JP5441104B2 - Nondestructive inspection method and apparatus - Google Patents

Description

  The present invention relates to a non-destructive inspection method and an apparatus therefor, and in particular, radiation (X-rays) is applied to piping or the like that is an inspection object, thereby detecting the intensity of transmitted radiation that has passed through the inspection object. This is useful when detecting the degree or the like.

  Non-destructive inspection using X-rays is widely used for inspection of piping in various plants including power generation facilities. This is to detect the degree of thinning by irradiating a pipe or the like, which is an inspection object, with X-rays and detecting the intensity of the transmitted radiation (see, for example, Patent Document 1).

  FIG. 4 is an explanatory view conceptually showing a mode of nondestructive inspection according to the prior art. In the nondestructive inspection, as shown in FIGS. 4A to 4C, from a radiation (X-ray) source 01 arranged on one side (left side in the figure) of the inspection object 03 which is a cylindrical pipe. Radiation is irradiated, and the radiation transmitted through the inspection object 03 is detected by a radiation detector 02 disposed on the opposite side (right side in the figure) of the inspection object 03. As a result, the horizontal axis represents the detector rotation position (relative position of the radiation detector 02 with respect to the inspection object 03), and the vertical axis represents the transmission signal intensity (the intensity of transmitted radiation detected by the radiation detector 02). As shown in FIG. 4D, when the thinned portion 04 exists in the inspection object 03, the transmitted signal intensity of the portion corresponding to the thinned portion 04 is higher than the flat normal portion 05. Has characteristics. The size of the convex shape in this case depends on the thinning amount, and therefore the thinning amount can be detected based on the degree of the convexity, in other words, the intensity of the transmitted signal.

JP 2006-177841 A

  By the way, in the prior art shown in FIG. 4, when there is a thinning portion of the thinning amount la as shown in FIG. 4A, a transmission signal intensity depending on the thinning amount la is obtained, and similarly FIG. When there is a thinning portion of the thinning amount lb as shown in (b), a transmission signal intensity depending on the thinning amount lb is obtained, and the thinning amounts lc1 and lc2 as shown in FIG. When the thinned portion exists, the transmission signal intensity depending on the thinning amount (lc1 + lc2) is obtained. Therefore, in the case of la = lb = (lc1 + lc2), these cases cannot be distinguished by the transmission signal intensity detected by the radiation detector 02.

  On the other hand, since the replacement of the inspection object 03 is evaluated based on the remaining thickness, in the case of the thinning amounts la and lb shown in FIGS. In the case of the thinning amount lc1 or lc2 shown in 4 (c), it may not be necessary to replace it.

  As described above, in the non-destructive inspection according to the conventional technique, even if a small amount of thinning that still has room for replacement has occurred in the opposing portions on the straight line passing through the center of the inspection object 03, Since the sum is detected as the thinning amount, it may be determined that the thinning amount has already exceeded the replacement limit. That is, inconveniences such as determining the replacement time earlier than necessary occur.

  An object of this invention is to provide the nondestructive inspection method and its apparatus which can detect the thinning amount of a test target object appropriately in view of the above-mentioned point.

A first aspect of the present invention that achieves the above object is to irradiate a radiation from a radiation source toward a cylindrical inspection object and to face the radiation source on a straight line passing through the center of the inspection object. and detects the radiation in the radiation detectors respectively disposed position that detect the position and the phase opposite shifted clockwise or counterclockwise direction from the position, the output of the radiation detectors in the respective detecting positions Based on the transmitted signal intensity representing the intensity of transmitted radiation that is a signal, an equation including the amount of thinning of the inspection object at the detection position as an unknown number is created, and the relative relationship between the radiation source and each radiation detector The position of the radiation source and the detection position of the radiation detector are moved by the same angle along the outer peripheral surface of the inspection object without changing the positional relationship. The same object is detected at least at three locations along the outer peripheral surface of the object, and the same number of equations as the unknowns are created, and the equations are simultaneously solved to solve the inspection object at each detection position. There is a nondestructive inspection method characterized in that the amount of thinning of the metal is obtained.

