JP2012002507A - Defect checking apparatus and checking method for pipes - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect any defect in pipes, such as cast iron pipes, without fail.SOLUTION: A defect checking apparatus 5 for detecting any defect in a cast iron pipe P comprises: a pump 7 that applies a load on the inside of the cast iron pipe P with a hydraulic pressure to generate acoustic emission (AE); AE sensors 1, 2 and 3 arranged in the axial direction of the cast iron pipe P to detect the AE; a generating position locating unit 50 that locates the generating position of the AE from the differences in detection time by the AE sensors 1, 2 and 3; and a defect detecting unit 60 that repeats three times a series of steps including detecting the load of the hydraulic pressure against the inside of the cast iron pipe P and the AE and identifying the generating position of the AE, and that, if the same generating position of the AE is duplicated three times, judges that a defect exists in this AE generating position.

Description

  The present invention relates to a pipe defect inspection apparatus and inspection method.

  Pipes used for water and sewage and gas transportation are subjected to various inspections after manufacturing at the factory, and products that pass these inspections are finished products. For such inspection, introduction of a highly accurate inspection device is desired in order to guarantee higher quality of the product.

  As a conventional inspection, there is a water pressure test (a test defined by an official standard, see Non-Patent Documents 1, 2 and 3) in which a water pressure is applied to the inside of the pipe and the presence or absence of water leakage is visually confirmed. is there. In addition, as the appearance inspection, there are a method of visually confirming and an eddy current flaw detection in which flaw detection is performed from a change in electromagnetic induction generated by flowing an eddy current through a part of a tube.

“JIS G 5526 Ductile Cast Iron Pipe”, Japanese Standards Association, revised on November 20, 1998, p. 6-7 “JWWA G 113 Ductile Cast Iron Pipe for Water Supply”, Japan Water Works Association, revised on November 18, 2005 “Ductile Pipe Telegraph JDPA T 26”, Japan Ductile Iron Pipe Association, September 2006, p. 27-28

  However, in the above-described water pressure test, the risk of oversight due to human error cannot be excluded by the method of visually confirming water leakage. Further, visual inspection or visual inspection by eddy current flaw detection failed to detect defects that did not appear on the outer surface of the tube.

  Therefore, the present invention provides a pipe defect inspection apparatus and inspection method capable of more reliably performing water leakage confirmation and detecting defects that are difficult to find in conventional visual inspection.

  In order to solve the above-mentioned problems, the invention described in claim 1 is a pipe defect inspection device for detecting the presence or absence of a pipe defect, a stress loading means for applying a stress to the pipe to generate acoustic emission, and a pipe A plurality of detectors arranged in the axial direction of the detector for detecting the acoustic emission, and a generation position specifying means for specifying the generation position of the acoustic emission from the difference in time when the acoustic emission is detected by each detection means. If a series of steps for detecting stress on the pipe, detecting acoustic emission, and specifying the generation position of the acoustic emission is repeated a plurality of times, and the specified generation positions of the acoustic emission overlap in the plurality of times, this Missing location where duplicate acoustic emissions occur Characterized by comprising a defect detection means for determining that there is.

The invention according to claim 2 is the defect inspection apparatus according to claim 1, wherein the stress load means applies a water pressure to the inside of the pipe.
Further, the invention according to claim 3 is the defect inspection apparatus according to claim 1 or 2, wherein the occurrence position specifying means removes a predetermined frequency component from the signal transmitted by the detection means detecting the acoustic emission. And an arithmetic unit that calculates the generation position of the acoustic emission based on the signal that has passed through the filter unit.

  On the other hand, the invention according to claim 4 is a method for inspecting a defect of a pipe, wherein the acoustic emission is generated by a stress applied to the pipe, and the acoustic emission is detected by a plurality of detection means arranged in the axial direction of the pipe. The acoustic emission generation position is identified from the difference in time at which the acoustic emission is detected by each detection means, and the stress load on the pipe, detection of acoustic emission, and identification of the generation position of the acoustic emission are performed. This step is repeated a plurality of times, and if the specified acoustic emission occurrence position overlaps a plurality of times, it is determined that there is a defect in the overlapped acoustic emission occurrence position.

