JPH07119593B2 - Pipe diagnosis method by comparing X-ray radiographic density - Google Patents

Description

TECHNICAL FIELD The present invention relates to a deterioration diagnosis of a pipe by a nondestructive inspection, and more particularly to a diagnosis method by comparing an X-ray radiographic density of the pipe in a building facility or the like.

[Conventional technology]

In general, pipes for water supply, hot water supply, and air conditioning in buildings, etc. will inevitably suffer from deterioration of strength due to corrosion, water leakage, pipe closure, etc. over a long period of time, and if left unattended, a fatal situation such as the termination of building functions may occur. I could invite you. For this reason, it is extremely important to check the deterioration of building piping in advance and prepare for an unexpected situation.

As a method for diagnosing such a pipe, nondestructive inspection by X-ray radiography has been conventionally performed, particularly for flaw detection of a welded portion.

7 and 8 show the conventional X for defect inspection of welded parts.
It is a figure which shows the piping diagnostic method by a radiographic imaging, FIG. 7 shows the case where an X-ray source is arrange | positioned in the center of a tube, FIG. 8 shows the case where an X-ray source is arrange | positioned outside a tube, 1 is an X-ray. Source, 2 is the test tube,
3 is an X-ray film.

In FIGS. 7 and 8, the film 3 is exposed to X-rays that have passed through the test tube 2, and the position, size and number of defects in the test tube 2 are examined by the image density on the film 3.

In addition, there is a local corrosion diagnosis method in the field of chemical plants as a method of using a pipe diagnosis method by X-ray radiography, which is a wall contour method for actually measuring an image of a pipe wall reflected on a film,
The remaining wall thickness of the tube is estimated by the contrast method which compares the blackness of the reference point in the center of the film with the blackness of other points.

Further, there is also a method in which a pipe having a known wall thickness and a pipe serving as a test body pipe are respectively subjected to X-ray photography and defect inspection is performed by comparing photograph densities.

Next, a method of inspecting a steel plate or the like using a conventional gradation meter will be described. FIG. 9 shows a conventional gradation meter which serves as a reference in which the thickness of the steel plate is changed stepwise, and FIG. It is a figure which shows the inspection method using the gradation meter of FIG.

In the figure, the gradation meter 4 is composed of square portions 4 ₁ , 4 ₂ and 4 _{3 in} which the thickness is changed in a stepwise manner. Film on top of the film, and take X-rays simultaneously while overlapping
Then, the degree of swelling of the test portion 5 from the base material 2 is estimated by exposing the test portion 5 to light and comparing the photographic density between the test portion 5 and the gradation meter 4.

FIG. 11 shows the case where the gradation meter of FIG. 9 is used for the inspection of the tube, and the gradation meter 4 is arranged at the inspection part in the tube, and the X-ray image is taken by the radiation source 1 and the case of FIG. Similarly, the inspection is performed by comparing the photographic density.

[Problems to be solved by the invention]

However, the conventional welded part inspection by X-ray radiography does not go beyond the scope of visual judgment of the photograph, and the degree of the defect cannot be quantitatively grasped, and the purpose is flaw detection,
It is premised on knowing the location, size, and number of defects, and cannot be used directly for deterioration diagnosis of piping. In particular, in diagnosing the deterioration of construction equipment, it is necessary to set the accuracy of reading the amount of corrosion wall thinning (remaining wall thickness) to about 0.1 mm, but this method cannot satisfy this condition.

Moreover, while the wall contour method in the local corrosion diagnosis method in the conventional chemical plant field is easy to photograph and measure the wall thickness, it is uneconomical because the number of photographs increases and the contour becomes unclear when the pipe diameter increases. It becomes difficult to measure, and the accuracy is at most ± 0.5 mm, and it is not possible to meet the 0.1 mm accuracy required in the field of building equipment. On the other hand, the contrast method is 2 to
It is economical because the thickness of the entire circumference can be estimated by taking three images, and there are advantages such as no inspection omissions, but the accuracy is rather poor, and a special technique is required to measure the thickness, and X-rays can be found in the erosion dents. When the absorbing substance accumulates, an error is likely to occur, and when it is applied to the building equipment field, the pipe in the building equipment field is in the form of general corrosion rather than local corrosion. It has the drawback of becoming too large.

