JP6776913B2 - Internal surface inspection method of pipe - Google Patents

Description

The present invention relates to a method for inspecting the inner surface of a tube using ultrasonic waves. In particular, the present invention relates to a method for inspecting the inner surface of a pipe capable of detecting minute irregularities on the inner surface of the pipe caused by peracid washing of the pipe.

Conventionally, in the manufacturing process of a pipe, a pickling treatment may be performed in which the pipe is immersed in a pickling solution such as sulfuric acid for the purpose of removing the oxidation scale generated on the inner and outer surfaces of the pipe.
After the pickling treatment, the pickling solution is removed from the tube, but over-pickling occurs due to the remaining pickling solution on the inner surface of the tube, and as a result, the inner surface of the tube has minute irregularities ( Hereinafter, this may be referred to as “inner surface microconcavities and convexities”) as appropriate.

The above-mentioned minute unevenness on the inner surface can also be detected by inserting an imaging means such as an ITV camera into the tube and visually observing the captured image by the operator.
However, in the tube manufacturing process, it takes a lot of time and effort to insert and remove the imaging means for all the tubes, so that it is difficult to inspect substantially all of the tubes.
Therefore, there is a demand for a method capable of inspecting the inner surface of all the tubes that have been pickled and detecting minute irregularities on the inner surface.

As a method for inspecting the inner surface of a pipe, for example, methods such as Patent Documents 1 to 4 have been proposed, but none of them is an effective method for detecting the above-mentioned minute unevenness on the inner surface.

JP-A-59-147259 Japanese Unexamined Patent Publication No. 6-347242 Japanese Unexamined Patent Publication No. 7-218459 Japanese Unexamined Patent Publication No. 2005-30880

The present invention has been made to solve the above-mentioned problems of the prior art, and provides a method for inspecting the inner surface of a pipe capable of detecting minute irregularities on the inner surface of the pipe caused by peracid washing of the pipe or the like. The task is to do.

As a result of diligent studies in order to solve the above problems, the present inventors have obtained the findings described in the following (A) to (C) and completed the present invention.
(A) The strength of the bottom echo signal when the inner surface of the pipe is vertically flawed from the outer surface of the pipe is attenuated by the minute unevenness on the inner surface.
(B) Since the intensity of the bottom surface echo signal is slightly attenuated due to the minute unevenness on the inner surface, the intensity of the bottom surface echo signal is attenuated due to the minute unevenness on the inner surface due to the change in the intensity of the bottom surface echo signal due to the eccentricity or uneven thickness of the tube. It becomes difficult to detect. In order to reduce the influence of eccentricity and uneven thickness of the pipe, evaluate the calculated strength distribution of the bottom echo signal obtained by applying the predetermined arithmetic processing described later to the intensity distribution of the bottom echo signal in the circumferential direction of the pipe. Is effective.
(C) Small unevenness on the inner surface can be detected by the magnitude of the statistical value obtained by performing statistical processing (processing to calculate the mean value, standard deviation, and the product of these) on the calculated intensity distribution of the bottom echo signal (healthy inner surface). Identifiable).

That is, the present invention provides a method for inspecting the inner surface of a pipe, which comprises the following first to fifth steps.
(1) First step: An ultrasonic probe is placed facing the outer surface of the tube.
(2) Second step: The ultrasonic probe is moved relatively in the circumferential direction of the tube, and ultrasonic waves are transmitted from the ultrasonic probe substantially perpendicular to the inner surface of the tube. The bottom surface echo reflected from the inner surface of the tube is received by the ultrasonic probe to acquire the intensity distribution of the bottom surface echo signal in the circumferential direction of the tube.
(3) Third step: The intensity distribution of the bottom echo signal acquired in the second step is subjected to a predetermined arithmetic process to acquire the calculated intensity distribution of the bottom echo signal.
(4) Fourth step: Statistical processing is performed on the calculated intensity distribution of the bottom echo signal acquired in the third step, and unevenness on the inner surface of the pipe is detected based on the magnitude of the statistical value obtained by the statistical processing. ..
In the arithmetic processing, the maximum value of the intensity within a predetermined point range from the point of interest is divided by the minimum value for each intensity of the plurality of points constituting the intensity distribution of the bottom echo signal, and the division is performed. This is a process in which the result is used as the calculation intensity of the point of interest.

