JP2010025676A - Ultrasonic flaw detecting method and device - Google Patents

Abstract

An ultrasonic flaw detection operation is easily and accurately performed on a multi-layer piping structure.
First, linear scanning is performed at a flaw detection refraction angle θ1 such that an ultrasonic beam from each transducer of the phased array probe 1 can directly hit a flaw detection target region R. Next, linear scanning similar to that described above is performed at a flaw detection refraction angle θ2 that can be reached after the ultrasonic beam is reflected once on the inner surface of the thick portion. In this case, one of the ultrasonic beams is reflected at one end side (crack opening position) of the defect portion d. Then, linear scanning similar to the above is performed at a flaw detection refraction angle θ3 that can be reflected after being reflected once on the inner surface of the thick portion and then reflected once on the outer surface of the thick portion. In this case, one of the ultrasonic beams is reflected on the other end side (crack tip position) of the defect portion d.
[Selection] Figure 3

Description

  The present invention relates to an ultrasonic flaw detection method and apparatus for carrying out ultrasonic flaw detection mainly on a multi-layer piping structure site in a nuclear facility.

  A welded part of a structure in a nuclear facility is a place where a defect such as a crack is likely to occur because various stresses such as residual stress concentrate. Conventionally, ultrasonic flaw detection is known as a technique for detecting defects generated at such welds. Ultrasonic flaw detection is a technology that determines whether or not a defect exists in an inspection object by transmitting an ultrasonic beam from an ultrasonic sensor called a probe to the inspection object and analyzing the reflected wave. is there.

  This ultrasonic sensor is called a single-type probe composed of one transducer having an ultrasonic transmission function and a reception function and a phased array probe having a plurality of such transducers. (For example, refer to Patent Document 1). In this phased array probe, a plurality of transducers are arranged in various shapes such as a line shape, a lattice shape, or an annular shape. By controlling the ultrasonic wave transmission timing of each transducer, The ultrasonic beam can be converged to an arbitrary position, and the flaw detection refraction angle can be changed to an arbitrary angle.

  In the example of Patent Document 1 described above, the phased array probe can be attached near the welding location, so that the flaw detection refraction angle does not need to be so large, and the ultrasonic beam transmitted from the vibrator is directly applied. It is possible to hit the defective part.

  By the way, in-furnace piping of a nuclear power plant or the like includes a portion having a multilayer piping structure as typified by, for example, core spray piping. This multi-layer piping structure part is formed by welding one or two or more sleeves on the outside of the piping part, and is located at a position far away from an area where a defect is expected to occur, that is, a flaw detection target area. However, since the probe can only be attached and the refraction angle of the flaw must be increased, the ultrasonic flaw detection work has been conventionally performed as follows.

  FIG. 11 is a partial cross-sectional view for explaining a conventional ultrasonic flaw detection technique for a multilayer pipe structure part. In this figure, an intermediate sleeve 102 is fixed to the outside of the inner pipe 101 by welding, and an outer sleeve 103 is fixed to the outer side thereof by welding. The flaw detection target region R is set over a range slightly wider than the arrangement range of the intermediate sleeve 102 and the outer sleeve 103, and a defect portion d such as a crack is present in the inner pipe 101 portion located in the flaw detection target region R. It is assumed that it has occurred.

  A single ultrasonic probe 105 serving as an ultrasonic sensor is a wedge member (for example, a resin such as acrylic) on the surface position of the inner pipe 101 that is separated from the multilayer pipe structure portion as described above along the axial direction of the inner pipe 101. Member) 104. The ultrasonic probe 105 is composed of a single transducer having a transmission function and a reception function. After the transmitted ultrasonic beam passes through the wedge member 104, the surface of the inner pipe 101 is refracted and refracted. Incident light is incident at an angle θ.

