JPH10274643A - Method and equipment for ultrasonically detecting flaw of pipe with inner surface fins - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a microdefect at the root part in the inner circumferential surface of a pipe with inner surface fins surely at high speed by projecting an ultrasonic wave to the center of the root part of the pipe from the outer surface side thereof at an angle substantially perpendicular to the diametral line of a pipe passing through the center of the root part. SOLUTION: An oblique angle probe 1 for flaw detection is disposed to project an ultrasonic wave from the outer surface side of a pipe P with inner surface fins to the center of a root part Rs formed in the inner circumferential surface thereof at an angle θsubstantially perpendicular to the diametral line of the pipe P passing through the center of the root part Rs. Since the magnitude of a shape echo signal from the side face at the crest part M is decreased in the vicinity of the root part Rs, a defect signal from a defect K can be distinguished easy from a shape echo signal from the crest part M and the detection accuracy is enhanced. According to the method, the defect K can be detected surely without an oversight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detection method for a tube with an internal fin by a pulse reflection method and an ultrasonic flaw detection apparatus for carrying out the method, and more particularly to a pipe generated at a valley bottom on the inner peripheral surface of the pipe. The present invention relates to an ultrasonic inspection method capable of reliably detecting a crack-like defect in an axial direction and an ultrasonic inspection apparatus therefor.

[0002]

2. Description of the Related Art Among steel pipes used in an ethylene manufacturing plant, a plurality of pipes (usually having a triangular round thread shape whose cross section is straight in the axial direction of the pipe in order to increase the heat transfer efficiency are formed.
8-12) There is a so-called inner finned tube in which fins are formed.

FIG. 8 is a cross-sectional view showing an example of the above-mentioned tube P with inner fins. The inner surface of the tube P has a peak portion (fin portion) M and a valley portion R. Such a tube P with internal fins
Is usually made of a high Cr-high Ni alloy, and is manufactured by a casting method or a hot extrusion tube manufacturing method represented by the Yugene Sejournet method.

[0004] When the above-mentioned tube P with internal fins is manufactured by the hot extrusion tube manufacturing method, the material of high Cr-Ni alloy is inferior in hot workability. In particular, there is a characteristic that the shape of the top is difficult to become a predetermined shape. For this reason, measures such as increasing the extrusion ratio are taken so that the shape of the peak M becomes a predetermined shape. In this case, however, the peak is concentrated on the lower surface of the valley R, that is, the center of the valley bottom Rs. As a result, a minute crack-like defect K extending in the pipe axis length direction may occur.

[0005] In the above case, if the occurrence of the defect K is overlooked, a serious accident may occur during its use. Therefore, it is necessary to inspect the defect K before shipping the product to remove and maintain the defect K. An ultrasonic flaw detection method is applied as a highly efficient nondestructive inspection method.

However, at the time of its application, as shown in FIG.
The same acute angle θ (approximately 40 to
(50 °), an extremely large shape echo signal is generated from the side surface of the peak M over the vicinity of the valley bottom Rs, and the minute defect K existing almost at the center of the valley bottom Rs. From the defect signal from
There is a problem that cannot be detected reliably.

For this reason, a minute defect K generated at the valley bottom Rs of the valley R of the tube P with the inner fins is removed at a high speed.
In addition, there has been a demand for the development of an ultrasonic flaw detection method capable of reliably detecting an ultrasonic flaw detection apparatus and an ultrasonic flaw detection apparatus for performing the method.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and an object of the present invention is to detect, at high speed and reliably, a minute defect occurring at the bottom of a valley. It is an object of the present invention to provide an ultrasonic inspection method for a tube with an internal fin and an ultrasonic inspection device for the tube with an internal fin for performing the method.

[0009]

The gist of the present invention is to provide an ultrasonic flaw detection method for a tube with an internal fin described in (a) below and an ultrasonic flaw detection apparatus for a tube with an internal fin described in (b) and (c) below. is there.

