Method for monitoring electric heating elements

Abstract

This invention provides a method for monitoring an electric heating element that can prevent false detection of spark generation during the stage when the applied current value is increased after the start of energizing the electric heating element. [Solution] A current-increasing step in which current is started to be supplied to the electric heating element used in the heating furnace and the current value is increased to a predetermined current value, and In the current value increase step, a spark occurrence determination step is performed to determine whether or not a spark occurs based on an abnormal change in the electrical information of the electric heating element. A method for monitoring an electric heating element, comprising: In the current value increase process, there is a detection invalid period T during which no abnormal change in the electrical information of the heating element is detected for a predetermined time after the start of energizing the heating element. n A method for monitoring electric heating elements, which involves setting the parameters.

Description

[Technical Field]

[0001] The present invention relates to a method for monitoring an electrically heated element used, for example, in the manufacture of glass fibers. [Background technology]

[0002] For example, when supplying molten glass to bushings for forming glass fibers or molded bodies for forming plate glass, it is necessary to keep the molten glass flowing inside the feeder warm and prevent excessive temperature drops. As a method for this, a method has been proposed in which an electric heating element is installed in the internal space of the feeder and the molten glass is heated by that heat (see, for example, Reference 1).

[0003] Electric heating elements may generate sparks when energized due to an abnormal increase in resistance. Sparks can damage the heating element itself and surrounding components, potentially disrupting subsequent operations. Therefore, it is desirable to detect sparks in an electric heating element and cut off the power supply to it. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2014 / 185132 [Overview of the project] [Problems that the invention aims to solve]

[0005] One method for determining spark occurrence is to continuously monitor the resistance value of an electrical heating element and determine that a spark has occurred if it falls outside the normal range. However, even if no spark occurs, the resistance value may fluctuate and fall outside the normal range due to factors such as unstable output control of the equipment, resulting in a false determination.

[0006] When an electric heating element is energized, the applied current is gradually increased, and once it reaches a predetermined operating current value, it is usually kept constant at that value. While sparks are relatively unlikely to occur when the current value is maintained at the operating current value, the above-mentioned misjudgment is particularly likely to occur when the applied current value is increased after the electric heating element is energized.

[0007] In view of the above circumstances, the present invention aims to provide a method for monitoring an electric heating element that can prevent false detection of spark generation during the stage when the applied current value is increased after the start of energizing the electric heating element. [Means for solving the problem]

[0008] [1] The present invention provides a method for monitoring an electric heating element, comprising: a current value increase step of starting to energize an electric heating element used in a heating furnace and increasing the current value to a predetermined current value; and a spark occurrence determination step of determining whether or not a spark occurs based on an abnormal change in electrical information in the electric heating element during the current value increase step, wherein in the current value increase step, a detection invalidation period is set during which no abnormal change in electrical information in the electric heating element is detected for a predetermined time after the start of energizing the electric heating element.

[0009] Spark generation is accompanied by abnormal changes in electrical information, such as an abnormal increase in the resistance value of an electrical heating element. By detecting such abnormal changes in electrical information, it is possible to determine that a spark has occurred in the electrical heating element. However, in the initial stages of the process in which the current value of the electrical heating element increases, the output control of the equipment tends to be unstable, making it easy for false detections of abnormal changes in electrical information to occur. Therefore, by setting a detection invalidation period during which abnormal changes in electrical information of the electrical heating element are not detected for a predetermined time after the start of energization of the electrical heating element, the above-mentioned false detections can be prevented. This improves the accuracy of determining spark generation in an electrical heating element.

[0010] [2] In the method for monitoring an electric heating element of the present invention, as described in [1] above, for example, resistance values ​​can be used as the electrical information.

[0011] [3] The method for monitoring an electric heating element of the present invention preferably further comprises, in [1] or [2] above, a power supply deactivation step of stopping the supply of power to the electric heating element after determining in the spark generation determination step that a spark has occurred in the electric heating element. In this way, if the electric heating element or surrounding components are damaged in connection with the spark generation of the electric heating element, it is possible to prevent further disruption to operations.

[0012] [4] In the method for monitoring an electric heating element of the present invention, it is preferable to keep the current value increase gradient constant in any of the above [1] to [3] steps. This makes it less likely for false detection of abnormal resistance changes to occur after the detection invalidation time has elapsed.

[0013] [5] In the method for monitoring the electric heating element, it is preferable that the current value rise gradient is 250 A / min or less as described in [4] above. By making the current value rise gradient relatively small in this way, even if a spark occurs during the current value rise process, the current value at that time can be kept relatively small, and damage to the electric heating element and surrounding components can be suppressed as much as possible.

[0014] [6] The method for monitoring an electric heating element of the present invention is preferable in any of the above [1] to [5] when the heating furnace is a heating furnace for manufacturing glass.

