JP2556584Y2 - Remote field eddy current sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a remote field eddy current sensor for inspecting corrosion thinning of pipes and the like, and particularly to pipe materials such as buried gas pipes, chemical plant pipes, heat exchanger pipes, especially cast iron pipes. The present invention relates to a remote field eddy current sensor in the case where maintenance is performed by a remote field eddy current method.

[0002]

2. Description of the Related Art Conventionally, to perform flaw detection on a metal tube by using a remote field eddy current method, an exciting coil and one or more receiving coils are required to be about twice as large as the tube diameter. The remote field eddy current sensor is configured by being spaced apart in the axial direction of the tube to constitute a remote field eddy current sensor, and the remote field eddy current sensor is inserted into a pipe to apply an excitation signal to an excitation coil. The applied excitation signal has a relatively low frequency (several tens of Hz to several hundreds of Hz) and a voltage of several volts to several tens of Hz.
V is used.

[0003] Electromagnetic waves generated by the excitation signal are divided into those that pass through the thickness of the test pipe and those that propagate in the pipe. The electromagnetic waves that propagate in the pipe are separated from the waveguide by the waveguide. Since the frequency is much lower than the assumed cutoff frequency, it is rapidly attenuated and hardly propagates. On the other hand, a wave that passes through the thickness of the pipe is called an indirectly propagated wave, which propagates along the pipe outside the pipe, attenuates slowly, and at the same time, partially passes through the pipe thickness again, and Penetrates the filter and is detected by the receiving coil.

Since the reception signal detected by the reception coil passes through the pipe thickness twice, it is very weak (several μV to several 1).
0 μV), and undergoes a phase change under the influence of the skin effect due to passage through the conduit wall thickness. In the remote field eddy current method, a phase change with good linearity is detected as a phase difference signal in relation to the pipe wall thickness, and is often used as information for inspection and diagnosis of a test metal pipe.

Generally, as shown in FIG. 4, a remote field eddy current sensor 31 includes an exciting coil 32 and a receiving coil 3.
The winding 34 of the receiving coil 33 is wound along the direction of travel of the remote field eddy current sensor 31 in the pipe. A plurality of, for example, about eight, receiving coils 33 are provided, and are arranged in contact with the inner wall of the test cast iron tube TU on a circumference having a center point on the same axis as the exciting coil 32.

[0006] In the remote field eddy current sensor 31 having this configuration, when diagnosing the test cast iron tube TU, a subtle change in the excitation voltage and the excitation frequency and the progress of the test cast iron tube TU of the remote field eddy current sensor 31 are performed. There is a difficulty that the depth of the defect of the test cast iron tube TU cannot be accurately evaluated from the received phase difference signal due to the influence of the vibration at the time.

When a plurality of receiving coils are used,
Depending on the arrangement status and number of the plurality of receiving coils for the remote field eddy current phenomenon, it is not possible to cope with the reduction of the inner diameter of the test cast iron tube TU due to the attachment of the test cast iron tube TU.
However, there is a drawback that highly accurate diagnosis cannot be performed for all the inner walls.

[0008]

[Purpose of the Invention] The present invention has been made in view of the above-mentioned difficulties, and it is possible to accurately evaluate the depth of a defect in a test metal tube based on a detected phase difference signal. It is an object of the present invention to provide a remote field eddy current sensor capable of coping with a reduction in the inner diameter and performing highly accurate diagnosis on all inner walls of a test cast iron pipe.

[0009]

In order to achieve this object, a remote field eddy current sensor according to the present invention is provided with an exciting coil for generating a remote field eddy current in a metal tube, and a forward running vehicle mounted with the exciting coil and running in the metal tube. Components,
A plurality of receiving coils provided in a predetermined distance from the exciting coil, and pressed radially by being pressed against the inner peripheral wall of the metal tube, and a rear running member mounted with the plurality of receiving coils and running in the metal tube, A connecting member for connecting the front running member and the rear running member, and a predetermined number of receiving coils for receiving the remote field eddy current are provided such that each magnetic path is perpendicular to the inner peripheral wall of the metal tube. is there.