According to the present invention, it is possible to acquire the calculated intensity distribution of the bottom echo signal by executing the first step to the third step. In other words, it is possible to acquire the calculation intensity of the bottom echo signals at a plurality of points. As will be described later, the calculated intensity of the bottom echo signal is such that the influence of the eccentricity and the uneven thickness of the tube is reduced as compared with the intensity of the bottom echo signal itself. Then, in the fourth step, statistical processing is performed on the calculated intensity distribution of the bottom echo signal (statistical processing is performed on the calculated intensity of the bottom echo signal at a plurality of points), and based on the magnitude of the obtained statistical values, the inner surface of the pipe is subjected to statistical processing. It is possible to detect unevenness.
According to the present invention, as a mechanical operation, the ultrasonic probe is arranged so as to face the outer surface of the tube (first step), and the ultrasonic probe is moved relatively in the circumferential direction of the tube (1st step). (2nd step) is all that is required (to inspect the entire inner surface of the tube, it is only necessary to move the ultrasonic probe relatively in the axial direction of the tube in addition to the circumferential direction of the tube). It is possible to automatically inspect the inside of all pipes with less effort than in the case of inserting and removing.

The present invention can be suitably used, for example, when the unevenness of the inner surface of the pipe is caused by per-pickling of the pipe.

According to the present invention, it is possible to detect minute irregularities on the inner surface of the pipe, and it is possible to automatically inspect the inner surface of all the pipes. The minute irregularities to be detected in the present invention include, for example, minute irregularities caused by over-pickling of pipes subjected to pickling treatment, scratches caused by insufficient lubrication during hot working, and cold. Scratches and the like caused by minute irregularities on the tool surface during machining can be mentioned.

It is explanatory drawing explaining the schematic structure of the inner surface inspection apparatus for carrying out the inner surface inspection method of the pipe which concerns on one Embodiment of this invention. It is explanatory drawing (when the eccentricity and uneven thickness of a pipe are small) for demonstrating the effectiveness of the arithmetic processing used in the inner surface inspection method which concerns on this embodiment. It is explanatory drawing (when the eccentricity and uneven thickness of a pipe are large) for demonstrating the effectiveness of the arithmetic processing used in the inner surface inspection method which concerns on this embodiment. An example of the test result (when the eccentricity and the uneven thickness of the pipe are small) comparing the inner surface inspection method according to the present embodiment and the inner surface inspection method according to the reference example is shown. An example of the test result (when the eccentricity and the uneven thickness of the pipe are large) comparing the inner surface inspection method according to the present embodiment and the inner surface inspection method according to the reference example is shown.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings, taking as an example a case where the detection target is minute irregularities on the inner surface of the pipe caused by peroxywashing the pipe. First, a schematic configuration of an internal surface inspection device for carrying out the internal surface inspection method for a pipe according to an embodiment of the present invention will be described.

<Rough configuration of the internal inspection device of this embodiment>
FIG. 1 is an explanatory diagram illustrating a schematic configuration of an internal surface inspection device for carrying out an internal surface inspection method for a pipe according to an embodiment of the present invention. FIG. 1 (a) shows a front view seen from the axial direction of the pipe, and FIG. 1 (b) shows a plan view.
As shown in FIG. 1, the internal surface inspection device of the present embodiment includes an ultrasonic probe 1 and a signal processing means 2 connected to the ultrasonic probe 1. Further, as will be described later, a mechanism unit (not shown) for moving the ultrasonic probe 1 relatively in the circumferential direction of the tube P and also in the axial direction is also provided.