(A) A pulse reflection method of an inner finned tube (P) which detects a defect generated in the inner peripheral valley bottom (Rs) of the inner peripheral valley (Rs) in the tube axis length direction by an oblique flaw detection method. An ultrasonic flaw detection method, wherein a center line of a valley bottom (Rs) of an inner peripheral surface of a tube with an inner fin (P) is substantially perpendicular to a diameter line (L) of a tube passing through the center of the valley bottom (Rs). An ultrasonic flaw detection method for a tube with an internal fin, wherein ultrasonic waves are incident from an outer surface side of the tube at an angle (θ) (first invention).

(B) An ultrasonic flaw detector used in the ultrasonic flaw detection method described in (a) above, wherein the inner finned pipe (P) has a valley bottom with respect to the center of the valley bottom (Rs) of the inner peripheral surface. An oblique probe (1) for receiving ultrasonic waves from the outer surface side of the tube at an angle (θ) substantially orthogonal to a diameter line (L) of the tube passing through the center of (Rs), and the oblique probe A shape echo signal detection gate circuit for outputting a shape echo signal of the surface near the valley bottom of the inner circumferential surface of the flaw detection signals received in (1) (4)
And a defect echo signal which is provided in parallel with the shape echo signal detection gate circuit (4) and which is present at the bottom of the inner peripheral surface of the pipe from among the flaw detection signals received by the oblique probe (1). A determination circuit (5) including a defect echo signal detection gate circuit (7) and estimating a passage position of a valley bottom in accordance with an output of the shape echo signal detection gate circuit (4);
ON / OF for controlling opening and closing of the defect echo signal detection gate circuit (7) according to the output of the determination circuit (5).
An ultrasonic inspection apparatus for a tube with internal fins, comprising an F control circuit (6) (second invention).

(C) An ultrasonic flaw detector used in the ultrasonic flaw detection method described in (a) above, wherein the inner finned pipe (P) has a valley bottom with respect to the center of the valley bottom (Rs) of the inner peripheral surface. An oblique probe (1) for receiving ultrasonic waves from the outer surface side of the tube at an angle (θ) substantially orthogonal to a diameter line (L) of the tube passing through the center of (Rs), and the oblique probe (1) is a vertical probe which is arranged so as to be out of phase in the circumferential direction of the tube, and in which ultrasonic waves are incident along the tube diameter line (L) from the outer surface side of the tube to the center of the bottom of the inner circumferential surface. (10) a defect echo signal detection gate circuit (40) for outputting a defect echo signal existing at the bottom of the inner circumferential surface of the tube from the flaw detection signals received by the oblique probe (1); From the flaw detection signals received by the vertical probe (10), a valley bottom detection for outputting a shape echo signal of the valley bottom surface of the inner peripheral surface of the tube. A gate circuit (50), ON to open and close control the defect echo signal detection gate circuit in accordance with the output of the valley portion detection gate circuit (50) (40) /
An OFF control circuit (60) is provided, and an oscillator (2) of the oblique probe (1) and an oscillator (20) of the vertical probe (10) are connected via a synchronization circuit (70). Ultrasonic inspection apparatus for tubes with internal fins (third invention).

As a result of various experiments, the present inventor found that the valley bottom Rs
In order to reliably detect the defect K generated in the above, instead of making the incident angle θ of the ultrasonic wave from the oblique probe an acute angle (see FIG. 8) as in the related art, as shown in FIG. Valley bottom Rs
Should be incident at an angle θ substantially orthogonal to the diameter line L of the tube passing through the center of the valley bottom Rs with respect to the center of the valley bottom Rs. Further, the discrimination between the defect signal from the defect K and the shape echo signal from the peak M can be performed with high accuracy by using the device configuration described in the above (b) or (c). The inventor has come to know the present invention.

As described above, when an ultrasonic wave is incident at an angle θ substantially orthogonal to the diameter line L of a tube passing through the center of the valley bottom Rs with respect to the center of the valley bottom Rs, The size of the shape echo signal of the peak M becomes as small as possible. As a result, the defect signal from the defect K and the shape echo signal from the peak M can be easily identified, and the detection accuracy of the defect K is improved. Therefore, the defect K can be detected without fail. become.