[0010]

In this remote field eddy current sensor,
When the remote field eddy current sensor provided with the rear running member runs through the metal tube before being connected, the remote field eddy current sensor smoothly advances along the center axis in the metal tube, so that the excitation voltage and the excitation frequency are slightly changed. In addition, the remote field eddy current sensor is less susceptible to vibration when traveling inside the test metal tube, and the depth of the defect in the test metal tube can be accurately evaluated based on the detected phase difference signal. It is possible to detect the phase difference signal of all parts without attenuating it, and it can cope with the reduction of the inner diameter of the tube due to the adhesion of the test metal tube, etc. A highly accurate diagnosis can be made.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the remote field eddy current sensor according to the present invention will be described in detail with reference to FIGS. As shown in FIG. 1, the remote field eddy current sensor SQ of the present invention has an exciting coil 1 wound around an exciting coil bobbin 2 formed of a synthetic resin or the like in the front, and an exciting coil mounting assembler supporting the exciting coil 1. 3
A front tip wheel mounting assembler 4, a front tip assembler mounting member 5 for supporting the front tip wheel mounting assembler 4 on a longitudinal axis of the test cast iron pipe TU, and a front tip mounted on the front tip wheel mounting assembler 4. Wheels 7a, 7b, 7c, front rear wheel mounting assembler 8, front rear end assembler mounting member 9, and front rear wheels 11a, 1a mounted on front rear wheel mounting assembler 8.
1b and 11c.

The front end assembler mounting member 5 and the front rear assembler mounting member 9 are provided with assembler mounting member flanges 6a, 6b, 10a, 10b, respectively. These assembler mounting member flanges 6a, 6b, 1
The front end wheel mounting assembler 4, the exciting coil mounting assembler 3, and the front rear end wheel mounting assembler 8 are mutually connected by 0a and 10b. The front end assembler mounting member 5 and the front rear assembler mounting member 9 are formed in a cylindrical shape, and the excitation coil 1 of the excitation coil mounting assembler 3 is formed.
The shield core P ₀ connected looks like to penetrate.

Also, rearward, a receiving coil mounting assembler 13, a rear tip wheel mounting assembler 14, and a rear tip assembler mounting member 15 for supporting the rear tip wheel mounting assembler 14 on the longitudinal axis of the test cast iron tube TU. , Rear tip wheels 17a, 17b, 17c mounted on the rear tip wheel mounting assembler 14, a rear rear wheel mounting assembler 18, a rear rear end assembler mounting member 19, and a rear rear wheel mounting assembler 1.
8 are provided with rear rear wheels 21a, 21b, 21c.

Rear rear wheels 21a, 21b, 21c, rear front wheels 17a, 17b, 17c, front rear wheel 11
a, 11b, 11c and front tip wheels 7a, 7b, 7c
Is formed of synthetic rubber or the like having a large friction coefficient so that the remote field eddy current sensor SQ does not slip during traveling. The rear-end assembler mounting member 15 and the rear-end assembler mounting member 19 are provided with assembler mounting member flanges 16a, 16b, 20a, 20b, respectively. These assembler mounting member flanges 16a, 16b, 20
a, 20b, the rear tip wheel mounting assembler 14, the receiving coil mounting assembler 13
And the rear rear wheel mounting assembler 18 is fastened to each other. Note that the rear front end assembler mounting member 15 and the rear rear assembler mounting member 19 are formed in a cylindrical shape, and the receiving coil mounting assembler 13 has the receiving coil RCn (n is 16 for the sake of clarity, RC ₁ , 6 at 12:00). Time is set to RC ₉ ).

The front rear end assembler mounting member 9 and the rear front assembler mounting member 15 are connected to the shield core P _0.
Are penetrated and connected to each other by a flexible connecting member 12 that can freely bend. The receiving coil RC ₁ is mounted on the top of a triangular receiving coil holding plate 22 as shown in FIG. Ends 22a, 22 of receiving coil holding plate 22
b is the claw 2 of the receiving coil mounting assembler 13
4a and 24b limit the amount of movement in the radial direction.
In addition, the receiving coil holding plate 22 moves the receiving coil R in the radial direction.
Three sheets of spring material 23a so as to push the C _1, 23b, 23
c is mounted, and both ends of the spring member 23c are elastically provided at ends 26a and 26b of a disk-shaped support 26 provided inside the receiving coil mounting assembler 13.