The ultrasonic probe 1 of the present embodiment includes, for example, a single transducer in order to improve the detection accuracy of the inner surface minute unevenness (the minute unevenness on the inner surface of the tube P caused by the per-pickling of the tube P). However, a line-focus type ultrasonic probe having a flaw detection frequency of 10 MHz and a focal length of 2 inches is preferably used.

The control / signal processing means 2 includes a pulser that supplies a pulse signal for transmitting ultrasonic waves from the ultrasonic probe 1 and a receiver that amplifies the echo signal output from the ultrasonic probe 1 that has received the echo. The intensity distribution and calculation of the bottom echo signal in the circumferential direction of the tube P based on the part that controls the transmission and reception of ultrasonic waves, such as, and the bottom echo signal output from the ultrasonic probe 1 as described later. It has a part that performs various signal processing functions such as creating an intensity distribution and performing statistical processing on the calculated intensity distribution of the bottom echo signal. In the present embodiment, since the ultrasonic probe 1 is relatively moved in the circumferential direction of the tube P by the mechanical unit and is also relatively moved in the axial direction, it is created by the control / signal processing means 2. The intensity distribution of the bottom surface echo signal is actually created based on the bottom surface echo signal obtained from the bottom surface portion of the spiral tube P with respect to the axial direction of the tube P. The "intensity distribution of the bottom echo signal in the circumferential direction of the tube P" in the present invention also includes the intensity distribution of the bottom echo signal in the spiral direction with respect to the axial direction of the tube P as described above.

As the mechanism unit, a mechanism that conveys the pipe P in the axial direction while rotating it in the circumferential direction can be exemplified. However, the present invention is not limited to this, and it is also possible to adopt a mechanism for moving the ultrasonic probe 1 in both the circumferential direction and the axial direction of the tube P. Further, a mechanism unit having a mechanism for rotating the ultrasonic probe 1 in the circumferential direction of the tube P and a mechanism for transporting the tube P in the axial direction, a mechanism for rotating the tube P in the circumferential direction, and an ultrasonic wave. It may be a mechanical unit including a mechanism for moving the probe 1 in the axial direction of the tube P.

<Internal inspection method according to this embodiment>
Hereinafter, the internal surface inspection method according to the present embodiment using the internal surface inspection device having the above-mentioned schematic configuration will be described.
In the inner surface inspection method according to the present embodiment, first, as shown in FIG. 1, the ultrasonic probe 1 is arranged so as to face the outer surface of the tube P (corresponding to the first step of the present invention).

Next, the mechanism unit relatively moves the ultrasonic probe 1 along the circumferential direction of the tube P (in the present embodiment, at the same time, the ultrasonic probe 1 is also relative to the axial direction of the tube P. (Move), the ultrasonic probe 1 transmits ultrasonic waves substantially perpendicular to the inner surface of the tube P, and the bottom surface echo B reflected from the inner surface of the tube P is received by the ultrasonic probe 1 and is super. The ultrasonic probe 1 outputs a bottom echo signal, and the control / signal processing means 2 creates an intensity distribution of the bottom echo signal in the circumferential direction of the tube P (corresponding to the second step of the present invention).
Specifically, the control / signal processing means 2 receives a bottom echo B (in this embodiment, a surface echo S) among the echoes received by the ultrasonic probe 1 at predetermined pitches in the circumferential direction of the tube P. By detecting the intensity of the bottom echo signal corresponding to the first received bottom echo signal after receiving the above, the intensity distribution of the bottom echo signal in the circumferential direction of the tube P is created. In the present embodiment, the intensity of the bottom echo signal at about 400 points per circumference of the pipe P is detected (for example, when the inner diameter of the pipe P is 27.4 mm, it is detected at a pitch of about 0.22 mm). The intensity distribution is created.

