JPH0664027B2 - Angle beam inspection head for pipes and angle beam inspection device for pipes using the same - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bevel flaw detection head for pipes and a bevel flaw detection device for pipes using the same, and is particularly used for detecting defects in a welded portion of an electric resistance welded pipe in a pipe axial direction. The present invention relates to a preferable bevel angle flaw detection head for pipes and a bevel angle flaw detection device for pipes using the same, which does not need to follow the welded portion and need not be adjusted when changing the pipe thickness.

[Prior art]

Generally, in order to detect defects in a welded portion of an electric resistance welded steel pipe in the pipe axis direction, a bevel flaw detection method is used. This method involves injecting ultrasonic waves obliquely to the inspection surface of the material to be inspected (hereinafter referred to as the "inspection tube"), and the internal and external surface defects of the inspection tube and the inside of the inspection tube are reflected from the reflected waves reflected by the defects of the inspection tube. The defect is detected. Further, in order to detect defects over the entire length of the welded portion of the electric resistance welded steel pipe, the ultrasonic probe is scanned parallel to the welded portion of the electric resistance welded steel pipe, and the ultrasonic beam is perpendicular to the welded portion. The method of propagating to is used. However, in the above-described oblique angle flaw detection method, variation in the distance from the point where the ultrasonic beam is incident to the defect portion, that is, the probe-
As the defect distance changes, the echo height from the defect becomes
It is known that there are large changes as shown in Fig. 11.
This is disclosed, for example, in FIG. 2 of JP-A-55-140148 and FIG. 1 of JP-B-57-8420. For this reason, it is difficult to determine the reference echo height, and there is a problem that accurate flaw detection becomes difficult when the probe-defect distance changes, and in order to mitigate this problem, the following method is adopted. It was That is, FIG. 12 is a structural explanatory view of a conventional example, and FIGS. 13 (A), (B) and (C) are respectively AA ′ of FIG.
It is a sectional view, a BB 'sectional view, and a CC' sectional view, but as shown in these drawings, a test tube such as an electric resistance welded steel tube
For example, three oblique angle probes 18a to 18c and 18d to 18f are arranged on one side of the welded portion 11 of 10 respectively, and an ultrasonic beam incident on the tube 10 to be inspected from these probes is welded to the welded portion 11. At the center of the, the light propagates to the outer surface (see FIG. 13 (A)), the center (see FIG. 13 (B)), and the inner surface (see FIG. 13 (C)). Further, as disclosed in, for example, Japanese Examined Patent Publication No. 57-8420, the twist amount of the weld and the length of the pipe to be inspected are preset, and then the length of the current position is sequentially detected to detect the probe. The displacement of the child from the welded portion is calculated to follow the welded portion, or, for example, as disclosed in JP-A-59-43354, the probe is arranged in the circumferential direction of the tube to be inspected. A plurality of transmission / reception coils are installed along the line, the signal levels of the reception / transmission coils are sequentially determined in time series, and the relative positions of the weld and the probe are held in a fixed relationship to follow the weld. Was doing. However, in the above-mentioned conventional example, firstly, there is a problem that the welding portion must be followed because the echo height greatly changes as described above when the distance between the probe and the defect changes. Secondly, there is a problem that the peak echo appearance position differs depending on the outer diameter and the tube thickness of the test tube. That is, the appearance position L of the peak echo is expressed by the following equation (1) and varies depending on the values of the outer diameter D and the tube thickness t of the test tube. Therefore, the distance between the probe and the welded portion has to be adjusted according to the tube thickness t. L = N · K · t · tan θr (1) Here, N is a coefficient by the skip number S (N = S / 0.
5) and K are correction coefficients determined by the refraction angle θr and t / D. Thirdly, there is also a problem that sensitivity adjustment work must be performed in order to set the sensitivity of the flaw detection apparatus main body by the peak echo.

[Problems to be achieved by the invention]

The present invention has been made in view of the above-mentioned problems, and all of the above-described first to third problems are solved, and particularly in the pipe axis direction in the welded portion of the pipe to be inspected such as the electric resistance welded steel pipe. It is an object of the present invention to provide a pipe bevel flaw detection head suitable for detecting a defect and a pipe bevel flaw detection device using the same.

