JPS623654A - Measuring instrument for crack depth in tube - Google Patents

Abstract

PURPOSE:To measure easily the depth of a crack of the inside wall of a tube by providing an electrode, which is pressed against the inside wall of the tube at measurement, on the outside periphery of a cylinder body mounted on a moving body moved in the tube. CONSTITUTION:A moving body 3 is moved at a uniform speed in the direction of an arrow; and when a welding position detecting sensor 7 detects a welding part 2 of a steel tube 1, a control pat issues a stop command to driving mechanisms 5a and 5b to stop the moving body 3. Next, the control part issues a movement start command to advance the moving body 3 for a length l between center positions of the sensor 7 and a cylinder body 8. When the part 2 reaches the center position of the cylinder body 8, the control part issues the stop command to mechanisms 5a and 5b to stop the moving body 3. Front ends of current supply electrodes 9 and 9b and potential difference detecting electrodes 10a and 10b are abutted on the inside wall of the tube 1 by a high pressure bomb 11. Currents are supplied from electrodes 9a and 9b to the inside wall of the tube 1 in this state to measure the potential between electrodes 10a and 10b, thus measuring the position and the depth of the crack.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention is a method for detecting cracks occurring in welded parts of the inner walls of pipes used in vibrine, etc., and for automatically measuring the depth of cracks in pipes. ∆ constant device (related to this).

[Prior Art] When constructing a pipeline for transporting crude oil, natural gas, etc., a large number of steel pipes are sequentially welded to form one pipeline. When the welding work is completed, it is necessary to confirm from the outer and inner circumferential surfaces of the tube that there are no cracks caused by insufficient penetration in the welded portion of the tube.

Conventionally, cracks that occur in welded parts of members made of conductive materials such as steel are detected, and the depth of the detected cracks is measured using the following procedure. In other words, two or more current supply electrodes are placed in pressure contact with each other between the welded portions of the steel surface using hydraulic or pneumatic pressure, and a pair of potential difference detection electrodes is connected between the current supply electrodes using a similar Pressure weld using the method. and,
A current is applied from an external current source through the current supply electrode to the steel containing the weld. In this state, information on the presence or absence of a crack and the crack depth are obtained by measuring the potential difference between the potential difference detection electrodes using a voltmeter or the like.

[Problems to be Solved by the Invention] However, when applying the above method to a welded part of a pipeline, it is relatively easy to inspect the welded part from the outer surface, but this is not possible when considering work efficiency etc. It was difficult to inspect the welded area from the inside of the tube unless a special jig was developed.

The present invention has been made based on these circumstances, and its purpose is to provide an electrode that is pressed against the inner wall of the tube at fixed DI times on the outer periphery of a cylindrical body mounted on a moving body that moves inside the tube. An object of the present invention is to provide an in-pipe crack depth measuring device that can easily measure the depth of cracks generated in the inner wall.

[Means for Solving the Problems] The apparatus for measuring the depth of cracks in a pipe according to the present invention has a movable body that moves in the axial direction inside a pipe made of a conductive material whose axis is parallel to the axis of the pipe. Equipped with a cylindrical body for holding electrodes, multiple current supply electrodes and multiple potential difference detection electrodes are arranged in the axial direction on the outer circumference of this cylindrical body, and an electrode extrusion mechanism is used to measure the crack depth on the inner wall of the tube. The current supply electrode and the potential difference detection electrode are pressed against the inner wall, and with the current supply source supplying current to the current supply electrode, the potential difference measuring section measures the potential difference between the potential difference detection electrodes pressed against the inner wall. measure. Furthermore, a position detection section detects the position of the moving body within the pipe at the time of measurement.

[Function] With the apparatus for measuring the depth of cracks in a pipe configured as described above, when the crack depth in the inner wall of the pipe is 01, the electrodes are arranged in the axial direction of the outer periphery of the cylindrical body mounted on the movable body by the electrode pushing mechanism. A current supply electrode and a potential difference detection electrode are pressed against the inner wall of the tube.

In this state, a current is supplied from the current supply source to the inner wall of the tube via the current supply electrode, and the potential difference measurement section measures the potential between the potential difference detection electrodes, and the position detection section detects the position. Ru.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an apparatus for measuring the depth of cracks in a pipe according to an embodiment. In the figure, reference numeral 1 indicates a steel pipe 1 constituting a vibrating line, and annular welded portions 2 are formed at regular intervals in the axial direction of this steel pipe 1. A moving body 3 called a pig traveling vehicle is inserted into the steel pipe 1.
Moving mechanisms 5a and 5b are fixed at two locations, front and back, on the central shaft 4, which is disposed at the axial center position of By rotating the wheels 6a and 6b, the steel pipe 1 can be freely moved in the axial direction.

