JPH073409B2 - In-pipe inspection probe - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an in-pipe inspection probe, and more particularly to an in-pipe inspection probe equipped with eddy current flaw detection means for detecting a defect existing in a cross section of a metal pipe and determining the position in the axial direction and the circumferential direction. Here, the “section of the pipe” has a meaning including the cross section at a certain position and the inner and outer peripheral surfaces in the vicinity thereof. In practice, the inner and outer peripheral surfaces are the main problem.

[Prior art]

As this type of in-pipe inspection probe, conventionally, a pair of coils are arranged in the pipe to be inspected, an eddy current is formed over the entire circumference of the cross section of the pipe, and the probe is present in the cross section of the pipe by monitoring the impedance change. There has been proposed an eddy current flaw detection means for detecting defects. With the in-pipe inspection probe described above, the position of the defect in the axial direction is known, but the position on the circumference is not known, and even if there are multiple defects on the same circumference, they are counted as one. Therefore, it has been proposed to use a sensor coil having an axis deviated from the central axis of the pipe to be inspected to detect the circumferential position of the defect. (JP-A-60-157047) However,
Although the principle was disclosed, a practically useful device was not realized.

[Problems to be Solved by the Invention]

The object of the present invention is to detect the presence of a defect, the position on the circumference of the pipe following the position in the axial direction of the pipe can be accurately known, and it is easy to move in and out of the pipe. It is to provide an in-pipe inspection device that is practically easy to use.

[Means for Solving the Problems]

The in-pipe inspection apparatus of the present invention which achieves the above-mentioned object is essentially composed of the following elements, and A is a cylindrical head member having an outer diameter close to the inner diameter of the pipe to be inspected, and is wound coaxially therewith. A pair of circumferentially wound coils arranged at a slight distance and generating an eddy current over the entire circumference of the cross section of the tube to detect an existing defect, and at least the outer peripheral surface of the head member. First eddy current flaw detection heads provided with three running rollers which rotate in the axial direction in contact with the inner surface of the pipe and assist the movement of the head member, and B (i) a cylindrical guide head member having at least an outer peripheral surface thereof. The guide head member is provided with three running rollers which rotate in the axial direction in contact with the inner surface of the pipe and assist the movement of the guide head member. Are those provided with a guide groove having an extension portion extending to the end point to expand radially connected gradually,
The orbiting roller of the rotary head member is connected to the in-groove roller constrained in the guide groove via a spring and a base,
When the rotary head is stationary, the in-groove roller is in the expanded portion and the orbiting roller is retracted in the radial direction to be housed in the rotary head member. A guide head configured to be pressed, (ii) a rotary head member that is supported by a common shaft with respect to the guide head and is rotatably provided adjacent to the guide head, and runs in the circumferential direction in contact with the inner surface of the pipe. The orbiting roller is provided so as to be able to move in and out in the radial direction of the tube, and a rotary coil sensor that is a locally wound coil that detects an existing defect by generating an eddy current in a part of the circumference of the tube cross section is provided. A rotating head, in which the orbiting roller advances in a radial direction to rotate in contact with the inner surface of the pipe during rotation, and (iii) a motor case which is adjacent to the rotating head and does not rotate itself. A second eddy current flaw detection head consisting of a rotary drive unit having a motor for driving the rotary head to rotate, and a first eddy current flaw detection head and a second eddy current flaw detection head connected to each other. A signal cable is connected to the eddy current flaw detection head.

[Action]

Needless to say, the first eddy current flaw detection head generates an eddy current over the entire circumference of the tube cross section by the circumferentially wound coil, and detects the presence of the defect by the change in impedance caused by the defect. At this time, the head is prevented from being shaken in the axial direction and rotated in the circumferential direction with the help of the traveling roller, and stable measurement can be performed. By placing the two coils at a small distance, high resolution can be obtained and the axial position of the defect can be precisely determined. The detected defect is then determined by the second eddy current flaw detection head to determine the position of the defect in the circumferential direction. At this time, the guide head prevents the second eddy current flaw detection head from moving in the axial direction and rotating in the circumferential direction, and moves the second eddy current flaw detection head to enable stable measurement. By placing two locally wound coils close together, detection with high resolution can be performed here as well.
The rotating head rotates only when it reaches the axial position where the existence of defects is recognized by the first eddy current flaw detection head when necessary, and does not rotate other than that. Can be shortened. The rotary head can be smoothly rotated by the revolving roller, and the locally wound coil can rotate close to the inner peripheral surface of the tube, so that the sensitivity can be kept high.

