Method and system for detecting a faulty cooling unit and rolling mill

Abstract

The present invention relates to a method for detecting a faulty cooling unit in a set of cooling units (106a), the cooling units (106a) being configured to provide coolant to working rolls (100a to 100b), the working rolls (100a to 100b) being arranged to process a workpiece (102) between the working rolls, the method comprising: varying a flow rate of coolant sprayed from a subset of the cooling units (106a); determining a flatness change value of the workpiece for at least each cooling unit in the subset of cooling units in response to varying the flow rate, the flatness change value indicating a flatness change of the workpiece downstream of the working rolls (100a to 100b); and detecting the faulty cooling unit based on comparing the flatness change value with a reference flatness change value.

Description

Technical Field

[0001] The invention relates to a method for detecting a faulty cooling unit in a collection of cooling units, the cooling units being configured to provide coolant to working rolls arranged to process a workpiece between the working rolls. The invention also relates to a corresponding control unit, a system and a rolling mill. Background Art

[0002] Metal rolling generally involves producing a metal workpiece with a reduced and uniform thickness by rolling the metal workpiece between two work rolls. In cold rolling, the metal workpiece is processed at a relatively low temperature below the crystallization temperature of the metal. Thermal control of the cold rolling mill is important because the temperature difference across the lateral direction of the work rolls affects the flatness of the product produced.

[0003] Thermal control can be provided by both a heating system and a cooling system. The cooling system typically includes nozzles arranged to spray a cooling fluid onto the work rolls. A faulty nozzle may affect flatness and, therefore, the quality of the final product.

[0004] Conventionally, an offline cooling test is performed in order to check the cooling system. To this end, the nozzles are controlled to spray the coolant onto the working rolls, whereby a visual inspection of the spray pattern is performed. However, this is both time-consuming and requires manual labor.

[0005] Therefore, there is room for improvement in evaluating cooling system operation in rolling mills. Summary of the invention

[0006] In view of the above and other deficiencies of the prior art, an object of the present invention is to provide a method for online diagnosis of the operation of a cooling unit in a rolling mill.

[0007] According to a first aspect of the present invention, there is provided a method for detecting a faulty cooling unit in a set of cooling units, the cooling units being configured to provide coolant to working rolls arranged to process a workpiece between the working rolls, the method comprising: varying a flow rate of coolant sprayed from at least one cooling unit; determining a flatness change value of the workpiece for at least at least one cooling unit in response to varying the flow rate, the flatness change value indicating a flatness change of the workpiece downstream of the working rolls; and detecting the faulty cooling unit based on comparing the flatness change value with a reference flatness change value.

[0008] The present invention is based at least in part on the recognition that by varying the flow rate of a cooling unit, the flatness of the workpiece will be changed, and that the change in flatness will be different for a fully functional cooling unit compared to a faulty cooling unit. Thus, the change in flow rate is used as an excitation on the work roll, and the measured change in flatness is the response to the excitation. Thus, the flatness response caused by the varying flow rate is evaluated for cooling unit diagnostics.

[0009] To this end, a flatness change value is determined. The flatness value indicates the flatness of the workpiece downstream of the cooling unit. The flatness value can be derived from a transverse strain profile of the workpiece, which is calculated based on the measured workpiece tension profile. Therefore, the flatness value can indicate the measured stress in the workpiece. Based on the transverse strain profile, the separated parts can be associated with the corresponding cooling unit by spatial correlation. Based on each of the multiple parts, a corresponding flatness change value can be determined, one flatness change value for each cooling unit. The flatness change value can be the difference between two flatness values. Flatness measurement techniques are known per se, including techniques based on measuring the workpiece tension profile.

[0010] The flatness change value indicates a change in flatness caused by changing the flow rate from one level to another. In other words, if the flatness of the workpiece is continuously measured, the effect of the change in flow rate on the flatness of the workpiece can be detected. Therefore, when the workpiece is fed between the work rolls, the flatness value changes in response to changing the flow rate of the coolant applied to the work rolls.