The invention described in claim 5 is the defect inspection method according to claim 4, wherein the stress load on the pipe is a water pressure load on the inside of the pipe.
Further, the invention described in claim 6 is characterized in that, in the defect inspection method according to claim 5, when water pressure is applied to the inside of the pipe, the leaking water leakage to the outside of the pipe is simultaneously inspected. To do.

  The occurrence position of acoustic emission is specified multiple times by the occurrence position specifying means, and the presence or absence of defects in the pipe is detected based on the specified occurrence position of acoustic emission, so that human errors can be prevented, and other than defects Defects that cannot be detected by visual inspection or eddy current flaw detection can be reliably detected without erroneous detection.

It is the schematic of the defect inspection apparatus of the pipe | tube in this invention. It is the partially cutaway enlarged view which showed the state which detects the acoustic emission (AE) which generate | occur | produces from the defect of a pipe | tube with the same defect inspection apparatus. It is a block diagram which shows the arithmetic unit of the same defect inspection apparatus. (A) is a graph which shows the detection of AE by an AE sensor, (b) is a figure for demonstrating the type | formula which calculates AE generating position. It is a graph which shows the energy of AE in each judgment point of a cast iron pipe, (a) is at the time of the 1st measurement, (b) is at the time of the 2nd measurement, (c) is at the time of the 3rd measurement. . It is a graph which shows the water pressure change in the pipe | tube in the test | inspection by the same defect inspection apparatus. It is a flowchart (the first half) for demonstrating the inspection method by the same defect inspection apparatus. It is a flowchart (latter half) for demonstrating the inspection method by the same defect inspection apparatus. It is a graph which shows the water pressure change in the pipe | tube in the modification of the test | inspection by the same defect inspection apparatus.

  Next, a tube defect inspection apparatus and inspection method according to an embodiment of the present invention will be described in detail based on specific examples with reference to the drawings. This defect inspection apparatus applies acoustic pressure (hereinafter referred to as AE) caused by defects (specifically, shown in Table 1 later) and other causes of cast iron pipes by applying water pressure to the inside of the cast iron pipe to be inspected. And the presence or absence of defects in the cast iron pipe. Pipes used for water supply are subjected to a water pressure test (a test prescribed by official standards) that applies water pressure to the inside of the pipe and visually confirms whether water has leaked to the outside. Can use the hydraulic loading process inside the tube in this test. Table 1 shows defects that occur in the manufacturing process of the cast iron pipe.

  As shown in FIGS. 1 and 2, this defect inspection apparatus 5 is a pump (a stress load means) that applies water pressure to a cast iron pipe P to be inspected (both ends are sealed with lids L in the water pressure loading process). 7 is an example) and three AE sensors (detection) arranged at intervals along the axial direction of the cast iron pipe P in order to detect AE generated from the cast iron pipe P in which water pressure is loaded inside 1, 2, 3, which is an example of a means, and an arithmetic device 10 that is electrically connected to these AE sensors 1, 2, 3 to determine the presence or absence of a defect n in the cast iron pipe P and the estimated position of the defect n; The display device 70 is configured to display the result of the arithmetic device 10.

  As illustrated in FIG. 3, the arithmetic device 10 includes a generation position specifying unit (which is an example of a generation position specifying unit) 50 that specifies an AE generation position, and an AE generation position specified by the generation position specification unit 50. And a defect detection unit 60 (which is an example of a defect detection means) for determining the presence / absence of a defect n in the cast iron pipe P and an estimated position of the defect n.

  The generation position specifying unit 50 includes a first amplifier unit 11, a second amplifier unit 12, and a third amplifier that amplify signals (hereinafter referred to as AE signals) transmitted from the AE sensors 1, 2, 3 that detect AE. A first filter unit 21, a second filter unit 22 and a third filter unit that allow only a frequency component of the 20 kHz to 1 MHz band to pass therethrough in order to remove the AE signal that is not clearly caused by the defect n of the cast iron pipe P. 23, and a first comparison for comparing a AE signal that has passed through each filter unit 21, 22, and 23 and a threshold value to prevent a minute scratch that does not lead to a defect from being mistaken as a defect. Unit 31, second comparison unit 32, third comparison unit 33, and timer circuit incorporating each time when the AE signal exceeds a threshold value in each comparison unit 31, 32, 33 (see FIG. And a calculation unit 40 for calculating each by not). Further, the calculation unit 40 calculates the AE occurrence position based on each time calculated as described above. Specifically, as shown in FIG. 4 (a), the time at which the AE corresponding to the AE signal exceeding the threshold value in the comparison units 31, 32, and 33 has reached the nearest AE sensor from the generation position. t1 [ms], the time when the next closest AE sensor is reached is t2 [ms], and the difference between these times t2 to t1 is Δt [ms], and as shown in FIG. Is D [mm], and the distance from the intermediate position of these AE sensors to the AE generation position N is K [mm], the sound velocity C [mm / ms] is used to calculate K by the following equation (1). Desired.