[0015] [7] The method for monitoring an electric heating element of the present invention is preferable in the case described in [6] above when the heating furnace is a feeder through which molten glass flows.

[0016] [8] The method for manufacturing glass fibers according to the present invention includes a step of heating and melting raw materials in a melting furnace to obtain molten glass, a step of flowing the molten glass through a feeder provided with an electric heating element, and a step of forming the molten glass into fibers by means of a bushing provided in parallel with the feeder. In the method for manufacturing glass fibers, when energizing the electric heating element, the monitoring method for the electric heating element described in [7] above is carried out.

Effects of the Invention

[0017] According to the monitoring method for the electric heating element of the present invention, it is possible to prevent misjudgment of spark generation at the stage of increasing the applied current value after the start of energization of the electric heating element.

Brief Description of the Drawings

[0018] [Figure 1] It is a longitudinal sectional view showing an outline of a glass fiber manufacturing apparatus. [Figure 2] It is a sectional view taken along line II-II in FIG. 1. [Figure 3] It is a flowchart showing the monitoring method for the electric heating element of the present invention. [Figure 4] It is a schematic graph for explaining an embodiment of the monitoring method for the electric heating element of the present invention.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, an embodiment in which the monitoring method for the electric heating element of the present invention is applied to a glass fiber manufacturing apparatus, particularly a feeder as a heating furnace, will be described with reference to the drawings. In the drawings, for convenience of explanation, a part of the configuration may be shown in an exaggerated or simplified manner. Also, the dimensional ratios of each part may be different from the actual ones.

[0020] FIG. 1 is a longitudinal sectional view showing an outline of a glass fiber manufacturing apparatus.

[0021] The manufacturing apparatus 1 comprises a melting furnace 2 that melts glass raw material Gr to form molten glass Gm, and a feeder 3 connected downstream of the melting furnace 2 and circulating the molten glass Gm inside. The walls that partition the melting space of the melting furnace 2 and the circulation space of the feeder 3 are made of refractory material such as brick.

[0022] An inlet 2a is provided at the upstream end of the melting furnace 2 for introducing glass raw materials Gr, which are a mixture of silica sand, limestone, soda ash, cullet, etc., into the furnace. A raw material supply means (not shown) such as a screw feeder is located at the inlet 2a.

[0023] The melting furnace 2 is further equipped with heating devices (not shown). These heating devices may include, for example, a gas burner or electric heater positioned above the molten glass Gm, or an electric heating device such as an electrode immersed in the molten glass Gm.

[0024] The glass raw material Gr introduced from the input port 2a is melted by heating with a heating device, thereby continuously forming molten glass Gm. The molten glass Gm flows into the feeder 3 from the downstream end of the melting furnace 2. The melting furnace 2 may melt the glass raw material Gr by gas combustion alone, by electric heating alone, or by a combination of gas combustion and electric heating.

[0025] At the bottom of the feeder 3, multiple bushings 4 made of platinum or a platinum alloy are provided at intervals in the longitudinal direction X of the feeder 3, i.e., in the flow direction of the molten glass Gm. Each bushing 4 is provided with multiple bushing nozzles (not shown). The molten glass Gm flowing down from each nozzle is stretched downward and formed into glass fibers Gf (glass filaments) of a predetermined diameter. After a sizing agent is applied, multiple glass fibers Gf are bundled together to form a glass strand.

[0026] Figure 2 is a cross-sectional view taken along line II-II in Figure 1. The feeder 3 is enclosed by a bottom wall 5, side walls 6a and 6b, and a ceiling 10, and is configured so that molten glass Gm flows on the bottom wall 5. Electric heating elements 11a and 11b are installed above the liquid surface of the molten glass Gm. The electric heating elements 11a and 11b have a U-shape and are fixed by inserting the terminals at both ends into the ceiling 10. As shown in Figure 1, the electric heating elements 11a, 11a... are installed so as to be aligned in the X direction of the feeder 3. Although not shown in Figure 1, electric heating elements 11b, 11b... are also installed in parallel with the electric heating elements 11a, 11a... so as to be aligned in the X direction of the feeder 3.

[0027] The electric heating elements 11a and 11b are electrically connected to the power supply 12. The power supply 12 may be an AC power supply or a DC power supply. In Figure 2, the two electric heating elements 11a and 11b are connected in series, but the figure is not limited to this, and multiple electric heating elements 11a, 11a... and electric heating elements 11b, 11b... arranged in the X direction in Figure 1 may be connected in series. Alternatively, each of the electric heating elements 11a and 11b may be connected to a separate power supply.

[0028] A state monitoring control unit 21 is connected to the electric heating element 11a. The state monitoring control unit 21 includes a potential difference acquisition unit 22, a resistance value calculation unit 23, an abnormality detection unit 24, and a spark generation determination unit 25. The state monitoring control unit 21 can be configured with a processor, memory, software, image display device, etc., which are not shown in the figures.

