Ultrasonic inspection method

Abstract

To provide an ultrasonic inspection method which enables thickness measurement of a pipe or the like having a protective material, such as an exterior panel consisting of a metal member, installed thereon from the outside without having to remove the exterior panel or the like.SOLUTION: An ultrasonic inspection method is provided, involving the use of an ultrasonic sensor provided on a surface of a target, a sensor coil connected to the ultrasonic sensor, and a transmission / reception coil provided on the outside of an exterior panel, where the exterior panel has an opening with a total width larger than a diameter of the coil in one direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrasonic inspection method for measuring thinning or defects occurring in piping in, for example, a nuclear power plant, a thermal power plant, or the like, by using ultrasonic waves. [Background technology]

[0002] The maintenance of components in power plants is necessary to maintain normal operation, and non-destructive testing technology plays a very important role. In particular, in nuclear power plants, it is important to ensure the integrity of primary reactor equipment such as recirculation system piping. At bent parts of piping where high-temperature, high-velocity steam flows, thinning due to erosion and corrosion such as impact corrosion can occur, which is known to be a problem in terms of equipment maintenance. For this reason, inspections are carried out in which ultrasonic pulses are irradiated from the outside of the piping, reflected waves from the inner wall surface of the piping are received, and the piping wall thickness is measured from the time difference between multiple reflected pulses.

[0003] In the conventional method, a vertical probe is used, and the probe is directly contacted with the outer surface of the pipe to inspect the pipe thickness directly below the probe. However, in the pipes through which high-temperature fluid flows during plant operation, insulation is wrapped around the outside of the pipe, and an exterior plate that holds the insulation is installed on the outside of the insulation.

[0004] Therefore, when inspecting wall thickness, it is necessary to first remove the insulation and exterior panels, and then restore them after the inspection. In addition, since the inspection involves directly contacting the probe with the inspection point, if the inspection point is at a high place, it is necessary to assemble scaffolding.

[0005] To solve these problems, a method has been reported in which a sensor, a receiving coil, and a transmitting coil are installed in advance on the surface of the object to be inspected, and signals are transmitted and received by electromagnetic induction coupling between the receiving coil and the transmitting coil, thereby performing inspection from a position away from the surface of the object to be inspected, as described in Patent Document 1, for example. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] GB2523266A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the method disclosed in Patent Document 1, electromagnetic induction coupling occurs when only insulation material made of non-metallic materials is wrapped around the pipe, but when an exterior panel made of metallic materials is installed on the outside of the insulation material, signals cannot be sent or received from the outside by electromagnetic induction coupling.

[0008] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide an ultrasonic inspection method for measuring the wall thickness of a pipe or the like that is equipped with a protective material such as an exterior plate made of a metal member, which can measure the wall thickness of the pipe or the like from the outside of the exterior plate without requiring removal of the exterior plate. [Means for solving the problem]

[0009] In order to achieve the above object, the ultrasonic inspection method of the present invention is characterized in that, in the ultrasonic inspection method, which comprises an ultrasonic sensor attached to the surface of a subject, a sensor coil electrically connected to the ultrasonic sensor, and a transmit / receive coil facing the sensor coil and arranged via a metal member arranged on the outside of the subject, an opening is provided in the metal member arranged on the outside of the subject. Effect of the Invention

[0010] According to the present invention, it is possible to measure the wall thickness of a pipe from the outside of a metal exterior plate without impairing the ability of the exterior plate to retain the heat insulating material and without requiring removal of the exterior plate. [Brief description of the drawings]

[0011] [Figure 1]1 is a diagram illustrating a configuration of an inspection device according to a first embodiment of the present invention. [Diagram 2] 1 is a side cross-sectional view illustrating a structure of a coil and a sensor in a first embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram for explaining an example in which a magnetic flux that induces electromagnetic induction is weakened, for comparison with the first embodiment of the present invention. [Figure 4] FIG. 2 is a diagram for explaining an example of a method for generating a magnetic flux that induces electromagnetic induction in the first embodiment of the present invention. [Diagram 5] FIG. 11 is a diagram illustrating a part of the configuration of an inspection device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The first embodiment will be described below with reference to the drawings. EXAMPLES

[0013] The present inspection method will be outlined below with reference to FIGS. 1 to 4. FIG. 1 is a diagram showing the configuration of an inspection device in this embodiment. The specimen 1 is, for example, a recirculation system pipe of a nuclear power plant or the like, a part of which is shown. The pipe is wrapped around the outside with a heat insulating material 2 made of a non-metallic material. A metal exterior plate 3 is placed to support the heat insulating material 2, and ultrasonic testing is performed to measure the wall thickness of the pipe.