[0011] The cooling unit may include various components for spraying coolant onto the work rolls. The cooling unit may include nozzles and valves, where the valves open and close the supply of coolant to the nozzles. Pressurized coolant flows through the open valves to the nozzles, from which the coolant is sprayed onto the work rolls. Failures may occur anywhere in the cooling unit, but most commonly they occur in the valves or nozzles.

[0012] A fault in a cooling unit can be caused by many possible situations and can be of different natures. For example, the fault may be a change in the spray angle from the nozzle, a change in the width of the spray, a complete or partial blockage of the nozzle or a valve failure, etc.

[0013] A change in flow rate means that the flow rate changes from one flow rate level to another flow rate level.

[0014] The flatness change value may be an absolute value of a difference between a first flatness value and a second flatness change value of the workpiece determined for the associated cooling unit.

[0015] The evaluation of the flatness change value may be performed in various ways, taking into account the reference flatness change value. For example, when the flatness change value for one of the cooling units deviates by more than a threshold value relative to the reference flatness change value for the same flow rate change, an indication that the corresponding cooling unit is faulty may be provided. The deviation may be the absolute value of the difference between the flatness change value and the reference flatness change value.

[0016] In one embodiment, the reference flatness change value may be a flatness change value determined based on a response to changing the flow rate of at least another of the cooling units. Thus, the assessment of a faulty cooling unit may be based on comparing the flatness change values ​​with each other. Furthermore, if this is performed for a set of cooling units, a cooling unit having an abnormal flatness response (e.g. a flatness change value that deviates by more than a threshold from at least some of the flatness values ​​of the other cooling units, or preferably from a median of the flatness change values ​​of all or some of the other cooling units) may be inferred to be a faulty cooling unit. This advantageously provides improved automation of faulty cooling unit detection, which at least does not require a large number of prior reference measurements.

[0017] In an embodiment, the reference flatness change value is based on a statistical value determined based on a set of flatness change values ​​determined in response to varying the flow rates of a plurality of sets of cooling units. Preferably, the reference flatness change value may be a median of the flatness change values ​​for all or part of the cooling units in the set of cooling units. This provides a more accurate determination of whether a cooling unit is faulty.

[0018] In some embodiments, the flow rate of a subset of cooling units is maintained constant. For example, each cooling unit in the subset of cooling units has a closest adjacent cooling unit, and when the flow rate of at least one cooling unit changes, the flow rate of the closest adjacent cooling unit is maintained substantially constant. This is advantageously used to detect a deviation from the spraying angle or deviation from the spraying width of the cooling unit. Therefore, it can be determined whether the cooling unit sprays coolant on an adjacent area of ​​the work roll, where it should not spray coolant. The flow rate is substantially constant should be interpreted broadly as a small change in the flow rate can be allowed, but such a change should be small enough not to significantly affect the flatness change measurement.

[0019] In an embodiment, at least one cooling unit may include a cooling unit spaced apart from a cooling unit whose flow rate is substantially constant when the flow rate of at least one cooling unit varies. In a possible embodiment, for example, the flow rate varies per second cooling unit, per third cooling unit, per fourth cooling unit, or per fifth cooling unit.

[0020] In some embodiments, when the flow rate of at least one cooling unit increases, the flow rate of at least one other cooling unit decreases. This is advantageously used to maintain a constant total flow rate of the coolant.

[0021] In an embodiment, the duration between consecutive flow rate changes may be longer than a predetermined duration. The predetermined duration is advantageously long enough to make the cooling effect on the work roll caused by the changing flow rate detectable and at least partially stabilized in the flatness measurement. Thus, the cooling effect on the flatness of the workpiece may be delayed and once the effect occurs, the flatness of the workpiece drifts for a certain time. Thus, after the flow rate changes from one level to another, the flow rate remains constant for at least the predetermined duration. This allows most of the flatness change to occur before the flatness is measured.

[0022] Furthermore, for each successive flow rate change, the duration between the flow rate changes is preferably equal. In other words, the successive durations are equal. Furthermore, for each of the cooling units, the durations are equal.