Further, in the conventional X-ray radiography, the condition of the pipes facing each other is photographed, and the pipe wall thickness is not photographed as it is. Furthermore, in the comparison of photographic densities, the pipe having a known wall thickness and the pipe being the test body are Since the images were taken on different films, the comparison conditions such as the energy characteristics of the X-ray generator, the voltage, the current, the film, and the development process are different when the images are compared, and there is a drawback that an accurate comparison cannot be performed.

Further, in the conventional inspection method using a gradation meter, the reference thickness differs depending on the X-ray incident angle on the gradation meter flat plate, and therefore the photographic density changes and an accurate comparison cannot be made. Further, in this inspection method, the difference in thickness between the test portion and the base material is required, but the material thickness itself of the test portion is not required. Furthermore, if you want to use a gradation meter for a tubular subject, it is difficult to place it inside a small-diameter tube, and even if it is placed outside, the protruding part will come out and you will not be able to compare, and water etc. will be inside the tube. In the case where the above liquid is contained, it is not possible to measure the difference in permeation concentration of the pipe and water.

The present invention is intended to solve the above problems, and
A pipe diagnostic method by X-ray radiographic density comparison that can measure the wall thickness of pipes with high accuracy by comparing radiographic densities by X-ray radiography and can also be applied to the deterioration diagnosis of pipes in the field of building equipment etc. The purpose is to provide.

[Means for solving problems]

Therefore, in the piping diagnosis method by the X-ray radiographic density comparison of the present invention, a monitor tube having the same material and the same diameter as the known thickness is circumscribed and juxtaposed to the test tube, and the circumscribed portion between the monitor tube and the test tube is placed. The X-ray generator, which has an irradiation focal point in the tangential direction, simultaneously shoots the X-rays on the same film, and the monitor tube and the test which can be identified from the photograph density data of the tube cross section read from the film. Match the outer wall position of the body tube to find the difference in photographic density at each position in the tube cross-sectional direction, and identify and compare the wall thickness change points of the monitor tube and the test body tube from the position where the obtained density difference greatly changes. Then, the thickness of the test tube is obtained.

[Action]

The piping diagnosis method by X-ray radiographic density comparison of the present invention is
By circumscribing a monitor tube of the same material and the same diameter of known thickness to the test tube and simultaneously performing X-ray transmission imaging on the same film, the dose of X-ray that affects the density of the visible image of the film,
Various conditions such as radiation quality, scattered radiation, and development processing conditions are made the same for the test body and the monitor tube, and the tube wall thickness of the monitor tube is changed stepwise to form a tubular tone meter. However, the wall thickness of the test tube can be grasped in stages, and the wall thickness of the test tube can be accurately determined by comparing the photographic density with that of the test tube shown on the same film.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram showing a pipe inspection method by X-ray photography according to the present invention, FIG. 2 is a diagram showing an image of a photographed pipe, and FIG. 3 is a diagram showing a configuration of a film image density reading device. X-ray generator focus, 11 is a monitor tube of known wall thickness, 12 is a test tube, 13 is a film, 14 is an image of the monitor tube, 15 is an image of the test tube, 16 is an image reading device, 17 is A / D converter, 1
8 is a computer.

As shown in FIG. 1, the test tube 12 and the monitor tube 11 are arranged side by side and circumscribed, and the X-ray generator focus 10 is set to the tangent position of the circumscribed portion. If a liquid such as water is contained in the test tube 12, the same liquid is also contained in the monitor tube. By filming X-rays in this way, a film image as shown in FIG. 2 is obtained.

Next, the created photographic film is read with an image density reading device.
Read the density value of the film image over 16 times, and read this in A /
After being converted into a digital signal by the D converter 17, computer processing is performed.

The wall thickness can be read numerically by comparing the film image density with the test body tube by changing the wall thickness of the monitor tube stepwise as described later.