Incidentally, Japanese Patent Application Laid-Open Nos. Sho 52-79686 and 59-94063 and Japanese Utility Model Application Laid-Open No. Sho 61-42463.
The publication discloses an ultrasonic inspection method and apparatus for a finned tube. However, the techniques shown therein all target tubes with external fins having a plurality of fins formed on the outer peripheral surface, and the above-mentioned figure is obtained from the angle probe for defect detection. However, there is no other method than the method in which ultrasonic waves are incident at the same acute angle θ as shown in FIG.

In addition, when the techniques disclosed in the above publications are applied to detect a defect K generated substantially at the center of the valley bottom Rs of the tube P with the inner fins, the following problems arise. There is also a drawback that occurs.

That is, in the technique disclosed in Japanese Patent Application Laid-Open No. 52-67986, the oblique probe is rotated around the axis of a tube with external fins, and the oblique probe is positioned at a position corresponding to the fin portion. When it comes, specifically, the transmission of the ultrasonic wave is cut off in accordance with the rotation angle of the tube, so that the obstacle of the shape echo signal due to the outer fin is removed. Therefore, when this method is applied to a tube P with internal fins, a shape echo signal is generated 8 to 12 times per rotation of the tube, and it is necessary to interrupt the transmission of ultrasonic waves each time.

However, the fins (peaks M) of the tube P with internal fins are not always straight and uniform in the circumferential direction due to the characteristics of the hot extrusion tube-making method, and a little spiral around the tube axis. It may be twisted or uneven in shape, and the tube rotation speed is not always constant. For this reason, a large error occurs in the timing of interrupting the transmission of the ultrasonic wave due to these effects, and the defect is often overlooked.

In the technique disclosed in Japanese Patent Application Laid-Open No. 59-94063, a tube with an external fin similar to that described above is to be inspected, and a bevel probe for defect detection and a fin detection around the tube axis. A vertical probe is disposed, and when the external fin is detected by the vertical probe, the reception signal output of the oblique probe is stopped. However, if this method is also applied to the tube P with internal fins as it is, defects are often overlooked for the same reason as described above. In addition, in the case of this method, as described in the same gazette, it is necessary to confirm data for each fine angle at the time of setup change when the pipe size to be inspected is different, which requires a large number of man-hours.

Further, in the technique disclosed in Japanese Utility Model Application Laid-Open No. Sho 61-42463, a shape echo signal of an external fin is generated by swinging an oblique probe around the axis of a tube with an external fin similar to the above. Only those parts that are not to be inspected. However, with this method, it is difficult to perform high-speed inspection because it is easy to swing the angle beam probe at high speed. When the number of fins is large as in the case of the pipe P, the size of the entire apparatus is increased and the equipment cost is high.

Further, in each of the above publications, an oblique angle probe for detecting a defect for surely detecting a defect K generated at a valley bottom Rs of a tube P having an inner fin to be inspected in the present invention. There is no description suggesting that the incident angle θ of the ultrasonic wave from the laser beam should be specified in the present invention. Therefore, the techniques disclosed in these publications are not helpful at all in making the present invention.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, a method of the present invention (first invention) and an apparatus for implementing the method (second invention and third invention) will be described below in detail. Will be described.

First, the method according to the first invention will be described. In the method of the present invention, as described above, the oblique probe 1 for detecting a defect is formed from the outer surface side of the inner finned tube P to the inner surface. An angle θ substantially perpendicular to the diameter line L of the pipe passing through the center of the valley bottom Rs with respect to the center of the valley bottom Rs formed on the peripheral surface.
(See FIG. 1 described above).

When the ultrasonic waves are incident as described above, the magnitude of the shape echo signal from the side surface of the peak M near the valley bottom Rs becomes as small as possible. As a result, the defect signal from the defect K and the shape echo signal from the peak M can be easily distinguished and the detection accuracy is improved, so that the defect K can be detected without fail. Is as described above.

