reduction at at least individual rolling stands and / or in the form of a change in the passes of the metal strip between two rolling stands.

[0097] The rolling mill can be a hot rolling mill for hot rolling of the metal strip or a cold rolling mill for cold rolling of the metal strip.

[0098] The countermeasures to be implemented according to the inventive method can be set not only in a real plant, in particular in a real rolling mill, but also within the framework of a simulation of the plant or parts thereof. In both cases, i.e., both during the actual operation of the plant and

[0099] Page 20 also applies to their simulation, allowing the effects of the recommended and implemented countermeasures on the operation of the plant or its components to be advantageously observed directly. The use of a simulation model of the plant or parts thereof, for example in the form of digital twins, can be advantageously employed to determine critical eigenmodes in order to identify critical frequencies during plant operation. By considering the results of the vibration analysis according to the invention and / or the recommended countermeasures, the simulation as a whole can be improved, which in turn can lead to further improvements in the method according to the invention and the countermeasures recommended therein.

[0100] The above-mentioned problem is further solved by a computer program product according to claim 22. The computer program product can be loaded into the memory of a digital computer and comprise software code sections with which the process steps b) to f) are carried out while the plant, in particular the rolling stand - optionally also only as a simulation - is operated and vibrations at the plant are detected in the form of a first temporal vibration signal with at least one acceleration sensor according to process step a) while the computer program product is running on the computer.

[0101] Finally, the aforementioned problem of the invention is solved by the rolling mill stand according to claim 23. As already mentioned above, the rolling mill stand comprises two work rolls which together form a roll gap for rolling a rolled product; at least one acceleration sensor for detecting vibrations of the rolling mill stand; at least one actuator for adjusting the rolling mill stand, in particular its work rolls, and for influencing the rolling process; and a control unit for controlling the at least one actuator. The rolling mill stand according to the invention is characterized in that the control unit is configured to control the actuator in accordance with the countermeasures recommended for reducing risk when carrying out the method.

[0102] Page 21 For this purpose, the control system includes the said computer with internal memory in which software code sections of the computer program product are stored for carrying out the method according to the invention while the rolling stand is operated and vibrations on the rolling stand in the form of at least the first temporal vibration signal are detected with the accelerometer according to step a).

[0103] Finally, it should be mentioned that the inventive method, or its testing and assessment of the risk according to process steps c) and d), can also be used to carry out a trend assessment by comparing the results from process steps c) and d) according to a current execution of the method with the results from previous runs of the method.

[0104] Overall, the method according to the invention offers a simple, cost-effective, easily integrated, and retrofittable software solution. The method provides reproducible recommendations for adjusting a system, independent of the operator's experience and decisions; however, the ultimate responsibility should always remain with the operator. The countermeasures recommended according to the method can lead to an increase in speed and thus an increase in production, but only insofar as quality requirements regarding thickness, flatness, and surface finish of the rolled product are maintained or corresponding losses are prevented.

[0105] When the inventive method is carried out in a system with active vibration damping in a rolling mill stand, vibrations are suppressed in this stand. This means that the peak amplitudes are sometimes small and the peak frequencies are not always discernible. Therefore, capturing the vibrations at the respective stand, as required for carrying out the inventive method, is not readily possible. In this case, this problem can be remedied by incorporating available information from the active system.

[0106] Page 22 Vibration damping system, such as the control signal of the system and its spectral analysis.

[0107] Page 23 Reference List

[0108] R1 Risk area

[0109] R2 risk area P1 peak

[0110] P2 Peak

[0111] P3 Peak

[0112] P4 Peak

[0113] P5 Peak P6 Peak

[0114] Page 24

Claims

Patent claims:

1. A method for operating a plant, for example a rolling mill, for processing a product in a work process, comprising the following steps in a first pass n=1: a) detecting vibrations on the plant in the form of a first temporal vibration signal with at least one first acceleration sensor while the plant is in operation; b) transforming the first vibration signal in a first time interval into the frequency domain, resulting in a first amplitude spectrum for the first time interval; c) defining at least one risk zone with at least one associated risk scale in the amplitude spectrum; checking whether at least one peak of the amplitude spectrum extends at least partially into the risk zone and interpreting this – if so – as a potential risk in the operation of the plant;d) Assessing the magnitude of the risk represented by the at least one peak extending into the risk area, using the risk scale assigned to the risk area; e) Determining at least one suitable countermeasure, in particular in the form of a suitable change to the plant settings or in the form of replacing a defective component of the plant, in order to change the magnitude of the risk determined in step d) in a desired manner or to maintain it at the same level; and f) Outputting the determined countermeasure to a plant controller and / or to a plant operator and / or storing the countermeasure.