【Example】

In FIG. 1, 10 is a first eddy current flaw detection head,
A cylindrical head member 11 having an outer diameter slightly smaller than the diameter of the inner peripheral surface 2 of the tube 1 and having bottoms at both ends, and a pair of circumferentially wound head members 11 arranged at appropriate distances from each other. Winding coil
It consists of 12,13. 14 and 15 are running rollers, 1 to each other
Each of the rollers is composed of three sets of rollers arranged on the peripheral surfaces of both ends of the coil support 11 at an angle of 20 degrees, and rotates while contacting with the inner peripheral surface 2 of the pipe 1, and Helps to move in the pipe. Reference numeral 16 denotes a connecting cylinder, which penetrates the center of the head member 11 from one end to the other end, and one end of which is connected to a control device (not shown) arranged outside the pipe 1 via a signal cable 17. It is connected. 40 is a second eddy current flaw detection head, which is a cylindrical guide head having an outer diameter slightly smaller than the diameter of the inner peripheral surface 2 of the pipe 1.
41, a cylindrical rotary head 42 having a similar outer diameter and rotatably connected to the guide head 41 and having a locally wound coil, and detachable from the other end of the connecting cylinder 16. It includes a motor 71 connected to the rotary head 42 so as to drive the rotation of the rotary head 42, and a drive unit 43 composed of a bottomed cylindrical motor case 43. Reference numeral 44 denotes a traveling roller, which is composed of three sets of rollers arranged on the peripheral surface of the guide head 41 at an angle of 120 degrees, and travels while contacting the inner peripheral surface 2 of the pipe 1.
Helps move the second eddy current flaw detection head. Reference numeral 45 denotes a shaft, the rotation axis of which coincides with the axis of the guide head 41, and is rotatably supported by the guide head 41 via a bearing 46. Reference numeral 47 is a guide groove provided on the end surface 41a of the guide head 41 facing the rotary head 42, and has an annular portion 47a and an expansion portion having a terminating portion (not shown) continuously extending in radius. It consists of 47b. 48 is the end wall of the rotary head 42, and the shaft 45
There is a hole 49 into which is inserted, and a through hole 50 extending in the radial direction is provided near the outer periphery. Reference numeral 51 denotes a revolving roller pivotally supported by a support frame 52, which is normally housed together with the support frame 52 in the rotary head 42, and when the rotary head 42 rotates, it is directed outward from a hole 53 on its peripheral surface. It projects and contacts the inner peripheral surface 2 of the tube 1. 54 is a guide space 56 formed between the end wall 48 and the intermediate wall 55.
Is a base that can move in the directions of arrows A and B, and is connected to the support frame 52 via a support rod 57. 58 is a support rod 57
Is a coil spring arranged around the circumference of the tube 1. The support frame 52 can be urged toward the inner peripheral surface 2 of the tube 1 to press the orbiting roller 51 against the inner peripheral surface 2 of the tube 1, and the orbiting roller pressed. The reference numeral 51 rotationally travels on the inner peripheral surface 2 of the pipe 1 in the circumferential direction. Reference numeral 59 is a groove roller, which is attached to the base 54 and is a through hole.
It is provided at the free end of a rod 60 passing through 50 and is constrained by a guide groove 47 of a guide head 41 to move. 61 is the other end wall of the rotary head 42, on which the encoder disk 62 is attached. 63 is the central hole 61a of the end wall 61
Further, the rotary shaft 42 is a fixed shaft that passes through the center hole 62a of the encoder disc 62 and is supported by the bearing 64 with respect to the center hole 61a, so that the rotary head 42 can rotate around it. A fixed ring 65 is arranged inside the rotary head 42 and is fixed to one end of the fixed shaft 63. 66
Is a movable ring disposed in the rotary head 42, and is fixed to the end wall 61 or the peripheral wall 67, and the inner peripheral surface thereof is in contact with the outer peripheral surface of the fixed ring 65. The fixed ring 65 and the movable ring 66 constitute one set of slip rings. 68 and 69 in FIG. 2 are coils arranged on the outer peripheral surface of the rotary head 42 in the direction of extension of the tube 1 and in close proximity to each other.
Connected to 65. A gear 70 is fixed to the encoder disc 62. A motor 71 is housed in the drive unit 43, and an output shaft 72 extends through the end wall 73. End wall 73
