JP2014044087A - Nondestructive inspection device using pulse magnetic field, and nondestructive inspection method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nondestructive inspection device which can be applied to inspection of heat insulation piping or the like, and uses pulse magnetic field for accurately detecting an actual signal of a defect in a piping body without influenced by deformation of an iron sheet outside the insulation piping; and to provide a nondestructive inspection method thereof.SOLUTION: The nondestructive inspection device using a pulse magnetic field nondestructively inspects a defect of an insulation piping 2. The nondestructive inspection device includes a pair of excitation coils 3-1 and 3-2 which applies the pulse magnetic field through the insulation piping 2 and can be arranged at an arbitrary position of the insulation piping 2; a pulse power source 8 for applying a pulse voltage to at least one of the pair of excitation coils 3-1 and 3-2; a magnetism sensor 4-1 which is arranged at an outer circumference of the insulation piping 2 between the pair of excitation coils 3-1 and 3-2 and detects a magnetic field parallel to an axial center direction of the insulation piping 2; and means for detecting, with the magnetism sensor 4-1, pulse magnetic field generated when at least one of the excitation coils 3-1 and 3-2 is driven by the pulse power source 8 driven by the pulse power source 8, and analyzing a response of the pulse magnetic field detected by the magnetism sensor 4-1.

Description

  The present invention is a non-destructive flaw detection method that uses non-destructive flaw detection for corrosion, fatigue, cracks, and other defects in pipes made of steel and the like, and heat insulation, etc. The present invention relates to a destructive inspection apparatus and a nondestructive inspection method.

  Conventionally, as a method for inspecting a defect in a steel material, there are an eddy current flaw detection method and a magnetic flux leakage flaw detection method using magnetism. In the eddy current flaw detection method, an alternating magnetic field is applied to a measurement object, and a change in eddy current generated in the measurement object is observed. That is, when an alternating magnetic field is applied to the measurement target, the distribution of eddy current changes in the portion having a defect relative to the portion having no defect in the measurement target, so the magnetic field generated by the eddy current also changes. A defect inspection is performed by detecting a change in the eddy current by a magnetic sensor such as a search coil or a magnetoresistive element (MR). On the other hand, in the leakage magnetic flux flaw detection method, a DC or AC magnetic field is applied to a measurement object, and a magnetic flux leaking from a defective portion is detected by a search coil or a magnetic sensor.

  There are various shapes of measurement objects in the eddy current flaw detection method and leakage magnetic flux flaw detection method using magnetism, but as a method for inspecting piping made of steel materials, a through coil, an insertion coil, or a top coil Is known (see Non-Patent Document 1). In particular, as a form of a coil that measures a pipe as a measurement target, a penetration coil that measures the pipe through the coil and an insertion coil that inserts the coil into the pipe for inspection are well known. For example, when inspecting a pipe having a single layer structure, a penetration coil is often used, and defects on the pipe surface are inspected.

  In another method using an insertion coil, in general, the solution in the pipe is emptied, the coil is inserted into the pipe, a magnetic field is applied by the excitation coil, and a defect is detected by the search coil or magnetic sensor. Changes in the magnetic field due to are detected. As the magnetic field applied by the exciting coil, a periodic magnetic field such as a sine wave or a temporal waveform such as a pulse (pulse method) is used. In this method, the detection unit is separated from the excitation coil by a predetermined distance, and a magnetic field is applied to the pipe by the excitation coil. There is a remote field method for detection by a detection unit.

  Thermal insulation piping having a double piping structure in which the periphery of the piping is kept warm by a heat insulating material and is covered with an outer sheet metal such as a thin steel plate outside the heat insulating material is often used in plants and the like. However, when such a defect inspection of a heat insulating pipe is performed, since it has a complicated structure called a double pipe structure, it is difficult to apply a through coil. An interpolated coil can be used as it is for the corrosion inspection inside the heat insulation pipe having a double pipe structure. As one of flaw detection methods using an internal coil, a remote field method using a pulse wave has been reported (see Patent Document 1). However, in the case of heat insulating piping, not only corrosion inside the piping but also corrosion on the outer surface of the piping, that is, the piping surface covered with the heat insulating material, is likely to occur. For this reason, the signal obtained by the flaw detection method using an insertion coil becomes very weak. In general, since it is difficult to magnetically inspect the heat insulating piping, as a method for inspecting the corrosion of the piping surface, a visual inspection or the like is performed by removing the heat insulating material covering the piping surface.

  When the inspection is performed using magnetism from the outside of the heat insulation pipe having a double pipe structure, the distance between the excitation coil and the detection coil (magnetic sensor) is increased due to the presence of the heat insulating material. Is considerably larger than the pipe diameter and the presence of the outer sheet metal outside the heat insulating material causes a problem that the signal change due to the defect becomes small. For this reason, a highly sensitive superconducting quantum interference device SQUID is used as a magnetic sensor, and a method of taking the difference using two or more SQUIDs in order to remove environmental noise and extract only weak signals has been reported. . As one of the methods, the present inventor has reported a method of capturing a weak magnetic signal by applying an alternating magnetic field with a pair of through coils and performing lock-in detection (see Patent Document 2).

  In addition, as a defect inspection method for applying lock-in detection by applying an alternating magnetic field to adiabatic piping with a pair of through coils, a magnetic sensor using a magnetoresistive element (MR) is used to measure the component parallel to the central axis of the piping. The inventor previously reported what to do. (See Patent Document 3). In the inspection method described in Patent Document 3, a weak magnetic field change caused by a defect can be efficiently captured by detecting parallel components.