According to a second aspect of the present invention, there is provided a radiation source that emits radiation toward a cylindrical inspection object, a detection position facing the radiation source on a straight line passing through a center of the inspection object, and the detection position The radiation source and the radiation detection without changing the relative positional relationship between each radiation detector disposed at a detection position shifted clockwise or counterclockwise from the radiation source, and the radiation source and each radiation detector. Moving means for integrally moving the detector along the outer peripheral surface of the object to be inspected, and the moving means for detecting radiation by each of the radiation detectors in at least three locations along the outer peripheral surface of the object to be inspected. Control means for controlling the radiation source and the radiation detectors to be moved by the same amount via each of the radiation sources, and the intensity of transmitted radiation that is an output signal of the radiation detectors at each detection position. Based on the transmitted signal intensity, create the same number of simultaneous equations as the unknowns including each thinning amount of the inspection object at each detection position as an unknown, and solve the simultaneous equations to check the inspection at each detection position A non-destructive inspection apparatus having arithmetic processing means for determining the thickness reduction of an object.

  According to the present invention, the amount of thinning for each thick portion can be detected even if radiation passes through a plurality of thick portions of the object to be inspected. Can be detected. As a result, it is possible to optimally determine the replacement timing of the pipes to be inspected based on the thinning amount.

The block diagram which shows the nondestructive inspection apparatus which concerns on the 1st Embodiment of this invention. The schematic diagram which shows the principal part of the nondestructive inspection apparatus which concerns on the 2nd Embodiment of this invention. The schematic diagram which shows the principal part of the nondestructive inspection apparatus which concerns on the 3rd Embodiment of this invention. Explanatory drawing which shows notionally the aspect of the nondestructive inspection which concerns on a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a nondestructive inspection apparatus according to a first embodiment of the present invention. As shown in the figure, in this embodiment, a cylindrical pipe is used as an inspection object 4, and positions P0, P1, P2, which are rotated around the inspection object 4 by 60 degrees counterclockwise. The radiation source 1 is sequentially moved to P3, P4, and P5, and the radiation transmitted through the inspection object 4 is detected at two positions around it by irradiating the inspection object 4 at each position P0 to P5. It is constituted as follows. That is, the radiation detectors 2 and 3 are arranged around the inspection object 4 at detection positions shifted in a clockwise direction and a counterclockwise direction from positions opposed to the radiation source 1 on a straight line passing through the center of the inspection object 4. Is arranged. Here, in this embodiment, the radiation source 1 and the radiation detectors 2 and 3 are arranged on the ring-shaped belt 8 at equal intervals of 120 degrees so that the relative positional relationship between them is kept constant. It is installed. As a result, the belt 8 moves around the inspection object 4 so that the radiation source 1 and the radiation detectors 2 and 3 are integrated with each other by 60 degrees while maintaining the mutual distance of 120 degrees. Move around.

  Thus, when the radiation source 1 is occupied at the position P0, the radiation detectors 2 and 3 are located at the positions P2 and P4, and the radiation source 1 is positioned as the radiation source 1 rotates. When occupied at P1, the radiation detectors 2 and 3 are at positions P3 and P5. When the radiation source 1 is occupied at position P2, the radiation detectors 2 and 3 are at positions P4 and P0. When the radiation source 1 is occupied at the position P3, the radiation detectors 2 and 3 are located at the positions P5 and P1, and when the radiation source 1 is located at the position P4, the radiation detectors 2 and 3 are used. Are positioned at positions P0 and P2, and the radiation source 1 is positioned at position P5, the radiation detectors 2 and 3 are positioned at positions P1 and P3, respectively.

  Signal intensities S02 and S04 based on transmitted radiation detected by the radiation detectors 2 and 3 when the radiation source 1 is occupied at the position P0 are given by the following equations (1) and (2).