The ultrasonic beam travels in the thick portion of the inner pipe 101 toward the flaw detection target region R, is reflected once at the position P1 on the inner surface of the thick portion, reaches the defect portion d, and hits the defect portion d. After the reflection, the ultrasonic probe 105 receives the signal along the same path. Depending on the type of the ultrasonic probe 105, the wedge member 104 may not be able to sufficiently increase the flaw detection refraction angle θ if it is directly attached to the inner pipe 101 surface. It is a member used for securing.
JP 2002-214204 A

  However, since the above-described conventional ultrasonic flaw detection technology uses the single ultrasonic probe 105 constituted by one transducer, the flaw detection refraction angle θ is a fixed value. The flaw detection refraction angle θ is set to a value that can pass through the flaw detection target region R, but is caused by a difference in various conditions such as the reflection position P1, the position of the defect portion d, or the material of the inner pipe 101. In some cases, it is difficult to detect the defective portion d.

  In such a case, the mounting position of the wedge member 104 and the ultrasonic probe 105 is changed, the shape of the wedge member 104 is changed, or the ultrasonic probe 105 is replaced with one having a different flaw detection angle characteristic. Therefore, various measures have to be tried, resulting in a lot of time and labor for the ultrasonic flaw detection work.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrasonic flaw detection method and apparatus capable of easily and accurately performing an ultrasonic flaw detection operation on a multi-layer piping structure site.

  As a means for solving the above-mentioned problems, the invention according to claim 1 is characterized in that a plurality of vibrations are formed at the surface position of the inner pipe portion spaced apart along the pipe axis direction from the multi-layer pipe structure formed by sleeve welding. A phased array probe having a child is attached, and when the ultrasonic beam transmitted from the phased array probe travels in the thick part of the inner pipe, the ultrasonic beam is connected to the outer surface and the inner surface of the thick part. The flaw detection refraction angle of the ultrasonic beam with respect to the inner pipe portion surface is sequentially changed so as to reach the flaw detection target area set in the multilayer pipe structure part while repeating reflection between them or without reflection. The presence or absence of a defective portion in the flaw detection target area is determined based on the reflected wave from the flaw detection target area received by the phased array probe.

  According to a second aspect of the present invention, in the first aspect of the present invention, when a defect portion exists in the flaw detection target area, the position and size of the defect portion are calculated using a beam path length and the flaw detection refraction angle. It is characterized by.

  According to a third aspect of the present invention, in the first aspect of the invention, the phased array probe sequentially changes the flaw detection refraction angle at a predetermined pitch angle, and performs an ultrasonic transmission / reception operation for each flaw detection refraction angle. A linear scan is performed by shifting a predetermined number of transducers sequentially performed along the pipe axis direction.

  According to a fourth aspect of the present invention, in the first aspect of the invention, the phased array probe performs sector scanning in which the flaw detection refraction angle is continuously changed sequentially. .

  According to a fifth aspect of the present invention, in the first aspect of the invention, an ultrasonic beam is incident on the surface of the inner pipe portion at a predetermined flaw detection refraction angle so that the inside of the inner pipe portion thick portion toward the flaw detection target region. A traveling secondary creeping wave is generated, the approximate position of the defect portion is obtained using the reflected wave of the secondary creeping wave, and then the flaw detection refraction angle is sequentially changed.

  According to a sixth aspect of the present invention, there is provided a phased array probe having a plurality of transducers attached to a surface position of an inner pipe portion that is separated from a multilayer pipe structure portion formed by sleeve welding construction along a pipe axis direction. When the ultrasonic beam transmitted from the child and the phased array probe travels in the thick part of the inner pipe, the ultrasonic beam is repeatedly reflected between the outer surface and the inner surface of the thick part, or Probe control means for sequentially changing the flaw detection refraction angle of the ultrasonic beam with respect to the inner pipe portion surface so as to reach the flaw detection target area set in the multi-layer pipe structure portion directly without reflection, and Defect portion detecting means for determining the presence / absence of a defect portion in the flaw detection target area based on a reflected wave from the flaw detection target area received by the phased array probe.

  The invention according to claim 7 is the invention according to claim 6, wherein the phased array probe is attached to the surface position of the inner pipe part in a state of being submerged in water or other liquid. It is characterized by that.

  The invention described in claim 8 is characterized in that, in the invention described in claim 6, the phased array probe is directly attached to the surface position of the inner piping section.