JP 2004-294341 A JP 2012-93095 A Japanese Patent No. 4487082

Nondestructive Inspection Technology Series “Eddy Current Testing I” Japan Nondestructive Inspection Association, pp. 32-43

  In particular, in the magnetic inspection method for insulative piping inspection, since the signal due to the defect of the piping is minute, there is a problem that the signal due to the defect is buried in the signal from the portion other than the defect. For this reason, as in Patent Documents 2 and 3 described above, the detection of defects is made highly sensitive by applying an alternating magnetic field such as a sine wave with a pair of through coils and performing lock-in detection and analyzing the signal intensity and phase. The inventor has developed an inspection method. However, in order to obtain a good signal by the inspection method, it is necessary to apply a large alternating magnetic field, and thus an alternating current power supply with a large amount of power supply is required. For example, when inspecting piping in a wide plant, a large power source is not portable, and when the power source cannot be transported, there is a problem of power supply to the inspection device such as where the power is taken from, which is a big problem in the inspection. There was a problem. In addition, a simpler circuit configuration that does not require a lock-in detection circuit or the like has been desired as the configuration of the measurement circuit included in the inspection apparatus.

  Therefore, the present invention can be applied to heat insulation piping inspection and the like, and the power capacity load is small, and a good magnetic signal can be obtained without lock-in detection as a circuit configuration. Nondestructive inspection using pulse magnetism An object is to provide an apparatus and a nondestructive inspection method.

The present invention has been proposed to solve the above problems, and the first aspect of the present invention is
It is a nondestructive inspection device using pulse magnetism for nondestructive inspection of defects in piping to be inspected,
A pair of exciting coils that are inserted through the pipe to be inspected and can be arranged at an arbitrary position with respect to the pipe to be inspected;
A pulse power supply for applying a pulse voltage to at least one of the pair of exciting coils;
A magnetic sensor that is disposed between the pair of excitation coils on the outer peripheral surface of the pipe to be inspected and detects a magnetic field parallel to the central axis direction of the pipe to be inspected;
Means for detecting a pulse magnetic field generated when at least one of the pair of excitation coils is driven by the pulse power source by the magnetic sensor, and analyzing a response of the pulse magnetic field detected by the magnetic sensor; This is a nondestructive inspection device using pulse magnetism.

The second aspect of the present invention is:
A power supply switching circuit that switches the current direction of one excitation coil and the other excitation coil of the pair of excitation coils to the same direction or the opposite direction, or switches to drive only one of the pair of excitation coils, This is a nondestructive inspection device using pulse magnetism.

The third aspect of the present invention is:
It is a nondestructive inspection apparatus using pulse magnetism provided with an electrical connection connector capable of dividing and connecting each excitation coil at a predetermined position on the coil circumference of the pair of excitation coils.

The fourth aspect of the present invention is
A non-destructive inspection apparatus using pulse magnetism in which a plurality of the magnetic sensors are arranged on the outer peripheral surface of the inspection pipe between the pair of magnetic coils.

The fifth aspect of the present invention is:
A magnetic detection magnetic coil corresponding to each of the pair of excitation coils is provided at an adjacent position or the same position with respect to both or one of the pair of excitation coils, and one of the pair of excitation coils. Non-pulsed magnetism with means to generate a pulsed magnetic field only on one side, and to analyze the pulsed magnetic field response obtained with the magnetic detection magnetic coil at a position away from the one exciting coil that generated the pulsed magnetic field It is a destructive inspection device.

The sixth aspect of the present invention is
Using the nondestructive inspection device according to claim 1,
A method for nondestructive inspection of defects in the pipe to be inspected,
Applying the pulsed magnetic field to the pipe to be inspected by inserting the pipe to be inspected into the pair of excitation coils and driving the pair of excitation coils by the pulse power source;
A step of detecting a magnetic field generated by the pair of exciting coils in parallel to a central axis direction of the pipe to be inspected by the magnetic sensor;
And analyzing the pulse intensity and signal time attenuation in the output signal of the magnetic sensor to identify defects in the pipe to be inspected, and a nondestructive inspection method using pulse magnetism.

The seventh aspect of the present invention is
Using the nondestructive inspection device according to claim 5,
A method for nondestructive inspection of defects in the pipe to be inspected,
Applying the pulsed magnetic field to the pipe to be inspected by inserting the pipe to be inspected into the pair of excitation coils and driving the pair of excitation coils by the pulse power source;
A step of detecting a magnetic field generated by the pair of exciting coils in parallel to a central axis direction of the pipe to be inspected by the magnetic sensor;
Analyzing the pulse intensity and signal time attenuation in the output signal of the magnetic sensor;
Only one of the pair of excitation coils is driven by a pulse power source to generate a pulse magnetic field, and the pulse magnetic field response obtained by the magnetic detection magnetic coil at a position away from the excitation coil that generated the pulse magnetic field is obtained. A non-destructive inspection method using pulsed magnetism, comprising a step of identifying a defect in the inspection pipe by analyzing.

  According to the first aspect of the present invention, a magnetic field in the direction of the central axis of the pipe to be inspected can be applied to a predetermined location of the pipe to be inspected by a pair of exciting coils inserted through the pipe to be inspected. Further, by providing a magnetic sensor disposed between the pair of exciting coils on the outer peripheral surface of the pipe to be inspected, a magnetic field parallel to the central axis direction of the pipe to be inspected can be detected. The magnetic field generated by the exciting coil is transmitted to the magnetic sensor through the piping to be inspected. In the middle, the magnetic field in the direction of the central axis of the pipe to be inspected leaks to the outside, but the magnetic field propagated by corrosion and defects differs. Here, the magnetic field generated by driving the excitation coil with a pulsed power supply is a pulsed magnetic field, so that the rising magnetic signal detected by the magnetic sensor is timed at the time of rising of the pulsed magnetic field and the time zone during which a constant magnetic field is applied thereafter. Attenuates with. By analyzing the peak value and attenuation characteristics of the detected pulse magnetic signal, it is possible to detect defects such as corrosion and cracks in the pipe with higher accuracy.