The other end of the fixed shaft 63 is inserted into and supported by the center hole of the. 74 is also a gear, and meshes with the gear 70 at the free end of the output shaft 72 of the motor 71. 75 is an optical sensor disposed on the outer peripheral portion of the end wall 73, detects the passage of a plurality of holes 62b opened at equal angles on the outer peripheral portion of the encoder disk 62, the rotational position of the rotary head 42, As a result, the rotational positions of the coils 68 and 69 are detected. A connecting member 76 extends from the other end wall 77 of the motor case 43, and can be attached to and detached from the other end of the connecting cylinder 16 of the eddy current flaw detection head 10 by rotating a screw member 78. To connect the coils 68, 69 to an external controller,
An electric wire (not shown) connected to the fixed ring 65 passes through a through hole in the fixed shaft 63 to supply electric power to the motor 71 and an electric wire for connecting the optical sensor 75 to the control device (both are shown in FIG. (Not shown) together with being guided from the through hole of the connecting member 76 into the connecting cylindrical body 16 of the eddy current flaw detection head 10 and then reaching the signal cable 17, and then connecting the coils 12 and 13 of the eddy current flaw detection head 10 to the control device. It is guided to the outside of the pipe 1 together with an electric wire (also not shown) for the purpose. The operation of the in-pipe inspection probe having the above-described configuration will be described. First, in this probe, with the guide roller 51 of the eddy current flaw detection head 40 housed in the rotary head 42, with the guide head 41 at the head, the arrow C in FIG. Is inserted into the tube 1 in the direction of and reaches a deep portion. After being inserted into the tube 1 to a predetermined position, the in-tube inspection probe moves in the direction of arrow D along the inner peripheral surface 2 of the tube 1 by winding the signal cable 21 little by little. By passing an AC current through the coils 12 and 13 of the eddy current flaw detection head 10 from a control device outside the tube 1 while moving the eddy current flaw detection head, an eddy current is formed over the entire circumference of the cross section of the tube 1.
At 10, it is monitored that the eddy currents in the cross section of the tube 1 are disturbed by the defects due to impedance changes of the coils 12, 13. Since the pipe inspection probe moves in the direction of arrow D, the pipe 1
If there is a defect in the cross section of the eddy current flaw detection head 10, its presence is detected first, and then for some time (the coils 12 and 13 of the first eddy current flaw detection head 10 and the coils 68 and 69 of the second eddy current flaw detection head 40). The time required to move the distance between the) and the in-pipe inspection probe of the present invention is stopped,
Electric power is supplied from the control device to the motor 71 via the signal cable 21. When the motor 71 rotates, the encoder disc 62 and thus the rotary head 42 rotate with respect to the guide head 41 and the motor case 43 via the gear 74 and the gear 70 of the output shaft 72. Along with that, the in-groove roller 59 moves in the guide groove 47 of the guide head 41 from the end portion of the expanded portion 47b toward the annular portion 47a. Then, the rod 60 fixed to the in-groove roller 59 moves in the through hole 50 toward the center, and the base 54 moves in the direction of arrow A. The orbiting roller 51 is in contact with the inner peripheral surface 2 of the tube 1 until the in-groove roller 59 returns from the annular portion 47a of the guide groove 47 to the expansion portion 47b. When the revolving roller 51 is in contact with the inner peripheral surface 2 of the tube 1, a desired frequency (generally, the first eddy current flaw detection head) is applied to the coils 68 and 69 via a slip ring having a fixed ring 65 and a movable ring 66. By passing an AC current of a frequency different from the frequency of the current applied to the coils 12 and 13 of the coil 10, for example, a higher frequency is preferable, an eddy current occurs in the local portion of the cross section of the tube 1 and the coils 68 and 69 Monitor whether the eddy currents are disturbed by defects due to impedance changes. The rotary head 42 continues to rotate with respect to the guide head 41 and the motor case 43, and the defect whose presence is detected by the first eddy current flaw detection head 10 is again microscopically monitored by using the eddy current. The rotation position of the rotary head 42 is
Since it is detected by the optical sensor 75 and the hole 62b of the encoder disk 62, the circumferential position of the defect can be confirmed.
The rotary head 42 includes a guide head 41 and a motor case 43.
For at least one revolution. When the inspection work by the second eddy current inspection head 40 is completed,
Rotate the motor 71 in the reverse direction so that the rotary head 42 moves to the guide head 41.
By rotating in reverse with respect to the motor case 43, the in-groove roller 59 is moved from the annular portion 47a of the guide groove 47 to the expanded portion 47b.
The orbiting roller 51 moves toward the end of the rotary head 42.
Return to the guide space 56 of. After that, the eddy current flaw detection probe is moved again in the direction of arrow D, and the above-described operation is repeated.

