JPH02187684A - Joint position detecting method - Google Patents

Abstract

PURPOSE:To detect a position of a joint by only executing a simple operation by inserting an antenna into an underground buried metallic tube, radiating a high frequency signal to the underground buried metallic tube from the antenna and propagating it in one direction in the underground buried metallic tube. CONSTITUTION:A pulser 31 generates a pulsative high frequency voltage (a frequency being higher than a cut-off use frequency determined from the pipe diameter of an underground buried metallic tube 22) by a periodical trigger signal from a control circuit 34. This high frequency voltage is applied to an antenna 28 through a directional coupler 32 and a cable 27, radiated into the underground buried metallic tube 22 from the antenna 28 and propagated in one direction in the underground buried metallic tube 22. On the other hand, a reflected wave which passed through the antenna 28 and the cable 27 from joints 22a, 22b of the underground buried metallic tube 22 is inputted to a CRT indicator 33 through the directional coupler 32. Subsequently, by detecting the receiving time of the reflected wave which returns through the antenna from the joint and executing an operation with a velocity of propagation in the underground buried metallic tube of a high frequency signal, a position of the joint can be detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a method for detecting the position of a joint (mechanical joint, threaded joint, etc.) of a metal pipe such as a gas pipeline buried underground without excavation. The present invention relates to a joint position detection method.

[Conventional technology]

Conventionally, to detect the position of a joint in a steel gas pipeline buried underground without digging, a magnetic sensor consisting of multiple coils is inserted into the gas pipeline, and the magnetic sensor is moved through the gas pipeline. The magnetic sensor detects changes in magnetic resistance at the joint, and also detects changes in the length of the connecting cable of the magnetic sensor.

A conventional example will be explained in more detail with reference to the drawings.

The magnetic sensor includes, for example, an excitation coil CLo and an excitation coil CL, as shown in FIGS.

It consists of a pair of detection coils CL, CL2 arranged on both sides of the gas conduit P in the tube axis direction, and these coils move in the gas conduit P as a unit.

If the magnetic sensor consisting of the excitation coil CLo and the pair of detection coils CL, CL2 is located at a position other than the joint of the gas pipe P, as shown in FIG. 4 (al), the excitation coil CL
magnetic circuit MC1 interlinked with o and detection coil CL.
magnetic resistance, excitation coil CLo, and detection coil C
The magnetic resistance of the magnetic circuit MC2 interlinked with L2 is the same, and the pair of detection coils JL/CL, CL2 (7) induced voltages v, , v2 are equal, for example, the pair of detection coils C
L.

Induced voltage V of CH2; differential voltage V2-V of V2.

As shown in FIG. 5(a), remains at zero regardless of the position of the magnetic sensor in the gas conduit P.

On the other hand, as shown in FIG. 4 (bl), the excitation coil CL.

If a magnetic sensor consisting of a pair of detection coils CL, CL2 is located at the joint pc of the gas pipe P, the magnetic resistance of the magnetic circuit MC and the magnetic circuit MC2 will change due to the difference in magnetic permeability between iron and gas. The magnetic resistance is no longer the same.

That is, the induced voltages v, , v2 of the pair of detection coils CL, CL2 take on different values when crossing the position of the joint pc, and for example, the induced voltages v, , v2 of the pair of detection coils CL, CL2 differ. The differential voltage v2-v is shown in Figure 5 +a
As shown in 1, the position of the joint pc in the gas conduit P swings between positive and negative directions.

FIG. 6 shows the configuration of a joint position detection device that detects the position of a joint of a gas conduit using the magnetic sensor.

In Fig. 6, 1 is a magnetic sensor having the above configuration, 2 is a cable, 3 is a gas pipe, 3a, 3b, 3c are joints in the gas pipe 3, 4 is a no-blow jig, 5 is a distance measuring device, 6 is a cable 7 is a distance indicator, 8 is a measuring device that receives the signal from the magnetic sensor 1, and 9 is a recorder. 10 is earth, 1
1 is a hole for inspection made in the ground 10, and 12 is the ground surface.

In this joint position detection device, a magnetic sensor 1 connected to the tip of a cable 2 is connected to a gas conduit 3 using a no-blow jig 4.
Insert into. Then, while winding the cable 2 around the cable drum 6, the output signal of the magnetic sensor 1 is measured by the measuring device 8.
The joints 3a, 3b of the gas conduit 3 are detected and recorded on the recorder 9, and the winding length of the cable 2 is measured using the distance measuring device 5 and displayed on the distance display 7.