  According to the second aspect of the present invention, the current direction of one excitation coil and the other excitation coil of the pair of excitation coils is switched to the same direction or the opposite direction, or only one of the pair of excitation coils is driven. A power supply switching circuit for switching to is provided. Thereby, when it drives with the electric current of the same direction with a pair of exciting coil, a magnetic field can be applied to a to-be-tested pipe in the same direction, and signal strength can be strengthened. In addition, when each pair of exciting coils is driven with currents in opposite directions, the applied magnetic fields entering the magnetic sensor cancel each other, so that only a signal change due to a defect can be extracted. In addition, when the inspection site of the piping to be inspected is a connection part or an end, the structure differs greatly at both ends of the piping to be inspected by driving only one excitation coil far from that part. Can also remove the effect.

  According to the third aspect of the present invention, by providing an electrical connection connector that can divide and connect a pair of excitation coils at predetermined positions on the circumference of the coil, the inspection pipe is passed through the excitation coil for inspection. Even when it is performed, the exciting coil can be appropriately separated from the piping to be inspected. For example, in a conventional through-type excitation coil, if there is no end to be introduced into the pipe to be inspected, the excitation coil cannot be installed unless the heat insulation pipe is cut off, but the excitation coil of the present invention is applied. Thus, the excitation coil can be divided and attached to the inspection pipe at any part of the inspection pipe.

  According to the fourth aspect of the present invention, a plurality of magnetic sensors are arranged on the outer peripheral surface of the inspection pipe between the pair of exciting coils, so that a defect is detected anywhere on the circumference of the inspection target pipe by the magnetic sensor. It can be identified and detected.

  According to the fifth aspect of the present invention, the magnetic detection magnetic coil is provided in a place adjacent to or the same place as both or only one of the pair of excitation coils, and a pulse magnetic field is applied to only one of the excitation coils. Means are provided for analyzing a pulse magnetic field response obtained by a magnetic coil for magnetic detection that is generated and separated from the excitation coil where the pulse magnetic field is generated. With this magnetic coil for magnetic detection, it is possible to detect changes in all magnetic field signals that have passed through the pipe to be inspected. By combining not only the pulse response of the magnetic sensor provided on the outer peripheral surface but also the information of the magnetic coil for magnetic detection, defects such as corrosion and cracks in the pipe can be detected with higher accuracy.

  According to the sixth aspect of the present invention, a pulse magnetic field parallel to the central axis of the pipe to be inspected can be applied to a predetermined location of the pipe to be inspected by driving the exciting coil with a pulse power supply. In addition, a signal generated from the pipe to be inspected can be captured at a place where the exciting coil is disposed. A signal captured by each magnetic sensor is a pulse-like magnetic response signal, and by analyzing the pulse intensity and signal time attenuation of the signal, a signal change due to a defect can be extracted with higher accuracy.

  According to the seventh aspect of the present invention, in accordance with the effect of the sixth aspect, information on the pulse magnetic field response transmitted through the entire inspection pipe obtained by the magnetic coil for magnetic detection can be added to the defect analysis. . By combining information from the magnetic sensor and the magnetic coil for magnetic detection in this way, signal changes due to defects can be extracted more accurately.

It is the schematic which shows the basic composition of the pulse magnetic inspection apparatus which concerns on Example 1 of this invention. It is the schematic which shows the structure of heat insulation piping. It is a figure which shows the heat insulation piping which has a defect, (a) is a cross-sectional schematic diagram which shows the heat insulation piping which has a defect, (b) is a photograph which shows the steel pipe surface inside the heat insulation piping which has a defect. It is a pulse magnetic response time waveform of the magnetic sensor when the adiabatic piping is not inserted. It is a comparison of pulse magnetic response time waveforms of a magnetic sensor when a pulse current is driven in the same direction through a pair of excitation coils and a normal heat insulation pipe and a defective heat insulation pipe are measured. It is a comparison of pulse magnetic response time waveforms of a magnetic sensor when a pulse current is driven in the same direction through a pair of excitation coils and a normal heat insulation pipe and a defective heat insulation pipe are measured. It is a pulse magnetic inspection apparatus concerning Example 2 of the present invention, and is a schematic diagram of an inspection part of a pulse magnetic inspection apparatus which arranged a plurality of magnetic sensors side by side. It is the pulse magnetic inspection apparatus which concerns on Example 3 of this invention, and is the schematic of the test | inspection part of the pulse magnetic test | inspection apparatus which made the test | inspection part separable and was easy to mount | wear with heat insulation piping. FIG. 11 is a schematic diagram showing a pulse magnetic inspection apparatus according to a fourth embodiment, which includes a pair of magnetic detection magnetic coils and a magnetic coil circuit for these magnetic detection magnetic coils in an inspection unit. Using the pulse magnetic inspection apparatus shown in FIG. 9, only one of the pair of excitation coils is driven, and the pulse magnetic response time waveform detected by the magnetic detection magnetic coil installed in the vicinity of the excitation coil on the opposite side is driven. This is a comparison between normal insulation piping and defective insulation piping.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In addition, members having similar uses and functions are denoted by the same reference numerals and description thereof is omitted.

FIG. 1 is a schematic diagram showing a basic configuration of a nondestructive inspection apparatus 1-1 (hereinafter referred to as a pulse magnetic inspection apparatus 1-1) using pulse magnetism according to an embodiment of the present invention.
The pulse magnetic inspection device 1-1 applies a pulse magnetic field to the heat insulation pipe 2 (see FIG. 2), which is the pipe to be inspected, and detects a change in the pulse magnetic field flowing through the heat insulation pipe 2, thereby detecting defects in the heat insulation pipe 2. A nondestructive inspection apparatus for flaw detection, an inspection unit 6-1 comprising a pair of excitation coils 3-1, 3-2, a magnetic sensor 4-1, and a cylindrical inspection unit base material 5-1, a magnetic sensor Circuit 7-1, pulse power supply 8, power supply switching circuit 9, and signal analysis device 10 as signal analysis means.

  The exciting coils 3-1 and 3-2 are a pair of coils, and can be disposed at an arbitrary position with respect to the heat insulating pipe 2 through the heat insulating pipe 2.