As shown in FIG. 3, the receiving coil RC ₁ mounted on the top of the receiving coil holding plate 22 includes a bobbin 28 made of a non-magnetic material such as a synthetic resin, and a bobbin 2.
8, and a coil 29 is wound around the ferrite 27. The receiving coil RC ₁ is arranged to the magnetic path to the inner wall of the test試鋳iron pipes TU are vertical. Receive coil RC shield core P ₁ connected to _one another shield core P _0, P ₂ rear rear formed in a cylindrical shape with to P ₁₆ assembler mounting member 19
Is connected to a device for measurement, diagnosis, etc., which is installed outside through a connection terminal (not shown). In an actual apparatus, a cable for metal flaw detection inspection of several tens of meters is wound around a cable drum and sequentially fed out into a test cast iron tube TU.

The thus constructed remote field eddy current sensor SQ is inserted into the test cast iron tube TU, and the metal material inspection cable is sequentially fed out into the test cast iron tube TU. Rear wheels 21a, 21b, 21
c, rear front wheels 17a, 17b, 17c, front rear wheels 11a, 11b, 11c and front front wheels 7a, 7
Since b and 7c uniformly press the inner wall of the test cast iron tube TU, the center point of the test cast iron tube TU smoothly advances along the axis, and the vibration accompanying the progress is absorbed by the elasticity of the four pairs of wheels. Is done.
For this reason, the receiving coil RC ₁ pressed against the inner wall of the test cast iron tube TU by the three spring members 23a, 23b, 23c.
The RC ₁₆ travels in close contact with the inner wall of the test cast iron tube TU and detects a phase difference signal with little noise.

The receiving coil RC ₁ is angular phase difference signal is 6dB attenuation in the inner wall of the test試鋳iron pipe TU on which 15 ° apart circumferentially. Therefore, another receiving coil R is located at a position separated by 15 degrees.
If C ₂ is provided, the attenuation of 6 dB is equivalent to 24 reception coils R
Interpolation can be performed between C _{1 and} RC ₂₄ . However, in practice, the optimum number may not be installed due to the physical structure such as the inner diameter of the test cast iron tube TU. In this case, the number may be slightly smaller than the optimum number.

[0019]

[Effect of the Invention] As is clear from the above description, according to the remote field eddy current sensor of the present invention, the excitation voltage,
It is hardly affected by subtle changes in the excitation frequency and vibration when the remote field eddy current sensor travels inside the test metal tube, and accurately evaluates the depth of defects in the test metal tube based on the received phase difference signal. In addition, it is possible to detect the phase difference signal of all parts of the inner peripheral wall of the metal tube without attenuating it. Highly accurate diagnosis can be made for all inner walls.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a remote field eddy current sensor according to the present invention.

FIG. 2 is a cross-sectional view illustrating a mounting part of a receiving coil of the remote field eddy current sensor according to the present invention.

FIG. 3 is a cross-sectional view showing a position of a magnetic path of a receiving coil and a test metal tube of the remote field eddy current sensor according to the present invention.

FIG. 4 is a cross-sectional view of a conventional remote field eddy current sensor.

[Explanation of symbols]

1 Exciting coil 7a, 7b, 7c Front end wheel (front running member) 11a, 11b, 11c Front rear end wheel (front running member) 17a, 17b, 17c... Rear rear end wheel (rear running member) 21a, 21b, 21c... Rear rear end wheel (rear running member) 12 ... flexible connecting member (connecting member) ) RC _{1 to} RC ₁₆・ ・ ・ ・ ・ ・ Reception coil YU ・ ・ ・ ・ ・ ・ Test cast iron tube (test metal tube)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeru Fujiwara 2-1-1-12 Nishichuo, Kure-shi, Hiroshima CXR Co., Ltd. Development Division (72) Inventor Toshihide Kawabe 2-Nishichuo, Kure-shi, Hiroshima No. 1-12 CXR Development Division (56) References JP-A-64-35261 (JP, A) JP-A-2-126153 (JP, A)

Claims (1)

(57) [Scope of request for utility model registration] An exciting coil (1) for generating a remote field vortex in a metal tube (TU), and a forward traveling member (7a, 7) mounted with the exciting coil and traveling in the metal tube (TU).
b, 7c, 11a, 11b, 11c) and, from said exciting coil is provided apart a predetermined distance, and a plurality of receiving coils (RC ₁ which is provided in the pressing has been radially to the inner peripheral wall of the metal tube ~RC ₁₆ ) and a rear running member (17a, 17a) mounted with the plurality of receiving coils and running in the metal tube.
b, 17c, 21a, 21b, 21c) and a connecting member (12) for connecting the front running member and the rear running member.
And a predetermined number of receiving coils for receiving the remote field eddy current are provided such that respective magnetic paths are perpendicular to an inner peripheral wall of the metal tube.