K = Δt · C / 2 (1)
Here, in FIG. 2, the defect is represented by n. However, since AE occurs as a cause other than defect n, the AE occurrence position is represented by N. Note that the AE occurrence position N is a position along the axial direction of the tube for convenience, and is not specified up to a position along the circumferential direction. Further, the distance S from the AE sensor closest to the AE generation position N to the AE generation position N is obtained by the following equation (2).

S = D / 2−K (2)
In this way, the AE occurrence position N is calculated. Usually, since there are a plurality of AE occurrence positions N, the calculation unit 40 further calculates the calculated AE occurrence positions N in the axial direction of the cast iron pipe P, etc. It is converted into position information data that is information on the presence or absence of occurrence of AE at each divided point (hereinafter referred to as a judgment point). In addition, as shown in FIG. 5, the calculation unit 40 calculates not only the presence / absence of occurrence of AE at the determination point but also the energy of the generated AE as position information data.

  On the other hand, in FIG. 3, the defect detection unit 60 converts the position information data at all the judgment points calculated by the calculation unit 40 into binary number data and stores it, and the cast iron pipe P based on the binary number data. And a determination unit 67 that determines the presence or absence of the defect n and calculates the estimated position of the defect n.

The storage unit 65 creates binary data having the same number of digits as the number M of all judgment points, and performs BitSet or BitReset on the binary data based on each position information data. Specifically, the storage unit 65 stores [1] in the digit at the decision point corresponding to the AE occurrence position N in the created M-digit binary data (BitSet) and corresponds to the AE occurrence position N. [0] is stored in the digit at the judgment point not to be executed (BitReset), and the binary data R is stored as an array. For example, the cast iron pipe P to be inspected is divided into nine equal parts (the number M of all judgment points is 10 obtained by adding 1 to 9 which is an equally divided number), and the first measurement shows the first , 2, 7, and 9 when the AE occurs, the binary data R created in the storage unit 65 has 10 digits, and the binary data R includes the first, second, seventh, and ninth from the left. [1] is stored in the second digit, [0] is stored in the other digits,
R (1) = 1100001010
Is stored in the storage unit 65. More specifically, the binary number data R (j) stored in the storage unit 65 is R (1) because j = 1 in the first measurement. R (1) has the number of digits by the number M of all judgment points (M = 10 in this example), and in this example, it is composed of 10 digits of binary numbers, that is, 10 numbers (0 or 1). Is done. Here, the digit represents the position along the axial direction of the cast iron pipe P, and the numerical value of the digit represents the presence or absence of occurrence of AE. That is, if the numerical value of a certain digit is [1], it means that AE has occurred at the position of the judgment point corresponding to that digit, and if it is [0], the position of the judgment point corresponding to that digit. Means that no AE occurs. Therefore, in R (1) in the above example, the numerical values of the first and second digits from the left are [1]. Therefore, the first and second judgment points mean that AE has occurred, and the third from the left Since the numerical value of the sixth digit is [0], it means that AE is not generated at the third to sixth judgment points. Similarly, since the value of the seventh digit from the left is [1], AE occurs at the seventh judgment point, and the value of the eighth digit from the left is [0], so the eighth judgment point. Means no occurrence of AE, and similarly, the ninth judgment point means occurrence of AE and the tenth judgment point means no occurrence of AE.