  The magnetic sensor 4-1 is a unit that is disposed between the pair of exciting coils 3-1 and 3-2 on the outer peripheral surface of the heat insulation pipe 2 and detects a magnetic field parallel to the central axis direction of the heat insulation pipe 2. is there.

  As shown in FIG. 2, the heat insulating pipe 2 is a cylindrical inspection object to be inspected by the pulse magnetic inspection apparatus 1-1 according to the present embodiment, and the heat insulating pipe 2 has a thickness of 7.2 mm. Steel pipe 2a. The periphery of the steel pipe 2a is covered with a heat insulating material 2b having a thickness of 50 mm, and the periphery of the heat insulating material 2b is covered with a molten zinc iron plate having a thickness of 0.3 mm as an outer cylinder 2c. Moreover, as a heat insulation piping with the defect used when test-evaluating the performance of the pulse magnetic inspection apparatus 1-1 which concerns on this embodiment, as shown in FIG. 3, the circumference of the center part of the steel pipe 2a surface which the heat insulation piping 2 has is shown. A heat insulating pipe having a concave thinning portion of 3.6 mm having a width of 10 mm along the direction and a defect depth half the thickness of the steel pipe 2 a was prepared. In order to distinguish the heat insulation piping 2 which formed the said defect in this steel pipe 2a surface from the heat insulation piping 2 without a defect, it calls the heat insulation piping 2A.

  The inspection unit 6-1 inserts the heat insulation pipe 2 which is the pipe to be inspected and applies a pulsed magnetic field, and detects a change in the magnetic field transmitted through the heat insulation pipe 2 by the magnetic sensor 4-1 including a magnetoresistive element. Here, as a magnetic sensor, in addition to a magnetoresistive element (MR element), a magnetic sensor capable of measuring magnetic signals from extremely low frequencies such as a magnetic impedance element, a Hall element, a flux gate, a superconducting quantum interference element (SQUID), etc. Can be used.

  The magnetic sensor circuit 7-1 is a circuit for driving the magnetic sensor 4-1, and measuring a magnetic field.

  The pulse power supply 8 can apply a pulse voltage to at least one of the pair of exciting coils 3-1 and 3-2. The pulse power supply 8 can output a square wave and can be driven at a predetermined repetition rate and duty ratio. The pulse power supply 8 is electrically connected to the power supply switching circuit 9.

  The power supply switching circuit 9 can switch the current direction of one excitation coil and the other excitation coil of the pair of excitation coils to the same direction or the opposite direction, or to switch only one of the pair of excitation coils. Circuit. The power source switching circuit 9 can select the direction of the current flowing through the pair of exciting coils 3-1 and 3-2 and operating both or only one of them. Here, if the current directions of both exciting coils 3-1 and 3-2 are operated in the same manner, a pulse magnetic field in the same direction can be applied to the heat insulating pipe 2.

  The signal analysis device 10 detects a pulse magnetic field generated when at least one of the pair of exciting coils 3-1 and 3-2 is driven by the pulse power supply 8 by the magnetic sensor 4-1, and the magnetic sensor 4. This is a signal analyzing means for analyzing the response of the pulse magnetic field detected by -1.

  Next, a method for inspecting the heat insulating pipe 2 using the pulse magnetic inspection apparatus 1-1 will be described.

  The inspection method applied to the pulse magnetic inspection apparatus 1-1 is a method for nondestructively inspecting a defect of the heat insulating pipe 2 that is the pipe to be inspected, and the heat insulating pipe 3-1 and the heat insulating pipe 2 are connected to the heat insulating pipe 2. A step of applying a pulsed magnetic field to the heat insulating pipe 2 by inserting the pipe 2 and driving the pair of exciting coils by the pulse power source 8, and the pair of exciting coils 3-1, 3-2 The step of detecting the generated magnetic field parallel to the central axis direction of the heat insulating pipe 2 by the magnetic sensor 4-1, and analyzing the pulse intensity and signal time attenuation in the output signal of the magnetic sensor 4-1. And a step of identifying defects in the pipe 2. Hereinafter, a method for nondestructive inspection of the heat insulating pipe 2 using the pulse magnetic inspection apparatus 1-1 will be described in detail.

In the pulse magnetic inspection apparatus 1-1, the pulse magnetic field waveform when the heat insulation pipe 2 is not inserted into the inspection unit 6-1; that is, the pair of exciting coils 3-1 and 3-2 is an arrangement place of the magnetic sensor 4-1. FIG. 4 shows the waveform of the pulse magnetic field to be formed. In FIG. 4, the magnetic sensor 4-1 shows the result of measuring a component parallel to the central axis of the heat insulating pipe 2. As a pulse magnetic field, a square wave with a duty ratio of 25% was applied at 50 Hz. As shown in FIG. 4, when the heat insulation pipe 2 that is the pipe to be inspected is not inserted, the pulsed magnetic field is detected with the substantially applied magnetic field waveform.
The unit of signal intensity shown in FIGS. 4 to 6 and 10 is [V].

  After inserting the heat insulation pipe 2A having defects as the pipe to be inspected and the heat insulation pipe 2 having no defects into the pulse magnetic inspection apparatus 1-1, a magnetic field is applied to each of the heat insulation pipe 2A and the heat insulation pipe 2 by applying a pulse magnetic field. FIG. 5 shows a comparison of measurement results of pulse intensity (signal intensity) and signal time attenuation in the output signal of the sensor 4-1. Here, the time waveform shown in FIG. 5 is normalized so that the signal intensity peaks have the same height. The defective heat insulation pipe 2A has a faster signal attenuation than the normal heat insulation pipe 2 and this is considered to be due to the fact that the signal attenuation is faster because the defect structure is thin. Thus, it was found that the pulse response characteristics change depending on the presence or absence of defects.