  The invention according to claim 9 is the invention according to claim 6, wherein the phased array probe is attached to the surface position of the inner pipe part via a wedge member for adjusting a change range of the flaw detection refraction angle. It is characterized by that.

  According to a tenth aspect of the present invention, in the sixth aspect of the invention, the phased array probe is characterized in that the plurality of transducers are arranged in a grid pattern.

  The invention described in claim 11 is the invention described in claim 6, wherein the phased array probe is characterized in that the plurality of transducers are arranged concentrically around an inner pipe. To do.

  According to the present invention, a phased array probe having a plurality of transducers is used as an ultrasonic sensor, and an ultrasonic beam transmitted from the phased array probe is subjected to multiple reflection within the thick part of the inner pipe. However, since the flaw detection refraction angle is sequentially changed so as to reach the flaw detection target region directly without reflection or even in a multilayer pipe structure part, ultrasonic flaw detection work can be performed easily and accurately. It is possible to implement.

  FIG. 1 is a block diagram showing a configuration of an ultrasonic flaw detector according to an embodiment of the present invention. It should be noted that the inner pipe 101, the intermediate sleeve 102, and the outer sleeve 103 that form the multilayer pipe structure portion are illustrated using the same reference numerals as in FIG.

  A phased array probe 1 having a plurality of transducers 2 arranged in a line is attached via a holding mechanism in a state of facing the surface of the inner pipe 101 (in this figure, a phased array probe). The illustration of the holding mechanism 1 and the drive mechanism 1 is omitted in order to avoid complication of the drawing. In the present embodiment, the phased array probe 1 is attached in a state of being submerged in water in the nuclear reactor, so that a so-called “water immersion flaw detection method” (a water gap is formed between the probe and the subject). This is an ultrasonic flaw detection method. However, the phased array probe of the present invention can be mounted in various containers other than the nuclear reactor, and may be used in a state of being submerged in other liquids as well as in water.

  The ultrasonic flaw detector 3 performs ultrasonic flaw detection on the flaw detection target region R of the multi-layer piping structure using the phased array probe 1. The probe control means 4 and the defect detection means 5 have. The probe control means 4 is capable of electronic scanning control such as so-called linear scanning and sector scanning, which sequentially delays the ultrasonic wave transmission timings of the plurality of transducers 2. The defective portion detection means 5 receives the reflected wave of the ultrasonic wave at the same timing corresponding to the ultrasonic wave transmission timing by the probe control means 4, and detects the defective portion by determining the level of the reflected echo. Is.

  The condition input means 6 is for setting and inputting various flaw detection conditions (for example, a change range or a pitch angle when changing the flaw detection refraction angle) to the ultrasonic flaw detector 3. The display device 7 is for displaying the set flaw detection conditions and the detection result by the defect portion detection means 5 on the display. An operator can perform an ultrasonic flaw detection operation by operating the condition input means 6 and the display device 7.

  Next, an ultrasonic flaw detection method according to each embodiment of the present invention performed using the ultrasonic flaw detection apparatus as described above will be described. FIG. 2 is a flowchart showing an outline of the ultrasonic flaw detection method according to the first embodiment.

  First, in Step 1, an appropriate phased array probe 1 is selected in consideration of the material, diameter, thickness, weld metal part size, etc. of the pipes 101 to 103 forming the multilayer pipe structure part. The phased array probe 1 is attached to a position facing the surface of the inner pipe 101 via a probe holding mechanism (not shown).

  Next, in step 2, the mounting angle of the phased array probe 1, that is, the inclination angle α of the phased array probe 1 with respect to the surface of the inner pipe 101 is adjusted (including a case where α is zero, that is, a parallel state).

  The inclination angle α is, for example, checked for a time lag until the ultrasonic wave is transmitted perpendicularly to the surface of the inner pipe 101 from the left and right transducers of the phased array probe 1 and the reflected wave is received. Can be obtained. That is, if the reception times of both transducers are the same, the phased array probe 1 is attached in parallel to the pipe surface, and if there is a deviation in the reception time, the phased array probe 1 It is attached at an inclination angle α proportional to the amount of deviation. In the present embodiment, it is assumed that the phased array probe 1 is attached in parallel to the pipe surface.