[0029] The potential difference acquisition unit 22 can measure the potential difference applied to the electric heating element 11a. Using the potential difference acquired from the potential difference acquisition unit 22 and the current value applied to the power supply 12, the resistance value applied to the electric heating element 11a can be calculated by the resistance value calculation unit 23. In this embodiment, the resistance value applied to the electric heating element 11a is used as electrical information. Alternatively, the potential difference acquired from the potential difference acquisition unit 22 may be used as electrical information.

[0030] The resistance value obtained by the resistance value calculation unit 23 is constantly monitored by the abnormality detection unit 24, and if an abnormal change in the resistance value is detected, the spark generation determination unit 25 determines whether or not a spark has occurred. An abnormal change in the resistance value of the electric heating element 11a refers to, for example, a situation where the difference between the measured resistance value and the average value of the resistance value over a predetermined period of time (for example, several seconds) exceeds a predetermined threshold. When a spark occurs in the electric heating element 11a, the resistance value rises sharply, so the above abnormal change in resistance value serves as an indicator for determining spark generation.

[0031] Figure 3 is a flowchart illustrating the method for monitoring an electric heating element according to the present invention. Figure 4 is a schematic graph illustrating embodiments of the method for monitoring an electric heating element according to the present invention, showing first and second embodiments with different current value rise gradients. These embodiments will be described in detail below based on Figures 3 and 4.

[0032] First, the first embodiment will be described. As shown in Figures 3 and 4, the application of current to the electric heating element 11a is started (step S1), and the current value is increased until a predetermined operating current value is reached. After reaching the operating current value, the current value is kept constant and the molten glass is heated. In this embodiment, an "abnormal change in resistance value" occurs in the electric heating element 11a at both time t1 and time t2.

[0033] In the current value increase process, the potential difference of the electric heating element 11a is continuously acquired by the potential difference acquisition unit 22 (step S2), and the resistance value calculation unit 23 calculates the resistance value based on the said potential difference and the current value acquired from the power supply 12 (step S3). Here, the resistance value calculation unit 23 calculates the average value R of the resistance value over a predetermined time immediately preceding the measurement. av The abnormality detection unit 24 calculates the measured resistance value and R at the same time. av Compare the resistance values ​​(Step S4). av If it is greater than R, proceed to step S5. av If the following conditions are met, return to step S2.

[0034] In this embodiment, for a predetermined time after starting energization of the electric heating element 11a, a detection invalidation time T during which an abnormal change in resistance value is not detected in the electric heating element 11a is set. Therefore, the spark generation determination unit 25 compares the time t from the start of the current value increase with the detection invalidation time T (step S5). For example, when the measurement time t is t1, since it is within the range of the detection invalidation time T, even if an abnormal change in resistance value occurs, detection is not performed and the process returns to step S2. On the other hand, the abnormal change in resistance value that occurred when the measurement time t was t2 is after the elapse of the detection invalidation time T, so detection is performed and it is determined that a spark has occurred (step S6). In the initial stage of the current value increase process of the electric heating element 11a, the output control of the device particularly tends not to be stable, the resistance value is likely to change, and false detection is likely to occur. Therefore, as described above, by setting the detection invalidation time T during which an abnormal change in resistance value occurring in the electric heating element 11a is not detected for a predetermined time after starting energization of the electric heating element 11a, false detection as described above can be prevented. Thereby, the determination accuracy of spark generation in the electric heating element 11a can be improved. n The detection invalidation time T can be appropriately set according to the operating current value, the current value increase gradient, etc. For example, it can be set to 10 to 300 seconds, particularly 15 to 100 seconds. Also, when the time from the start of the current value increase until it reaches the operating current value is defined as the current value increase time T0, T / T0 can be set to 0.05 to 0.5, particularly 0.1 to 0.3. n For example, when the measurement time t is t1, since it is within the range of the detection invalidation time T, even if an abnormal change in resistance value occurs, detection is not performed and the process returns to step S2. n On the other hand, the abnormal change in resistance value that occurred when the measurement time t was t2 is after the elapse of the detection invalidation time T, so detection is performed and it is determined that a spark has occurred (step S6). n In the initial stage of the current value increase process of the electric heating element 11a, the output control of the device particularly tends not to be stable, the resistance value is likely to change, and false detection is likely to occur. n Therefore, as described above, by setting the detection invalidation time T during which an abnormal change in resistance value occurring in the electric heating element 11a is not detected for a predetermined time after starting energization of the electric heating element 11a, false detection as described above can be prevented.