  The power source switching circuit 8 switches the current flowing in the exciting coil 3-2, which is one of the pair of exciting coils, to be in the opposite direction to the current flowing in the exciting coil 3-1. The switching can be performed by the exciting coil 3-1, and the same measurement function can be obtained if the directions flowing through the exciting coils 3-1 and 3-2 are reversed. Due to this reverse-phase current, a reverse magnetic field is generated in the heat insulating pipe 2 from each of the exciting coil 3-1 and the exciting coil 3-2. Therefore, the magnetic field at the location where the magnetic sensor 4-1 is disposed is canceled and the applied magnetic field. The time waveform of the pulse itself is not measured. However, when the heat insulation pipe 2 is inserted, the magnetic field transmitted through the pipe itself is detected even though the remaining signal is small, the component that is not canceled by the left and right excitation coils 3-1 and 3-2. FIG. 6 shows a comparison of the measurement results obtained by inserting the heat insulating pipe 2 into the pulse magnetic inspection apparatus 1-1. In the heat insulating pipe 2 which is a normal pipe, peaks appear at the rising and falling edges, but the defective heat insulating pipe 2A has almost no signal. Here, since FIG. 6 also shows the change in signal strength, unlike FIG. 5, the signal strength itself is shown without being normalized by the peak value. As described above, when the exciting coils 3-1 and 3-2 are operated in the reverse phase, the applied magnetic field itself can be canceled, so that only the signal change due to the pipe to be inspected can be extracted.

  According to the first embodiment, a magnetic field in the central axis direction of the heat insulating pipe 2 can be applied to a predetermined place of the pipe to be inspected by the pair of exciting coils 3-1 and 3-2 inserted through the heat insulating pipe 2. Further, a magnetic field parallel to the central axis direction of the heat insulation pipe 2 is detected by providing the magnetic sensor 4-1 disposed between the pair of exciting coils 3-1 and 3-2 on the outer peripheral surface of the heat insulation pipe 2. can do. The magnetic field generated by the exciting coils 3-1 and 3-2 is transmitted to the magnetic sensor 4-1 through the heat insulating pipe 2. In the middle, the magnetic field in the central axis direction of the heat insulating pipe 2 leaks to the outside, but the magnetic field propagated due to corrosion and defects differs. Here, by driving the exciting coils 3-1 and 3-2 with a pulse power source to generate a pulsed magnetic field, the magnetic sensor 4 is used at the time of rising of the pulsed magnetic field and in a time zone during which a constant magnetic field is applied thereafter. The rising magnetic signal detected at −1 attenuates with time. By analyzing the peak value and attenuation characteristics of the detected pulse magnetic signal, it is possible to detect defects such as corrosion and cracks in the pipe with higher accuracy.

  Furthermore, in the pulse magnetic inspection apparatus 1-1, the current directions of one excitation coil and the other excitation coil of the pair of excitation coils 3-1, 3-2 are respectively switched to the same direction or the opposite direction, or a pair of excitation coils A power supply switching circuit 8 is provided for switching so that only one of the coils is driven. Thereby, when it drives with the electric current of the same direction with a pair of exciting coil 3-1, 3-2, a magnetic field can be applied to the heat insulation piping 2 in the same direction, and signal strength can be strengthened. In addition, when the pair of exciting coils 3-1 and 3-2 are driven with currents in opposite directions, the applied magnetic fields entering the magnetic sensor 4-1 cancel each other, so that only the signal change due to the defect occurs. Can be extracted. In addition, when the inspection part of the heat insulating pipe 2 is a connection part or an end part, the structure differs greatly at both ends of the pipe to be inspected by driving only one excitation coil far from the part. Can also remove the effect.

  Next, another embodiment of the pulse magnetic inspection apparatus according to the present invention will be described with reference to FIG.

  The pulse magnetic inspection apparatus 1-2 according to the present embodiment is a nondestructive inspection apparatus that detects defects by detecting a change in the pulse magnetic field transmitted to the heat insulation pipe 2 (see FIG. 2) that is a pipe to be inspected. As shown in FIG. 7, the inspection unit 6-2, the magnetic sensor circuit 7-2, and the pulse power source 8, the power source switching circuit 9, and the signal analysis unit which is a signal analysis unit which are not shown in FIG. 10 is mainly provided. A pair of exciting coils 3-1 and 3-2, an inspection part base material 5-1, a pulse power source 8, a power source switching circuit 9, and a signal analysis device 10 as signal analysis means are the same as those in the first embodiment, and are described in detail. Description is omitted.

  Between the pair of exciting coils 3-1 and 3-2 of the inspection unit 6-2, a plurality of magnetic sensors (the same as the magnetic sensor 4-1 used in the first embodiment) are provided on the outer peripheral surface of the heat insulating pipe 2. In the embodiment, eight are arranged side by side (not shown in FIG. 7, but four magnetic sensors 4-6 to 9 are arranged behind the inspection unit 6-2 in addition to the magnetic sensors 4-2 to 5). Have been). The magnetic sensors 4-2 to 9 are arranged at the same distance from each of the exciting coils 3-1 and 3-2, that is, at the center between the exciting coil 3-1 and the exciting coil 3-2. Magnetic field measurement data obtained by the eight magnetic sensors 4-2 to 9 are analyzed by the signal analysis device 10. As the number of magnetic sensors increases, the spatial resolution can be improved. Therefore, the magnetic sensor circuit 7-2 is a circuit capable of simultaneously measuring multiple channels. In the first embodiment, a single magnetic sensor is measured, and detection is possible when there is a defect over the entire circumference of the pipe to be inspected or when there is a defect directly under the magnetic sensor. However, it is difficult to detect a defect at a position away from the location of the magnetic sensor. For this reason, the measurement leakage can be reduced by arranging the magnetic sensors 4-2 to 9 over the entire circumference of the inspection section 6-2 as in the present embodiment. Further, since the surface data can be obtained by moving the inspection unit 6-2 in a state of being inserted into the pipe to be inspected and performing multipoint measurement, various acquired data such as a pulse response time waveform attenuation rate and pulse intensity are stored in space. Since mapping corresponding to the position can be performed, defect information can be obtained visually.

