JP2012107811A - Radiant tube having defect self-detection function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiant tube where a radiant tube in which a defect such as a crack has occurred during operation can be easily specified by imparting a self-detection function for detecting defects such as a crack to the radiant tube itself, and which allows release from inspection work that is extremely high in load and an improved level of operation stability.SOLUTION: After coating an insulating material 12 having heat resistance on the entire surface of a radiant tube body 11, a conductive material 13 is continuously wrapped in a spiral over the entire length of the radiant tube body 11 on the surface of the insulating material 12. A circuit is formed by mounting a power source 21 and a lamp 22 on the conductive material 13. By turning off the lamp 22, the generation of the crack of the radiant tube body 11 is detected.

Description

  The present invention relates to a radiant tube having a function of self-detecting defects generated in the radiant tube.

  In general, in an annealing facility such as a steel production process, a burner (radiant tube burner) using a radiant tube (heating radiation tube) is often used as a heating means. For example, it is used for annealing furnaces such as CAL (continuous annealing line) and CGL (continuous hot dip galvanizing line), and the number of these radiant tubes reaches several tens to several hundreds in one furnace. In order to properly anneal materials (steel strips, etc.) that pass through an annealing furnace, these radiant tubes must of course be healthy. To that end, it is necessary to replace the radiant tubes regularly. It is. However, there is a demand to continue using the radiant tube for as long as possible in terms of both cost and operation, and depending on operational reasons, there are situations where it is necessary to continue using it even if periodic replacement is omitted. .

  On the other hand, in the annealing furnace, it is necessary to change the heat generation amount of the radiant tube depending on the material (steel strip or the like) that passes basically in a high temperature atmosphere of several hundred degrees. Also, when repairing an annealing furnace, it is necessary to lower the furnace temperature to near room temperature so that workers can enter the furnace, and then immediately raise the furnace temperature to the specified furnace temperature so that it can be put into normal production as soon as possible after repair. There is. As a result, the radiant tube is subjected to many repeated thermal loads and thermal stresses.

  For the reasons described above, the radiant tube exceeding the allowable limit may have a defect such as a crack during operation. As a result, if the internal pressure of the radiant tube is higher than the furnace pressure (internal pressure), the atmosphere inside the furnace becomes abnormal due to the combustion gas leaking from the inside of the radiant tube, and the surface of the steel strip is oxidized and the quality of the temper color, etc. Defects may occur. Conversely, if the internal pressure of the radiant tube is lower than the furnace pressure, the gas inside the furnace may be sucked from the crack, and as a result, the furnace pressure decreases, and the air outside the furnace is moved to any part of the furnace. As a result, the quality defect may occur in the same manner.

  Therefore, if a quality defect occurs on the surface of a steel strip or the like during operation, there may be a case where the radiant tube has been cracked. In that case, identify the radiant tube where the crack has occurred and take some measures. It is necessary to do. Often, this specific survey must be carried out while continuing the operation, but the vicinity of the annealing furnace is around 60 ° C where the ambient temperature is high due to radiation from the furnace wall, etc., so the burden of the survey work is very high. There is also a risk of heat stroke. Therefore, development of a technique that can easily identify a radiant tube that has cracked during operation is strongly expected.

  On the other hand, for example, techniques disclosed in Patent Documents 1 and 2 have been proposed for investigating a crack in a radiant tube.

  In the technique described in Patent Document 1, a probe for eddy current flaw detection is arranged outside a radiant tube, and a crack of the radiant tube is inspected nondestructively by eddy current flaw detection.

  In addition, the technique described in Patent Document 2 discloses that a radiant tube disposed in a heat treatment furnace filled with nitrogen gas or the like for oxidation prevention has a negative pressure in the radiant tube. In this state, air is circulated, the oxygen component of the air is analyzed on the entry side and the exit side of the radiant tube, and the presence or absence of cracks in the radiant tube is detected by a change in oxygen concentration.

Japanese Patent No. 2743109 JP-A-3-295435

  However, as a result of investigations by the present inventors, it has been found that the techniques described in Patent Documents 1 and 2 have the following problems.