[0014] The inspection device comprises a sensor 10 arranged on the surface of the specimen 1, a sensor probe 20 arranged on the outside of the exterior panel 3 relative to the sensor 10, an ultrasonic flaw detector 30 that controls the sensor probe 20 to transmit or record signals, a calculation device 40 that calculates the thickness, etc. of the specimen 1 based on the signals recorded by the ultrasonic flaw detector 30, a display device 50 that displays the measurement results calculated by the calculation device 40, a memory device 60 that saves the measurement results calculated by the calculation device 40, and an input device 70 that inputs instructions to the calculation device 40.

[0015] The sensor 10 is composed of an ultrasonic transducer 11 and a sensor coil 12. The sensor probe 20 is composed of a transmission coil 21 and a reception coil 22. The ultrasonic flaw detector 30 is composed of a pulser 31, a receiver 32, and a data recording unit 33. Based on a command from a calculation device 40, a drive signal is output from the pulser 31 to the transmission coil 21. When the transmission coil 21 is driven, a current is generated in the sensor coil 12 by electromagnetic induction, and ultrasonic waves are propagated from the ultrasonic transducer 11 to the inside of the test object 1. The ultrasonic signal reflected inside the test object 1 is converted into a voltage signal by the sensor coil 12, and a current is generated in the reception coil 22 by electromagnetic induction again. The voltage signal generated in the reception coil 22 is output to the data recording unit 33 via the receiver 32. The data recording unit 33 is composed of, for example, a hard disk or a memory. The calculation device 40 has a ROM that stores a program and a CPU that executes processing according to the program.

[0016] The sensor coil 12, the transmitter coil 21, and the receiver coil 22 are each configured by winding a conductor in a spiral shape on an xy plane parallel to the surface of the subject 1. The sensor coil 12, the transmitter coil 21, and the receiver coil 22 are arranged facing the heat-insulating material 2 and the exterior plate 3, and are arranged in the following order from the surface side of the subject 1: sensor coil 12, heat-insulating material 2, exterior plate 3, transmitter coil 21, and receiver coil 22. In this embodiment, the exterior plate 3 is provided with an exterior plate opening 4. The exterior plate opening 4 is, for example, in a rectangular shape elongated in the x-axis direction, that is, in a slit shape, as shown in FIG. 1.

[0017] In FIG. 1, the sensor coil 12, the transmitter coil 21, and the receiver coil 22 each have three turns, but this is an embodiment of the present invention, and the number of turns of the coils is not limited to this. In FIG. 1, the receiver coil 22 is disposed inside the transmitter coil 21, but the transmitter coil 21 may be disposed inside the receiver coil 22. For the sake of visibility in the explanatory diagram, the test object 1, the sensor 10, the heat retaining material 2, the exterior plate 3, and the sensor probe 20 are shown separated from each other, but in reality, the test object 1, the sensor 10, the heat retaining material 2, the exterior plate 3, and the sensor probe 20 are disposed close to each other in the z-axis direction in the diagram. In addition, the test object 1 is assumed to be, for example, a pipe, but is shown and explained as a flat plate without a curved surface for ease of explanation.

[0018] Fig. 2 is a diagram showing the configuration and detailed arrangement of the sensor 10 and the sensor probe 20, as viewed from the side. The transmitting coil 21 is a conductor wound in a spiral shape on the xy plane, which generates a magnetic field having a component perpendicular to the z-axis direction. The magnetic field perpendicular to the z-axis direction generates a current in the sensor coil 12 due to electromagnetic induction. In the electromagnetic induction generated at this time, the generated magnetic field varies depending on the characteristics of the exterior panel opening 4. This will be explained below with reference to Figs. 3 and 4.