[Means for achieving the object]

The present invention provides a plurality of bevel probes for a pipe bevel flaw detection head for a pipe used for inspecting defects in the pipe axis direction of a subject pipe by an ultrasonic bevel flaw detection method. In order to arrange the angle probes in a circumferential direction of the pipe efficiently without gaps, each of the bevel probes is composed of a vertical probe and an acoustic wedge, and a cross section of the acoustic wedge in the pipe circumferential direction of the test tube. The shape is wider than the test tube side on the vertical probe side, and has a radiation angle shape of a radiation angle β determined by the outer diameter of the test tube and the width of the vertical probe. Further, the acoustic wedge has a cross-sectional shape inclined so as to have an incident angle θi in the tube circumferential direction so as to excite or receive ultrasonic waves obliquely in the tube circumferential direction of the test tube. And excites ultrasonic waves in a direction perpendicular to the mounting surface of the acoustic wedge that is orthogonal to the incident angle θi. An arc shape of a concentric circle with the tube to be inspected, in which the vertical probe for receiving is attached and a plurality of the oblique probes are mounted in an array form in the circumferential direction of the tube without a gap and in an inclined arrangement. A side plate, and is provided in front of and behind the plurality of beveled probes in an array, holding a gear gap between the surface of the tube to be tested and the acoustic wedge,
The above problem is solved by providing a pair of wear-resistant shoes that prevent wear of the acoustic wedge. Further, the present invention solves the above-described problems in a bevel angle flaw detection device for a pipe, which is equipped with the above-mentioned bevel angle flaw detection head for a pipe to detect a test tube.

[Action]

