JP3119321B2 - Detection method of target points in buried pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a serious defect such as a reduction in wall thickness of a buried pipe and a target portion such as a joint.

[0002]

2. Description of the Related Art There is a remote field eddy current type flaw detector as one of devices for inspecting the state of corrosion of a buried pipe or detecting a joint or the like.

In this flaw detection apparatus, a flaw detection sensor having a transmission coil and a reception coil separated by a predetermined distance is caused to travel through a buried pipe by a traveling device capable of measuring the distance, and the propagation time of electromagnetic waves from the transmission coil to the reception coil is measured. In addition to detecting a defect such as corrosion thinning or a through-hole or a target portion such as a joint by a change in the target, the target portion such as the defect is measured by a traveling distance of a flaw detection sensor.

[0004]

Since the measurement of the position based on the traveling distance is a measurement using a one-dimensional scale, if the pipe is curved, the position where a defect or the like is detected cannot be accurately measured as a two-dimensional position. .

[0005] Therefore, in the case of repairing a pipe location in which such a defect or the like is detected by excavation, useless excavation or misidentification of another pipe that happens to be close to the excavated location is performed. In some cases, such inconveniences may occur. An object of the present invention is to solve such a problem.

[0006]

According to the present invention, there is provided a pig for generating an alternating magnetic field from a built-in transmitting coil while moving in a buried pipe, and a receiving apparatus for receiving the alternating magnetic field from the transmitting coil. A receiving device provided with a coil is used, and the receiving device has a first symmetrically disposed first device.
Of the pair of receiving coils and the first pair of receiving coils.
From the second pair of receiving coils provided before and after on the symmetry axis
And the winding axes of these receiving coils are parallel to the target axis.
A first and second pair of receiving means are provided with the configured position adjusting means.
Set the receiver so that the reception levels of the coils are equal.
Adjust the position to determine the relative position of the receiver coil and transmitter coil.
Move the receiver to follow the pig while keeping the
Is dynamic, while moving in this way, continuously measures the reception level of the alternating magnetic field from the transmitting coil by a receiving coil, it proposes a method of detecting the presence and location of the target location by the scope of the reception level has changed.

Further, the present invention relates to such a method,
Use one of these receiving coils for receiving level measurement
It is proposed to adopt a configuration in which:

[0008]

In the above construction, the pig is driven by pulling or pushing by a wire while generating an AC magnetic field from a built-in transmitting coil, driven by a self-propelled driving mechanism, or driven by gas pressure. The target is moved inside the buried pipe. On the other hand, the receiving device moves while following the movement of the pig so that the relative positional relationship between the receiving coil and the transmitting coil built therein is constant.
The reception level of the AC magnetic field from the transmission coil is continuously measured by the reception coil.

Assuming that the relative positional relationship between the reception coil and the transmission coil is constant, the reception level of the AC magnetic field received by the reception coil from the transmission coil through the buried pipe is as follows:
It depends on the condition of the buried pipe.

That is, if a part of the wall of the buried pipe is reduced in thickness due to corrosion or the like, an alternating magnetic field leaking to the outside through the wall increases, and the reception level in this range increases. Therefore, the presence of the range where the reception level becomes high detects the thinned portion, and at the same time, the position as the projection position on the ground can be detected.

On the other hand, in a portion where the thickness of the wall of the buried pipe is equivalently thick, such as a joint portion, the alternating magnetic field leaking therethrough decreases, so that the reception level in this range becomes low. Therefore, the presence of the range in which the reception level becomes low detects the joint portion, and at the same time, the position as the projection position on the ground can be detected.

As described above, according to the present invention, it is necessary to move the receiving device following the movement of the pig so as to keep the relative positional relationship between the receiving coil and the transmitting coil built therein.