Each position of 3c is detected.

[Problem to be solved by the invention]

The conventional example described above has a problem in that the joint position detection device for detecting the positions of the joints 3a3b, 3c of the gas conduit 3 is large-scale and extremely expensive. Also, the joint 3a
, 3b, and 3c, two to three workers are required and the labor cost is high. Also,
It is necessary to excavate a hole 11 as large as about 1M for detecting the joint position. Furthermore, it takes a long time (about 4 hours) to detect the position of one joint.

Therefore, an object of the present invention is to be able to detect the joint position with a simple and inexpensive device, to reduce the number of workers required for detection, to allow the hole diameter to be drilled in the ground surface for detection to be small, and to be short. It is an object of the present invention to provide a joint position detection method that can detect a joint position based on time.

[Means to solve the problem]

The joint position detection method of the present invention involves drilling a hole reaching from the ground surface to the underground metal pipe, drilling a through hole in the pipe wall of the underground metal pipe through the hole, and passing the hole and the through hole through the underground metal pipe. An antenna is inserted into the underground metal pipe, and a high-frequency signal with a frequency higher than the cutoff frequency determined by the pipe diameter of the underground metal pipe is radiated from the antenna into the underground metal pipe only in one direction of the pipe axis. The waves are propagated in a metal tube, and the reflected waves are received by the antenna. Then, the distance from the antenna insertion position of the underground metal pipe to the joint is detected based on the reception time of the reflected wave.

[For production]

In the configuration of this invention, the antenna is inserted into the underground metal pipe through a hole provided in the ground surface directly above the underground metal pipe and a through hole provided in the wall of the underground metal pipe.

In this state, a high frequency signal having a frequency higher than a cutoff frequency determined from the pipe diameter of the underground metal pipe is radiated from the antenna into the underground metal pipe only in one direction of the pipe axis. As a result, the high frequency signal radiated from the antenna propagates inside the underground metal pipe in one direction of the pipe axis.

If there is a joint in the underground metal pipe, the characteristic impedance of the underground metal pipe changes at this joint, causing reflection of high-frequency signals, and as some of the high-frequency signals return via the antenna. become.

The position of the joint can be detected by detecting the reception time of the reflected wave returning from the joint via the antenna and calculating the propagation speed of the high-frequency signal in the underground metal pipe.

In this case, the high frequency signal is radiated from the antenna into the underground metal pipe only in one direction of the pipe axis, so the direction of the joint can be determined based on the orientation of the antenna.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 to 3. In this joint position detection method, as shown in FIG. 1, a hole 24 with a diameter of about 10 cm is created by poling on the ground surface 23 directly above an underground metal pipe 22, such as an iron gas conduit, buried in the ground 21. to drill. This hole 24 needs to reach the outer surface of the underground metal pipe 22.

After providing the hole 24, the underground metal pipe 22 is inserted through the hole 24.
A through hole 25 for inserting the antenna is bored in the pipe wall.

After providing the hole 24 and the through hole 25, an antenna (for example, a dipole antenna) 28 connected to the tip of the cable 27 pulled out from the joint position detection device 26 is passed through the hole 24, and then passed through the through hole 25 to the underground metal pipe 22. Insert inside. The antenna 28 is provided with a shielding plate (or a reflecting plate) 29 made of a radio wave absorption band on the back so that the high frequency signal transmitted from the joint position detection device 26 through the cable 27 is radiated in only one direction. It is configured. The radial direction is set in one direction (upstream side or downstream side) of the pipe axis of the underground metal pipe 22.

Note that since the above-mentioned through hole 25 is opened using a no-blow jig or the like, gas will not be ejected from the underground metal pipe 22.

In this state, the joint position detection device 26 outputs a high frequency signal (for example, monopulse, etc.) with a frequency higher than the cutoff frequency determined by the pipe diameter of the underground metal pipe 22 at regular intervals, and this high frequency signal connects the cable 27. The radiation is radiated from the through antenna 28 into the underground metal pipe 22, and propagates in one direction within the underground metal pipe 22 as shown by arrow A1.

A joint 22a is provided in the middle of the underground metal pipe 22.