[0035] Thereby, the determination accuracy of spark generation in the electric heating element 11a can be improved. n The detection invalidation time T can be appropriately set according to the operating current value, the current value increase gradient, etc. For example, it can be set to 10 to 300 seconds, particularly 15 to 100 seconds. n Also, when the time from the start of the current value increase until it reaches the operating current value is defined as the current value increase time T0, T / T0 can be set to 0.05 to 0.5, particularly 0.1 to 0.3.

[0036] After determining that a spark has occurred based on an abnormal change in resistance, it is preferable to stop the power supply to the electric heating element 11a (step S7). This prevents damage to the electric heating element 11a itself or surrounding components that may occur as a result of the spark, thus preventing disruption to subsequent operations. In this case, by switching the circuit supplying power to the electric heating element 11a to a bypass circuit (not shown), it is possible to stop the power supply to the electric heating element 11a while maintaining the power supply to the electric heating element 11b.

[0037] Furthermore, if the current rise gradient is not constant during the current rise process, the change in resistance may become large even if no spark occurs, potentially leading to a false detection of an abnormal change in resistance. Therefore, it is preferable to keep the current rise gradient constant. In this way, the detection invalid time T is reduced. n After this period, misjudgments of spark generation based on abnormal changes in resistance become less likely.

[0038] The above describes an example of spark generation detection for the electric heating element 11a, but as shown in Figure 2, the electric heating element 11b is also connected to the potential difference acquisition unit, and the presence or absence of spark generation based on abnormal changes in resistance can be determined in the same way.

[0039] The second embodiment differs from the first embodiment in that the current value rise gradient is smaller, but otherwise it is the same as the first embodiment. In the second embodiment as well, there is a detection invalid time T during which an abnormal change in the resistance value of the electric heating element 11a is not detected for a predetermined time after energizing the electric heating element 11a. n This is set. Therefore, the detection invalidation time T n Abnormal resistance value changes occurring within the range of time t1 are not detected, and detection invalid time T n Any abnormal change in resistance value that occurs at time t2 after the elapsed time is detected and determined to be a spark. This improves the accuracy of determining spark generation in the electric heating element 11a.

[0040] In the first embodiment, since the current value rise gradient is relatively large, the detection invalid time T n When a spark occurs after a certain period has elapsed (for example, at time t2), the current value tends to increase, and as a result, there is a risk of increased damage to the electric heating element 11a and surrounding components when a spark occurs. On the other hand, in the second embodiment, since the current value rise gradient is relatively small, the detection invalid time T n The current value at the time of spark generation (for example, at time t2) after a certain period of time can be kept relatively small. As a result, damage to the electric heating element 11a and surrounding components at the time of spark generation can be suppressed as much as possible. From the viewpoint of suppressing damage to the electric heating element 11a and surrounding components at the time of spark generation as much as possible, a small current value rise gradient is preferable, specifically 250 A / min or less, 200 A / min or less, 150 A / min or less, and especially 100 A / min or less. However, if the current value rise gradient is too small, it will take a long time to reach the operating current value, and productivity will decrease, so it is preferable that it be 10 A / min or more, 30 A / min or more, and especially 50 A / min or more. [Explanation of symbols]

[0041] 3 Feeders 11a, 11b Electric heating element

Claims

1. A current-increasing step in which current is started to be supplied to the electric heating element used in the heating furnace and the current value is increased to a predetermined current value, and In the current value increase step, a spark occurrence determination step is performed to determine whether or not a spark occurs based on an abnormal change in the electrical information of the electric heating element. A method for monitoring an electric heating element, comprising: A method for monitoring an electric heating element, comprising setting a detection invalidation period in which, during the current value increase process, abnormal changes in electrical information in the electric heating element are not detected for a predetermined time after energizing the electric heating element.

2. The method for monitoring an electric heating element according to claim 1, wherein the electrical information is a resistance value.

3. The method for monitoring an electric heating element according to claim 1, further comprising a power supply deactivation step of stopping the supply of power to the electric heating element after determining in the spark generation determination step that a spark has occurred in the electric heating element.

4. The method for monitoring an electric heating element according to claim 1, wherein the current value increase gradient is kept constant during the current value increase step.

5. The method for monitoring an electric heating element according to claim 4, wherein the current value rise gradient is 250 A / min or less.

6. The method for monitoring an electric heating element according to any one of claims 1 to 5, wherein the heating furnace is a heating furnace for manufacturing glass.

7. The method for monitoring an electric heating element according to claim 6, wherein the heating furnace is a feeder through which molten glass flows.

8. A process of heating and melting raw materials in a melting furnace to obtain molten glass. The process of flowing the molten glass through a feeder equipped with an electric heating element, A process of forming the molten glass into fibers using a bushing attached to the feeder, A method for manufacturing glass fibers, having the following characteristics: When energizing the aforementioned electric heating element, the method for monitoring the electric heating element described in claim 7 is performed. A method for manufacturing glass fibers.

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