[0023] Flatness can be measured in various possible ways and using various devices. One such device is usually called a shape meter, which measures the lateral shape of the workpiece and based on this can derive an indication of the flatness of the workpiece. In addition, so-called strain gauges can be used to perform flatness measurements. As known to those skilled in the art, strain gauges measure the lateral distribution of stress in the workpiece, for example in N / mm 2 The unit is , and based on this, an indication of the flatness of the workpiece can be derived.

[0024] In some embodiments, a flatness change value can be determined for a cooling unit whose flow rate is maintained substantially constant. This allows detection of faults associated with a cooling unit spraying when it should not, or detection of an adjacent cooling unit spraying in an erroneous area unrelated to the cooling unit.

[0025] Preferably, the workpiece may be a metal strip.

[0026] According to a second aspect of the present invention, a control unit is provided, the control unit being configured to detect a faulty cooling unit in a set of cooling units, the cooling units being configured to supply coolant to working rolls, the working rolls being arranged to process a workpiece between the working rolls, the control unit being configured to: in response to a change in flow rate of the coolant sprayed from at least one of the cooling units, acquire, for each of at least one of the cooling units, flatness data indicating a flatness change value of the workpiece, the flatness change value indicating a flatness change of the workpiece downstream of the working rolls; and detect the faulty cooling unit based on comparing the flatness change value with a reference flatness change value.

[0027] The control unit may be configured to control the valve for varying the flow rate of the coolant provided to the nozzle of the at least one cooling unit. Thus, the control unit may be communicatively connected to the control circuitry or control mechanism of the valve so that the control unit may send a control signal to the valve to cause the flow rate to vary.

[0028] For example, the magnitude of the flow rate change may depend on the material of the metal strip and the temperature difference between the coolant and the work rolls. The flow rate change should be large enough to cause a sufficiently large flatness change and be detectable. As an example, the flow rate change may be between 0% and 100% flow rate, or between 10% and 100% flow rate, or between 10% and 90% flow rate, between 20% and 80% flow rate, between 30% and 70% flow rate. However, other possible flow rate changes are also contemplated as long as the flatness response is detectable.

[0029] Further effects and features of the second aspect of the present invention are largely similar to those described above in conjunction with the first aspect of the present invention.

[0030] According to a third aspect of the present invention, a system for detecting a faulty cooling unit in a set of cooling units is provided, the cooling unit being configured to provide coolant to working rolls, the working rolls being arranged to process a workpiece between the working rolls, the system comprising: a sensing device for measuring a flatness value of the workpiece downstream of the working rolls; and a control unit, the control unit being configured to: receive flatness data from the sensing device, the flatness data indicating the flatness measured in response to a changing flow rate; determine, based on the flatness data, a flatness change value of the workpiece for each cooling unit in at least one cooling unit, the flatness change value indicating a change in flatness of the workpiece downstream of the working rolls; and compare the flatness change value with a reference flatness change value to detect a faulty cooling unit.

[0031] Further effects and features of the third aspect of the present invention are largely similar to those described above in conjunction with the first and second aspects of the present invention.

[0032] A rolling mill is also provided, comprising: at least two working rolls configured to process a workpiece between the at least two working rolls; and a system according to an embodiment of the third aspect of the present invention.

[0033] The rolling mill may be a cold rolling mill.

[0034] Further features and advantages of the present invention will become apparent when studying the appended claims and the following description. Those skilled in the art realize that different features of the present invention can be combined to create embodiments other than those described in the following, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] These and other aspects of the present invention will now be described in more detail with reference to the accompanying drawings showing example embodiments of the invention, in which:

[0036] Figure 1A Conceptually illustrates a working roll for processing a workpiece and a spray pattern of a coolant on the working roll according to one embodiment of the present invention;

[0037] Figure 1B is a conceptual diagram of a collection of cooling units that apply coolant to a work roll;

[0038] Figure 1C yes Figure 1A A side view of a working roll in FIG. 1 , and a conceptual diagram of a system according to an embodiment of the present invention;

[0039] Figure 1D is a diagram conceptually illustrating a flatness measurement result;

[0040] Figure 1E is a diagram conceptually illustrating absolute flatness change values;

[0041] Figure 2 is a flow chart of method steps according to an embodiment of the present invention; and

[0042] Figure 3 is a graph illustrating oppositely varying cooling unit flow rates according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In the detailed description of the present invention, various embodiments of the present invention are described herein with reference to specific embodiments. When describing the embodiments, specific terms are used for clarity. However, the present invention is not intended to be limited to the specific terms so selected. Although specific exemplary embodiments are discussed, it should be understood that this is done only for illustrative purposes. Those skilled in the relevant art will recognize that other components and configurations may be used without departing from the scope of the present invention.