22b, reflection occurs at the joints 22a and 22b, and part of the high frequency signal is reflected by the arrow A2. As shown by A3, the reflected wave returns via the antenna 28 and the cable 27, and the joint position detection device 26 receives this reflected wave. The joint position detection device 26 detects the reception time of the reflected waves by the joints 22a and 22b based on the emission time of the high frequency signal.

The distances LA and LB from the position of the through hole 25 of the underground metal pipe 22 to the joints 22'a and 22b of the underground metal pipe 22 are as follows:
It can be easily determined from the reception time of the reflected waves by the joints 22a and 22b and the propagation speed (2) of the high frequency signal inside the underground metal pipe 22.

In the above, the number of joints 22a and 22b that can be detected is about five at maximum due to attenuation of reflected waves. Note that in order to detect the positions of the joints 22a and 22b, it is necessary to sufficiently match the impedance between the joint position detection device 26 and the cable 27 and between the cable 27 and the antenna 28.

In this joint position detection method, the underground metal pipe 22
An antenna 28 is inserted into the underground metal pipe 22 through a hole 24 provided in the ground surface 23 directly above the ground and a through hole 25 provided in the pipe wall of the underground metal pipe 22. At this time, since a no-blow jig or the like is used, gas will not blow out from the underground metal pipe 22.

In this state, a high frequency signal with a frequency higher than the cutoff frequency determined by the pipe diameter of the underground metal pipe 28 is transmitted from the antenna 28 into the underground metal pipe 22 in one direction (upstream side or downstream side) of the pipe axis. only radiated. As a result, the high frequency signal radiated from the antenna 28 is transmitted to the underground metal pipe 22.
It will propagate inside the tube only in one direction along the tube axis. By reversing the direction of the antenna 28, a high frequency signal can be radiated in the other direction of the tube axis, and the position of the joint in the other direction of the tube axis can be detected.

If there are joints 22a and 22b in the underground metal pipe 22,
The characteristic impedance of the underground metal pipe 22 changes at the joints 22a and 22b, and a high-frequency signal is reflected, and a part of the high-frequency signal is used as a reflected wave to detect the joint position via the antenna 28 and cable 27. It will return to device 26.

By detecting the reception time of the reflected waves returning from the joints 22a and 22b via the antenna 28 and calculating the general speed of transmission of the high frequency signal in the underground metal pipe 22, the joint 2
The positions of 2a and 22b can be detected. In this case, the high frequency signal is radiated from the antenna 28 into the underground metal pipe 22 only in one direction of the tube axis, so the direction of the joints 22a, 22b can be determined based on the direction of the antenna 28.

FIG. 2 shows a waveform diagram of a received signal that returns to the joint position detection device 26 via the antenna 28 and cable 27 and is received by the joint position detection device 26 when a high frequency signal is radiated from the antenna 28. ing. This second
The waveform diagram in the figure depicts the waveform of the reflected wave received by the antenna 28 based on the timing at which the high-frequency signal is radiated from the antenna 28, and shows the time required for a round trip from the joint position detection device 26 to the antenna 28. is ignored. In FIG. 2, pulse P at time t.

indicates a transmission pulse outputted from the antenna 28 as a high frequency signal, and the pulse PA at time tA is the transmission pulse output from the underground metal pipe 2.
The pulse P at time tB shows the reflected wave returning from the joint 22a of No. 2 to the joint position detection device 26 via the antenna 28.
B is the antenna 28 from the joint 22b of the underground metal pipe 22.
It shows the reflected wave that returned to the joint position detection device 26 via .

Hereinafter, the joint 22 of the underground metal pipe 22 will be explained based on FIG.
The procedure for detecting the positions of a and 22b will be specifically explained.

From the through hole 25 of the underground metal pipe 22 to the joint 22a22b
The distances LA and LB to the underground metal pipe 22 are LA-■, × (tA-to)/2, respectively (1
)LB=V,X (tB-t o)/2 ・,,,
,,(represented by 21).

FIG. 3 is a block diagram showing a specific configuration of the joint position detection device 26 described above. In FIG. 3, 31 is a pulser that generates a pulsed high-frequency voltage, 32 is a directional coupler, and 3
3 is a CRT display, and 34 is a control circuit.