As shown in FIGS. 1 and 2 and FIG. 3A or FIG. 3B, the oblique angle flaw detection head for a pipe according to the present invention has a vertical probe 14 having a rectangular contact surface and a radiation angle. A plurality of beveled probes 12 each having a width in the tube circumferential direction of, for example, several mm or less, which are composed of an acoustic wedge 15 having a circular width, are arranged in an array in the tube circumferential shape. Here, the number n of the bevel probe 12 (n = 6 in the figure) is
It can be determined so that the maximum one skip distance S or more in the test tube 10 can be covered. Since the probes are arranged in an array along the pipe circumference, the width of the acoustic wedge 15 in the pipe circumferential direction is processed into a radial angle of, for example, β °, and the probe is the same as the test pipe 10. It is attached to side plates 16a and 16b having an arc shape of a center circle. Further, wear-resistant shoes 17a and 17b are attached to the front and rear of the probe group in order to hold the gear between the acoustic wedge 15 and the surface of the tube 10 to be tested and prevent the acoustic wedge 15 from being worn. Therefore, it is possible to easily perform flaw detection on the tubular material,
As will be described later, it is not necessary to follow the welded portion, and no adjustment is required when changing the pipe thickness.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. An embodiment of the bevel flaw detection head for steel pipes according to the present invention has a structure as shown in FIGS. 1 and 2 and FIGS. 3 (A) and 3 (B). That is, the oblique probe 12 is composed of a vertical probe 14 having a rectangular contact surface and an acoustic wedge 15 having a radial width (for example, several mm or less). It is attached to the wedge 15 by means of machine screws or the like (not shown). Generally, a transducer is directly bonded to the acoustic wedge to form a bevel probe, but the acoustic wedge in the present embodiment has a radial cross-sectional shape that varies depending on the outer diameter of the test tube, as described later. Need to have. Therefore, in this embodiment, the oblique probe 12 is formed by mounting the acoustic wedge 15 on the vertical probe 14. The vertical probe 14 is a generally used one. For example, "Introduction to nondestructive testing" (corporate association
It is possible to use a very general vertical probe, which is mentioned in detail on the 39th page of the Japan Non-Destructive Inspection Association (1992) together with the beveled probe using figures and the like. The vertical probe propagates the generated ultrasonic wave perpendicularly to the surface of the test body in contact with it. In the above-mentioned “Introduction to Non-Destructive Testing”, the vertical probe is explained, for example, the vibrator and damper (holding body) to be used. The vertical probe has a built-in vibrator that applies a DC pulse voltage to generate ultrasonic waves. A piezoelectric material is used as the oscillator material. Typical examples are crystal and zircon / lead titanate porcelain (abbreviation: zirnamama). Also, for example,
An electrode is attached to the surface by silver plating, and when a DC pulse voltage is applied, the vibrator expands and contracts in the thickness direction at a resonance frequency determined by its thickness.
Further, in the above-mentioned vertical probe, a holding body which plays a role of a damper for quickly stopping vibration is attached to the vibrator and housed in a case. In general, one probe can perform both transmission and reception. In addition, a thin film (not shown) made of oil or the like exists between the contact surface of the vertical probe 14 and the mounting surface of the acoustic wedge 15, and the vertical probe 14 and the acoustic wedge 15 are acoustically coupled to each other. ing. On the other hand, each bevel probe 12 is partitioned by an acoustic dividing plate (not shown). The acoustic wedge 15 has a radial width as described above,
Specifically, the width of the test pipe (electric resistance welded steel pipe) 10 in the circumferential direction is β
It has a radial angle of ゜. Further, when the speed of sound of the incident wave incident on the acoustic wedge 15 and the speed of sound of the refracted wave refracted by the test tube 10 are Ci and Cr, respectively, the relationship between the entrance angle θi of the incident wave and the refraction angle θr of the refracted wave The following equation (2) is established according to the so-called Snell's law. Cr / sin θr = Ci / sin θi (2) Therefore, in order to obtain the desired refraction angle θr, the shape of the acoustic wedge 15 is formed so that the incident angle becomes the incident angle θ. By the way, the acoustic wedge 15 has a radial width as described above, and the radiation angle β ° of the width is determined by the outer diameter of the test tube 10 and the width of the vertical probe 14. By processing the width of the acoustic wedge 15 in the pipe circumferential direction to the radiation angle β ° as described above,