FIG. 4 is a diagram showing an example of analysis of the read image. FIG. 4 (A) is a cross-sectional view of a monitor tube and a test body tube placed side by side, FIG. 4 (B) is a view showing a photographic film, and FIG. FIG. 6C is a diagram showing a change in photographic density on the XX cross section of FIG. In the figure, 11 is a monitor tube, 12 is a test tube, and 19 is a rust bump.

The focus position of the X-ray generator is on the tangent line of the monitor tube 11 and the test body tube 12 as shown in FIG. 1, and the photographic density at the arbitrary position XX cross section of FIG. It is processed and graphed as shown in FIG. The positions X ₁ and X _{A in the} figure correspond to the inner wall and the outer wall of the monitor tube, respectively, and the positions X ₂ and X _B correspond to the inner wall and the outer wall of the test tube, respectively.

Next, the graph of FIG. 5 (A) is obtained by combining the graphs of FIG. 4 (C) with X _A and X _B points so as to be line-symmetrical about the axis O. D (X ₁ ) in the figure is the photographic density of the monitor tube, D
(X ₂ ) indicates the photographic density of the test tube.

Further, FIG. 5 (B) is a graph showing the difference between the photographic densities D (X ₁ ) and D (X ₂ ). By reading the X coordinate where the difference in concentration between the two greatly changes, the wall thickness change point X ₁ of the monitor tube and the test tube change point X ₂ are obtained. Since the wall thickness of the monitor tube is known, if this is t ₁ and the wall thickness of the test tube is t ₂ , As a result, the wall thickness of the test tube can be obtained.

Next, a monitor tube used in the present invention in which the wall thickness is changed stepwise, that is, a tubular gradation meter will be described.

FIG. 6 is a view showing a tubular tone meter according to the present invention. FIG. 6A is a perspective view of the tubular tone meter in which the outer diameter is made constant and the inner diameter is changed stepwise to change the wall thickness. Figure (B) is a perspective view of a tubular gradation meter cut in the vertical direction, Figure (C) is a vertical cross-sectional view, and Figure (D) is a wall thickness by changing the outer diameter in a stepwise manner while keeping the inner diameter constant. Fig. (E) is a perspective view obtained by cutting the tubular gradation meter in the longitudinal direction, Fig. (F) is a longitudinal sectional view, and 20 and 26 are tubular gradation meters. 21, 22, 23
Is an inner wall of the tube, 24, 25, 30, 31 are stoppers, and 27, 28, 29 are outer walls of the tube.

In the figure, the tubular gradation meter 20 has a constant outer diameter and a stepwise change in inner diameter, so that the wall thicknesses of the inner wall portions 21, 22, 23 are changed to t ₀ , t ₁ , t ₂ , It is possible to compare the concentration with various test tube of different. If the test tube contains a liquid, the same liquid is sealed inside, and plugs 24 and 25 are provided at both ends of the tube so that the conditions can be the same. By using a meter, it is possible to compare the concentration with a test tube containing water.

The tubular gradation meter 26 has a constant inner diameter, and the outer diameter is changed stepwise so that the wall thicknesses of the outer wall portions 27, 28, 29 are t ₀ , t ₁ , t _2.
, And the usage is the same as the tubular tone meter 20.

In addition, the inner diameter R is made for each aperture from 10A to 100A, and l is 15
~ 25mm, L is about 150mm. By making the cross section of the tonometer circular in this way, X-rays passing through the center of the circle can maintain the same photographic density regardless of the irradiation angle, and a tubular tone meter of the same diameter as the small aperture tube of the subject can be arranged. By X-ray radiography, the thickness of the subject can be directly compared with the gradation meter.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, a monitor tube and a test tube are circumscribed to perform simultaneous X-ray photography,
By comparing the photographic densities on the same film, it is possible to compare the wall thicknesses of the two and to accurately determine the wall thickness of the test tube, so that it is possible to perform a deterioration diagnosis of the pipes. In addition, the film density of the photographed film is read by an image density reading device and processed by a computer to obtain ± 0.1 m
It is possible to measure with an accuracy of about m, and it can be applied to the deterioration diagnosis of piping in the field of building equipment. In addition, by changing the tube wall thickness of the monitor tube stepwise and setting it as a tubular gradation meter, the tube wall thickness can be calculated numerically even on the film, and liquid such as water enters the test tube. In such a case, it is possible to accurately determine the tube wall thickness by inserting the same liquid such as water in the test tube into the tube by plugging the tubular tone meter under the same conditions.