S02 = Sn × η0 × exp (−u × (−l2 / cos θ)) (1)
S04 = Sn × η0 × exp (−u × (−14 / cos θ)) (2)

Here, S02: the signal intensity detected by the radiation detector 2 at the position P2 when the radiation source 1 is occupied at the position P0 (that is, the subscript “0” of S is the radiation source 1). Represents the position, and the superscript “2” of S represents “2” of the position P2 of the radiation detector 2 (hereinafter the same)).
S04: At the position P4 when the radiation source 1 is occupied at the position P0
Signal intensity detected by the radiation detector 3;
Sn: signal intensity when there is no thinning (normal inspection object),
η0: Transmission effect coefficient from position P0 to positions P2, P4 (including angle θ and thinning effect),
exp (): increase in signal intensity due to thinning near positions P2 and P4,
u: source weak coefficient (obtained in advance),
u ′: u / cos θ,
l2, l4: The amount of thinning of the inspection object 4 at the positions P2, P4.

  If the ratio of the above formulas (1) and (2) is taken, the following formula (3) is obtained.

    S02 / S04 = exp (u ′ × (l2−14)) (3)

  Since the left side and u ′ of the above equation (3) are constants, equation (3) is an equation in which the thinning amounts l2 and l4 of the inspection object 4 at positions P2 and P4 are unknowns.

  Signal intensity (S13, S15), (S24, S20), (S35, S31), (S40, S42) detected by the radiation detectors 2 and 3 by moving the radiation source 1 to other positions P1 to P5, By taking the ratio of (S51, S53), the amount of thinning of the inspection object 4 at the positions (P3, P5), (P4, P0), (P5, P1), (P0, P2), (P1, P3) Equations (4) to (8) are obtained, where is an unknown.

S13 / S15 = exp (u ′ × (l3−15)) (4)
S24 / S20 = exp (u ′ × (l4-l0)) (5)
S35 / S31 = exp (u ′ × (l5-l1)) (6)
S40 / S42 = exp (u ′ × (l0−l2)) (7)
S51 / S53 = exp (u ′ × (l1-l3)) (8)

    In the above formula, ln is the amount of thinning of the inspection object 4 at the position Pn (n = 0 to 5).

  The above equations (3) to (8) are six equations in which the thickness reduction amounts l0 to l5 of the inspection object 4 at the positions P0 to P5 are six unknowns. Therefore, the respective thinning amounts 10 to 15 can be obtained by solving an equation in which the equations (3) to (8) are combined.

  The arithmetic processing unit 5 processes the output signals of the radiation detectors 2 and 3 at the respective positions P0 to P5 and performs calculations based on the above formulas (3) to (8), so that the inspection objects at the respective positions P0 to P5 are obtained. 4 is obtained, and a signal representing them is sent to the determination unit 9. The determination unit 9 sends out an output signal OUT indicating this when the detected thinning amount 10 to 15 exceeds a predetermined value and becomes thin. This output signal OUT becomes a warning signal indicating the time of replacement of the inspection object 4 or the like.

  Here, the control unit 6 controls the overall function of the nondestructive inspection apparatus. Typically, control of predetermined arithmetic processing in the arithmetic processing unit 5 and drive control of the belt 8 by the driving unit 7 are performed. The drive unit 7 moves the radiation source 1 to the radiation detectors 2 and 3 to predetermined positions P0 to P5 under the drive control of the control unit 6. That is, the radiation source 1 and the radiation detectors 2 and 3 rotate integrally by the same amount without changing the relative positional relationship.

  In this embodiment, the radiation detection is performed at the positions P2 and P4 where the intensity of the radiation transmitted through the inspection object 4 at the angle θ is the radiation irradiated from the radiation source 1 toward the inspection object 4 at the position P1. Detected by devices 2 and 3, respectively. As a result, an intensity signal reflecting the thickness reduction amounts l2 and l4 of the inspection object 4 at the positions P2 and P4 is obtained. The same detection is performed by moving the radiation source 1 to the positions P1 to P5 while rotating the same amount by the same amount without changing the relative positions of the radiation source 1 and the radiation detectors 2 and 3, respectively. A signal having an intensity reflecting the thinning amount (l3, l5), (l4, l0), (l5, l1), (l0, l2), (l1, l3) of the inspection object 4 is obtained. By taking the ratios as shown in equations (3) to (8) based on these signals, six equations can be made with the thinning amounts 10 to 15 as unknowns. Therefore, the respective thinning amounts 10 to 15 can be obtained by solving them in a simultaneous manner. Therefore, it is possible to individually detect the thinning amounts 10 to 15 at the positions P0 to P5 of the inspection object 4 based on the thinning amounts 10 to 15 data, and to know the degree of thinning accurately and appropriately. it can.