Next, in the second AE measurement (j = 2), for example, when AE occurs at the third, sixth, and seventh decision points, the binary number data R stored in the storage unit 65 is similarly processed. [1] is stored in the third, sixth, and seventh digits from the left, and [0] is stored in the other digits.
R (2) = 0010011000
It becomes. Further, in the third AE measurement (j = 3), for example, when AE occurs at the first, fourth, fifth, seventh, and ninth judgment points, the binary number data R stored in the storage unit 65 is also Similarly, [1] is stored in the first, fourth, fifth, seventh and ninth digits from the left, and [0] is stored in the other digits.
R (3) = 1001101010
It becomes. In this manner, the storage unit 65 stores a plurality of binary data R (1) to R (J) as an array for the number of times AE is measured J.

  On the other hand, the determination unit 67 compares a plurality of binary number data R (1) to R (J) stored in the storage unit 65 by each digit, and is common to each binary number data R (1) to R (J). If there is a digit [1], the fact that there is a defect n in the cast iron pipe P and a judgment point corresponding to the digit are displayed on the display device 70, and binary data R (1) to R (J) If there is no common digit [1], it is displayed on the display device 70 that the cast iron pipe P has no defect n. This is because the occurrence of AE is not caused only by defect n, but is caused by other than defect n such as bubble collapse, but AE caused by defect n always occurs from the same position and causes other than defect n. Since AE occurs by chance, it is mistakenly recognized that there is a defect n at the position where the AE is caused by other than the defect n by determining that the defect n exists at the position where the AE has occurred J times in succession. It is because it can prevent.

  In the determination unit 67, in the above example, in R (1) to R (3), the first digit from the left is [1] for R (1) and [0] for R (2). , R (3) is [1], not [1] in common, and it is determined that there is no defect n at the first determination point. However, similarly, when comparing the second digit from the left, the third digit,... And the tenth digit, the seventh digit is [1] in R (1). ], R (2) is [1], and R (3) is [1]. Therefore, it is commonly [1], and it is determined that there is a defect n at the seventh determination point. On the other hand, except for the seventh digit, R (1) to R (3) do not become [1] in common, so the defect n exists only at the seventh judgment point. Accordingly, the display device 70 displays that the cast iron pipe P has the defect n and that the position of the defect n is the seventh determination point.

  Next, an inspection method using the defect inspection apparatus 5 for the cast iron pipe P will be described. In this inspection method, the process from the load of water pressure to the inside of the cast iron pipe P to the identification of the AE generation position N (that is, measurement) is repeated J times. However, if the total number of times J is small, the inspection accuracy decreases. On the other hand, the cast iron pipe P having no defect n may be determined as a defective product. On the other hand, if the total number of times of measurement J is large, the inspection takes time. Therefore, as shown in Step 1 of FIG. 7, the total number of measurements J is suitably three.

  First, as shown in FIG. 1, three AE sensors 1, 2, 3 are arranged at intervals along the axial direction of the cast iron pipe P, and both ends of the cast iron pipe P are sealed with lids L. Next, water is injected into the cast iron pipe P from the opening (not shown) of one lid L by the pump 7, and air is discharged from the cast iron pipe P by an air vent valve (not shown) provided on the upper portion of the lid L. Is done. Then, when the cast iron pipe P becomes full of water, the air vent valve is closed. In addition, the air in the cast iron pipe P is not completely discharged and may remain in the cast iron pipe P as small bubbles. Thereafter, the pump 7 is further pressurized to apply water pressure inside the cast iron pipe P. Due to this water pressure change, AE is generated due to the defect n of the cast iron pipe P and other causes (such as remaining bubbles), and is detected by the AE sensors 1, 2 and 3.

  Each AE signal transmitted from each AE sensor 1, 2, 3 that detects these AEs is amplified by each amplifier unit 11, 12, 13, and the frequency component only in the 20 kHz to 1 MHz band is converted to each filter unit 21, Those passing through 22 and 23 and not obviously caused by the defect n of the cast iron pipe P are removed. In the comparison units 31, 32, and 33, the threshold value is compared with the AE signal that has passed through the filter units 21, 22, and 23 in order not to mistake a minute scratch or the like as a defect. In addition, the calculation unit 40 calculates the time when the AE signal exceeds the threshold, and based on the time when the AE signal exceeds the threshold, the AE occurrence position is calculated by the above formulas (1) and (2). N is specified. In FIG. 7, the process from the load of water pressure to the inside of the cast iron pipe P to the step of specifying the AE generation position N is shown as “measurement” (Step 2).