Next, the control / signal processing means 2 performs a predetermined arithmetic process on the created bottom echo signal intensity distribution to create an arithmetic intensity distribution of the bottom echo signal (corresponding to the third step of the present invention).
Specifically, the control / signal processing means 2 sets the maximum value of the intensity within a predetermined number of points from the point of interest to the minimum value for each intensity of the plurality of points constituting the intensity distribution of the bottom echo signal. The calculation intensity distribution of the bottom echo signal is created by performing an operation in which the points of interest are calculated by dividing by and using the result of the division as the calculation intensity of the point of interest. In the present embodiment, when the bottom echo signal is detected within a range of 10 points from the point of interest (when the bottom echo signal is detected at intervals of about 0.22 mm) for each intensity of about 400 points constituting the intensity distribution of the bottom echo signal. The calculated intensity distribution of the bottom echo signal is created by dividing the maximum value of the intensity in the range of 2 mm) by the minimum value.

The points from the points of interest in the above arithmetic processing may be appropriately set so that the minute inner surface irregularities to be detected can be detected. If the score from the point of interest is too small compared to the score corresponding to the size of the inner surface minute unevenness to be detected, it becomes difficult to detect the inner surface minute unevenness. Therefore, the lower limit of the score from the point of interest may be set to a value larger than the score corresponding to the size of the inner surface minute unevenness to be detected. In order to detect the inner surface minute unevenness more reliably, the lower limit of the score from the point of interest may be set to 1.5 times or more the score corresponding to the size of the inner surface minute unevenness to be detected. On the other hand, if the score from the point of interest is too large, it becomes difficult to reduce the influence of the eccentricity and the uneven thickness of the pipe P. Therefore, the upper limit of the score from the point of interest may be set to a value smaller than the score corresponding to 1/4 circumference of the pipe P, for example. Preferably, the lower limit of the score from the point of interest may be set to less than three times the score corresponding to the size of the inner surface minute unevenness to be detected. The size of the minute unevenness on the inner surface means the length in the direction in which the ultrasonic probe 1 is relatively moved in the circumferential direction of the tube P.
According to the above setting method, for example, in the case where the inner diameter of the tube P is 27.4 mm and the intensity of the bottom surface echo signal of about 400 points per circumference is to be detected for the inner surface minute unevenness having a size of 1.0 mm. The lower limit of the score from the point of interest may be set to 5 points, and preferably the lower limit of the score from the point of interest may be set to 7 points. Further, the upper limit of the points from the point of interest may be set to 100 points, preferably 14 points, independently of the lower limit of the points from the points of interest.

Hereinafter, the effectiveness of the above arithmetic processing will be described.
2 and 3 are explanatory views for explaining the effectiveness of the arithmetic processing used in the internal inspection method according to the present embodiment. Specifically, FIG. 2 is an explanatory diagram when the eccentricity and the uneven thickness of the pipe are small. FIG. 3 is an explanatory diagram when the eccentricity and the uneven thickness of the pipe are large. FIG. 3A of each figure is a diagram schematically showing the states of the tube P and the bottom echo B. F1 shown in (a) of each figure indicates an inner surface minute unevenness existing at a position where ultrasonic waves transmitted perpendicularly to the outer surface of the tube P are incident from the circumferential position P1 of the tube P. Further, F2 shown in (a) of each figure indicates an inner surface minute unevenness existing at a position where ultrasonic waves transmitted perpendicularly to the outer surface of the tube P are incident from the circumferential position P2 of the tube P. The dimensions of the inner surface microconcavo-convex F1 and the inner surface microconcavo-convex F2 are the same. FIG. 3B of each figure is a diagram schematically showing the intensity distribution of the bottom echo signal. FIG. 3C of each figure is a diagram schematically explaining the differential intensity distribution of the bottom echo signal. FIG. (D) of each figure is a diagram schematically explaining the calculated intensity distribution of the bottom echo signal.