  In the present embodiment, the thinning occurs only at the positions (for example, the positions P0 and P3) facing each other on the straight line passing through the center of the inspection object 4, and this is the non-destructive technique according to the prior art shown in FIG. If it is known in advance by the inspection method, calculation based on the above equations (3) to (8) may be performed assuming that l0 ≠ 0, l3 ≠ 0, and l1 = l2 = l4 = l5 = 0. By this method, it is possible to easily detect the thinning amounts l0 and l3 of a limited part (positions facing each other on a straight line passing through the center of the inspection object 4 that cannot be determined by the prior art).

  In the first embodiment as described above, radiation is detected at six positions P0 to P5 around the inspection object 4, but this may be detected at least at three positions. When the radiation source 1 and the radiation detectors 2 and 3 are integrally moved around the inspection object 4 by the same amount, an equation with the same amount of thinning as the number of detection positions can be obtained. is there. Therefore, if the number of detection positions is three or more, the radiation source 1 and the radiation detectors 2 and 3 are integrally moved around the inspection object 4 by the same amount, and the thinning amount is unknown at each position. If each equation is created and solved by simultaneous, it is possible to detect each amount of thinning at an arbitrary location.

  FIG. 2 is a schematic view showing a main part of a nondestructive inspection apparatus according to the second embodiment of the present invention. As shown in the figure, in the nondestructive inspection apparatus according to this embodiment, when the radiation source 1 is occupied at the position P0, one radiation detector 12 is located at the position P3 and the other radiation detector 13 is located. Radiation detectors 12 and 13 are arranged so as to occupy P4. That is, the radiation detectors 12 and 13 are located on a straight line passing through the center of the inspection object 4 and at positions opposite to the radiation source 1 and positions shifted from this position in the clockwise or counterclockwise direction (in this embodiment, in the counterclockwise direction). The detection position is shifted to the belt 8 together with the radiation source 1 and the same amount of the circumference of the inspection object 4 as the belt 8 rotates without changing the relative positional relationship with the radiation source 1. It is configured to move by 60 degrees (in this embodiment).

  Thus, when the radiation source 1 is occupied at the position P0, the radiation detectors 12 and 13 are located at the positions P3 and P4, and the radiation source 1 is positioned as the radiation source 1 rotates. When occupied at P1, the radiation detectors 12 and 13 are at positions P4 and P5, and when the radiation source 1 is occupied at position P2, the radiation detectors 12 and 13 are at positions P5 and P0. When the radiation source 1 is occupied at the position P3, the radiation detectors 12 and 13 are located at the positions P0 and P1, and when the radiation source 1 is located at the position P4, the radiation detectors 12 and 13 are located. Are positioned at positions P1 and P2, and the radiation source 1 is positioned at position P5, the radiation detectors 12 and 13 are positioned at positions P2 and P3, respectively.

  The signal intensities S03 and S04 based on the transmitted radiation detected by the radiation detectors 12 and 13 when the radiation source 1 is occupied at the position P0 are given by the following equations (9) and (10).

S03 = Sn × exp (−u × (10 + 13)) (9)
S04 = Sn ′ × η0 × exp (−u ′ × (−14))
= Sn ′ × exp (−u × (−10 / cos θ)) ×
exp (−u ′ × (−14)) (10)

here,
Sn: signal intensity when there is no thinning (normal inspection object),
(Measurement at a position of angle = 0 (for example, P0-P3)),
Sn ′: signal intensity when there is no thinning (normal inspection object),
(Measurement at a position of angle = ± θ (for example, P0-P2, P0-P4)),
η0: exp (−u × (−10 / cos θ)),
u ′: u / cos θ,
l0, l3, l4: The amount of thinning of the inspection object 4 at the positions P0, P3, P4.

From the above equation (9), l0 + l3 = k03 (11)
From the above equation (10), l0 + l4 = k04 / u ′ (12)

  Since the right side of the above formulas (11) and (12) is a constant, these are equations in which the thinning amounts l0, l3 and l4 of the inspection object 4 at positions P0, P3 and P4 are unknowns.