According to the present invention, the receiving device is symmetrically disposed.
A first pair of receiving coils, and the first pair of receiving coils
A second pair of receiving coils provided before and after on the axis of symmetry of the coil;
And the winding axis of these receiving coils is
It has established a parallel arrangement position adjusted manually stage and, first, second
The receiving levels of the two pairs of receiving coils will be equal
By adjusting the position of the receiving device
And the relative positional relationship between the transmission coil and the
Therefore, even if the projected position on the ground is an unknown
Transmission device, the phase of the reception coil and transmission coil built into it.
Move following the pig so that the positional relationship is constant.
Can be moved.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing the basic concept of the method of the present invention. Reference numeral 1 is the pig, the second transmission coil which is a built in this pig 1, 3
Is an oscillator. The pig 1 is configured to move in the buried pipe 4 by an appropriate method as described later. On the other hand, reference numeral 5 denotes a receiving device, which has a transmitting coil 2
And a receiving coil 6 for receiving an AC magnetic field from the receiver and measuring means 7 for measuring the reception level. The frequency of the AC magnetic field generated from the transmission coil 2 can be appropriately selected, for example, from a frequency range normally used in a pig locator. For example, in the case of a ferromagnetic buried pipe
It can be selected from the range of 10 to 100 Hz, and in the case of stainless steel pipe, polyethylene pipe, etc.
It can be appropriately selected from a range up to about Hz.

FIG. 2 shows a planar arrangement of the receiving coil 6 and the like in the embodiment of the receiving apparatus 5 applied to the present invention. In this embodiment, in addition to the above-mentioned receiving coil 6, the receiving coil 6 is arranged symmetrically. The first pair of receiving coils 8a and 8b provided and the second pair of receiving coils 9a and 9b provided before and after on the symmetry axis s of the first pair of receiving coils 8a and 8b are provided. Of the receiving coils 8a, 8b, 9a, and 9b are arranged in parallel with the target axis s to provide position adjusting means. In this embodiment, the receiving coil 6 is provided separately from the receiving coils 8a, 8b, 9a, 9b, which are components of the position adjusting means. However, in the embodiment of FIG. The receiving coil 9a, which is an element, is also used. In FIGS. 2 and 3, reference numeral 10 denotes control means for comprehensively controlling the measuring means 7 and the position adjusting means.

When the above-mentioned receiving device 5 is applied, the buried pipe 4 to be detected may be one whose projection position on the ground is not known, and the pig 1 moves inside the buried pipe 4. The driving method used in the conventional pig locator is also the driving method used, for example, driving by pulling or pushing by a cable, driving by a self-propelled mechanism such as a self-propelled robot, pressure of gas flowing through the buried pipe 4. And the like can be used.

The pig 1 is moved into the buried pipe 4 while generating an AC magnetic field from the built-in transmitting coil 2 in this way, and the receiving device 5 is moved following the movement of the pig 1 and the receiving coil 6 is moved. Thus, the reception level of the AC magnetic field from the transmission coil 2 is continuously measured and recorded on an appropriate recording medium such as recording paper or a magnetic recording medium.

At this time, a pair of left and right receiving coils 8a, 8b
When the receiving device 5 is moved right and left so that the receiving levels become equal, the target axes s of the receiving coils 8a and 8b are located immediately above the winding axis of the transmitting coil 2 when the receiving levels become equal. When the receiving device 5 is moved back and forth so that the reception levels of the pair of front and rear reception coils 9a and 9b become equal, when the reception levels become equal, the transmission coil 2 is located at the central position of these. Is adjusted as follows. In this manner, by moving the receiving device 5 so that the receiving level is equal for each pair, the receiving device 5 is pig 1 in a state where the relative positional relationship between the receiving coil 6 and the transmitting coil 2 is constant. It can be moved following the movement of.

Assuming that the relative positional relationship between the receiving coil 6 and the transmitting coil 2 is constant, the receiving level of the AC magnetic field that leaks from the transmitting coil 2 through the wall of the buried pipe 4 and is received by the receiving coil 6 becomes It depends on the state of the buried pipe 4.