  First, regarding the technique described in Patent Document 1, when a probe for eddy current flaw detection is arranged outside a radiant tube, a radiant tube with a temperature of several hundred degrees Celsius cannot be measured as it is, but in a state where it is close to room temperature. This method is premised on an offline survey, and is difficult to implement during operation.

  Moreover, although the technique described in Patent Document 2 can be implemented during operation, as described above, since the ambient temperature in the vicinity of the annealing furnace is high at about 60 ° C., such a thermal environment (high temperature Atmosphere) It is very expensive to conduct survey work to analyze the oxygen component of air by making the inside of the radiant tube negative pressure from the furnace pressure one by one for tens or hundreds of radiant tubes. It takes a lot of time and further improvements are desired.

  The present invention has been made in view of the above circumstances, and by providing a self-detecting function of defects such as cracks to the radiant tube itself, the radiant tube in which defects such as cracks have occurred during operation can be easily obtained. It is an object of the present invention to provide a radiant tube which can be specified as follows, and can be freed from extremely high-load investigation work, and as a result, increases the operational stability.

  In order to solve the above problems, the present invention has the following features.

  [1] A radiant tube characterized in that a conductive material is continuously applied to the surface of a radiant tube main body made of a material having low conductivity or is continuously wound.

  [2] The radiant tube according to the above [1], wherein the conductive material is continuously applied in a spiral shape on the surface of the radiant tube main body, or is continuously wound in a spiral shape.

  [3] It is characterized in that an insulating substance is applied to the surface of the radiant tube body, or a conductive substance is continuously applied after the surface is covered with an insulating substance, or continuously wound. The radiant tube according to [1] or [2].

  [4] A radiant tube comprising a radiant tube main body made of a material having low conductivity, and a conductive material continuously embedded therein.

  [5] The radiant tube according to [4], wherein a conductive substance is continuously embedded in a spiral shape inside the radiant tube main body.

  [6] The above-mentioned [1] to [1], wherein an energization circuit is established using the conductive substance, and it is detected that a defect has occurred in the radiant tube main body due to the energization circuit becoming incomplete. 5] The radiant tube according to any one of the above.

  In the present invention, the radiant tube itself has a self-detection function for defects such as cracks, and it is possible to easily identify a radiant tube in which defects such as cracks have occurred during operation. It can be linked to the release of the project and the level of operational stability.

It is a figure which shows the radiant tube which concerns on one Embodiment of this invention. In one Embodiment of this invention, it is a figure which shows the procedure which checks the soundness of a radiant tube. In one Embodiment of this invention, it is a figure which shows the other procedure which checks the soundness of a radiant tube.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a radiant tube 10 according to an embodiment of the present invention. In general, the shape of the radiant tube is often U-shaped or M-shaped, and the radiant tube 10 here is U-shaped, but the shape is not limited.

  In this embodiment, first, a heat-resistant insulating material (for example, a heat-resistant insulating paint) 12 is applied to the entire surface of the radiant tube body 11 made of a low-conductivity material (for example, silicon carbide), or The entire surface of the radiant tube body 11 is covered with a heat-resistant insulating substance (for example, heat-resistant acrylic resin) 12.

  Next, a conductive substance (for example, conductive paint) 13 is continuously applied to the surface of the insulating substance 12 at a spiral interval over the entire length of the radiant tube main body 11, or a conductive substance ( For example, a copper wire) 13 is continuously wound spirally over the entire length of the radiant tube body 11. Here, it is desirable that the spiral line of the conductive material 13 is as thin as possible and that the interval between the lines is as narrow as possible.

  After that, the conductive material 13 is energized to form an energization circuit. The circuit elements are a power source 21 and a lamp (or light emitting diode) 22.

  And as shown to Fig.2 (a), if the radiant tube main body 11 is healthy, since the electroconductive substance 13 is also continuous and the energization circuit is materialized, the lamp | ramp 22 will light. On the other hand, as shown in FIG. 2B, when a defect such as a crack occurs in the radiant tube main body 11, a disconnection 14 occurs in the conductive material 13, the circuit is not established, and the lamp 22 is turned off. Thereby, the defect of the radiant tube 10 (radiant tube main body 11) is detected instantaneously, and quick response becomes possible.

  The soundness of the radiant tube 10 (radiant tube body 11) may be checked by periodically monitoring the lighting state of the lamp 22.