A welding position detection sensor 7 formed of, for example, an eddy current detection device is attached to the central axis 4 of the movable body 3 to detect when the movable body 3 has reached the welded portion 2 position of the steel pipe 1. . Furthermore, the central axis 4 has a steel pipe 1 whose openings at both ends are covered.
A cylindrical body 8 having a slightly smaller diameter is attached. A total of four needle-shaped electrodes, current supply electrodes 9a, 9b and potential difference detection electrodes 10a, 10b, are arranged in the axial direction of the outer circumference of this cylindrical body 8, such that the current supply electrodes 9a, 9b are located at both ends. Arranged. Sixteen sets of electrode groups each consisting of four needle-like electrodes are arranged at equal intervals in the outer circumferential direction of the cylindrical body 8.

Note that the center position of the welding position detection sensor 7 and the center position of the cylindrical body 8 are separated from each other by a distance in the axial direction.

A ring-shaped high-pressure cylinder 11 is attached to the center shaft 4 at a position adjacent to the cylindrical body 8, and a measurement processing section 12 housed in a cylindrical case is attached to a position near the end of the center shaft 4. A distance measuring roller 13 for measuring the moving distance of the movable body 3 from the opening of the steel pipe is attached to a case housing the measurement processing section 12 via a support arm.

2 and 3 are schematic cross-sectional views showing the inside of the cylindrical body 8. The needle-shaped current supply electrodes 9a, 9b and the potential difference detection electrode 10 are arranged in the axial direction of the outer peripheral surface of the cylindrical body 8.
Four through holes 14 are bored through which the a and 10 b pass. One end of each current supply electrode 9a, 9b and potential difference detection electrode 10a, 10b is connected to a cylinder 15, respectively.
is fixed to the drive shaft. Moreover, inside the cylindrical body 8, a (4 x 16)
All individual electrodes 9a, 9b, 10a,
A connected annular air reservoir 16 is formed in the cylinder 15i of 10b, and this air reservoir 16 is connected to the high pressure cylinder 11 via an electromagnetic control valve 17.

Therefore, when the electromagnetic control valve 17 is wide open, the high pressure air in the high pressure cylinder 11 drives each cylinder 15 through the air reservoir 16, and all the current supply electrodes 9a attached to the drive shaft of each cylinder 15, 9b and potential difference detection electrodes 10a, 10b are moved toward the outer circumference of the cylindrical body 8, and the tips of each electrode are pressed against the inner wall of the steel pipe 1 as shown in FIG.

Also, when the opening degree of the electromagnetic control valve 17 is reduced, air pockets 16
The air pressure within each electrode 9a, 9b decreases.

10a and 10b return to their original positions. FIG. 3 shows the case where the electromagnetic control valve 17 is wide open when the center position of the cylindrical body 8 coincides with the welded part 2 of the steel pipe 1. 19 is sandwiched between them. Thus, each cylinder 15. Air pocket 16. The electromagnetic control valve 17 and the high pressure cylinder 11 constitute an electrode pushing mechanism.

FIG. 4 is a radial cross-sectional view of the cylindrical body 8. As shown in the figure, there are four electrodes 9a, 9b, '10a.

16 from (1) to (16) consisting of 10b
The electrode groups are arranged at equal angular intervals in the circumferential direction.

FIG. 5 is a block section showing the measurement processing section 12, and the control section 21 composed of a micro pressure sensor etc. receives a welding position detection signal from a welding position detection sensor 7 and a distance A1.
A distance signal C from the 1J constant roller 13 is input. Further, the control unit 21 sends a drive signal a to the drive mechanisms 5a and 5b that rotationally drive the small wheels 6a and 6b, and
A drive signal d is sent to the electromagnetic control valve 17 that connects the air reservoir 16 to the
Send out. Further, the control unit 21 controls the current supply source 23
A current changeover switch 22 that sequentially switches the current supplied from the cylindrical body 8 to each current supply electrode 9a, 9b arranged on the outer periphery of the cylindrical body 8, and a cylindrical body 8 whose potential difference is to be measured in synchronization with this current changeover switch 22. Each potential difference detection electrode 10a is arranged on the outer periphery of the electrode 10a.

10b. The potential difference between the potential difference detection electrodes 10a and 10b via this meter r The distance signal from the distance measuring roller 13 is input to this recorder 27.