  In step 3, using the condition input means 6 described above, the change range and pitch angle when the flaw detection refraction angle is changed, and further the water distance (the ultrasonic wave travels in water between the transducer and the pipe surface). Set various flaw detection conditions such as distance. In the present embodiment, the flaw detection refraction angle is set to change in three stages of θ1, θ2, and θ3 (θ1> θ2> θ3) at the pitch angle Δθ.

  In step 4, ultrasonic transmission / reception operations, that is, ultrasonic flaw detection, are performed for each flaw detection refraction angle θ1, θ2, and θ3 by linear scanning of the plurality of transducers 2 of the phased array probe 1. Waveform data obtained by this ultrasonic flaw detection is collected by the defect detection means 5.

  In step 5, the defect detection means 5 detects a defect d such as a crack existing in the flaw detection target region R from the waveform data collected by the ultrasonic flaw detection in step 4.

  In step 6, the defect detection means 5 further performs an evaluation of the defect including the calculation of the position and size of the defect d using the beam path length and the flaw detection refraction angle.

  Next, the operation of step 4 described above will be described in detail. FIGS. 3A and 3B are explanatory diagrams of the ultrasonic flaw detection operation in the linear scanning in Step 4, where FIG. 3A is a case of direct ultrasonic irradiation, FIG. 3B is a case of ultrasonic single reflection, and FIG. The case of 1.5 reflections is shown respectively.

  First, in FIG. 3A, the phased array probe 1 performs linear scanning at a flaw detection refraction angle θ1 such that the ultrasonic beam from each transducer can directly hit the flaw detection target region R. In this linear scanning, a predetermined number of transducers among a plurality of transducers 2 are grouped, and transducers that perform ultrasonic transmission / reception operations within the range of one group are arranged along the axial direction of the inner pipe 101. Further, the transducers belonging to the one group are shifted in the same manner.

  For example, assuming that the total number of transducers 2 provided in the phased array probe 1 is 100, these transducers are represented by symbols v1 to v100. Now, the number of transducers used for transmission (and reception) of ultrasonic waves is 11, and the 11 transducers are grouped into one group. Then, at first, the transducers sequentially transmit ultrasonic waves at predetermined delay timings from v1 to v11 within the range of groups v1 to v11. Next, the transducers sequentially transmit ultrasonic waves at predetermined delay timings from v2 to v12 within the range of groups v2 to v12. Similarly, each transducer sequentially transmits ultrasonic waves at a predetermined delay timing within the range of each group of v3 to v13, v4 to v14,..., V90 to v100. That is, a group of eleven transducers that sequentially transmit ultrasonic waves at a predetermined delay timing gradually approach the flaw detection target region R side. At this time, the center oscillator of the groups v1 to v11 is v6, and the center oscillator of the groups v2 to v12 is v7. Similarly, the center transducers in the subsequent groups are v8, v9,..., V95, respectively. 3 (a) to 3 (c), the linear beam obliquely incident from the transducer 2 to the surface side of the inner pipe 101 is illustrated with the beams from these central transducers as representatives of each group. Is.

  In this way, in FIG. 3A, the phased array probe 1 performs linear scanning at the flaw detection refraction angle θ1 until all the transducers v1 to v100 finish the transmission / reception operation. It is assumed that the defective part d existing in the flaw detection target area R cannot be detected.

  Next, in FIG. 3B, the phased array probe 1 can reach the flaw detection target region R after being reflected once by the inner surface of the thick portion of the inner pipe 101. A linear scan similar to the above is performed at a flaw detection refraction angle θ2. In this case, as the linear scanning is performed, the ultrasonic beam catches the defect portion d, and the ultrasonic beam from a certain transducer is reflected at one end side (crack opening position) of the defect portion d. . This reflected wave traces the same path as the emitted wave in the opposite direction and is received by the same vibrator and collected by the defect detection means 5 as a reflected echo signal.