  In addition, a sensor (voltage sensor, current sensor, etc.) may be installed instead of the lamp 22 and the detected values (voltage, current) may be monitored as shown in FIG. That is, when the detected value (voltage, current) becomes zero, a defect such as a crack has occurred in the radiant tube body 11. Incidentally, if the detection values of the sensors are monitored in this way, centralized monitoring of a large number of radiant tubes 10 becomes easy.

  Thus, in this embodiment, the radiant tube 10 itself has a self-detection function for defects such as cracks, and the radiant tube 10 (radiant tube main body 11) in which defects such as cracks have occurred during operation can be quickly performed. Therefore, a very high load investigation work itself is not necessary, and a defect investigation time such as a crack is also unnecessary, so that the radiant using the radiant tube 10 in which a defect such as a crack has occurred is used. By quickly extinguishing the tube burner, normal operation can be continued without stopping the operation. As a result, it directly leads to operational merits such as reduction of defective rate of steel strips and productivity improvement.

  In this embodiment, the conductive substance 13 is attached in a spiral shape, but it may be attached continuously even if it is not in a spiral shape. For example, the conductive material 13 may be attached so as to reciprocate in the longitudinal direction of the radiant tube body 11.

  In this embodiment, the surface of the radiant tube body 11 is covered with the heat-resistant insulating material 12 and the conductive material 13 is attached. The conductive material 13 may be directly attached to the surface of the radiant tube main body 11 without being covered with the conductive material 12.

  In this embodiment, the conductive substance 13 is attached to the surface of the radiant tube main body 11. Alternatively, the conductive substance 13 may be embedded in the radiant tube main body 11.

  The Example of this invention is shown.

  In this example, the soundness of the radiant tube 10 (radiant tube main body 11) was monitored based on the above-described embodiment of the present invention.

  That is, first, the insulating material 12 was applied to the surface of a new radiant tube body 11 by spraying. Thereafter, a normal φ1 mm copper wire 13 as a conductive material was continuously wound around the surface of the insulating material 12 at intervals of 5 mm to form an energizing circuit, the lamp 22 was incorporated, and the lighting of the lamp 22 was confirmed.

  And several radiant tubes 10 produced as mentioned above were prepared, and installed in the annealing furnace of the steel strip.

  Several months later, the lamp 22 installed in one of the radiant tubes 10 was extinguished, and thus the burner using the radiant tube 10 was immediately extinguished.

  Previously, cracks in the radiant tube could not be found, or it took a long time to identify the crack, so the burner using the radiant tube could not be extinguished and a quality defect occurred in the steel strip. The example did not cause any operational problems. As a result, it was possible to avoid the occurrence of downtime and surface quality defects of the steel strip due to the descending speed of the line without any difficulty.

  Later, when the radiant tube 10 that entered the furnace during periodic repair of the annealing furnace and the lamp 22 was turned off was checked, a crack with a width of about 1 mm × length of about 50 mm occurred on the surface of the radiant tube main body 11. It was confirmed that the copper wire 13 was disconnected at the position where the crack occurred. In addition, it was confirmed that the surface of the radiant tube main body 11 was healthy for the remaining radiant tubes 10 in which the lamps 22 continued to be lit.

10 Radiant tube 11 Radiant tube body 12 Insulating material 13 Conductive material 14 Disconnection 21 Power supply 22 Lamp

Claims (6)

  A radiant tube comprising a radiant tube body made of a material having low electrical conductivity, wherein the conductive material is continuously applied to the surface or continuously wound.   The radiant tube according to claim 1, wherein the surface of the radiant tube main body is formed by continuously applying a conductive material in a spiral shape or continuously winding in a spiral shape.   The insulating material is applied to the surface of the radiant tube main body, or the surface is covered with the insulating material, and then the conductive material is continuously applied or continuously wound. The radiant tube according to 1 or 2.   A radiant tube comprising a radiant tube body made of a material having low conductivity and a conductive material continuously embedded in the radiant tube body.   The radiant tube according to claim 4, wherein a conductive substance is continuously embedded in a spiral shape inside the radiant tube main body.   An energization circuit is established using the conductive substance, and it is detected that a defect has occurred in the radiant tube main body due to the energization circuit not being established. The described radiant tube.

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