In the inspection, the tube P with internal fins is screwed and conveyed to the bevel probe 1 fixedly arranged at a predetermined position in the longitudinal direction of the tube, or at a predetermined position. The non-rotating conveyance of the tube P with the inner fins in the longitudinal direction of the tube P with the axis centered on the center of rotation of the oblique probe 1 provided to rotate on the same circumference. Done in

Next, an apparatus for identifying a defect signal from the defect K from among signals received by the oblique probe 1 will be described. (Second invention) using the received signal of the first embodiment and the oblique probe 1
(Third invention) using a vertical probe for detecting the inner surface shape and using the received signals of both.
There is a street.

FIG. 2 is a block diagram showing the configuration of the apparatus according to the second invention. As shown in FIG. 2, the oblique probe 1, the oscillator 2, the amplifier 3, the shape echo signal detection gate circuit 4,
It comprises a judgment circuit 5, an ON / OFF control circuit 6, a defect echo signal detection gate circuit 7, and a display device (or a recording device) 8.

As described above, the oblique probe 1 has a valley bottom portion Rs with respect to the center of the valley bottom portion Rs of the tube P with inner fins.
The angle is adjusted so that an ultrasonic wave can be incident at an angle θ (see FIG. 1 described above) substantially orthogonal to the diameter line L of the tube passing through the center of s.

An electric pulse signal from the oscillator 2 is received and oscillated into the material from the oblique probe 1 and propagates through the material, and is reflected by the peak M and the defect K on the inner surface of the tube and obliquely reflected. The ultrasonic wave received by the angle probe 1 is converted into an electric pulse signal, that is, a flaw detection signal in the angle beam probe 1. Also,
The flaw detection signal is amplified by the amplifier 3 and then input to both the shape echo signal detection gate circuit 4 and the defect echo signal detection gate circuit 7 provided in parallel.

Here, the shape echo signal detection gate circuit 4
A gate is set for a predetermined time based on the result of a preliminary flaw detection performed at a low speed on the inner finned tube P to be inspected at a low speed and determined by a worker on a waveform monitor (not shown). As shown by the thick solid line in FIG. 3A, only the flaw detection signal from the valley bottom Rs of the valley R and the side surface of the ridge M near the valley R is input to the determination circuit 5.

On the other hand, the judgment circuit 5 discriminates the flaw detection signal from the side face of the valley bottom Rs and the ridge M obtained based on the flaw detection result of the test material having the valley bottom Rs formed with an artificial defect. A threshold value ARM (shown by a dashed line in (a) of FIG. 3) is set, and as shown in (b) of FIG.
The time between the end points where the flaw detection signal level exceeds a preset threshold value ARM is input to the ON / OFF control circuit 6 as the gate time.

In the same manner as above, the ON / OFF control circuit 6 identifies a predetermined center position of the valley bottom based on the flaw detection result of the test material having the valley bottom Rs formed with an artificial defect. T of the timer time and the gate time is set, as shown in FIG. 3 (c), from the end point of the gates time input from the determination circuit 5 after a predetermined time T ₁ elapses
An ON / OFF command signal for outputting the flaw detection signal input from the amplifier 3 to the display device 8 is transmitted to the defect echo signal detection gate circuit 7 only during the _two- hour gate time.

According to the apparatus configured as described above, the boundary between the valley bottom Rs and the peak M is identified by the determination circuit 5, so that even if the rotational speed of the tube fluctuates, it is hardly affected. . Moreover, the shape echo from the ridge M is almost removed by the boundary identification between the valley Rs and the ridge M, and the diameter of the pipe L passing through the center of the valley Rs is substantially perpendicular to the center of the valley Rs. The flaw detection signal from the very small valley bottom Rs of the shape echo signal can be output by the synergistic effect of making the ultrasonic wave incident at the desired angle θ.

As a result, when the display device 8 has a defect K substantially at the center of the valley bottom Rs, the defect echo signal is clearly displayed as shown in FIG. 3D. Therefore, the defect K can be detected with high accuracy.

Further, in the apparatus according to the second aspect of the present invention, since only one probe is required to directly contact the tube with internal fins P to be inspected, the entire apparatus can be made compact and equipment costs can be reduced. Can be.

Next, a description will be given of an apparatus (third invention) that uses a vertical probe for detecting the inner surface shape in addition to the oblique probe 1 and uses both received signals.