[0044] Figure 1A Work rolls 100a and 100b are conceptually illustrated as being arranged to process a workpiece 102 therebetween. The work rolls 100a and 100b may be included in a rolling mill processing apparatus 500 such as a cold rolling mill, and the work rolls 100a and 100b are configured to process a workpiece in the form of a metal strip 102 .

[0045] During processing of the metal strip, as is known in the art, the flatness of the final product depends to some extent on the temperature variation across the width of the work rolls 100a and 100b. Therefore, effective thermal control of the work rolls 100a-100b is very important. Cooling of the work rolls 100a-100b is provided by applying a coolant to each work roll 100a-100b by a cooling unit arranged near the work rolls 100a-100b. Figure 1A , the spray patterns or zones 104 of the various cooling units are conceptually illustrated. Note that not all spray patterns or zones are numbered.

[0046] Figure 1B Conceptually illustrated is a top view of a collection of cooling units 106a to 106n arranged to provide coolant 101 to the work roll 100a. The flow rates from the cooling units can be individually controlled to vary the flow rate of coolant provided to the work roll 100a from each of the cooling units 106a to 106n.

[0047] Figure 1B A flatness profile 105 is conceptually illustrated, representing the flatness of the workpiece 102 downstream of the work rolls 100a-100b, e.g., a "conceptual tension profile". A set of flatness change values ​​Va to Vn can be determined from the flatness profile 105. Here, the flatness change value Vf is illustrated as the difference between the flatness value of the flatness profile 105 and the flatness value from a previously determined flatness reference profile 107. Thus, the flatness profiles 107 and 105 are profiles across the width of the workpiece 102 at two different time instances, the flatness profile 107 before the flow rate changes or at least before the effects of the changing flow rate are detected, and the flatness profile 105 in response to the changing flow rate. The flatness profile of the workpiece 102 can be continuously monitored, whereby a flatness change can be determined based on comparing the flatness profiles to each other. Note that a "flatness profile" can refer to a transverse strain profile that is indicative of the flatness profile of the workpiece.

[0048] Figure 1C 1 is a side view of work rolls 100a to 100b processing a work piece 102. The work piece 102 is fed between the rotating work rolls 100a to 100b, whereby the separation between the work rolls 100a to 100b is used to reduce the thickness of the work piece 102 between the work rolls 100a to 100b and to perform flattening. The cooling units 106a and 108 are arranged to provide a spray of coolant 101 to the respective work rolls 100a and 100b. Each cooling unit includes a valve 302 and a nozzle 308. It should be understood that Figure 1C The components shown in FIG. 1 are not drawn to scale but are conceptual diagrams shown to facilitate understanding of the embodiments presented herein.

[0049] As mentioned above, coolant is used for thermal control of the work rolls 100a-100b. Temperature variations across the lateral direction of the work rolls 100a-100b will affect the flatness of the workpiece downstream of the work rolls 100a-100b, for example at the location of a sensing device 202 configured to measure the flatness of the workpiece 102. Such a sensing device may be provided as a shape gauge, such as a so-called "strain gauge", which may be configured to measure changes in pressure against the roll caused by deviations from the flatness of the workpiece. Shape gauges are generally known per se.

[0050] Figure 1D The flatness measurement of a workpiece is conceptually illustrated. The measurement provides a set of flatness values, each represented by a bar in the graph 600, one of which is numbered 602. The flatness change value is the change in height of the bar in response to changing the flow rate of the coolant. For example, in response to changing the flow rate from one cooling unit from one level to another, the height of the bar 602 (i.e., the flatness value represented by the bar 602) may change to a second flatness value represented by a second bar 604 shown as a dashed line. The difference between the two flatness values ​​is the flatness change value V.