  According to the second embodiment, a plurality of magnetic sensors 4-2 to 9 are arranged on the outer peripheral surface of the heat insulating pipe 2 between the pair of excitation coils 3-1, 3-2, whereby the excitation coil 3-1. 3-2, it is possible to identify and detect which position on the circumference of the heat insulating pipe 2 has a defect by the magnetic sensors 4-2 to 9 at the same distance from each of 3-2.

  Next, another embodiment of the pulse magnetic inspection apparatus according to the present invention will be described with reference to FIG.

  The pulse magnetic inspection apparatus 1-3 according to the present embodiment is a nondestructive inspection apparatus that detects defects by detecting a change in the pulse magnetic field transmitted to the heat insulating pipe 2 (see FIG. 2) that is a pipe to be inspected. As shown in FIG. 8, the inspection unit 6-3 and the magnetic sensor 4-1, the magnetic sensor circuit 7, the pulse power supply 8, the power supply switching circuit 9, and the signal analyzing means not shown in FIG. The signal analysis device 10 is mainly provided. The magnetic sensor 4-1, the magnetic sensor circuit 7, the pulse power supply 8, the power supply switching circuit 9, and the signal analysis device 10 as signal analysis means are the same as those in the first embodiment, and detailed description thereof is omitted.

  The inspection part 6-3 has a structure in which the inspection part base material 5-3 can be divided in half so that the inspection part 6-3 can be easily attached to the heat insulation pipe 2, and can be sandwiched at any position of the heat insulation pipe 2. Here, the exciting coils 3-3 and 3-4 can be easily disconnected and electrically connected by the coil connection connectors 11-1 and 11-2. This structure can also be applied to the first and second embodiments.

  According to the third embodiment, the coil connection connectors 11-1 and 11-2, which are electrical connection connectors capable of dividing and connecting the pair of exciting coils 3-3 and 3-4 at predetermined positions on the coil circumference, are provided. Thereby, even if it is a case where a test | inspection is carried out by making the heat insulation piping 2 penetrate the excitation coils 3-3 and 3-4, the excitation coils 3-3 and 3-4 can be appropriately separated from the heat insulation piping 2. For example, in the conventional through-type excitation coil, if there is no end portion to be introduced into the heat insulation pipe, the excitation coil cannot be installed unless the heat insulation pipe is separated, but by applying the excitation coil of the present invention, In any part of the pipe to be inspected, the exciting coil can be divided and attached to the pipe to be inspected.

  Next, another embodiment of the pulse magnetic inspection apparatus according to the present invention will be described with reference to FIG. FIG. 9 is a schematic diagram showing a basic configuration of a pulse magnetic inspection apparatus 1-4 according to the fourth embodiment of the present invention.

  The pulse magnetic inspection apparatus 1-4 according to the present embodiment is a nondestructive inspection apparatus that detects defects by detecting a change in the pulse magnetic field transmitted to the heat insulating pipe 2 (see FIG. 2) that is a pipe to be inspected. The pair of exciting coils 3-1 and 3-2, the magnetic sensor 4-1, the inspection unit base material 5-1, the magnetic sensor circuit 7-1, the pulse power source 8, the power source switching circuit 9, and the signal shown in the first embodiment The signal analysis apparatus 10 that is an analysis unit is the same as that of the first embodiment, and a detailed description thereof is omitted.

The pulse magnetic inspection apparatus 1-4 includes a pair of exciting coils 3-1 and 3-2 and a magnetic sensor 4-1 in an inspection unit 6-4 included in the pulse magnetic inspection apparatus 1-4. Further, a pair of magnetic detection magnetic coils 12-1 and 12-2 are disposed adjacent to the outside of the excitation coils 3-1 and 3-2. A magnetic coil circuit 13 is attached to the magnetic coils 12-1 and 12-2 for magnetic detection. The magnetic coil circuit 13 is a circuit for driving the magnetic detection magnetic coils 12-1 and 12-2 and measuring a magnetic field. Thus, a pulse magnetic field is generated only in one of the pair of excitation coils 3-1 and 3-2, and the magnetic coil for magnetic detection 12-located at a position away from the one excitation coil that generated the pulse magnetic field. The pulse magnetic field response obtained by one of the magnetic coils 1 and 12-2 is analyzed by the signal analysis device 10. That is, the output obtained by the magnetic coil for magnetic detection 12-1 or 12-2 is taken into the signal analysis device 10 together with the output of the magnetic sensor 4-1, and the signal analysis device 10 determines the presence or absence of a defect.
As in this embodiment, not only both of the pair of excitation coils 3-1 and 3-2 but also only one of the pair of excitation coils 3-1 and 3-2 is magnetically detected. A magnetic coil may be provided.
In the present embodiment, the magnetic detection magnetic coils 12-1 and 12-2 are provided at positions adjacent to the pair of excitation coils 3-1, 3-2. The structure which provides the magnetic coil for a magnetic detection in the same position as the coils 3-1 and 3-2 may be sufficient.

  Next, a method for inspecting the heat insulating pipe 2 using the pulse magnetic inspection apparatus 1-4 will be described.