  In FIG. 3C, the phased array probe 1 causes the ultrasonic beam from each transducer to be reflected once to the flaw detection target region R by the inner surface of the thick portion of the inner pipe 101, and further to the thick portion. Linear scanning similar to that described above is performed at a flaw detection refraction angle θ3 that can be reached after being reflected once on the outer surface. Even in this case, the ultrasonic beam catches the defect portion d while performing linear scanning, and the ultrasonic beam from a certain transducer is reflected on the other end side (crack tip position) of the defect portion d. To do. Similarly to the case of the flaw detection refraction angle θ2, this reflected wave is received by the same transducer following the same path as the emitted wave in the opposite direction, and is collected by the defect detection means 5 as a reflected echo signal.

  In the case of FIG. 3C, in the technical field, the reflection on the outer surface of the thick portion that is the surface on the ultrasonic incident side is not counted as one time, but is counted as 0.5 times. Instead of expressing “2 times reflection”, it is expressed as “1.5 times reflection”.

  Next, a method for obtaining the position of the defective portion d based on the reflected echo signal in the cases of FIGS. 3B and 3C will be described with reference to FIGS. In the present embodiment, the position and size of the defect portion d are calculated as follows using the beam path length and the flaw detection refraction angle.

  4A and 4B are explanatory diagrams for the defect position calculation in the case of ultrasonic single reflection in FIG. 3B, FIG. 4A is a waveform diagram showing the echo height at the crack opening position, and FIG. It is the elements on larger scale for demonstrating the calculation of a crack opening position.

  When the defect detection means 5 collects the reflected echo signals as shown in FIG. 4A, the peak point of this signal waveform is specified as the crack opening position, and the beam path length W2 is calculated. In FIG. 4B, the beam path W2 passes through the water and enters the surface position P0 of the inner pipe 101 through the water, and reflects at the position P1 on the inner surface of the thick portion. This is the distance of the path connecting these positions P0, P1, and d1 when the crack opening position d1 is reached.

  In this embodiment, in order to specify the position and size of the defective portion d, a coordinate system in the horizontal direction (Y direction) and the vertical direction (Z direction) is set, and distances Y and Z from a certain reference position are calculated. To do. Although this reference position need not be particularly limited, in the present embodiment, the reference position in the Y direction is the position of the end surface 102a of the intermediate sleeve 102, and the reference position in the Z direction is the position of the outer surface of the thick part of the inner pipe 101. To do. Then, the position of the crack opening position d1 is specified by the distances Yc and Zc from the respective reference positions in the Y and Z directions.

  These distances Yc and Zc are t, where the thickness of the inner pipe 101 is t, and yc is the distance from the reference position (end face 102a) of the transducer that has transmitted the ultrasonic beam that has reached the crack opening position d1. Then, it can obtain | require by following (1), (2) Formula. The distance yc can be obtained immediately since the mounting position of the phased array probe 1 is known in advance (step 1) and the position of the transducer in the phased array probe 1 is also known. .

Yc = W2 · sinθ2−yc (1)
Zc = 2 ・ t−W2 ・ cosθ2 (2)

FIG. 5 is an explanatory diagram of defect position calculation in the case of 1.5 reflections of ultrasonic waves in FIG. 3 (c), (a) is a waveform diagram showing the echo height at the crack tip position, ) Is a partially enlarged view for explaining the calculation of the crack tip position.

  When the defect detection means 5 collects the reflected echo signals as shown in FIG. 5A, it specifies the peak point of this signal waveform as the crack tip position and calculates the beam path length W3. In FIG. 5B, the beam path W3 is such that an ultrasonic beam transmitted from a certain transducer 2 passes through water and enters the surface position P′0 of the inner pipe 101, and the position P ′ of the inner surface of the thick portion. 1 and the distance of the path connecting these positions P ′ 0, P ′ 1, P 2, d 2 when reaching the crack tip position d 2 after being reflected at the position P 2 on the outer surface of the thick part.

  Then, the crack tip position d2 is specified by the distances Yt and Zt from the respective reference positions in the Y and Z directions. These distances Yt and Zt are t and the thickness of the inner pipe 101 is t, and the distance from the reference position (end face 102a) of the transducer that transmits the ultrasonic beam that has reached the crack tip position d2 is yt. Then, it can obtain | require by following (3), (4) Formula. The distance yt can be obtained immediately since the mounting position of the phased array probe 1 is known in advance (step 1) and the position of the transducer in the phased array probe 1 is also known. .