[0051] Figure 1E 700 is a graph of measured absolute flatness change values, one of which is indicated as 702, for flow rate changes in each cooling unit relative to position along the width of the workpiece. Graph 700 illustrates a reference flatness change value, which in a preferred embodiment is the median of the absolute flatness change values. Graph 700 further conceptually illustrates two different threshold levels applicable to the embodiments described herein. An upper threshold and a lower threshold. Thus, if the absolute flatness change value exceeds the upper threshold, or if the absolute flatness change value is below the lower threshold, it can be inferred that the corresponding cooling unit is faulty.

[0052] Figure 1E A deviation D between the absolute flatness change value 702 and the reference flatness change value is illustrated. If this deviation D is greater than a threshold value given by the difference between the reference flatness change value and, for example, an upper threshold level, it can be inferred that the corresponding cooling unit is faulty. Note that the difference between the reference flatness change value and the upper threshold value may be different from the difference between the reference flatness change value and the lower threshold value. Thus, there may be an upper threshold value and a lower threshold value, which are used depending on whether the absolute flatness change value is greater or less than the reference flatness change value.

[0053] Figure 2 is a flow chart of method steps according to an embodiment of the present invention. Figure 2 The method steps in Figures 1A to 1D Give a description.

[0054] The method is for detecting a faulty cooling unit in a set of cooling units 106 configured to provide coolant to working rolls 100a - 100b arranged to process a workpiece 102 between the working rolls.

[0055] In step S102 of the method, the flow rate of the coolant sprayed from at least one cooling unit 106f of the cooling units 106a to 106n is changed. In response to changing the flow rate, in step S104, for each cooling unit of the at least one cooling unit, a flatness change value Vf of the workpiece 102 is determined, see also Figure 1D V in . The flatness variation value indicates the flatness variation of the workpiece 102 downstream of the working rolls 100a to 100b. The flatness is determined by the sensing device 202 downstream of the working rolls 100a to 100b.

[0056] In step S106 , a faulty cooling unit is detected based on comparing the flatness variation value Vf with a reference flatness variation value.

[0057] In one possible implementation, when a flatness change value for one of the cooling units deviates from a reference flatness change value by more than a threshold, an indication that the corresponding cooling unit is faulty is provided.

[0058] For example, if the flatness variation value Vf exceeds the reference flatness variation value by more than an acceptable degree, ie, exceeds a threshold value, it can be inferred that the cooling unit 106f is a faulty cooling unit.

[0059] As above combined Figure 1B As described, the flatness change value reflects a change in the flatness of the workpiece. The flatness change value is the difference between flatness values ​​determined at different times when the workpiece is fed between the workpieces. Therefore, the flatness value used to determine the flatness change value reflects the flatness at two different times and therefore reflects the position on the workpiece. When processing the workpiece, at least one of the flatness values ​​can be determined in response to a changing flow rate. The difference between the flatness values ​​can be the absolute value of the difference. In other words, the flatness change value determined for the cooling unit is based on the evolution of the flatness in response to a change in the flow rate. Go to Figure 1C and Figure 1D, the sensing device 202 continuously measures the flatness of the workpiece 102 as the workpiece is fed through the work rolls 100a to 100b. Thus, before the flow rate changes from one level to another, or at least before the effects of the changing flow rate appear in the workpiece, a flatness value 602 can be obtained and compared with a flatness value 604 obtained after the flow rate change, when the cooling effect on flatness appears, see also reference Figure 3 The difference between the flatness values ​​reflects the flatness response caused by the flow rate change.

[0060] The reference flatness change value may be based on a flatness change value determined in response to changing the flow rate of at least another cooling unit in the cooling units. In other possible implementations, the reference flatness change value may be based on a statistical value determined based on a set of flatness change values ​​determined in response to changing the flow rate of a plurality of sets of cooling units. Preferably, the reference flatness change value may be a median value of the flatness change values ​​for the cooling units 106a to 106n. Further reference Figure 1D , a flatness change value V is determined for each of the flatness values, for example, each bar position shown in the figure. A flatness change value is determined for each of the cooling units, in other words, each bar 602 in the figure 600 can be associated with a corresponding cooling unit. Subsequently, the median of all flatness change values ​​is determined and used as a reference flatness change value. If the flatness change value deviates too much from the median of the flatness change value, i.e., is greater than a threshold value, it is inferred that the corresponding cooling unit is faulty. Other statistical values ​​may be applied, such as standard deviation (determining whether the flatness change value is within a predetermined number of standard deviations from the reference flatness value), percentiles, etc.