  Further, as shown in Step 3 of FIG. 7, the calculation unit 40 converts the AE occurrence position N into position information data that is information on the presence / absence of occurrence of AE at the determination point. Specifically, in the j-th measurement, if the judgment point corresponding to the AE occurrence position N is the m-th judgment point, E (j, m) is converted to AE occurrence. Thereafter, as shown in FIG. 6, the water pressure in the cast iron pipe P is reduced to such an extent that the generation of AE is suppressed (for example, 1 MPa). As will be described later, whether or not AE occurs at E (j, m) (Step 7 in FIG. 7) is used by the determination unit 67 for BitSet (Step 8) or BitReset (Step 9) of R (j).

  Here, in Step 4 in FIG. 7, since the current measurement number j is 1 and the total measurement number J is 3, j ≧ J is not satisfied, and 1 is added to the current measurement number j in Step 5. 2 and measurement of the second time (j = 2) is started (Step 2).

  Then, the second measurement (j = 2) and the third measurement (j = 3) are performed, and the water pressure is applied to the inside of the cast iron pipe P as in the first measurement described above. Then, the AE is detected and converted into position information data, and the water pressure in the cast iron pipe P is reduced. Here, since AE is generally less likely to occur as the number of measurements is repeated, the water pressure applied in the subsequent measurement is set higher than in the previous measurement. Specifically, as shown in FIG. 6, the second measurement loads a higher water pressure than the first measurement, and the third measurement loads a higher water pressure than the second measurement. To do. Since the water pressure test is also performed in the third measurement, the water pressure in the cast iron pipe P is increased to 6 MPa, and the water pressure is maintained for 5 seconds. Here, the load water pressure of 6 MPa and the holding time of 5 seconds are public as described in the nominal diameters 75 to 250 in “JIS G 5526 Ductile Iron Pipe” and “JWWA G 113 Ductile Iron Pipe for Waterworks”. It is established as a standard. In the third measurement, the total number of measurements J is 3, which is the same as the current number of measurements j (Step 4), and the next (fourth) measurement is not performed. Therefore, as shown in FIG. In the decompression of the pipe P, the drainage is performed and all the water in the cast iron pipe P is discharged.

  Here, the relationship between Step 3 in FIG. 7 and FIG. 5 will be described. When converting the AE occurrence position N into position information data in Step 3 of FIG. 7, the calculation unit 40 multiplies the AE size [dB] at the determination point by the detection time [s] of the AE. [DBs] is calculated. 5A is a graph showing the energy of AE at each judgment point in the first measurement, FIG. 5B is the second measurement, and FIG. 5C is the graph. It is a graph of the energy of AE in the 3rd measurement.

  Thereafter, in the arithmetic unit 10, as shown in Step 6 in FIG. 7, the position information data at the first determination point (m = 1) in the first measurement (j = 1), that is, E (1, 1 ). If it is determined that AE is generated at E (1,1) (Step 7), that is, if there is AE energy at the position corresponding to the first determination point in FIG. As shown in Step 8, [1] is stored in the first digit from the left of R (1) in the storage unit 65 (BitSet). On the other hand, if it is not determined at this E (1,1) that AE has occurred, that is, if there is no AE energy at the position corresponding to the first determination point in FIG. [0] is stored in the first digit from the left of R (1) in the storage unit 65 (BitReset). In this way, BitSet or BitReset is repeated from the first determination point to the mth determination point (Step 11). If BitSet or BitReset is performed at all judgment points, that is, if m ≧ M with all judgment points being M (Step 10), then in the second measurement (j = 2) (Step 13), all BitSet or BitReset is performed at the determination point and stored in the storage unit 65 as R (2). Thereafter, in the same manner, BitSet or BitReset is performed at all judgment points in the third measurement (j = 3) and stored in the storage unit 65 as R (3). Here, since j is 3 and coincides with the total number of measurements J (Step 12), the calculation by the defect detection unit 60 exits the loop of Step 7 to Step 13 shown in FIG.