Yt = W3 · sinθ3−yt (3)
Zt = 3 ・ t−W3 ・ cosθ3 (4)

FIG. 6 shows the defect portion d, that is, the defect position d, that is, the position [Yc, Zc] of the crack opening position d1 and the position [Yt, Zt] of the crack tip position d2 obtained as described above. It is explanatory drawing about an example of the method of calculating the position and magnitude | size of a crack. In the case of a crack as shown in FIG. 6, “crack position” usually refers to the position of the crack opening position d1, and “crack size” usually refers to the vertical direction from the position d1. It is often specified by the depth h and the inclination angle β.

  In FIG. 6, assuming that the depth in the vertical direction from the crack opening position d1 is h, and the horizontal distance connecting the tip position of the depth h and the crack tip position d2 is j, the inclination angle β of the defect d is β. Can be obtained by the following equation (5). Thereby, the ultrasonic flaw detection method according to the first embodiment of the present invention is completed.

β = tan-1 (j / h)
= Tan-1 {(Yt-Yc) / (Zt-Zc)} (5)

In the ultrasonic flaw detection method according to the first embodiment described above, linear scanning by a plurality of transducers is possible, and the flaw detection refraction angle is only controlled by delaying the respective ultrasonic transmission timings of the plurality of transducers. The phased array probe, which can be easily changed, is effectively used, and not only the ultrasonic direct method for the flaw detection target area, but also the ultrasonic multiple reflection method is used together. It becomes possible to easily and accurately detect a defective portion existing in the multilayer pipe structure portion.

  FIG. 7 is an explanatory diagram of an ultrasonic flaw detection method according to the second embodiment of the present invention. In the method according to the second embodiment, sector scanning is performed in which the flaw detection refraction angle is continuously and sequentially changed.

  In the first embodiment, linear scanning is first performed with the flaw detection refraction angle set to θ1, then linear scanning is performed with θ2 obtained by reducing θ1 by the pitch angle Δθ, and then θ2 is set to the pitch angle Δθ. Linear scanning was performed with a reduced θ3. On the other hand, in the second embodiment, as indicated by the arrows in FIG. 7 by sector scanning, the flaw detection refraction angle is continuously reduced from θ1 to θ3, and the ultrasonic beam is shaken in a fan shape. The ultrasonic beam can quickly catch the defective portion d in the flaw detection target region R.

  In this case, in the present embodiment, the vibrator used for sector scanning is a predetermined number of vibrators arranged at predetermined positions. For example, by controlling the ultrasonic wave transmission timing of 11 transducers v90 to v100 belonging to the group closest to the flaw detection target region R out of 100 transducers v1 to v100 of the phased array probe 1, As described above, it is possible to perform sector scanning in which the flaw detection refraction angle is continuously reduced from θ1 to θ3.

  However, in the case where a sufficient level of reflected echo signals cannot be obtained by such sector scanning of only specific transducers, the group to which these 11 transducers belong is moved to the right, at a more preferable position. Similar sector scanning can be performed again. For example, this time, sector scanning in which the flaw detection refraction angle is continuously reduced from θ1 to θ3 using eleven vibrators v80 to v90 can be performed. According to such a method, it is possible to reliably detect the presence of the defective portion d without overlooking it.

  FIG. 8 is an explanatory diagram of an ultrasonic flaw detection method according to the third embodiment of the present invention. In the method according to the third embodiment, the ultrasonic beam is incident on the surface of the inner pipe 101 so as to have a predetermined flaw detection refraction angle θ0 (for example, 30 °), and thus the head is directed to the flaw detection target region R. After generating a secondary creeping wave that travels in the thick portion of the inner pipe 101 and using the reflected wave of this secondary creeping wave to determine the approximate position of the defective portion, the ultrasonic wave according to the first embodiment The flaw detection method is carried out.