[0061] For example, now turn to Figure 1B , if it is the median of the flatness variation values ​​Va to Vn, or the median of the flatness variation values ​​for at least a subset of the cooling units (e.g., flatness variation values ​​Vb to Vm), the flatness variation value Vf will deviate significantly from the median of the flatness variation values ​​Va to Vn, and if only the subset is considered, will deviate significantly from the median of the subset Vb to Vm. In other words, the flatness variation value Vf can be considered to be abnormal with respect to the other flatness variation values, from which it can be inferred that the cooling unit 106f is faulty. Preferably, the median of all flatness variation values ​​is used, however, it is contemplated to use a subset of the flatness variation values. In the case of a subset, the end values ​​for the edge of the workpiece, such as Va and Vn, can be considered as a subset.

[0062] Typically, the duration between consecutive flow rate changes is longer than the predetermined duration. For example, a first flow rate change is performed to a first flow rate level, which is maintained for a duration equal to the predetermined duration. In this way, the effect on flatness caused by the changing flow rate can appear and be detectable in the flatness measurement result. After the measurement, the flow rate can be changed to a second flow rate level, and so on.

[0063] Figure 3 1 is a diagram schematically illustrating a flow rate variation scheme according to an embodiment of the present invention. The y-axis represents the flow rate and the x-axis represents time. In this diagram, the dotted line represents the relationship between the coolant flow rate of the first cooling unit 106b and time, and the solid line represents Figure 1B The relationship between the coolant flow rate of the second cooling unit 106e indicated in FIG. 1 and time. The dashed line may also represent the first subset of cooling units, and the solid line may equally well represent the second subset of cooling units. Thus, the flow rate for the subset of cooling units may be based on Figure 3 Make changes to the scheme in.

[0064] Figure 3 The flow rates of the two cooling units 106b and 106e are shown to be variable, and when the flow rate of the first cooling unit 106b increases, the flow rate of the second cooling unit 106e decreases, and vice versa. For example, at time t1, the flow rate of the first cooling unit 106b increases from F1 to F2, while the flow rate of the second cooling unit 106e decreases from F2 to F1. At time t2, the flow rate of the first cooling unit 106b decreases from F2 to F1, while the flow rate of the second cooling unit 106e increases from F1 to F2.

[0065] Before switching to another flow rate, a duration T for maintaining the flow rate elapses from t1 to t2 to allow the effect of the flow rate change on the flatness of the workpiece to occur and be measurable. Flatness is measured before the duration ends, but after the predetermined duration Tth has elapsed to ensure that the flatness effect is measurable.

[0066] For each successive flow rate change, the duration T during which the flow rate is maintained constant (i.e., the duration between flow rate changes) is preferably equal, in other words, the continuous durations are equal. In addition, the durations for each cooling unit in the cooling unit are preferably equal. Figure 3 As shown in , the duration T is the same for consecutive durations between flow rate changes. Furthermore, it is preferred that the flatness measurements for determining the flatness change values ​​are performed after an equal time (eg a predetermined duration Tth) has passed since the corresponding flow rate changes.

[0067] For two cooling units or two subsets of cooling units, varying the flow rates in opposite directions advantageously maintains the total flow of coolant closer to constant than if the flow rates of all cooling units were varied in the same manner. This provides better overall cooling during cooling unit testing.

[0068] To improve the ability to detect overlapping coolant sprays, it is advantageous to keep at least one or two cooling units constant between cooling units of varying flow rates.

[0069] In other words, to further improve the ability to detect the effects of overlapping sprays, the flow rates of a subset of cooling units are maintained constant when the flow rates of the selected cooling units are varied. For example, the flow rates of cooling units 106c to 106d arranged between cooling unit 106b and cooling unit 106e may be maintained substantially constant.