[0019] 3 is a diagram for explaining a magnetic field generated by electromagnetic induction when an exterior plate 3 without an opening is arranged. When a current flows through the transmitting coil 21, a coil magnetic flux 23 is generated. When this coil magnetic flux 23 penetrates the surface of the exterior plate 3, an eddy current 24 is generated on the surface of the exterior plate 3 coaxially with the transmitting coil 21 because the exterior plate 3 is a metal member. This eddy current 24 generates an eddy current magnetic flux 25. The eddy current magnetic flux 25 is generated in an opposing direction on the same axis as the coil magnetic flux 23, so the magnetic fluxes in the z-axis direction shown in FIG. 3 cancel each other out. Therefore, the magnetic flux penetrating the sensor coil 12 arranged on the opposite side of the exterior plate 3 from the transmitting coil 21 becomes small, and when an exterior plate 3 without an opening is arranged, measurement by electromagnetic induction becomes difficult.

[0020] In this embodiment, a means for enabling measurement by electromagnetic induction is provided on a metal member disposed on the outside of the test object. For example, an exterior panel opening 4 is provided on the exterior panel 3. This allows the wall thickness of the pipe to be measured from the outside of the metal exterior panel 3 without impairing the ability of the exterior panel 3 to retain the heat insulation material and without requiring removal of the exterior panel 3.

[0021] FIG. 4 is a diagram for explaining a magnetic field generated by electromagnetic induction when an exterior plate 3 having an exterior plate opening 4 is arranged. When a current flows through the transmission coil 21, a coil magnetic flux 23 is generated. When this coil magnetic flux 23 penetrates the surface of the exterior plate 3, the transmission path of the current is blocked by the exterior plate opening 4, so that eddy currents are not generated coaxially with the transmission coil 21, but are generated on both sides of the exterior plate opening 4. Therefore, magnetic flux is not generated in a direction opposite to the coil magnetic flux 23 on the same axis due to the eddy current, and the magnetic flux in the z-axis direction of the coil magnetic flux 23 is not canceled. Therefore, a magnetic flux is generated that penetrates the sensor coil 12 arranged on the opposite side of the transmission coil 21 with respect to the exterior plate 3, and when an exterior plate 3 having an exterior plate opening 4 is arranged, measurement by electromagnetic induction is possible. At this time, it is preferable that the condition of the exterior plate opening 4 for blocking the transmission path of the current be satisfied as follows:

[0022] L1>D (1) Here, L1 is the long side length of the exterior panel opening 4 of the slit, and D is the outermost diameter of the transmitting coil 21. In other words, it is desirable to make the long side length of the exterior panel opening 4 longer than the outermost diameter of the transmitting coil 21. With the configuration described above, it becomes possible to transmit and receive signals to the ultrasonic transducer 11 from the outside of the exterior panel 3 without the need to remove the exterior panel 3, and it is possible to measure the wall thickness of a pipe or the like.

[0023] If the shape of the exterior panel opening 4 does not satisfy formula (1), for example, if L1 is equal to or smaller than D, a current equivalent to eddy current 24 as shown in FIG. 3 will be generated outside the exterior panel opening 4 without impeding its transmission path, and eddy current flux 25 will be generated coaxially with coil flux 23 in the opposing direction, causing the magnetic fluxes in the z-axis direction to cancel each other out.

[0024] In this embodiment, the slit shape is shown as a basic requirement of the ultrasonic measurement method, and for example, the shape of the exterior panel opening 4 may be an ellipse instead of a rectangle. In this case, it is desirable that the major axis of the ellipse is larger than the outermost diameter of the coil. In addition, the waveform and frequency of the ultrasonic waves transmitted from the pulser, the refraction angle at which the ultrasonic waves propagate, the method of displaying the inspection results, etc. are not limited. In addition, each device structure or method is not limited, and may be replaced with another structure or method that can obtain the same effect. EXAMPLES