  That is, when an ultrasonic beam is incident on the inner pipe 101 from the phased array probe 1 so as to have a predetermined flaw detection refraction angle, a longitudinal wave called a primary creeping wave that propagates along the outer surface of the thick portion. And a transverse wave are also generated, which proceeds toward the inner surface (bottom surface) of the thick portion. When this transverse wave collides and reflects on the inner surface of the thick part, a part of this transverse wave is mode-converted into a longitudinal wave, and a secondary creeping wave propagating along the inner surface of the thick part is generated. Since this secondary creeping wave has the property of propagating along the material surface, it exhibits a great effect in detecting a defect occurring on the material surface. However, this secondary creeping wave may have a large attenuation characteristic depending on the material.

  Therefore, if a secondary creeping wave is first generated to obtain the approximate position of the defect portion d and then linear scanning is performed for each flaw detection refraction angle as described in the first embodiment, an efficient ultrasonic wave It can perform flaw detection work. This is because, in this case, since the approximate position of the defect portion d has already been obtained, it is not necessary to change the flaw detection refraction angle so much, and it is only necessary to change the flaw detection refraction angle within a certain range.

  FIG. 9 is an explanatory diagram of an ultrasonic flaw detection method according to the fourth embodiment of the present invention. In the embodiments described so far, ultrasonic flaw detection is performed by a so-called water immersion method in which the phased array probe 1 is attached while being immersed in water in the furnace, but depending on the state of the surface of the inner pipe 101. The phased array probe 1 can be directly attached to the surface of the inner pipe 101 (but with a contact medium interposed), and ultrasonic flaw detection can be performed by a so-called direct contact method. According to this direct contact method, the attenuation amount of ultrasonic waves can be reduced as compared with the water immersion method.

  FIG. 10 is an explanatory diagram of an ultrasonic flaw detection method according to the fifth embodiment of the present invention. In this embodiment, a phased array probe is performed via a wedge member 8 similar to the wedge member 104 in the conventional example shown in FIG. 11 (however, a contact medium is interposed between the wedge member 8 and the inner pipe 101). The child 1 is attached to the surface of the inner pipe 101. Although the wedge member 8 is used, this fifth embodiment is also classified as a direct contact method.

  Since the phased array probe 1 can freely change the flaw detection refraction angle θ, such a wedge member 8 is not necessarily required. However, when the range of the flaw detection refraction angle in which the ultrasonic beam can reach the flaw detection target region is known in advance, the range of change of the flaw detection refraction angle can be obtained by using the wedge member 8 having such a specific shape. The ultrasonic flaw detection work can be performed more efficiently.

  In each of the above-described embodiments, the phased array probe 1 is assumed to be a type in which the transducers 2 are arranged in a line, but the transducers 2 are in a lattice shape (planar shape). It may be arranged. According to this, ultrasonic flaw detection can be performed not only on the flaw detection target region R in front of the phased array probe 1 but also on other side regions.

  Alternatively, a phased array probe 1 in which the transducers 2 are concentrically arranged around the inner pipe 101 can also be used. According to this, an ultrasonic beam can be sent to the whole circumference part of the flaw detection target area | region R, and oversight of the defect part d can be prevented more reliably.

1 is a block diagram showing the configuration of an ultrasonic flaw detector according to an embodiment of the present invention. 1 is a flowchart showing an outline of an ultrasonic flaw detection method according to a first embodiment of the present invention. FIG. 5 is an explanatory diagram of ultrasonic flaw detection operation in linear scanning in Step 4 of FIG. 2, (a) in the case of direct ultrasonic irradiation, (b) in the case of single ultrasonic reflection, (c) in the ultrasonic wave 1. Each case of 5 reflections is shown. It is explanatory drawing about the defect position calculation in the case of the ultrasonic once reflection in FIG.3 (b), (a) is a wave form diagram which shows the echo height in a crack opening position, (b) is a crack opening position. The elements on larger scale for demonstrating the calculation of. It is explanatory drawing about the defect position calculation in the case of 1.5 times of ultrasonic reflection in FIG.3 (c), (a) is a wave form diagram which shows the echo height in a crack tip position, (b) is a crack. The elements on larger scale for demonstrating the calculation of a front-end | tip position. FIG. 2 is an explanatory diagram illustrating an example of a method for calculating a position and a size of a defective portion d in FIG. 1. Explanatory drawing of the ultrasonic flaw detection method which concerns on the 2nd Embodiment of this invention. Explanatory drawing of the ultrasonic flaw detection method which concerns on the 3rd Embodiment of this invention. Explanatory drawing of the ultrasonic flaw detection method which concerns on the 4th Embodiment of this invention. Explanatory drawing of the ultrasonic flaw detection method which concerns on the 5th Embodiment of this invention. The partial cross section figure for demonstrating the conventional ultrasonic flaw detection technique with respect to a multilayer piping structure site | part.