It is easy to arrange the acoustic wedges 15 on the circumference of the test tube 10 in an array as shown in FIG. In order to arrange the bevel probe for transmitting and receiving ultrasonic waves in the pipe circumferential direction at the narrowest interval in the pipe circumferential direction, an acoustic wedge 15 which is an important component in the bevel probe is shown in FIG. The shape has a radial width as shown. That is, the cross-sectional shape of the acoustic wedge 15 in the tube circumferential direction of the test tube 10 as described below mainly with reference to FIG. First, the desired center length of the wedge is lmm and the width of the upper surface of the wedge is ωmm. Further, it is assumed that the ultrasonic wave is incident on the point P ₀ of the circle A (radius = r) which is the outer circumference of the test tube 10 at the incident angle θi. At this time, the line segment Q ₂ P in FIG.
₂ ′, line segment P ₂ ′ P ₁ ′, line segment P ₁ ′ Q ₁ , line segment Q ₁ Q
_The acoustic wedge 15 indicated by ₂ is as follows. Points ± ω / 2 from Q ₀ on the upper surface of the acoustic wedge 15 are set as points Q ₁ and Q ₂ , respectively. In order to cause an ultrasonic wave to enter the point P _{0 of the} circle A (radius = r), which is the outer circumference of the test tube 10 by Q ₀ , at the incident angle Qi, the upper surface of the acoustic wedge 15 has a line segment P ₀ Q It becomes a line segment Q ₁ Q ₂ orthogonal to ₀ . Also, the line segment P
₀ Q ₀ is an imaginary circle B of radius r ′ (= r · sin θi)
Located on an extension of the tangent to. Also, the points Q ₁ and Q ₂
Draw a tangent to each through a circle B of each line segment R ₁ Q
₁ and a line segment R ₂ Q ₂ . Assuming that the intersection points of the line segment R ₁ Q ₁ and the line segment R ₂ Q ₂ with the circle A are point P ₁ and point P ₂ , respectively, the point Q _{1 on} the upper surface of the acoustic wedge 15 will be described.
The incident angle from the circle to the point P _{1 of the} circle A is θi. Similarly, the incident angle from the upper surface Q ₂ of the acoustic wedge 15 to the point P _{2 of} QA is θi.
Becomes The lower surface of the acoustic wedge 15 is a line segment P ₁ ′ P ₂ ′ orthogonal to the line segment OP _0, and the sectional shape of the acoustic wedge 15 in the circumferential direction of the test tube 10 is a quadrangle Q ₁ Q ₂ P ₂ Let'P ₁ '. At this time, the line segment Q ₁ P ₁ ′ and the line segment Q ₂ P ₂ ′ have an angle of β. Further, β is a value approximately obtained by the following equation. That is, at least according to the following equation, this β is obtained in accordance with the outer diameter r of the test tube 10 and the width ω of the acoustic wedge 15 (that is, the width of the vertical probe). ^{β ≒ sin - 1 [ω /} (r · cosθi + l)] ... (3) Further, FIG. 3 (A), as it is better illustrated in (B), consisting of a vertical probe 14 and the acoustic wedge 15 The bevel probe 12 is a side plate 16 having an arc shape concentric with the tube 10 to be inspected.
It is held by a and 16b via machine screws or the like (not shown). The side plates 16a and 16b are used to easily hold the bevel probe 12 on the circumference of the test tube 10 in an array. In addition, wear-resistant shoes 17a and 17b are attached to the front and rear of the above-mentioned bevel probe group through small screws or the like (not shown). The shoes 17a and 17b are used to prevent wear of the acoustic wedge 15 and to hold a gear gap between the acoustic wedge 15 and the surface of the test tube 10. 1 and 3, the number of the angle probe 12 is six, but the present invention is not limited to this number, and this number is as described above. The test tube
It is determined by 10 dimensional ranges (maximum skip distance). On the other hand, the steel bevel angle flaw detection device of the present invention using the above-described bevel angle flaw detection head for steel pipe has the following configuration. That is, the oblique angle flaw detection head for steel pipes described in detail with reference to FIGS. 1 and 2 and FIG.
A pair of left and right sides are installed opposite to 11 to form a bevel flaw detection device for steel pipes. According to the method of exciting the bevel probe 12 in the above bevel flaw detection head for steel pipes, the bevel flaw detectors for steel pipe are roughly classified into those of the simultaneous excitation type of all channels and those of the sequential excitation type of individual channels. The all-channel simultaneous excitation type bevel flaw detection device for steel pipes simultaneously excites all the channels 1 to n of each bevel probe 12 in the bevel flaw detection head for steel pipe and alternately excites each bevel flaw detection head to the right and left alternately. By doing so, the welded portion 11 of the test tube 10 is detected. FIG. 4 is a block diagram showing a conventional oblique angle flaw detection apparatus for steel pipes of the all-channel simultaneous excitation system. This bevel angle flaw detector for steel pipes has a total of n probes, namely N
o.1 probe ~ No.n probe is used. Further, as described above, one pulsar P, one receiver R, and one gate unit G are provided for a plurality of probes. In this all-channel simultaneous excitation method, one pulsar P simultaneously excites all of the plurality of probes, and ultrasonic waves are simultaneously propagated from all these probes to an object to be inspected. That is. The ultrasonic wave propagating in this way is in the form of a pulse and is for an extremely short time. In this all-channel simultaneous excitation method, after the ultrasonic waves have been propagated in this way for a short time, the receiver R immediately receives the ultrasonic waves propagated to the plurality of probes. The receiver R and the gate unit G detect ultrasonic waves reflected by, for example, a flaw or the like to be inspected in an object to be inspected. In such an oblique angle flaw detector for steel pipes of the simultaneous excitation type, as shown in FIG. 4, only one set of pulsar P, receiver R and gate unit G is used for a plurality of probes. It is composed. Therefore, in view of the small number of the pulsar P, the receiver R, and the gate unit G, it is possible to reduce the scale (size reduction, etc.) of the oblique angle flaw detection device for steel pipes. In addition, the individual-channel sequential-excitation-type bevel flaw detector for steel pipe is used for all the angle-of-angle probes 12 in the bevel flaw detection head for steel pipe.