For example, as shown in FIG. 4, when the wall of the buried pipe 4 has a thinned portion 11 due to corrosion, an alternating magnetic field leaking from the transmitting coil 2 to the outside of the buried pipe 4 via the thinned portion 11 increases. Therefore, the reception level in the range corresponding to the thinned portion 11 increases. When the pig 1 reaches the joint portion 12 as shown in FIG. 5, the wall of the buried pipe 4 is equivalently thicker at this portion, so that the AC magnetic field leaking therethrough is reduced. For this reason, the reception level in the range corresponding to the joint portion 12 is reduced.

Therefore, a change in the reception level via the reception coil 6 is monitored every moment, or the recorded data is analyzed to observe the presence or absence of a range in which the reception level has changed. Then, when there is a range where the reception level is high, the thinned portion 11 is used. When there is a range where the reception level is low, the joint 12 is used as their position, that is, their projection position on the ground. The position can be detected.

When the buried pipe 4 is inclined, the reception level also changes in accordance with the inclination. This change is almost monotonically increasing or decreasing. Since it does not appear as a change within the range, it is easy to distinguish it from the detection target.

As described above, when the receiving apparatus 5 of the embodiment shown in FIG. 2 or FIG. 3 is used, even if the buried pipe 4 to be detected does not know the projection position on the ground,
The position adjusting means can move the pig 1 following the movement of the pig 1 so as to keep the relative positional relationship between the receiving coil 6 and the transmitting coil 2 constant. Thus, the above-described detection of the thinned portion 11 and the joint portion 12 is performed. be able to.

[0024]

As described above, according to the present invention , the receiving apparatus includes the left side.
A first pair of receiving coils disposed symmetrically to the right,
Second pair of receiving coils provided before and after the pair of receiving coils on the symmetry axis.
A pair of receiving coils, the windings of these receiving coils
Is provided in parallel with the target axis.
Therefore, the buried pipe to be detected is projected on the ground
Even if you do not know, the receiving coil and the transmitting coil
Follow the pig movement so that the relative positional relationship of
Thus, it is possible to detect a serious defect such as corrosion thinning in a buried pipe and a target portion such as a joint with a simple device configuration.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a basic concept of the present invention.

FIG. 2 is an explanatory diagram showing a planar arrangement of a receiving coil and the like in an embodiment of a receiving apparatus applied to the present invention.

FIG. 3 is an explanatory diagram showing a planar arrangement of a receiving coil and the like in another embodiment of the receiving apparatus applied to the present invention, together with an explanation of the operation of the present invention.

FIG. 4 is an explanatory diagram showing an example of a serious defect of a buried pipe detected by the present invention and a change in a reception level due to the serious defect.

FIG. 5 is an explanatory diagram showing an example of a joint portion of a buried pipe detected according to the present invention and a change in a reception level due to the joint portion.

[Explanation of symbols]

 Reference Signs List 1 pig 2 transmitting coil 3 oscillator 4 buried pipe 5 receiving device 6 receiving coil 7 measuring means 8a, 8b receiving coil 9a, 9b receiving coil 10 control means 11 thinning part 12 joint part

Claims (2)

(57) [Claims] 1. A pig for generating an AC magnetic field from a built-in transmission coil while moving inside a buried pipe, and a receiving device provided with a receiving coil for receiving an AC magnetic field from the transmitting coil . The first one arranged symmetrically
Pair of receiving coils and symmetry of the first pair of receiving coils
And a second pair of receiving coils provided before and after on the axis.
The winding axes of these receiving coils are parallel to the target axis.
And a pair of first and second receiving cores.
Of the receiving device so that the reception levels of the
Adjust the position to adjust the relative position of the receiving coil and the transmitting coil.
The receiver follows the movement of the pig while keeping the
, Wherein the receiving coil continuously measures the receiving level of the AC magnetic field from the transmitting coil while detecting the position, and detects the presence and position of the target portion from the range in which the receiving level has changed. Method of detecting target points in pipes 2. A receiving level measurement of one of the receiving coils.
2. The structure according to claim 1, wherein the structure is also used for
Method for Detecting Target Locations in Buried Pipes