JPH0933379A - Method for inspecting pipe by electromagnetic wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detecting precision and working easiness in the detection of a leakage position such as corroded hole generated in a pipe such as gas pipe by use of electromagnetic waves. SOLUTION: A number of emitting parts having directivity in the direction orthogonal to an axis are connected in the axial direction into a long form. For example, a long transmitting antenna 9 such as leakage coaxial cable is inserted to a range to be inspected of a pipe 1 to emit an electromagnetic wave from the inner part of the pipe, and the electromagnetic wave 7 leaked from a leakage position 6 such as a hole of the pipe to the outside is probed and received while receiving antenna 4 is moved along the pipe within the range to be inspected, thereby, the leakage position of the pipe is detected. The leakage position of the pipe can be detected by using an electromagnetic wave having a frequency lower than the cutoff frequency of the electromagnetic wave as the circular waveguide of the pipe, and when a buried pipe is inspected, the influence of the attenuation of electromagnetic wave by earth and concrete an be reduced. Since the synchronous movement of the transmitting and receiving antennas is not needed, the labor on field construction is reduced, and the generation of an inspection error is also reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection method for detecting leak points such as corrosion holes formed in a gas pipe by using electromagnetic waves.

[0002]

2. Description of the Related Art As one of methods for detecting a leaked portion such as a corrosion hole formed in a gas pipe, a detection method using electromagnetic waves has been proposed. The first inspection method using this electromagnetic wave
As shown in FIG. 2, as shown in FIG. 2, the electromagnetic wave is excited by the transmitter 3 from the exciter 2 which is attached by cutting the metal gas pipe 1 at an appropriate position, and the inspection target range is set in the same manner as the circular waveguide. While propagating and moving the receiving antenna 4 along the gas pipe 1 in the range to be inspected outside, the electromagnetic wave 7 leaking from the leaking point 6 is searched, and the leaking point 6 is detected by being received by the receiving device 5. There is a way. As a second method of the inspection method using electromagnetic waves, instead of exciting the electromagnetic waves in the gas pipe as in the first method, the transmitting antenna 8 is moved into the gas pipe 1 in the inspection target range, At the same time, there is a method in which the electromagnetic wave 7 leaking from the leaking point 6 is searched while the receiving antenna 4 is moved along the pipe in the inspection target range, and the leaking point 6 is detected by being received by the receiving device 5.

[0003]

In the first method, electromagnetic waves having a frequency lower than the cut-off frequency of the circular waveguide cannot be propagated to the gas pipe, so that soil, concrete or the like can be used for inspection of buried pipes. It may not be possible to reduce the frequency in order to reduce the amount of attenuation due to. According to the second method, it is difficult to move the transmitting antenna and the receiving antenna in synchronization with each other, and particularly in the case of the transmitting antenna, smooth movement is difficult. Then, this invention aims at solving such a subject.

[0004]

In order to solve the above-mentioned problems, according to the present invention, there is provided a transmitting antenna having a long length in which a large number of radiating portions having directivity in a direction orthogonal to an axis are connected in the axial direction. While radiating electromagnetic waves from the inside of the pipe by inserting it into the inspection target area of the pipe, while moving the receiving antenna along the pipe in the above inspection target range, search for electromagnetic waves leaking outside from leakage points such as holes in the pipe Then, it is proposed to detect the leaked part of the pipe by receiving it.

In the present invention, in the above structure,
It is proposed that the transmitting antenna be a long helical antenna whose directivity is adjusted in a direction orthogonal to the axis, a leaky coaxial cable, or a twisted pair leaky cable.