FIG. 4 is a diagram showing an arrangement of the oblique probe 1 and the vertical probe. In FIG. 4, reference numeral 10 denotes a vertical probe for detecting the inner surface shape. The oblique probe 1 is arranged in a different phase from the oblique probe 1 arranged in the same state as above, so that ultrasonic waves are incident toward the axis of the tube P with internal fins.

FIG. 5 is a block diagram showing the structure of an apparatus according to the third invention. As shown in FIG.
It comprises oscillators 2 and 20, amplifiers 3 and 30, a defective echo signal detection gate circuit 40, a display device (which may be a recording device) 8, a valley bottom detection gate circuit 50, an ON / OFF control circuit 60, and a synchronization circuit 70. I have.

The above-described bevel probe 1 is the same as that of the device according to the second invention, and has a valley bottom Rs of a tube P with an inner fin.
The angle is adjusted so that an ultrasonic wave can be incident at an angle θ (see FIG. 1 described above) substantially orthogonal to the diameter line L of the tube with respect to the center of the tube. As described above, the vertical probe 10 is arranged so as to be out of phase with the oblique probe 1, so that ultrasonic waves can be made incident on the axis of the tube P with internal fins. The angle is adjusted and arranged.

An electric pulse signal from the oscillator 2 is received, oscillated into the material from the oblique probe 1 and propagated through the material, and is reflected at the peak M or the defect K on the inner surface of the tube to be oblique. The ultrasonic wave received by the angle probe 1 is converted into an electric pulse signal, that is, a flaw detection signal in the angle beam probe 1. Also,
This flaw detection signal is input to the defect echo signal detection gate circuit 40 after being amplified by the amplifier 3.

On the other hand, in response to the electric pulse signal from the oscillator 20, the vertical probe 10 oscillates and enters the material from the vertical probe 10, propagates through the material, and is reflected by the inner surface of the tube and received by the vertical probe 10. The sound wave is converted into an electric pulse signal, that is, an inner surface shape signal in the vertical probe 10. The inner shape signal is amplified by the amplifier 30 and then input to the valley detection gate circuit 50.

Here, the valley bottom detection gate circuit 50 includes:
Preliminary flaw detection is performed at a low speed on the pipe P with an inner fin to be inspected, and a reflection (flaw detection) signal from the valley bottom Rs obtained in advance based on a result determined by an operator on a waveform monitor (not shown) is obtained. A threshold ARM for detection (indicated by a dashed line in (b) of FIG. 6) is set, and the time between the end point and the start point where the inner surface shape signal level exceeds the preset threshold ARM is indicated by ( As shown in c), a gate time is input to the ON / OFF control circuit 60.

Then, when the above gate time is inputted, O
The N / OFF control circuit 60 operates during the gate time (FIG. 6).
(D)) only the defective echo signal detection gate circuit 4
For ON, an ON / OFF command signal for outputting the flaw detection signal input from the amplifier 30 to the display device 8 is transmitted.

The synchronization circuit 70 controls the oscillation timing so that the ultrasonic waves oscillated by the oblique probe 1 and the vertical probe 10 do not interfere with each other in the material. .

According to the apparatus configured as described above, the inner surface shape signal of the vertical probe 10 is transmitted to the valley bottom detection gate circuit 5.
0, the position of the valley bottom Rs is determined, and the flaw detection signal of the oblique probe 1 is output only during that time, so that the shape echo from the peak M is almost removed and the center of the valley bottom Rs is removed. Combined with the incidence of ultrasonic waves at an angle θ substantially perpendicular to the diameter line L of the tube passing through the center of the valley bottom Rs, it is possible to output only a flaw detection signal from the valley bottom Rs having an extremely small inner shape signal. it can.

As a result, when the display device 8 has a defect K substantially at the center of the valley bottom Rs, the defect echo signal is clearly displayed as shown in FIG. 6E. Therefore, the defect K can be detected with high accuracy.