  The signal intensity (S14, S15), (S25, S20), (S30, S31), (S41, S42) detected by the radiation detectors 12 and 13 by moving the radiation source 1 to other positions P1 to P5, Based on (S52, S53), the thinning amount of the inspection object 4 at the positions (P4, P5), (P5, P0), (P0, P1), (P1, P2), (P2, P3) is set as an unknown. Obtain the following equation:

Position P0 of radiation source 1; l0 + l3 = k03 l0 + l4 = k04 / u ′
Position P1 of radiation source 1; l1 + l4 = k14 l1 + l5 = k15 / u ′
Position P2 of radiation source 1; l2 + l5 = k25 l2 + l0 = k20 / u ′
Position P3 of radiation source 1; l3 + l0 = k30 l3 + l1 = k31 / u ′
Position P4 of radiation source 1; l4 + l1 = k41 l4 + l2 = k42 / u ′
Position P5 of radiation source 1; l5 + l2 = k52 l5 + l3 = k53 / u ′

  In the above formula, ln is the amount of thinning of the inspection object 4 at the position Pn (n = 0 to 5).

  The above equation is six equations in which each of the thinning amounts l0 to l5 of the inspection object 4 at the positions P0 to P2 or P3 to P5 is six unknowns. Therefore, each of the thinning amounts 10 to 15 can be obtained by solving the above equations belonging to any group of the positions P0 to P2 or P3 to P5 simultaneously.

  As described above, according to the present embodiment, the necessary number of equations (six in this example) are obtained by moving the radiation source 1 by a half circumference. Therefore, the radiation source 1 is moved by half the circumference around the inspection object 4 by the same amount (60 degrees in this example), and the decrease at each position P0 to P5 obtained by dividing the entire circumference of the inspection object 4 into six equal parts. Meat amounts 10 to 15 can be detected.

  It should be noted that the predetermined calculation processing of the output signals of the radiation detectors 12 and 13 as described above, the processing when the thinning amount 10 to 15 exceeds the predetermined value, and the radiation source 1 by driving the belt 8. And the structure regarding the integral movement etc. of the radiation detectors 12 and 13 is the same as that of 1st Embodiment shown in FIG.

  Further, in this embodiment, if it is known in advance that l4 = 0, the calculation based on the above formulas (9) and (10) can be used to determine the limited part (the center of the inspection object 4 that cannot be determined by the prior art). It is possible to easily detect the thinning amounts l0 and l3 at positions facing each other on a straight line passing through.

  FIG. 3 is a schematic view showing a main part of a nondestructive inspection apparatus according to the third embodiment of the present invention. As shown in the figure, the nondestructive inspection apparatus according to this embodiment is a case where the radiation detector 12 in the second embodiment shown in FIG. 2 is removed and only the radiation detector 13 is used. That is, the radiation detector 13 is a position shifted in a clockwise direction or a counterclockwise direction from a position facing the radiation source 1 on a straight line passing through the center of the inspection object 4 (detected position shifted in the counterclockwise direction in this embodiment). And the radiation source 1 together with the radiation source 1 and the same amount (60 in this embodiment) around the inspection object 4 as the belt 8 rotates without changing the relative positional relationship with the radiation source 1. It is configured to move in degrees.

  Thus, when the radiation source 1 is occupied at the position P0, the radiation detector 13 is located at the position P4. Then, as the radiation source 1 rotates, the radiation source 1 is located at the position P1. When position is occupied at position P5, when position is occupied at position P2, position is P0. When position is occupied at position P3, position is P1. When position is occupied at position P4, position is P2. When occupied at the position P5, the position is occupied at the position P3.

  The signal intensity S04 based on the transmitted radiation detected by the radiation detector 13 when the radiation source 1 is occupied at the position P0 is given by the above equation (10). As a result, the relationship of the above formula (12) can be derived. That is, l0 + l4 = k04 / u ′. The right side of this equation is a constant and is an equation in which the thinning amounts l0 and l4 of the inspection object 4 based on the detection result at the position P4 by the radiation detector 13 are unknown.