  The inspection method applied to the pulse magnetic inspection apparatus 1-4 is a method for nondestructively inspecting a defect of the heat insulating pipe 2 which is the pipe to be inspected, and the heat insulating pipe is connected to the pair of exciting coils 3-1 and 3-2. 2 and driving the pair of excitation coils 3-1 and 3-2 by the pulse power supply 8, and applying a pulse magnetic field to the heat insulating pipe 2, and the pair of excitation coils 3-1. The magnetic sensor 4-1 detects a magnetic field parallel to the central axis direction of the heat insulating pipe 2 generated by 3-2, and analyzes the pulse intensity and signal time attenuation in the output signal of the magnetic sensor 4-1. A magnetic field is generated by driving only one of the pair of excitation coils 3-1 and 3-2 by a pulse power source to generate a pulse magnetic field, and being located away from the excitation coil that generated the pulse magnetic field. Magnetic carp 12-1 or the defect identification step by the magnetic coils 12-1 and 12-2 for identifying the defect of the heat insulating pipe 2 by analyzing the pulse magnetic field response obtained by the magnetic coil for detection 12-2; Have. In the present embodiment, in addition to the inspection method described in the first embodiment, the defect specifying step using the magnetic coils for magnetic detection 12-1 and 12-2 is added. In the following, the defect identification process performed using the magnetic coils for magnetic detection 12-1 and 12-2 will be described.

  In the defect identification step by the magnetic detection magnetic coils 12-1 and 12-2, information on the pulse magnetic field response obtained by the magnetic detection magnetic coils 12-1 and 12-2 is used. More specifically, the magnetic detection magnetic coils 12-1 and 12-2 can obtain a change in time of the magnetic flux passing through the coils as a voltage output as a principle of operation, so that a DC magnetic field like the magnetic sensor 4-1. It is not possible to detect low frequency signals such as. For this reason, the time response waveform shown in FIG. 10 is also large as a signal where the rise and fall time changes are large. As shown in FIG. 10, there is a difference in the pulse magnetic response time waveform between the normal heat insulation pipe 2 and the defective heat insulation pipe 2A, and the normal heat insulation pipe 2 showed faster attenuation. Thus, by combining the measurement information of the magnetic coils for magnetic detection 12-1 and 12-2 with the measurement information obtained by the magnetic sensor 4-1, the inspection accuracy can be further increased. The circuit configuration in which the magnetic coils for magnetic detection 12-1 and 12-2 are used in combination with the magnetic sensor 4-1 and the magnetic sensors 4-2 to 9 as in the present embodiment can also be applied to the first to third embodiments. .

  According to the fourth embodiment, the magnetism detecting magnetic coils 12-1 and 12-2 are provided in a place adjacent to or the same place as both or only one of the pair of exciting coils 3-1 and 3-2. A magnetic field is generated only in one of the coils 3-1 and 3-2, and the magnetic coil for magnetic detection 12-farther from one of the exciting coils 3-1 and 3-2 where the pulse magnetic field is generated. 1 or 12-2 is provided with a signal analyzer 10 which is a means for analyzing the pulse magnetic field response obtained. The magnetic coils for magnetic detection 12-1 and 12-2 can detect changes in all magnetic field signals that have passed through the heat insulating pipe 2. By combining not only the pulse response of the magnetic sensor 4-1 provided on the outer peripheral surface but also the information of the pulse magnetic field response by the magnetic coils for magnetic detection 12-1 and 12-2, corrosion of pipes, cracks, etc. Defects can be detected with higher accuracy. That is, according to the fourth embodiment, in accordance with the effect in the first embodiment, information on the pulse magnetic field response transmitted through the entire inspection pipe obtained by the magnetic coils for magnetic detection 12-1 and 12-2 is added to the defect analysis. can do. Thus, by combining the information from the magnetic sensor 4-1 and the magnetic coils for magnetic detection 12-1 and 12-2, it is possible to extract signal changes due to defects more accurately.

  According to the present invention, since a pulse power supply is used instead of an AC power supply, a power supply capacity load is small, and a good magnetic signal can be obtained without lock-in detection as a circuit configuration. A destructive inspection apparatus and a nondestructive inspection method can be provided.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications, design changes, and the like are included in the technical scope without departing from the technical idea of the present invention.

  The present invention is a nondestructive inspection apparatus for detecting defects on the surface, inside, and inside of steel pipes or steel pipes covered with a heat insulating material used in many places such as petroleum plants and chemical plants. In the conventional flaw detection inspection method using magnetism, since the signal change due to the defect is weak, it cannot be applied to the steel pipe using the heat insulating material, so the heat insulating material is removed and the inspection is performed. According to the present invention, the present invention can be applied to inspection of defects on the surface, inside, and inside of a pipe not only with a steel pipe but also with a heat insulating material.

1-1 Pulse Magnetic Inspection Device 1-2 Pulse Magnetic Inspection Device 1-3 Pulse Magnetic Inspection Device 1-4 Pulse Magnetic Inspection Device 2 Heat Insulating Pipe 2a Steel Pipe 2b Heat Insulating Material 2c Molten Zinc Iron Plate 3-1 Excitation Coil 3-2 Excitation Coil 3-3 Excitation Coil 3-4 Excitation Coil 4-1-9 Magnetic Sensor 5-1 Inspection Part Base Material 5-3 Inspection Part Base Material 6-1 Inspection Part 6-2 Inspection Part 6-3 Inspection Part 6-4 Inspection Unit 7-1 Magnetic Sensor Circuit 7-2 Magnetic Sensor Circuit 8 Pulse Power Supply 9 Power Supply Switching Circuit 10 Signal Analyzer 11-1 Electrical Connection Connector 11-2 Electrical Connection Connector 12-1 Magnetic Coil for Magnetic Detection 12- 2 Magnetic coil for magnetic detection 13 Circuit for magnetic coil

The present invention has been proposed to solve the above problems, and the first aspect of the present invention is
It is a nondestructive inspection device using pulse magnetism for nondestructive inspection of defects in piping to be inspected,
A pair of exciting coils that are inserted through the pipe to be inspected and can be arranged at an arbitrary position with respect to the pipe to be inspected;
A pulse power supply for applying a pulse voltage to at least one of the pair of exciting coils;
A magnetic sensor that is disposed between the pair of excitation coils on the outer peripheral surface of the pipe to be inspected and detects a magnetic field parallel to the central axis direction of the pipe to be inspected;
A pulse magnetic field generated when at least one of the pair of excitation coils is driven by the pulse power source is detected by the magnetic sensor, and a peak value of the signal of the pulse magnetic field detected by the magnetic sensor and a time decay of the signal are analyzed. comprising a signal analysis unit for the,
The pulse power source drives the pair of exciting coils to apply a pulse magnetic field having a predetermined repetition frequency and a duty ratio to the pipe to be inspected, which is a square wave,
The signal analyzing means is a non-destructive inspection apparatus using pulse magnetism that identifies a defect by comparing a peak value of a signal of a pulse magnetic field and time decay of the signal in the presence or absence of a defect in the inspection pipe .