[0025] A second embodiment of the present invention will be described with reference to FIG. In the inspection device of this embodiment, the exterior plate opening 4 shown in FIG. 1 of the first embodiment has a different shape. In the first embodiment, the exterior plate opening 4 has a rectangular shape that is long in the x-axis direction. In the second embodiment, for example, an exterior plate opening 4 having a shape obtained by combining a long rectangular shape with a square is provided. At this time, eddy currents 24 are generated on both sides of the exterior plate opening 4 by the coil magnetic flux 23, and eddy current magnetic flux 25 is generated in an opposing direction on an axis different from that of the coil magnetic flux 23. Due to the repulsion of the opposing magnetic fluxes, the magnetic flux lines by the coil magnetic flux 23 are generated so as to avoid the surface of the exterior plate 3, and the magnetic flux density that penetrates vertically downward along the Z-axis in the square portion of the exterior plate opening 4 is improved.

[0026] In this case, it is desirable that the following formula (2) be satisfied as a condition for the opening shape combined with the long rectangular shape: D>W>L2 (2) Here, L2 is the short side length of the exterior panel opening 4, W is the side length of the square portion, and D is the outermost diameter of the transmitting coil 21. In other words, it is desirable to make the side length of the square portion longer than the short side length of the exterior panel opening 4. Also, it is desirable to make the outermost diameter of the transmitting coil 21 longer than the side length of the square portion.

[0027] Due to the above-mentioned action, it is possible to strengthen the magnetic flux passing through the sensor coil 12 arranged on the opposite side of the exterior plate 3 from the transmission coil 21, thereby making it possible to increase the signal strength.

[0028] If the length W of one side of the square portion does not satisfy formula (2), for example if W is equal to or smaller than L2, the square portion of the exterior panel opening 4 is included in the rectangular shape, resulting in the same as in Fig. 4 of Example 1. Also, if W is equal to or larger than D, the exterior panel opening 4 becomes larger than the diameter of the transmission coil 21, so that eddy current 24 is not generated, and therefore it is difficult to generate the opposing magnetic flux that is the effect of this embodiment.

[0029] In the example of Figure 5, the opening shape combined with the long rectangular shape is a square, but it may be, for example, a rectangular shape with a side direction different from that of the square, and the shape may be a polygon other than a rectangle or square, a circle, an ellipse, etc. [Explanation of symbols]

[0030] 1. Subject 2 Heat insulation material 3 Exterior plate 4 Exterior plate opening 10 Sensors 11 Ultrasonic transducer 12 Sensor coil 20 Sensor Probe 21 Transmitting coil 22 Receiving coil 23 Coil flux 24 Eddy current 25 Eddy current magnetic flux 30 Ultrasonic flaw detector 31 Parsa 32 Receiver 33 Data recording section 40 Computing equipment 50 Display device 60 Storage device 70 Input Device

Claims

1. An ultrasonic inspection method comprising an ultrasonic sensor attached to a surface of a subject, a sensor coil electrically connected to said ultrasonic sensor, and a transmit / receive coil facing said sensor coil and disposed via a metal member disposed on the outside of the subject, characterized in that an opening is provided in said metal member disposed on the outside of the subject.

2. 2. The ultrasonic inspection method according to claim 1, An ultrasonic inspection method, characterized in that the overall width of an opening in any one direction of the metal member is larger than the diameter of a transmit / receive coil, and the overall width in a direction perpendicular thereto is smaller than the diameter of the transmit / receive coil.

3. 2. The ultrasonic inspection method according to claim 1, 4. The ultrasonic inspection method according to claim 1, wherein the opening provided in the metal member is slit-shaped.

4. 2. The ultrasonic inspection method according to claim 1, an ultrasonic inspection method characterized in that the opening shape provided in the metal member is a superposition of a first opening shape whose overall width in one direction is greater than the diameter of a transmit / receive coil and whose overall width in a direction perpendicular to the first opening shape is smaller than the diameter of the transmit / receive coil, and a second opening shape whose longest overall width is greater than the minimum width of the first opening shape and smaller than the diameter of the transmit / receive coil.

5. An ultrasonic inspection method comprising an ultrasonic sensor attached to a surface of a test object, a sensor coil electrically connected to said ultrasonic sensor, and a transmitting / receiving coil facing said sensor coil and arranged via a metal member arranged on the outside of the test object, characterized in that a means is provided on the metal member arranged on the outside of the test object to enable measurement by electromagnetic induction.

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