While maintaining the state of being able to receive the signal, each angle probe is sequentially excited, for example, from No. 1 to No. n one by one, and the welded portion 11 of the tube 10 to be inspected is detected. . FIG. 5 is a block diagram showing a conventional oblique angle flaw detection apparatus for steel pipes of the individual channel sequential excitation system. The individual-channel sequential excitation type oblique angle flaw detection device for steel pipes uses a total of n probes, that is, No. 1 to No. n probes. In this individual channel sequential excitation system, each probe has a channel unit including a pulser P, a receiver R, and a gate unit G, that is, No. 1 channel unit U1 to No. n channel unit Un. Further, this individual channel sequential excitation type oblique angle flaw detection device for steel pipes includes a main clock generator 32 and a clock distributor 34.
With. The clock distributor 34, at the main excitation timing according to the clock pulse of a constant cycle generated by the main clock generator 32, the No. 1 probe to No. n probe described above, respectively corresponding to the above. No. 1 channel unit U1 to No. n The pulsar P provided in the channel unit Un
The ultrasonic wave is generated by sequentially exciting the ultrasonic wave. The timing at which each of these probes excites ultrasonic waves is defined as No. 1 probe excitation timing to No. n probe excitation timing. Further, in this individual channel sequential excitation type oblique angle flaw detection device for steel pipes, while one probe excites ultrasonic waves at the probe excitation timing, the other transducers respectively correspond to corresponding channel unit units. The receiver R and the gate unit G included in U1 to Un are used to receive ultrasonic waves reflected by a flaw or the like in an object to be inspected. That is, ultrasonic waves are sequentially generated from each probe having a different arrangement position, and ultrasonic waves reflected by a flaw or the like are received by a plurality of other probes having different arrangement positions that do not generate ultrasonic waves. Is to do. Therefore, according to the bevel flaw detector for steel pipes of the individual channel sequential excitation method, the existence position of defects in the welded portion of the object to be inspected such as the inspection pipe is geometrically determined from the beam path of the defect echo. Can be clarified. The individual channel sequential excitation type oblique angle flaw detection device for steel pipes requires the pulsar P, the receiver R, and the gate unit G for each probe, as compared with the above-mentioned all-channel simultaneous excitation type. However, the scale of the device becomes large. FIG. 6 is a diagram showing the timing of sequential excitation in the above-mentioned individual channel sequential excitation system steel bevel flaw detector. In this figure, the transmission of the bevel probe is carried out one by one by each bevel probe (No. 1 to No. n bevel probe) one by one. The reception of the reflected echo is performed by all the bevel probes. As shown in FIG. 7, an outer surface N5 machined to an outer diameter of 406.4 mm and a pipe thickness of 9.52 mm using the bevel flaw detection head for steel pipe of the present invention
When a test tube of a notch (notch probe 0.48 mm) was inspected, the results shown in FIGS. 8 to 10 were obtained. FIG. 8 is a diagram showing distance amplitude characteristics for each probe investigated using the bevel flaw detection head for steel pipe of the present invention.
(A) to (C) are bevel probes (specifically, No. 2 to N).
Distance amplitude characteristics for each bevel probe in o.4 are shown.
In FIGS. 8A to 8C similar to the conventional example, the peak echo height is shown at the skip point, and it can be seen that the echo height greatly changes when the distance between the bevel probe and the defect changes. . On the other hand, FIG. 9 shows distance-amplitude characteristics when each bevel probe in the bevel flaw detection head for steel pipes of the present invention is of the all-channel simultaneous excitation system. It can be seen that the height change is extremely small. Further, FIG. 10 shows the concept of distance-amplitude characteristics when each bevel probe in the bevel flaw detection head for steel pipes of the present invention is an individual sequential excitation system, but the output for each probe is shown. Since it follows the envelope curve of, the change in echo height is extremely small even if the distance between the bevel probe and the defect changes, as in the case of the simultaneous excitation method for all channels. Although the present invention is applied to the flaw detection of the steel pipe in the above-mentioned embodiments, the application target of the present invention is not limited to this, and it is apparent that the present invention can be similarly applied to the flaw detection of tubular materials in general.