[0006]

Since a long transmitting antenna in which a large number of radiating parts having directivity in the direction orthogonal to the axis are continuous in the axial direction is inserted into the inspection target range of the pipe and electromagnetic waves are radiated from the respective radiating parts, Only the receiving antenna side can be moved along the pipe in the inspection range to detect leaking electromagnetic waves. Since the electromagnetic wave does not have to propagate inside the tube as a circular waveguide, the usable frequency is not limited to the cutoff frequency as a circular waveguide or more.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 schematically shows the overall configuration of an embodiment in which the method of the present invention is applied to detection of a leak location in a gas pipe,
The same components as those in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof will be omitted. In the present invention, as described above, the gas pipe 1 for the long transmission antenna 9 in which a large number of radiation portions having directivity in the direction orthogonal to the axis are connected in the axial direction.
Of the electromagnetic wave emitted from these radiating parts, and in this state, the receiving antenna 4 and the receiving device 5 are moved along the gas pipe 1 in the range to be inspected to search for the leaking electromagnetic wave 7. I do.

As an example of the long transmitting antenna 9 used in the present invention, a leaky coaxial cable used for mobile communication or a twisted pair leaky cable can be used. It is possible to insert a drive cable for a pipe exploration device or the like which has been widely used from the past into the gas pipe 1 by using an insertion mechanism or the like which can be moved in a live state of the gas pipe.

In addition to this, as the long transmission antenna 9,
A helical antenna in which the length of one turn of the helical wire is made extremely smaller than the wavelength of the electromagnetic wave to be radiated or n times the wavelength (n is an integer of 2 or more) is used to adjust the directivity in the direction orthogonal to the axis. It can be arranged in a long length and can be handled in the same manner as the above-mentioned cable by covering the helical wire with an insulator to form a cable.

In addition to the above, the transmitting antenna 9 may have an appropriate structure such as a large number of small antennas connected in a cable.

Further, in the above embodiments, the object of inspection is a gas pipe, but the present invention can be applied to an appropriate metal pipe in addition to the gas pipe.

[0012]

As described above, the present invention has the following effects in an inspection method for detecting leak points such as corrosion holes formed in gas pipes using electromagnetic waves. The leak point can be detected by using the electromagnetic wave with a frequency lower than the cutoff frequency of the electromagnetic wave as the circular waveguide of the pipe, and when the buried pipe is targeted, the influence of the attenuation of the electromagnetic wave by the soil and concrete can be considered. It can be reduced. Since it is not necessary to move the transmitting and receiving antennas in synchronism with each other, it is possible to reduce the labor on site construction and reduce the occurrence of inspection errors and the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an overall configuration of an embodiment in which the method of the present invention is applied to detection of a leak point in a gas pipe.

FIG. 2 is a schematic diagram showing an overall configuration of an example of a conventional method for detecting a leaked portion of a gas pipe using electromagnetic waves.

FIG. 3 is a schematic diagram showing an entire configuration of another example of a conventional leak detection method for a gas pipe using electromagnetic waves.

[Explanation of symbols]

 1 Gas Pipe 2 Excitation Unit 3 Transmitter 4 Receiving Antenna 5 Receiving Device 6 Receiving Point 6 Leakage Electromagnetic Wave 8 Transmitting Antenna 9 Long Transmitting Antenna

Claims (4)

[Claims] 1. A transmission antenna having a long length in which a large number of radiating portions having directivity in a direction orthogonal to an axis are connected in the axial direction is inserted into a range of a pipe to be inspected, and electromagnetic waves are radiated from the inside of the pipe. While moving the receiving antenna along the pipe in the range to be inspected externally, the leaking point of the pipe is detected by searching and receiving the electromagnetic wave leaking outside from the leaking point such as the hole of the pipe. Method of inspecting tubes with electromagnetic waves 2. The method for inspecting a pipe by electromagnetic waves according to claim 1, wherein the transmitting antenna is a long helical antenna whose directivity is adjusted in a direction orthogonal to the axis. 3. The method for inspecting a pipe by electromagnetic waves according to claim 1, wherein the transmitting antenna is a leaky coaxial cable. 4. The method for inspecting a pipe by electromagnetic waves according to claim 1, wherein the transmitting antenna is a twisted pair leak cable.