[Brief description of drawings]

FIG. 1 is a diagram showing a pipe inspection method by X-ray photography according to the present invention, FIG. 2 is a diagram showing an image of a photographed pipe, FIG. 3 is a diagram showing a configuration of a film image density reading device, and FIG. Is a diagram showing an example of analysis of the read image. FIG. 7A is a cross-sectional view of a monitor tube and a test tube that are arranged side by side, and FIG.
Is a diagram showing a photographic film, and FIG.
FIG. 5 is a diagram showing a change in photographic density of the X section, and FIG. 5 is a diagram for comparing photographic densities of the monitor tube and the test body tube.
Is a diagram showing a photographic density, FIG. 6B is a diagram showing a photographic density difference, and FIG. 6 is a diagram showing a tubular gradation meter according to the present invention. FIG. A perspective view of a tubular gradation meter in which the wall thickness is changed by changing it in a stepwise manner, the same figure (B) is a perspective view obtained by cutting the tubular gradation meter of FIG. (A) in the vertical direction, and the same figure (C) is a figure. FIG. 3D is a vertical cross-sectional view of the tubular gradation meter of FIG.
Is a perspective view of a tubular gradation meter in which the wall thickness is changed by changing the outer diameter in a stepwise manner while keeping the inner diameter constant, and FIG.
Fig. 7F is a vertical cross-sectional view of the tubular gradation meter of Fig. 7D, and Fig. 7 is a conventional X-ray with the radiation source arranged in the center of the tube. FIG. 8 is a diagram showing a pipe inspection method by transmission radiography, FIG. 8 is a diagram showing a conventional pipe inspection method by X-ray transmission radiography in which a radiation source is arranged outside the pipe, and FIG. 9 is a diagram showing a conventional gradation meter. FIG. 10 is a diagram showing a conventional method for inspecting a flat plate by X-ray transmission imaging using a gradation meter, and FIG. 11 is a diagram showing a method for inspecting a pipe by conventional X-ray transmission imaging using a gradation meter. . 10 …… X-ray generator focus, 11 …… Monitor tube, 12 …… Test tube, 13 …… Film, 14 …… Monitor tube image, 15…
… Image of test tube, 16 …… Image reading device, 17 …… A /
D converter, 18 …… Computer, 19 …… Rust bump, 20,26 …… Tubular gray scale, 24,25,30,31 …… Spigot,

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Haruo Kito, 2-16-1, Kyobashi, Chuo-ku, Tokyo Shimizu Construction Co., Ltd. (72) Hiroshi Ishihara 2--16-1, Kyobashi, Chuo-ku, Tokyo Shimizu Incorporated (72) Inventor Tetsuo Saito 2-16-1 Kyobashi, Chuo-ku, Tokyo Shimizu Constructed In-house (72) Inventor Koji Nagata 2-16-1 Kyobashi, Chuo-ku, Tokyo Constructed Shimizu (56) References JP 55-154445 (JP, A) JP 58-169016 (JP, A) JP 56-46405 (JP, A) Actual development Sho 58-148662 (JP, U)

Claims (1)

[Claims] 1. An X-ray generator having an irradiation focus on the tangential direction of the circumscribed portion between the monitor tube and the test tube, wherein a monitor tube of the same material of the same thickness and the same diameter is circumscribed and juxtaposed to the test tube. X-ray irradiation at the same time with the instrument and the transmission image is taken on the same film,
Match the outer wall positions of the monitor tube and the test tube identified from the photograph density data of the tube cross section read from the photographic film to find the difference in photographic density at each position in the tube cross section direction, and the obtained density difference changes greatly. A method for diagnosing piping by comparing X-ray radiographic densities, characterized in that the wall thickness change points of the monitor tube and the test tube are identified and compared from the position to determine the wall thickness of the test tube.