Next, the operation of the apparatus for measuring the depth of cracks in a pipe constructed as described above will be explained using the time chart shown in FIG.

First, the moving body 3 is moved at a constant speed in the direction of the arrow in FIG. Then, at time tQ, the welding position detection sensor 7 detects the welded part 2 of the steel pipe 1 and sends out a welding position detection signal.
The control unit 21 issues a momentary stop command to each drive mechanism 5a, 5b to stop the movement of the moving body 3. Immediately, a movement start command a is issued to move the movable body 3 forward by a distance l between the center position of the welding position detection sensor 7 and the cylindrical body 8. Note that this distance l is detected by the distance signal C from the distance measuring roller 13. When the welding part 2 reaches the center position of the cylindrical body 8 at time t2, a stop command is sent to the drive mechanisms 5a and 5b to stop the movable body 3. At the same time, a drive signal d is sent to the electromagnetic control valve 17 to increase the opening degree of the electromagnetic control valve 17 and send the air in the high pressure cylinder 11 to the air reservoir 16. Then,
The air pressure in the air reservoir 16 increases, and each cylinder 15 operates to press the tips of the current supply electrodes 9a, 9b and the potential difference detection electrodes 10a, 10b against the inner wall of the steel pipe 1, as shown in FIG. At time t3, each electrode 9a, 9b, 10
When electrodes a and 10b are brought into contact with the inner wall at a predetermined pressure, the operation of the electromagnetic control valve 17 is stopped to maintain the pressing pressure of each electrode at a constant value.

At the same time, a current switching signal e is sent to the current switching switch 22, and current supplying electrodes 9a belonging to the (1)th electrode group shown in FIG. 9b, and a specified current f is supplied from the current supply source 23 to the corresponding current supply electrodes 9a and 9b for a period T.
Supply astride. In synchronization with this period T1, a measurement switching signal g is sent to the measurement switching switch 24, and the potential difference detection electrodes IQa, 10b corresponding to the previous current switching signal e are connected to the potential difference measuring section 25. Therefore, the potential difference measurement unit 25 measures the potential difference between the potential difference detection electrodes 10a and 10b during the period T1 from t3 to t4. The measured value obtained by the potential difference measuring section 25 is subjected to signal processing at the signal processing section 26 during the same period T1, and then recorded on a recording paper by the recorder 27 together with the distance signal value obtained from the distance measuring roller 13. .

When the measurement of the potential difference for the (1)th electrode group is completed at time t4, the current switching signal e and the Will constant switching signal g
The electrode group to be measured is moved to the (2)th electrode group. Then, the potential difference between the potential difference detection electrodes IQa and 10b is measured using the same procedure as in step (1), and the recorder 27
Recorded at. In this way, they were arranged on the outer circumference of the cylindrical body 8 at time t5. When the measurement of the potential difference between the (1)th to (16th)th electrode groups is completed, the electromagnetic control valve 1
A drive signal d is sent to I, and the opening degree of the electromagnetic control valve 17 is reduced. Then, the air pressure in the air reservoir 16 decreases 17
Then, the cylinder 15 operates to open each electrode 9a.

b, 10. b) Retract to the original position shown in Figure 2. When the backward movement ends at time t6, the drive mechanisms 5a and 5b are driven again to restart the movement of the moving body 3.

With such a crack depth measuring device, after the potential difference measurement at the welded part 2 of each steel pipe J constituting the vibrating line is completed and the movable body 3 is taken out of the steel pipe 1, it is recorded on the recorder 27. By examining the potential difference and position data, it is possible to determine whether or not a crack 19 exists in the inner wall of the steel pipe 1, and if so, the depth of the crack as well as its position.

FIG. 7 shows the crack depth Ap of a pipe according to another embodiment of the present invention.
1 is a schematic cross-sectional view of the fixed lid device, and the same parts as in the embodiment of FIG. 1 are denoted by the same symbols.

In this embodiment, the electrodes 9a, 9b, ], Oa.

The diameter of the cylindrical body 31 that supports each electrode is set to less than half the diameter of the steel pipe 1 in order to reduce the number of membranes 10b. Both ends of this cylindrical body 31 are supported by rotating arms 32 that are rotationally driven around the central axis 4. and,
As shown in FIG. 8, current supply electrodes 9a, 9b and potential difference detection electrodes 10a, 10b are arranged on the outer peripheral surface of the cylindrical body 31, as in the previous embodiment. Each electrode 9a, 9
b.