Explanation of symbols

1: phased array probe 2: transducer 3: ultrasonic flaw detector 4: probe control means 5: defect detection means 6: condition input means 7: display device 8: wedge member R: flaw detection target area θ1˜ θ3: Flaw detection angle d: Defect portion d1: Crack opening position d2: Crack tip position

Claims (11)

Attach a phased array probe having a plurality of transducers to the surface position of the inner piping part that is separated from the multilayer piping structure part formed by the construction of sleeve welding along the pipe axis direction,
When the ultrasonic beam transmitted from the phased array probe travels through the thick part of the inner pipe, the ultrasonic beam repeats or does not reflect between the outer surface and the inner surface of the thick part. Directly change the flaw detection refraction angle with respect to the inner pipe part surface of the ultrasonic beam so as to reach the flaw detection target area set in the multilayer pipe structure part,
Based on the reflected wave from the flaw detection target area received by the phased array probe, the presence or absence of a defect portion in the flaw detection target area is determined.
An ultrasonic flaw detection method characterized by the above. When a defect portion exists in the flaw detection target region, the position and size of the defect portion are calculated using a beam path length and the flaw detection refraction angle.
The ultrasonic flaw detection method according to claim 1. The phased array probe sequentially changes the flaw detection refraction angle at a predetermined pitch angle, and shifts a predetermined number of transducers that sequentially perform ultrasonic transmission / reception for each flaw detection refraction angle along the pipe axis direction. To perform linear scanning,
The ultrasonic flaw detection method according to claim 1. The phased array probe performs sector scanning in which the flaw detection refraction angle is continuously changed sequentially.
The ultrasonic flaw detection method according to claim 1. By making an ultrasonic beam incident on the surface of the inner pipe part at a predetermined flaw detection refraction angle, a secondary creeping wave traveling in the thick part of the inner pipe part toward the flaw detection target region is generated, and this secondary creeping is performed. After obtaining the approximate position of the defect portion using the reflected wave of the wave, the flaw detection refraction angle is sequentially changed,
The ultrasonic flaw detection method according to claim 1. A phased array probe having a plurality of transducers attached to the surface position of the inner pipe part spaced apart from the multilayer pipe structure part formed by the construction of sleeve welding along the pipe axis direction;
When the ultrasonic beam transmitted from the phased array probe travels through the thick part of the inner pipe, the ultrasonic beam repeatedly reflects between the outer surface and the inner surface of the thick part or does not reflect. A probe control means that sequentially changes the flaw detection refraction angle with respect to the inner pipe portion surface of the ultrasonic beam so as to reach the flaw detection target region set directly in the multilayer pipe structure site;
Based on the reflected wave from the flaw detection target region received by the phased array probe, a defect portion detection means for determining the presence or absence of a defect portion in the flaw detection target region;
An ultrasonic flaw detector characterized by comprising: The phased array probe is attached to the surface position of the inner pipe part in a state immersed in water or other liquid.
The ultrasonic flaw detector according to claim 6. The phased array probe is directly attached to the surface position of the inner piping part.
The ultrasonic flaw detector according to claim 6. The phased array probe is attached to the surface position of the inner piping part via a wedge member for adjusting the change range of the flaw detection refraction angle.
The ultrasonic flaw detector according to claim 6. The phased array probe is a plurality of transducers arranged in a grid pattern.
The ultrasonic flaw detector according to claim 6. The phased array probe is one in which the plurality of transducers are arranged concentrically around an inner pipe.
The ultrasonic flaw detector according to claim 6.

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