The fourth aspect of the present invention is
A nondestructive inspection apparatus using pulsed magnetism in which a plurality of the magnetic sensors are arranged on the outer peripheral surface of the pipe to be inspected between the pair of magnetic coils.

The sixth aspect of the present invention is
Using the nondestructive inspection device according to claim 1,
A method for nondestructive inspection of defects in the pipe to be inspected,
By passing the pipe to be inspected through the pair of exciting coils and driving the pair of exciting coils by the pulse power source , the pipe to be inspected is a square wave having a predetermined repetition rate and a duty ratio. and applying a pulse magnetic field,
A step of detecting a magnetic field generated by the pair of exciting coils in parallel to a central axis direction of the pipe to be inspected by the magnetic sensor;
And analyzing the pulse intensity and signal time attenuation in the output signal of the magnetic sensor to identify defects in the pipe to be inspected, and a nondestructive inspection method using pulse magnetism.

According to the first aspect of the present invention, a magnetic field in the direction of the central axis of the pipe to be inspected can be applied to a predetermined location of the pipe to be inspected by a pair of exciting coils inserted through the pipe to be inspected. Further, by providing a magnetic sensor disposed between the pair of exciting coils on the outer peripheral surface of the pipe to be inspected, a magnetic field parallel to the central axis direction of the pipe to be inspected can be detected. The magnetic field generated by the exciting coil is transmitted to the magnetic sensor through the piping to be inspected . In the course of that the magnetic field in the central axis direction of the inspected pipe leak out, but varies the magnetic field propagated by corrosion or defects. Here, the magnetic field generated by driving the excitation coil with a pulsed power supply is a pulsed magnetic field, so that the rising magnetic signal detected by the magnetic sensor is timed at the time of rising of the pulsed magnetic field and the time zone during which a constant magnetic field is applied thereafter. Attenuates with. By analyzing the peak value and attenuation characteristics of the detected pulse magnetic signal, it is possible to detect defects such as corrosion and cracks in the pipe with higher accuracy.

Claims (7)

It is a nondestructive inspection device using pulse magnetism for nondestructive inspection of defects in piping to be inspected,
A pair of exciting coils that are inserted through the pipe to be inspected and can be arranged at an arbitrary position with respect to the pipe to be inspected;
A pulse power supply for applying a pulse voltage to at least one of the pair of exciting coils;
A magnetic sensor that is disposed between the pair of excitation coils on the outer peripheral surface of the pipe to be inspected and detects a magnetic field parallel to the central axis direction of the pipe to be inspected;
Means for detecting a pulse magnetic field generated when at least one of the pair of excitation coils is driven by the pulse power source by the magnetic sensor, and analyzing a response of the pulse magnetic field detected by the magnetic sensor. Non-destructive inspection equipment using pulse magnetism.   Provided with a power supply switching circuit that switches the current direction of one excitation coil and the other excitation coil of the pair of excitation coils to the same direction or the opposite direction, or to switch only one of the pair of excitation coils. The nondestructive inspection apparatus using pulse magnetism according to claim 1.   3. The pulse magnetism according to claim 1, wherein an electrical connection connector capable of dividing and connecting each excitation coil at a predetermined position on a coil circumference of the pair of excitation coils is provided. Had non-destructive inspection equipment.   The non-pulse using the pulse according to any one of claims 1 to 3, wherein a plurality of the magnetic sensors are arranged on the outer peripheral surface of the inspection pipe between the pair of exciting coils. Destructive inspection equipment.   A magnetic detection magnetic coil corresponding to each of the pair of excitation coils is provided at an adjacent position or the same position with respect to both or one of the pair of excitation coils, and one of the pair of excitation coils. A means for generating a pulse magnetic field only on one side and analyzing a pulse magnetic field response obtained by a magnetic coil for magnetic detection at a position away from one excitation coil that generated the pulse magnetic field is provided. A nondestructive inspection apparatus using the pulse according to any one of 1 to 4. Using the nondestructive inspection device according to claim 1,
A method for nondestructive inspection of defects in the pipe to be inspected,
Applying the pulsed magnetic field to the pipe to be inspected by inserting the pipe to be inspected into the pair of excitation coils and driving the pair of excitation coils by the pulse power source;
A step of detecting a magnetic field generated by the pair of exciting coils in parallel to a central axis direction of the pipe to be inspected by the magnetic sensor;
Analyzing the pulse intensity and signal time attenuation in the output signal of the magnetic sensor to identify a defect in the pipe to be inspected, and a nondestructive inspection method using pulse magnetism. Using the nondestructive inspection device according to claim 5,
A method for nondestructive inspection of defects in the pipe to be inspected,
Applying the pulsed magnetic field to the pipe to be inspected by inserting the pipe to be inspected into the pair of excitation coils and driving the pair of excitation coils by the pulse power source;
A step of detecting a magnetic field generated by the pair of exciting coils in parallel to a central axis direction of the pipe to be inspected by the magnetic sensor;
Analyzing the pulse intensity and signal time attenuation in the output signal of the magnetic sensor;
Only one of the pair of excitation coils is driven by a pulse power source to generate a pulse magnetic field, and the pulse magnetic field response obtained by the magnetic detection magnetic coil at a position away from the excitation coil that generated the pulse magnetic field is obtained. A non-destructive inspection method using pulsed magnetism, comprising: a step of identifying a defect in the inspection pipe by analyzing.

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