In the inspection, as in the case of the second invention, the tube P with the inner fin is attached to the oblique probe 1 and the vertical probe 10 which are fixedly arranged at predetermined positions. The oblique probe 1 and the vertical probe 10 provided to rotate along the same circumference at a predetermined position by being screwed and conveyed in the longitudinal direction of the tube axis are provided with an axis centered at the rotation center thereof. In this state, the pipes P with the inner fins are conveyed non-rotatably in the longitudinal direction of the pipes.

The sensitivity adjustment in the device according to the third aspect of the present invention can be performed as follows, and the sensitivity adjustment at the time of changing the dimensions of the inner finned tube P is extremely simple. That is, using a test material having an artificial defect formed at a position slightly deviated from the center of the valley bottom Rs,
The test material is fixed at the position where the artificial defect was detected. Next, the vertical probe 10 is moved right above the artificial defect, and then the vertical probe 10 is moved so that the inner surface echo at the center of the valley bottom Rs is detected. The sensitivity is adjusted so as to be higher than the threshold by a certain level.

In the ultrasonic flaw detection method and apparatus according to the present invention, an ultrasonic wave is incident at an angle θ substantially perpendicular to the diameter line L of a tube passing through the center of the valley bottom Rs with respect to the center of the valley bottom Rs. Therefore, it is practically impossible to detect a minute defect generated at the valley bottom Rs on the opposite side of the center of the valley from the incident direction of the ultrasonic wave (left side of the defect K in FIG. 1). Therefore, it is necessary to perform the inspection by applying the ultrasonic wave from the direction shown in FIG. 1 and the ultrasonic wave from the opposite direction to that shown in FIG.

[0050]

FIG. 8 shows the dimensions (D, d ₁ , d ₂ , t,
h) is a value (mm) shown in Table 1 and is a tube with inner fins having 8 fins (peaks M). As shown in FIG. 7, the center of the valley bottom and both sides 2 mm away from the center are shown in FIG. At the position
Length 25mm, width 0.5mm, depth 0.5mm and 1
The method of the present invention (the ultrasonic incident angle θ = 90 in FIG. 1) was applied to a test material on which artificial defects K ₁ , K ₂ , and K ₃ mm were formed.
°) and the conventional method (the ultrasonic incident angle θ = 45 in FIG. 8).
°) and the ultrasonic inspection test was performed.

[0051]

[Table 1]

In any case, the oblique probe has a transducer diameter of 9.5 mmφ and an ultrasonic beam diameter of 0.
Those having a size of 9 mm × 3 mm were used. In signal processing,
In each case, the device according to the third invention was used.

As a result, according to the method of the present invention, the artificial defects K ₁ and K _{2 of} any depths formed at the center of the valley bottom and at the valley bottom on the ultrasonic wave incident side also cause obstruction of the inner surface echo. Only the defective echo is displayed on the display device without receiving it,
Could be detected. Furthermore, artificial defects K ₃ that the magnitude of the signal at this time can not be detected by half, the result of the inspection by the incidence of the ultrasound from the opposite direction, could be detected in the same manner as described above.

[0054] In contrast, if the previous method, the inner surface shape echo is large, the artificial defect K ₁ depth 0.5mm and 1mm formed in the groove bottom center, displayed on both the display device Was not detected.

[0055]

According to the present invention, since the inner shape echo from the valley bottom of the tube with the inner fin is as small as possible, the defect echo from the minute defect generated at the valley bottom is clearly defined as the inner shape echo. The defect at the bottom of the valley can be identified, and the defect can be almost surely detected without missing the defect.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an ultrasonic wave incident mode by an oblique probe in a flaw detection method of the present invention.

FIG. 2 is a block diagram showing an example of a flaw detector according to the present invention, and showing a configuration of the apparatus when only a reception signal of an oblique probe is used.

FIG. 3 is a diagram showing a relationship between signals in the flaw detector shown in FIG. 2;

FIG. 4 is a schematic cross-sectional view showing an incident state of ultrasonic waves by a bevel probe and a vertical probe in the flaw detection method of the present invention.

FIG. 5 is a block diagram showing another example of the flaw detector according to the present invention, showing the configuration of the flaw detector in a case where both the reception signal of the oblique probe and the reception signal of the vertical probe are used.