【The invention's effect】

As is clear from the above description, the in-pipe inspection device of the present invention has the following effects. Since the coil spacing of the eddy current flaw detection head is narrow and its resolution is high, it is possible to accurately know the axial position and the circumferential position of the defect existing in the cross section of the pipe. The rotating coil is attached to a rotating head equipped with a revolving roller, and the rotating head can rotate close to the inner surface of the pipe with the front and rear eddy current flaw detection heads securely holding the rotation axis. It is possible to detect in detail the position in the circumferential direction and the degree of the defect, and even if there are multiple defects on the same circumference, know their number and position accurately. You can The circular roller advances in the radial direction only when the rotary head rotates and contacts the inner surface of the tube, and is retracted when it does not rotate, so it is easy to insert the probe into the tube and move within the tube, and to perform flaw detection work. Can be performed quickly and efficiently without damaging the tube.

[Brief description of drawings]

The drawings each show an embodiment of the present invention,
FIG. 1 is a sectional view of a portion, and FIG. 2 is a sectional view of another portion. 1 ...... Tube 2 ...... Inner surface 10 ...... First eddy current flaw detection head 12, 13 ...... Circular winding coil 14, 15 ...... Traveling roller 16 ...... Connection cylinder 17 ...... Signal cable 40 ...... Second Eddy current flaw detection head 41 …… Guide head 42 …… Rotating head 43 …… Motor case 44 …… Traveling roller 47 …… Guide groove 51 …… Orbiting roller 62 …… Encoder disk 68, 69 …… Locally wound coil 71… … Motor 75… Optical sensor

Claims (3)

[Claims] 1. A cylindrical head member consisting essentially of the following elements: A. A cylindrical head member having an outer diameter close to the inner diameter of the tube to be inspected, coaxially wound thereon and arranged a short distance away. And a pair of circumferentially wound coils which generate an eddy current over the entire circumference of the pipe cross section and detect an existing defect, and at least three of them are arranged on the outer peripheral surface of the head member and contact the inner surface of the pipe. A first eddy current flaw detection head having a traveling roller which rotates in the axial direction and assists the movement of the head member, and B (i) a cylindrical guide head member, at least three of which are arranged on the outer peripheral surface and contact the inner surface of the pipe. The guide head member is equipped with a traveling roller that rotates in the axial direction and assists the movement of the guide head member, and the guide head member is connected to the annular portion centered on the rotation axis of the rotary head and the radius gradually increases to the end point. It has a guide groove with an extension to
The orbiting roller of the rotary head member is connected to the in-groove roller constrained in the guide groove via a spring and a base,
When the rotary head is stationary, the in-groove roller is in the expanded portion and the orbiting roller is retracted in the radial direction to be housed in the rotary head member. A guide head configured to be pressed, (ii) a rotary head member that is supported by a common shaft with respect to the guide head and is rotatably provided adjacent to the guide head, and runs in the circumferential direction in contact with the inner surface of the pipe. The orbiting roller is provided so as to be able to move in and out in the radial direction of the tube, and a rotary coil sensor that is a locally wound coil that detects an existing defect by generating an eddy current in a part of the circumference of the tube cross section is provided. When the rotating roller is rotated, the orbiting roller advances in the radial direction to come into contact with the inner surface of the pipe to orbit, and (iii) a motor case existing adjacent to the rotating head and not rotating by itself. A second eddy current flaw detection head consisting of a rotation drive unit that has a motor for rotating the rotation head inside, and a first vortex flow connecting the first eddy current flaw detection head and the second eddy current flaw detection head. An in-pipe inspection probe with a signal cable connected to the flaw detection head. 2. In the second eddy current flaw detection head, the rotary head and the drive unit are rotatably coupled by a slip ring composed of an outer movable ring fixed to the rotary ring and an inner stationary ring extending from the drive unit. The in-pipe inspection probe according to claim 1, wherein the gear is provided on the output shaft of the motor and the gear is fixed to the outer movable ring so that the gear is driven to rotate. 3. In a second eddy current flaw detection head, an encoder disk having holes formed at equal angles on a circumference centered on the rotation axis of the rotary head is attached to a position facing the drive unit side. The in-pipe inspection probe according to claim 1, further comprising an optical sensor for detecting passage of the hole.