As shown in FIG. 2A, the ultrasonic waves transmitted from the circumferential positions P1 and P2 of the pipe P are scattered by the inner surface microconcavities and convexities F1 and F2, respectively. The intensity of the bottom surface echo B reflected from the inner surface of the tube P is the ultrasonic wave transmitted perpendicularly to the outer surface of the tube P from the inner surface of the tube P having no minute irregularities on the inner surface (for example, the circumferential positions P3 and P4 of the tube P). It is smaller than the intensity of the bottom surface echo B reflected from the incident inner surface). Therefore, as shown in FIG. 2B, the intensity of the bottom surface echo signal is attenuated at the circumferential positions P1 and P2 of the tubes P in which the inner surface minute irregularities F1 and F2 are present, respectively. On the other hand, as shown in FIG. 2B, the intensity of the bottom surface echo signal for the inner surface of the tube P in which the inner surface has no minute irregularities (the ultrasonic waves transmitted from positions other than the circumferential positions P1 and P2 of the tube P). The strength of the bottom echo signal) also gradually fluctuates due to the influence of the eccentricity and the uneven thickness of the tube P. For example, the intensities of the bottom echo signals at the circumferential positions P3 and P4 of the tube P are different from each other. Therefore, if it is simply attempted to detect the inner surface minute unevenness based on the intensity of the bottom surface echo signal (for example, it is determined that the inner surface minute unevenness exists when the intensity of the bottom surface echo signal is less than a predetermined threshold value), for example , There is a possibility that a portion where the strength of the bottom echo signal is attenuated due to the eccentricity or uneven thickness of the tube P is erroneously detected as an inner surface minute unevenness.

Therefore, in order to reduce the influence of the eccentricity and uneven thickness of the tube P and make it possible to detect minute irregularities on the inner surface, the present inventors first apply differential processing in the circumferential direction of the tube P to the intensity distribution of the bottom surface echo signal. I thought about giving it. Specifically, for each intensity of a plurality of points constituting the intensity distribution of the bottom echo signal as shown in FIG. 2 (b), the maximum value to the minimum intensity within a predetermined point range from the point of interest. The differential intensity distribution of the bottom echo signal as shown in FIG. 2C is created by performing an operation of subtracting the value and using the subtracted result as the differential intensity of the point of interest by sequentially shifting the points of interest. I thought about doing it. In the differential intensity distribution of the bottom echo signal, since the gradual fluctuation component of the intensity due to the eccentricity and uneven thickness of the tube P such as the intensity distribution of the bottom echo signal is reduced, the eccentricity and uneven thickness of the tube P are reduced. It is possible to detect minute irregularities on the inner surface while reducing the influence of. For example, as shown in FIG. 2C, by comparing the differential intensity of the bottom echo signal with a predetermined threshold value Th, it is possible to detect both the inner surface minute irregularities F1 and F2 having the same dimensions.

However, as shown in FIG. 3A, when the eccentricity and wall thickness of the tube P are large, for example, a position (tube) in a direction orthogonal to the eccentric direction (the left-right direction of the paper surface in FIG. 3A). The ultrasonic waves transmitted from the circumferential positions P2 and P4) of P have a large deviation from 90 ° in the angle of incidence on the inner surface of the tube P. Therefore, even when the reflection is performed on the inner surface of the tube P in which the inner surface has no minute irregularities, the intensity of the bottom echo B reflected in the same direction as the ultrasonic wave transmission direction is greatly attenuated. Further, for the ultrasonic waves transmitted from the positions in the same direction as the eccentric direction (circumferential positions P1 and P3 of the tube P), the positions in the same direction as the eccentric direction (right direction on the paper surface in FIG. 3A). The propagation distance until the bottom surface echo B is received changes depending on whether the position is (the circumferential position P1 of the tube P) or the opposite position (the circumferential position P3 of the tube P). Therefore, the intensity of the bottom surface echo B fluctuates even when the reflection is performed on the inner surface of the tube P in which the inner surface has no minute irregularities.