In this joint position detection device 26, the pulser 31 generates a pulsed high frequency voltage (frequency higher than the cutoff frequency determined by the pipe diameter of the underground metal pipe 22) in response to a periodic trigger signal from the control circuit 34. This high frequency voltage is applied to the antenna 28 through the directional coupler 32 and the cable 27, is radiated from the antenna 28 into the underground metal pipe 22, and propagates in the underground metal pipe 22 in one direction. On the other hand, the joint 22a22b of the underground metal pipe 22
The reflected wave is input to the CR7 display 33 through the directional coupler 32 via the antenna 28 and cable 27 . The CR7 display 33 displays the received signal, which is a reflected wave, in a waveform according to the horizontal sweep signal given from the control circuit 34. The waveform displayed on this CR7 display 33 is the waveform diagram shown in FIG. and,
Each time LA, 1B on the waveform diagram can be measured by reading the scale on the screen of the CR7 display 33.

According to this embodiment, the antenna 28 is connected to the underground metal pipe 2.
2, radiates a high frequency signal from the antenna 28 to the underground metal pipe 22, propagates in one direction inside the underground metal pipe, and receives reflected waves that return from the joints 22a and 22b via the antenna 28. However, the joint position can be detected with a simple and inexpensive device that only processes the received reflected waves.

In addition, a hole 2 reaching the underground metal pipe 22 from the ground surface 23
At the same time, a through hole 25 is drilled in the tube wall of the underground metal pipe 22, and a cable 27 with an antenna 28 connected to the tip is passed through the hole 24 and the through hole 25 to the underground metal pipe 22. It is only necessary to insert the antenna 28 and look at the screen of the CR7 display 33, so the number of workers for detection can be reduced.
, ; <-(Zumu.

Furthermore, since it is only necessary to insert the 2-/nana 284 at the tip of the cable 27 into the underground metal pipe 22, the hole 24 extending from the ground surface 23 to the underground metal pipe 22 has a diameter of approximately 0 cm. The through hole 25 provided in the underground metal pipe 22 only needs to have a diameter of about 3 cm, making the drilling process extremely simple.

Also, by simply drilling the hole 24 and the through hole 25, inserting the antenna 28 into the underground metal pipe 22, and then looking at the screen of the CRT display 33 in the joint 1-position detection device 26 and performing simple calculations. , the positions of the joints 22a, 22b can be detected, and the positions of the joints 2'la, 22b can be detected in a short time of about 30 minutes.
The position of b can be found.

Further, by setting the antenna 28 once, the positions of a plurality of joints (up to five) upstream and downstream of the through hole 25 can be detected.

〔Effect of the invention〕

According to the joint position detection method of the present invention, a hole is made from the ground surface to the underground metal pipe, a through hole is made in the pipe wall of the underground metal pipe through the hole, and a through hole is inserted into the underground metal pipe from the through hole. An antenna is inserted into the underground metal pipe, and a high-frequency signal is radiated from the antenna into the underground metal pipe to propagate in one direction inside the underground metal pipe, and the counterwave is generated. The joint position can be detected with a simple and inexpensive device that receives the antenna and processes the received reflected waves, and the number of workers required for detection is small, and the joint position can be detected in a short time. Can be done. Furthermore, the holes drilled in the ground for detection can be made with small inner diameters, as the antenna only needs to be passed through.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the configuration of an embodiment of the present invention;
Figure 2 is a received waveform diagram of reflected waves, Figure 3 is a block diagram showing the specific configuration of the joint position detection device, Figure 4 is a schematic diagram showing the configuration of the magnetic sensor used in the conventional example, and Figure 5 is the magnetic sensor. FIG. 6 is a schematic diagram showing the overall configuration of a conventional joint position detection device. 21...Earth, 22...Underground metal pipe, 22a2
2b...Joint, 23...Ground surface, 24...Hole, 2
5... Through hole, 26... Joint position detection device, 27.
... Cable, 28... Antenna, 29... Shielding plate -610 = Diagram time - V2-V. f MC. C2 (a) (a) Figure (b)

Claims (1)

[Claims] Drilling a hole that reaches from the ground surface to the underground metal pipe, and drilling a through hole in the wall of the underground metal pipe through the hole, and inserting the hole into the underground metal pipe through the hole and the through hole. An antenna is inserted into the underground metal pipe, and a high frequency signal having a frequency higher than a cutoff frequency determined by the pipe diameter of the underground metal pipe is radiated from the antenna into the underground metal pipe only in one direction of the pipe axis. A method for detecting a joint position, characterized in that the antenna propagates in the pipe, receives a reflected wave with the antenna, and detects the distance from the antenna insertion position of the underground metal pipe to the joint based on the reception time of the reflected wave.