A slip ring 33 is attached to the central shaft 4 in order to send compressed air to the cylinder 15 that drives the electrodes 10a and 10b, supply current to the current supply electrodes 9a and 9b, and further detect the potential difference between the potential difference detection electrodes 10a and 10b. installed on. Further, the rotating arm 32 is rotationally driven around the central shaft 4 by a drive motor (not shown). Therefore, the electromagnetic control valve 1
7, compressed air is sent to the air reservoir 16 inside the cylindrical body 31 via the slip ring 33 and the rotary arm 32, and the cylinder 15 is driven to cause each electrode to protrude from the outer peripheral surface as shown in FIG. Then, only one row of electrode groups provided on the outer periphery is pressed against the inner wall of the steel pipe 1. When the rotary arm 32 is rotated in this state, each electrode group provided at eight locations on the outer periphery of the cylindrical body 31 is sequentially pressed against the inner wall of the steel pipe 1. However, in this embodiment, each potential difference detection electrode 10a provided on the outer periphery of the cylindrical body 31 does not need to be provided with a special current changeover switch and a total A11l changeover switch.
, 10b are sequentially recorded on the recorder 27. As a result, the total potential difference is i41+1 over the entire circumference of the inner wall of the welded portion 2 of the steel pipe 1. In this case, it is not very important which position on the circumference of the steel pipe 1 each potential difference data obtained by the recorder 27 corresponds to. In other words, if it is determined that a crack has occurred at even one location on the circumference, that welded part 2
This is because the whole thing needs to be repaired or re-welded.

If the tube crack depth measuring device is configured in this way,
By simply attaching the slip ring 33, which has a simple configuration, the total number of electrodes used can be reduced, and each changeover switch can also be eliminated, thereby reducing the manufacturing cost of the entire device.

Note that the present invention is not limited to two consecutive embodiments. In the embodiment, each cylinder 15 is driven by compressed air, but hydraulic pressure may also be used.

In addition, the number of overflow poles arranged in the axial direction of the cylindrical body 8.31 is 4.
Although it is set as a book, there may be four or more.

Further, the distance measuring roller 13 is removed and a counter is provided in the control unit 21 to count the number of pulses of the welding position detection signal from the welding position detection sensor 7. It may also be detected whether it is located at the welding part 2. Further, the distance measuring roller 13 may also be used for each wheel 6a, 6b of the drive mechanisms 5a, 5b.

[Effects of the Invention] As explained above, according to the present invention, by providing an electrode on the outer periphery of a cylindrical body mounted on a movable body moving inside a pipe, which is pressed against the inner wall of the pipe during measurement, The depth of cracks can be easily measured.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view showing a crack depth measuring device in a pipe according to an embodiment of the present invention, Figs. 2 to 4 are cutaway sectional views showing main parts of the same embodiment, and Fig. 5 6 is a block diagram showing a schematic configuration of the same embodiment, FIG. 6 is a time chart showing the operation of the same embodiment, and FIG. 7 is a schematic cross-sectional diagram showing a crack depth measuring device in a pipe according to another embodiment of the present invention. 8 are cutaway sectional views showing the main parts of the same embodiment. 1... Steel pipe, 2... Welded part, 3... Moving object, 4...
・Central axis, 5a, 5b... Drive mechanism, 5a, 5b...
・Wheel, 7... Welding position detection sensor, 8, 31...
Cylindrical body, 9a, 9b...Electrode for current supply, 10a, 10
b- potential difference detection electrode, 11... high pressure cylinder, 12.
...Total 71$J processing section, 13...Distance measuring roller, 1
4...Through hole, 15...Cylinder, 16...Air pocket, 17...Solenoid control valve, 18...Signal cable, 19...Crack, 21...Control unit, 22...・Current selection switch, 23...Current supply source, 24...Total 7I
pj changeover switch, 25...potential difference measuring section, 26...
・Signal processing unit, 27...Recorder, 32...Rotating arm, 3
3...Slip ring.

Claims (1)

[Claims] A movable body that moves in the axial direction inside a tube formed of a conductive material, a cylindrical body for holding an electrode that is mounted on the movable body and whose axis is parallel to the axis of the tube, and A plurality of current supply electrodes and a plurality of potential difference detection electrodes arranged in the axial direction on the outer periphery, and an electrode that brings the current supply electrodes and the potential difference detection electrode into pressure contact with the inner wall when measuring a crack depth on the inner wall of the tube. an extrusion mechanism, a current supply source that supplies current to the current supply electrode, a potential difference measurement unit that measures a potential difference between the potential difference detection electrode that is pressed against the inner wall, and detects the position of the moving body in the pipe. 1. A crack depth measuring device in a pipe, characterized in that it is equipped with a position detecting section.