Therefore, as shown in FIG. 3 (b), the fluctuation component of the intensity of the bottom echo signal due to the eccentricity and uneven thickness of the tube P becomes larger than the fluctuation component in the case shown in FIG. 2 (b). Therefore, the intensity of the bottom surface echo B is attenuated due to the eccentricity or uneven thickness of the tube P. When the inner surface minute unevenness F2 exists at the circumferential position P2 of the tube P, the amplitude of the intensity of the bottom surface echo signal (peripheral). The intensity difference from the bottom echo signal) is the bottom echo signal when the inner surface minute unevenness F1 exists at the circumferential position P1 of the tube P in which the intensity of the bottom echo B is not attenuated even if the eccentricity or the uneven thickness of the tube P is large. It is much smaller than the amplitude of the intensity of. That is, even if the inner surface microconcavities and convexities F1 and F2 have the same dimensions, the amplitude of the intensity of the bottom echo signal greatly differs depending on the existing position. As shown in FIG. 3C, the differential intensity of the bottom echo signal also differs depending on the amplitude difference of the intensity of the bottom echo signal. Therefore, for example, when the differential intensity of the bottom surface echo signal is compared with a predetermined threshold value Th, one of the inner surface minute irregularities F1 can be detected even if the inner surface minute irregularities F1 and F2 have the same dimensions. A situation may occur in which the other inner surface microconcavo-convex F2 cannot be detected.

Therefore, as a result of further diligent studies on a process capable of further reducing the influence of the eccentricity and the uneven thickness of the tube P as compared with the above differential process, the present inventors have made the above-mentioned arithmetic process on the intensity distribution of the bottom echo signal. I came up with the idea that I should give it. The above-mentioned arithmetic processing is a process of dividing the maximum value by the minimum value, instead of subtracting the minimum value from the maximum value of the intensity of the bottom echo signal within a predetermined number of points from the point of interest as in the differential processing. Therefore, even if the eccentricity and the uneven thickness are large and the inner surface minute irregularities F1 and F2 having the same dimensions have an amplitude difference in the intensity of the bottom surface echo signal, they are created as shown in FIG. 3 (d). It can be expected that the calculated intensities of the bottom echo signals will be the same if the inner surface minute irregularities F1 and F2 have the same dimensions. Therefore, for example, as shown in FIG. 3D, by comparing the calculated intensity of the bottom surface echo signal with a predetermined threshold value Th, it is possible to detect both the inner surface minute irregularities F1 and F2 having the same dimensions. .. As shown in FIG. 2D, even when the eccentricity and the uneven thickness of the pipe P are small, it is naturally possible to detect both the inner surface minute irregularities F1 and F2 having the same dimensions.

In the inner surface inspection method according to the present embodiment, statistical processing is performed on the calculated intensity distribution of the bottom echo signal created as described above, and minute irregularities on the inner surface are detected based on the magnitude of the statistical value obtained by the statistical processing. (Corresponding to the fourth step of the present invention). As the statistical processing, a process of calculating the average value and the standard deviation can be considered, but in the present embodiment, a process of calculating the average value × the standard deviation is performed as a preferable embodiment. Further, in the present embodiment, the statistical value (mean value × standard deviation) is calculated for each calculated intensity distribution (calculated intensity of about 400 points) for one round of the pipe P (one rotation of the pipe P).