【The invention's effect】

According to the present invention as described above in detail, even if the distance between the probe and the defect changes, the echo height changes only slightly, and it is necessary to follow the welded portion as in the conventional example. Disappear. Moreover, since there is no echo height peak, it is sufficient to always set the bevel probe head at a fixed position regardless of the outer diameter and thickness of the tube to be inspected. It has excellent effects such as eliminating the need for adjusting the sensitivity of the main body.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a pipe bevel flaw detection head for pipes according to the present invention and a pipe bevel flaw detection device using the same, and FIG. 2 is an acoustic wedge of the pipe bevel flaw detection head for pipes according to the present invention. Sectional drawing which shows sectional shape, FIG. 3 (A) is the top view seen from the arrow A direction of FIG. 1, FIG. 3 (B) is the top view seen from the arrow B direction of FIG. 1, FIG. 4 is a block diagram showing a conventional oblique-angle flaw detector for steel pipes of all-channel simultaneous excitation type, and FIG. 5 shows a conventional oblique-angle flaw detector for steel pipes of individual channel sequential excitation type. FIG. 6 is a block diagram showing the same, FIG. 6 is a diagram showing the timing of sequential excitation in the above-described individual channel sequential excitation type oblique angle flaw detection apparatus for steel pipes, and FIG. 7 is a sectional view for explaining the operation of the embodiment of the present invention. FIGS. 8 (A), 8 (B), and 8 (C) are oblique angle flaw detection heads for steel pipes of the present invention. Fig. 9 is a diagram showing an example of distance-amplitude characteristics of each probe investigated by using Fig. 9, and Fig. 9 is a line showing an example of distance-amplitude characteristics when the bevel probe is of the all-channel simultaneous excitation method. Figures and 10 are diagrams showing the concept of distance-amplitude characteristics when the bevel probe is an individual sequential excitation method, and Fig. 11 shows an example of distance-amplitude characteristics in the conventional bevel flaw detection method. Fig. 12 is a plan view showing an example of the configuration of a conventional bevel flaw detector for steel pipes, and Figs. 13 (A), (B), and (C) are A of Fig. 12, respectively.
FIG. 6 is a cross-sectional view taken along line -A ', line BB', and line CC '. 10 …… Inspected tube, 11 …… Welded part, 12 …… Blade probe, 13 …… Ultrasonic beam, 14 …… Vertical probe, 15 …… Acoustic wedge, 16a, 16b …… Side plate, 17a, 17b ... Shew, 32 ... Main clock generator, 34 ... Clock distributor P ... Pulsar, R ... Receiver, G ... Gate unit, U _{1 to} Un ... Channel unit.

Claims (2)

[Claims] 1. A pipe bevel flaw detection head for a pipe used for inspecting a defect in a tube axis direction of a subject pipe by an ultrasonic bevel flaw detection method, comprising: In order to arrange the angle probes in a circumferential direction of the pipe efficiently without gaps, each of the bevel probes is composed of a vertical probe and an acoustic wedge, and a cross section of the acoustic wedge in the pipe circumferential direction of the test tube. A radiation angle β whose shape is determined by the outer diameter of the test tube and the width of the vertical probe, the width of which is wider on the vertical probe side than on the test tube side.
And the cross-sectional shape of the acoustic wedge has an incident angle θi in the tube circumferential direction so as to excite or receive ultrasonic waves obliquely in the tube circumferential direction of the test tube. And a plurality of the slanted angles with which the vertical probe that excites or receives ultrasonic waves in a vertical direction is attached to a mounting surface of the acoustic wedge that is orthogonal to the incident angle θi. The probe is mounted in an array in the circumferential direction of the pipe in a state of no gaps and in a slanted arrangement, and has side plates in an arc shape concentric with the pipe to be inspected. A wear-resistant 1 which is provided before and after the probe, holds a gear gap between the surface of the tube to be inspected and the acoustic wedge, and prevents abrasion of the acoustic wedge.
An oblique angle head for pipes, characterized by having a pair of shoes. 2. A bevel angle flaw detector for a pipe, comprising the bevel angle flaw detection head for a pipe according to claim 1 for flaw detection of a pipe to be inspected.