  Therefore, the inspection object at positions P5, P0, P1, P2, and P3 based on the signal intensities S15, S20, S31, S42, and S53 detected by the radiation detector 13 by moving the radiation source 1 to other positions P1 to P5. The following equation is obtained in which the amount of thinning of the object 4 is unknown.

Position P0 of radiation source 1; l0 + l4 = k04 / u ′
Position P1 of radiation source 1; l1 + l5 = k15 / u ′
Position P2 of radiation source 1; l2 + l0 = k20 / u ′
Position P3 of radiation source 1; l3 + l1 = k31 / u ′
Position P4 of radiation source 1; l4 + l2 = k42 / u ′
Position P5 of radiation source 1; l5 + l3 = k53 / u ′

  In the above formula, ln is the amount of thinning of the inspection object 4 at the position Pn (n = 0 to 5).

  The above equations are six equations with six unknowns for each of the thinning amounts 10 to 15 of the inspection object 4 at positions P0 to P5. Therefore, the respective thinning amounts 10 to 15 can be obtained by solving the above equations simultaneously.

  In addition, the above-mentioned predetermined calculation processing of the output signal of the radiation detector 13, the processing when the thinning amount 10 to 15 exceeds the predetermined value, the radiation source 1 driving the belt 8, and the radiation The configuration relating to the integral movement of the detectors 12 and 13 is basically the same as that of the first embodiment shown in FIG.

  In this embodiment, radiation is detected at six positions P0 to P5 around the inspection object 4. However, this may be detected at least at three positions. This is because when the radiation source 1 and the radiation detector 13 are integrally moved around the inspection object 4 by the same amount, an equation with the same amount of thinning as the number of detection positions can be obtained. Therefore, if the number of detection positions is three or more, the radiation source 1 and the radiation detector 13 are integrally moved around the inspection object 4 by the same amount, and the thinning amount is set to an unknown number at each position. By creating an equation and solving them simultaneously, it is possible to detect the amount of thinning at an arbitrary location.

  The present invention performs nondestructive inspection of piping and the like, and can be effectively used in the industrial field in which the device is manufactured and sold.

DESCRIPTION OF SYMBOLS 1 Radiation sources 2, 3, 12, 13 Radiation detector 4 Inspection object 5 Arithmetic processing part P0-P5 Position 10-l5 Thinning amount

Claims (2)

Irradiating radiation from a radiation source toward a cylindrical inspection object, and a detection position shifted in a clockwise or counterclockwise direction from a position facing the radiation source on a straight line passing through the center of the inspection object; and detects the radiation in the radiation detectors respectively disposed position you said phase counter, based on the transmission signal intensity representing the intensity of the transmitted radiation, which is the output signal of the radiation detectors in the respective detecting positions , Each creating an equation including the amount of thinning of the inspection object at the detection position as an unknown,
Further, by moving the position of the radiation source and the detection position of the radiation detector by the same angle along the outer peripheral surface of the inspection object without changing the relative positional relationship between the radiation source and each radiation detector. While detecting the same radiation in at least three locations along the outer peripheral surface of the object to be inspected, each creating the same number of the equations as the unknown,
A non-destructive inspection method characterized by obtaining the amount of thinning of the inspection object at each detection position by solving these equations simultaneously. A radiation source that emits radiation toward a cylindrical inspection object;
Each radiation detector disposed at a detection position opposite to the radiation source on a straight line passing through the center of the inspection object and a detection position shifted from the detection position in a clockwise direction or a counterclockwise direction,
Moving means for moving the radiation source and each radiation detector integrally along the outer peripheral surface of the inspection object without changing the relative positional relationship between the radiation source and each radiation detector;
The radiation source and each radiation detector are moved by the same amount through the moving means so that the radiation detectors detect radiation at at least three locations along the outer peripheral surface of the inspection object. Control means for controlling;
Based on the transmitted signal intensity representing the intensity of transmitted radiation, which is the output signal of each radiation detector at each detection position, the same number of simultaneouss as the unknowns including each thinning amount of the inspection object at each detection position as an unknown number A nondestructive inspection apparatus comprising: an arithmetic processing unit that creates an equation and obtains a thinning amount of the inspection object at each detection position by solving the simultaneous equations.

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