[0070] In an advantageous embodiment, each cooling unit of the at least one cooling unit has a nearest neighbor cooling unit, for example, the above cooling units 106c to 106d where the flow rate is maintained constant are nearest neighbors to the corresponding cooling units 106b and 106e where the flow rate varies.

[0071] The at least one cooling unit 106a to 106n may include cooling units spaced apart from the cooling units, such as cooling units 106c to 106d, and when the flow rate of the at least one cooling unit varies, the flow rate of the cooling units 106c to 106d is maintained substantially constant.

[0072] In an embodiment, a flatness change value may be determined for a cooling unit whose flow rate is maintained constant. Thus, even for a cooling unit whose flow rate does not change in the current flow rate change, a flatness change value may be determined. This improves the ability to detect cooling units spraying coolant when they should not, or spraying zones receiving coolant when they should not, which may indicate a fault in an adjacent cooling unit.

[0073] The total number of cooling units or the number of cooling units in a subset are shown here for exemplary purposes only and may include any number of cooling units, depending on the particular mill setup at hand. For example, a mill may include 10, 15, 20, 25, 30, 35, 40, 50, 60 or any other number of cooling units.

[0074] The number of cooling units in the subset for which the flow rate is varied may be any subset of cooling units arranged to provide coolant to the work rolls. The subset may even be a single cooling unit, although a preferred embodiment includes having every third cooling unit in the subset. In other words, the flow rates of cooling units 106c, 106f, 106i, and 106l may be varied simultaneously to determine the flatness change value. The flow rates of the remaining cooling units may be maintained substantially constant. After the flatness change values ​​of cooling units 106c, 106f, 106i, and 106l are determined, the flow rates of the set of the remaining cooling units are varied, and so on, until the flatness change values ​​of all cooling units are determined.

[0075] Go to again Figure 1C In one embodiment, the control unit 300 is configured to detect a faulty cooling unit in the set of cooling units. As described above, the cooling units 106a to 106n, 108 are configured to provide coolant to the working rolls 100a to 100b, which are arranged to process the workpiece 102.

[0076] The control unit 300 is configured to acquire, for each of the at least one cooling unit, flatness data indicating a flatness change value of the workpiece 102 in response to a change in the flow rate of the coolant sprayed from at least one of the cooling units 106a to 106n. The flatness change value indicates a flatness change of the workpiece downstream of the work roll. In other words, the control unit 300 communicates with the sensing device 202 to receive the flatness data from the sensing device 202. The flatness data may include the flatness change value itself, or the control unit 300 processes the flatness data to calculate the flatness change value.

[0077] The control unit 300 is configured to detect a faulty cooling unit based on comparing the flatness change value with the reference flatness change value in the above-described manner.

[0078] The control unit 300 may be connected to a valve 302 that controls the flow rate of the cooling unit. The control unit 300 may receive a control signal from the valve 302 that the flow rate is changing, whereby after a predetermined duration threshold Tth has elapsed, the control unit acquires flatness data.

[0079] In other possible embodiments, the control unit 300 initiates a flatness measurement procedure to detect a faulty cooling unit. To this end, the control unit controls the valve 302 to change the flow rate of the coolant provided to the nozzle 308 of the corresponding cooling unit 106a to 106n. Therefore, the control unit 300 transmits a control signal to the valve 302 to instruct it to open or close, so that the flow rate of the cooling unit is changed.

[0080] The valve 302 is configured to control the flow of pressurized coolant from the reservoir to the nozzle through the component.

[0081] Turn again Figures 1A to 1C , and especially Figure 1C , further provides a system 400 for detecting a faulty cooling unit in a set of cooling units, the cooling units being configured to provide coolant to work rolls, the work rolls being arranged to process a workpiece between the work rolls. The system includes a sensing device 202 for measuring a flatness value of a workpiece 102 being processed downstream by the work rolls. The system also includes a control unit 300, the control unit 300 being configured to: receive flatness data from the sensing device 202, the flatness data indicating a flatness measured in response to a changing flow rate; based on the flatness data, for each cooling unit in at least one cooling unit, determine a flatness change value of the workpiece, the flatness change value indicating a flatness change of the workpiece downstream of the work rolls 100a to 100b; and compare the flatness change value with a reference flatness change value to detect a faulty cooling unit.