2. The method according to claim 1, characterized in that, Page 25 that the risk scale is an amplitude risk scale for assessing an amplitude risk and / or a frequency risk scale for assessing a frequency risk.

3. A method according to one of the preceding claims, characterized in that individual risk scales are provided for different risk cases, and that in step e) the countermeasure taken to change the magnitude of the risk determined in step d) in a desired manner or to maintain it unchanged is selected depending on the risk case, wherein, for example, a higher risk or less severe countermeasures can be selected for output-optimized operation of the plant than if the plant is to be operated in a quality- or maintenance-optimized manner.

4. Method according to one of claims 2 or 3, - after completion of step b) - characterized by: - Check whether at least one of the peaks of the amplitude spectrum has a peak frequency that is proportional to known fundamental frequencies of rotating components inside or outside the system; - Identifying such peaks; - Performing steps c), d), e) and f) for the peaks thus identified, using a frequency risk scale for the risk assessment according to step d) which rates the frequency risk lower for peaks with frequencies not proportional to the fundamental frequencies than for peaks with frequencies proportional to the fundamental frequencies.

5. Method according to one of claims 2 or 3, - after completing step b) - characterized by Page 26 - Check whether at least one of the peaks of the amplitude spectrum has a peak frequency that is not proportional to known fundamental frequencies of rotating components inside or outside the plant; - Identifying such peaks; and - Performing steps c), d), e) and f) for the peaks thus identified, using for the risk assessment according to step d) an amplitude risk scale which rates the amplitude risk for the identified peaks as higher, reduced or unchanged than another amplitude risk scale which rates the amplitude risk e.g. for peaks with a peak frequency proportional to known fundamental oscillations of other rotating components of the plant.

6. Method according to one of the preceding claims, characterized in that step e) optionally also includes identifying the component for whose peaks an increased risk was identified in the risk assessment in step d); and that in step f) the component thus identified is signaled to the operator or to the automatic process control of the plant, optionally including the output of maintenance recommendations for this component, in particular if it is determined that the respective risk has increased for a currently processed product compared to a previously processed product.

7. Method according to one of the preceding claims, characterized in that the recommended countermeasure is initiated in real time during the current work process for the processing of the currently processed product and / or as a preset for a subsequently processed product. Page 27 8. Method according to one of the preceding claims, characterized in that the method is carried out by a self-learning algorithm.

9. Method according to one of the preceding claims, characterized in that the amplitude spectrum generated in step b) is interpolated in the frequency domain before its peaks are tested in step c).

10. Method according to one of the preceding claims, characterized in that in step a) the operation of the plant means the following alternatives: - an idle operation of the plant, during which no product is processed; or - normal operation of the plant, during which the product is processed.

11. Method according to one of claims 2 to 10, characterized in that in step d) the risk assessment is carried out by checking whether the peak with its amplitude on the amplitude risk scale exceeds an amplitude risk threshold and / or whether the peak with its frequency on the frequency risk scale exceeds a frequency risk threshold or whether the peak with its amplitude and frequency exceeds or falls below an overall threshold based on a combination of the two risk scales and, depending on the result, falls into a first partial risk area below the respective threshold, into a second partial risk area between two thresholds or into a third partial risk area above one of the thresholds.

12. Method according to claim 11, characterized in that if the peak with its amplitude and / or frequency falls below one of the threshold values ​​in the first partial risk area, as a countermeasure Page 28 It may be planned to increase the actual operating speed of the plant and observe the effects of this change; or that if the peak with its amplitude and / or frequency falls into the second sub-risk area between two of the thresholds, the countermeasure may be to maintain the current actual speed of the plant; or that if the peak with its amplitude and / or frequency falls into the third sub-risk area above one of the thresholds, the countermeasure may consist of recommending a reduction of the actual speed.

13. Method according to one of the preceding claims, characterized in that the following step g) follows the method step f): g) Implementing the countermeasure in the form of a corresponding change in the settings of the plant, and further operation of the plant with the changed setting.