4 and 5 show the inner surface inspection method according to the present embodiment described above and the inner surface inspection method according to the reference example (differential intensity distribution created by subjecting the intensity distribution of the bottom echo signal to the differential intensity distribution). An example of a test result is shown in which the same statistical processing as that of the internal surface inspection method according to the morphology is performed, and a method of detecting minute irregularities on the inner surface based on the magnitude of the statistical value obtained by the statistical processing) is compared. FIG. 4 shows an example of the test results obtained when the eccentricity and the uneven thickness of the tube P are small (substantially absent). FIG. 5 shows an example of the test results obtained when the eccentricity and the uneven thickness of the tube P are large. (A) of each figure shows an example of the image taken by the ITV camera on the inner surface of the tube P used for the test. (B) of each figure shows the distribution of statistical values (mean value × standard deviation) obtained by the inner surface inspection method according to the present embodiment in the axial direction of the pipe P. (C) of each figure shows the distribution of statistical values (mean value × standard deviation) obtained by the internal inspection method according to the reference example in the axial direction of the pipe P. (B) and (c) of each figure show the distribution of the statistical values obtained for both the part where the inner surface minute unevenness is generated and the healthy part where the inner surface minute unevenness is not generated. .. The test results shown in FIGS. 4 and 5 were obtained under the following test conditions.
(1) flaw detection frequency of ultrasonic probe 1: 5 MHz
(2) Rotation speed of pipe P: 64 m / min
(3) Transfer speed of pipe P: 4.4 m / min (equivalent to transporting 10 mm in the axial direction of pipe P per rotation of pipe P)

When the eccentricity and the uneven thickness of the pipe P shown in FIG. 4 are small, even with the inner surface inspection method according to the present embodiment shown in FIG. 4 (b), the inner surface according to the reference example shown in FIG. 4 (c). Even with the inspection method, the statistical values obtained at the site where the inner surface micro-concavities and convexities occur are larger than the statistical values obtained at the healthy site. Therefore, for example, the inner surface minute unevenness can be detected by setting a predetermined threshold value between the statistical values of both parts and determining that the inner surface minute unevenness exists if the threshold value or more is set.

On the other hand, when the eccentricity and the uneven thickness of the tube P shown in FIG. 5 are large, the statistics obtained at the site where the inner surface minute unevenness is generated by the inner surface inspection method according to the reference example shown in FIG. There is no significant difference between the values and the statistics obtained at healthy sites. Therefore, it is not possible to set a threshold value between the statistical values of both parts, and it is not possible to detect minute irregularities on the inner surface. On the other hand, in the inner surface inspection method according to the present embodiment shown in FIG. 5 (b), the statistical value obtained at the site where the inner surface minute unevenness occurs is larger than the statistical value obtained at the healthy site. Therefore, it is possible to detect minute irregularities on the inner surface as in the case where the eccentricity and the uneven thickness of the tube P are small.

1 ... Ultrasonic probe 2 ... Control / signal processing means P ... Tube

Claims (2)

The first step of arranging the ultrasonic probe facing the outer surface of the tube,
The ultrasonic probe was moved relatively in the circumferential direction of the tube, and ultrasonic waves were transmitted from the ultrasonic probe substantially perpendicular to the inner surface of the tube and reflected from the inner surface of the tube. The second step of receiving the bottom echo with the ultrasonic probe and acquiring the intensity distribution of the bottom echo signal in the circumferential direction of the tube, and
The third step of acquiring the calculated intensity distribution of the bottom echo signal by performing a predetermined arithmetic process on the intensity distribution of the bottom echo signal acquired in the second step,
In the fourth step, the calculated intensity distribution of the bottom echo signal acquired in the third step is subjected to statistical processing, and the unevenness of the inner surface of the pipe is detected based on the magnitude of the statistical value obtained by the statistical processing.
Including
In the arithmetic processing, the maximum value of the intensity within a predetermined point range from the point of interest is divided by the minimum value for each intensity of the plurality of points constituting the intensity distribution of the bottom echo signal, and the division is performed. This is a process in which the result is the calculation strength of the point of interest.
A method for inspecting the inner surface of a pipe. The unevenness of the inner surface of the pipe is caused by the peracid washing of the pipe.
The method for inspecting the inner surface of a pipe according to claim 1.