FIG. 6 is a diagram illustrating a relationship between signals in the device illustrated in FIG. 5;

FIG. 7 is a schematic front sectional view showing an aspect of forming an artificial defect on a valley bottom of a test material used in a test of an example.

FIG. 8 is a schematic cross-sectional view showing an example of an inner surface shape of a tube with an inner fin.

FIG. 9 is a schematic cross-sectional view showing an incident state of ultrasonic waves by a beveled probe when a conventional ultrasonic flaw detection method is applied to a tube with internal fins.

[Explanation of symbols]

 1: oblique probe, 10: vertical probe, 2, 20: oscillator, 3, 30: amplifier, 4: shape echo signal detection gate circuit, 5: judgment circuit, 50: valley bottom detection gate circuit, 6 , 60: ON / OFF control circuit, 7: defect echo signal detection gate circuit, 70: synchronous circuit, 8: display device, K: defect, M: peak (fin), R: valley, Rs: valley bottom .

Claims (3)

[Claims] 1. An ultra-fine finned tube (P) having a pulse reflection method for detecting a defect generated in a valley bottom (Rs) of an inner peripheral surface of the inner fin tube (Rs) in a longitudinal direction of the tube by an oblique flaw detection method. An ultrasonic flaw detection method, wherein an angle substantially perpendicular to a diameter line (L) of a pipe passing through the center of the valley bottom (Rs) with respect to the center of the valley bottom (Rs) of the inner peripheral surface of the inner finned pipe (P). (7) An ultrasonic flaw detection method for a tube with an inner fin, wherein ultrasonic waves are incident from the outer surface side of the tube. 2. An ultrasonic flaw detector used for the ultrasonic flaw detection method according to claim 1, wherein the inner finned pipe (P) has a valley bottom (Rs) with respect to a center of the valley bottom (Rs) on the inner peripheral surface. ) Is approximately perpendicular to the diameter line (L) of the tube passing through the center of ()
The angle beam probe (1) that makes ultrasonic waves incident from the outer surface of the tube
A shape echo signal detection gate circuit (4) for outputting a shape echo signal of the surface near the valley bottom of the inner peripheral surface of the flaw detection signals received by the oblique probe (1); and the shape echo signal. A defect echo signal detection gate circuit which is provided in parallel with the detection gate circuit (4) and outputs a defect echo signal existing at the bottom of the inner peripheral surface of the tube from among the flaw detection signals received by the oblique probe (1). (7), a judgment circuit (5) for estimating the passage position of the valley bottom according to the output of the shape echo signal detection gate circuit (4), and the judgment circuit (5) according to the output of the judgment circuit (5). And an ON / OFF control circuit (6) for controlling the opening and closing of the defect echo signal detection gate circuit (7). 3. An ultrasonic flaw detector used in the ultrasonic flaw detection method according to claim 1, wherein the inner finned pipe (P) has a valley bottom (Rs) with respect to a center of the valley bottom (Rs) on the inner peripheral surface. ) Is approximately perpendicular to the diameter line (L) of the tube passing through the center of ()
The angle beam probe (1) that makes ultrasonic waves incident from the outer surface of the tube
And the bevel probe (1) are arranged with a phase shift in the circumferential direction of the pipe, and are superimposed along the pipe diameter line (L) from the outer surface of the pipe to the center of the bottom of the inner circumferential surface. A vertical probe (10) that receives a sound wave, and a defect echo signal that outputs a defect echo signal existing at the bottom of the inner peripheral surface of the tube from among the flaw detection signals received by the angle beam probe (1). Detection gate circuit (40)
And a valley bottom detection gate circuit (50) for outputting a shape echo signal of the valley bottom surface of the pipe inner peripheral surface from among the flaw detection signals received by the vertical probe (10), and a valley bottom detection gate circuit ( An ON / OFF control circuit (60) for opening and closing the defect echo signal detection gate circuit (40) in accordance with the output of the oblique probe (1). An ultrasonic inspection apparatus for a tube with an inner fin, wherein the oscillator (20) of the probe (10) is connected to the oscillator (20) via a synchronous circuit (70).