14. Method according to claim 13, following method step g), characterized by simple or multiple repetitions of steps a) to g) for an n=n+1'th time period with n=2 to N, wherein the n'th time period with n>2 lies in a first period while a first product is being processed, or in a second period while a second product is being processed, wherein at each repetition in method step b) a new n+Ttes amplitude spectrum is generated which, in the case of a changed risk assessment according to method step d), necessitates a new countermeasure according to method step f).

15. Method according to claim 14, characterized in that Page 29 that the repetitions end when either a predetermined number of repetitions is reached or when a currently processed product has finished being processed.

16. A method according to one of the preceding claims, characterized in that the system comprises at least one rolling stand for processing the product in the form of a rolled product by rolling during a rolling process; wherein the rolling stand has two work rolls which together open a roll gap for rolling the rolled product; wherein the rolling stand has at least one adjusting element for adjusting the rolling stand and influencing the rolling process; and wherein the components of the rolling stand as a system are, for example, rolls, roll bearings, rollers, bearings and / or gears in transmissions.

17. Method according to claim 16, characterized in that the actuator is a speed control for the rotary-driven work rolls; and that in step e) as a countermeasure, a change in the speed of the work rolls and thus the throughput speed of the rolled product through the rolling stand is primarily recommended and / or brought about by a suitably appropriate change in the setting of the speed control.

18. Method according to claims 16 and 17, characterized in that – in the case of a rolling mill as a plant with a plurality of rolling stands arranged one behind the other in a through-running direction – steps a) to e) are carried out individually and independently of one another, at least for some of the rolling stands; and Page 30 that, if speed control is available as an actuator, the recommendations given for the individual rolling stands for changing the speed of their work rolls are coordinated and converted into an optimal speed for the work rolls of the last rolling stand, according to the principle of maintaining mass flow.

19. Method according to claim 18, characterized in that the coordination of the rotational speeds of the work rolls and their conversion into the optimal rotational speed for the last rolling stand is carried out according to the principle of maintaining mass flow as follows: with Ai Cross-sectional area of ​​the rolled product before the i'th rolling stand Ai+i Cross-sectional area of ​​the rolled product before the i+ 1 'th rolling stand Vi speed of the rolled product before the i'th rolling stand; Vi+i speed of the rolled product before the i+ 1 'th rolling stand, where the conversion of the speed vi of the rolled product into the The rotational speed of the working rollers is determined according to the following formula (2): with the rotational speed of the working rollers Vi speed of the rolled product di diameter of the working rolls.

20. Method according to one of claims 17 to 19, characterized in that in step e) in addition to changing the rotational speed of the working rollers Page 31 Optionally, as a countermeasure via the speed control, a change is made in the positioning of pressure cylinders on the mounting pieces of the rolls of the rolling stand to move the rolls in or against the rolling direction; and / or that in step e) in addition to the primary recommendation to set a specific speed of the work rolls, optionally as a countermeasure via the speed control, a specific adjustment of the pass plan is initiated, for example, the adjustment of the thickness reductions and / or the draws of the metal strip on at least some of the rolling stands.

21. Method according to one of claims 16 to 20, characterized in that the rolling process is a process for hot or cold rolling of the metal strip.

22. Use of the countermeasures recommended according to the method of one of the preceding claims in the simulation of the plant or parts of the plant to simulate the effects of the countermeasures on the operation of the plant or parts thereof.

23. Computer program product that can be loaded into the memory of a digital computer and comprises software code sections with which the process steps b) to e) according to at least one of the preceding process claims are carried out while the plant - optionally also only as a simulation - is operated and vibrations on the plant are detected in the form of a first temporal vibration signal with at least one acceleration sensor according to process step a), and the computer program product runs on the computer.

24. Rolling mill, in particular a cold rolling mill, with two work rolls which together form a roll gap for rolling a rolled product; at least one acceleration sensor for detecting vibrations Page 32 of the rolling stand; at least one actuator for adjusting the rolling stand, in particular its work rolls, and for influencing the rolling process; and a control system for controlling the at least one actuator; characterized in that the control system is configured to control the actuator in accordance with the countermeasures recommended when carrying out the method according to one of claims 1 to 21, in order to change the magnitude of the risk to the plant determined in step d) in a desired manner or to maintain it at an unchanged level.

25. Rolling stand according to claim 24, characterized in that the control system has a computer with an internal memory in which software code sections are stored for carrying out at least one of the process steps according to the method claimed in claims 1 to 21, while the rolling stand is operated and vibrations on the rolling stand are detected by the accelerometer in the form of the first temporal vibration signal. Page 33

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