[0082] The system may include at least one valve 302 configured to control the flow of coolant from the coolant reservoir to the cooling unit.

[0083] It should be noted that the drawings are not drawn to scale but instead provide conceptual illustrations of the embodiments.

[0084] The control unit may include a microprocessor, a microcontroller, a programmable digital signal processor, or another programmable device. The control unit may also or alternatively include a dedicated integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. In the case where the control unit includes a programmable device such as a microprocessor, a microcontroller, or a programmable digital signal processor as described above, the processor may also include computer executable code that controls the operation of the programmable device.

[0085] Even though the invention has been described above with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art.

[0086] Moreover, variations to the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed invention, by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A method for detecting a faulty cooling unit in a set (106a to 106n) of cooling units, the cooling units being configured to provide coolant to working rolls (100a to 100b) arranged to process a workpiece (102) between the working rolls (100a to 100b), the method comprising: changing a flow rate of a coolant sprayed from at least one of the cooling units (S102); In response to varying the flow rate, determining (S104) a flatness change value of the workpiece, at least for the at least one cooling unit, the flatness change value indicating a flatness change of the workpiece downstream of the work roll; as well as A faulty cooling unit is detected (S106) based on comparing the flatness change value with a reference flatness change value. 2 . The method of claim 1 , wherein when the flatness change value for one of the cooling units deviates from the reference flatness change value by more than a threshold value, an indication is provided that the corresponding cooling unit is faulty. 3 . The method according to claim 1 , wherein the flatness change value is a difference between flatness values ​​determined at different times.

4. The method according to any one of claims 1 and 2, wherein the reference flatness change value is based on one or more of the flatness change values ​​determined in response to changing the flow rate of at least another one of the cooling units.

5. The method according to any one of claims 1 and 2, wherein the reference flatness change value is based on a statistical value determined based on a set of flatness change values ​​determined in response to varying the flow rate of a plurality of sets of the cooling units.

6. The method according to any one of claims 1 and 2, wherein the flow rate to a subset of cooling units is maintained substantially constant.

7. The method according to any one of claims 1 and 2, wherein each of the at least one cooling unit has a closest adjacent cooling unit, and when the flow rate of the at least one cooling unit changes, the flow rate of the closest adjacent cooling unit remains substantially constant.

8. The method according to any one of claims 1 and 2, wherein the at least one cooling unit comprises a cooling unit spaced apart from a cooling unit whose flow rate is maintained substantially constant when the flow rate of the at least one cooling unit varies.

9. The method according to any one of claims 1 and 2, wherein the duration between consecutive flow rate changes is longer than a predetermined duration.

10. The method according to any one of claims 1 and 2, wherein the flatness change value is determined for a cooling unit in which the flow rate is maintained constant.

11. The method according to any one of claims 1 and 2, wherein the at least one cooling unit comprises every second cooling unit, every third cooling unit, every fourth cooling unit or every fifth cooling unit in the set of cooling units.

12. A system (400) for detecting a faulty cooling unit in a collection of cooling units, the cooling units being configured to provide coolant to working rolls arranged to process a workpiece between the working rolls, the system comprising: a sensing device (202) for measuring a flatness value of the workpiece downstream of the working roll, and A control unit configured to: receiving flatness data from the sensing device, the flatness data indicating flatness measured in response to a varying flow rate, determining, for each cooling unit of at least one cooling unit, a flatness change value of the workpiece based on the flatness data, the flatness change value indicating a flatness change of the workpiece downstream of the work roll; as well as The flatness variation value is compared with a reference flatness variation value to detect a faulty cooling unit.

13. The system according to claim 12, the control unit being configured to control a valve (302) for varying the flow rate of the coolant provided to the at least one cooling unit.

14. A rolling mill (500), comprising: at least two working rolls configured to process a workpiece between the at least two working rolls; And a system according to any one of claims 12 and 13.

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