  Next, as shown in Step 14 in FIG. 8, the determination unit 67 compares the three binary data R (1) to R (3) stored in the storage unit 65 with each digit, and these binary data. If there is a digit [1] in common, RESULT = 1, and if there is no digit [1] in common, RESULT = 0. If RESULT = 0 (Step 15), the fact that there is no defect n in the cast iron pipe P is displayed on the display device 70 (Step 16). If RESULT = 0 is not satisfied (Step 17), the fact that the cast iron pipe P has the defect n and The position of the defect n is displayed on the display device 70. If it demonstrates in FIG. 5, description of a broken line will specify the position where the energy which generate | occur | produces AE in common in (a)-(c) of FIG. 5, ie, the load of the water pressure to the inside of the cast iron pipe P-AE generation | occurrence | production position. This process is repeated three times (multiple times), and the process is performed at the AE occurrence position that is duplicated in three times, and the position indicated by the broken line corresponds to the position of the defect n. Except for the location indicated by the broken line in FIG. 5, the AE generation position (position where the energy generated by AE is present) is not common in (a) to (c), and the position has no defect n. Thus, by repeating the measurement three times (a plurality of times), it is mistaken that the cast iron pipe P has the defect n based on the AE detected from the cause other than the defect n of the cast iron pipe P. To prevent. More specifically, AE always occurs from the same position as long as it is caused by defect n. However, if it is caused by something other than defect n such as bubble collapse, it occurs by chance. It is determined that there is a defect n at the position where the AE that has occurred repeatedly (multiple times) is repeated, so that there is a defect n at the position where the AE that occurs by accident (that is, the cause other than the defect n) occurs. Can be prevented from being mistaken, and inspection accuracy is improved.

  Then, the inspector knows the presence or absence of the defect n of the cast iron pipe P and the position of the defect n from the display on the display device 70, and determines the cast iron pipe P without the defect n as a healthy product. On the other hand, the inspector discriminates the cast iron pipe P having the defect n as a defective product, but since the position of the defect n is a position along the axial center direction of the cast iron pipe P, the position along the circumferential direction is determined. Need to be examined by an inspector.

Below, the test | inspection using the defect inspection apparatus mentioned above was performed experimentally with respect to the defective cast iron pipe and the healthy cast iron pipe.
The test conditions and results are shown in Table 2.

表２に示した上記試験では、呼び径、中摺（管の内面への粉体塗装のための下地処理）の有無に関係なく、全ての欠陥品の鋳鉄管から欠陥が検知され、健全品の鋳鉄管からは欠陥が検知されなかった。

In the above tests shown in Table 2, defects were detected from all defective cast iron pipes regardless of the nominal diameter and the presence of intermediate rails (primary treatment for powder coating on the inner surface of the pipe). No defects were detected from the cast iron pipe.

  Thus, since the presence or absence of defects in the cast iron pipe is detected by the arithmetic unit using the AE signal, human errors can be prevented, and further, the inner surface that cannot be detected by visual inspection or eddy current flaw detection without erroneously detecting other than defects. Defects can be reliably detected.

  In addition, since it is an inspection method that can use the water pressure test process that is generally performed, it is possible to detect defects in cast iron pipes by AE without significantly increasing the inspection process by combining with the water pressure test process. Can do.

  By the way, in the pressure reduction in the first measurement and the second measurement in the above embodiment, the water pressure in the cast iron pipe P is set to 1 MPa. However, the pressure is not limited to this, and as shown in FIG. In addition, the pressure may be reduced to the extent that the generation of AE is suppressed. Further, the water pressure change as shown in FIG. In these inspection methods, the inspection time can be shortened compared to the inspection methods shown in the above embodiments.

Moreover, in the said Example, although the water pressure to be loaded was made high as measurement was repeated, as shown in FIG.9 (c), you may make the water pressure to load constant.
Furthermore, in the said Example, although the water pressure test was performed by the 3rd measurement, a water pressure test may be performed by the 1st time or the 2nd measurement, and the water pressure test must not be performed in this inspection. Also good.

  Moreover, in the said Example, although the series of processes which perform the load of the water pressure to the inside of the cast iron pipe P, the detection of AE, and specification of AE generating position were repeated 3 times, it is limited to this number (3 times). In order not to reduce the inspection accuracy, it may be performed a plurality of times.

  Moreover, although the number of AE sensors 1, 2, and 3 was demonstrated as three, if it is multiple, you may increase / decrease according to the length of the cast iron pipe P. Even if the cast iron pipe is long, if the number of AE sensors is increased, the distance until the AE reaches the AE sensor does not become long, and the accuracy of AE detection can be improved.

  Moreover, in the said Example, although the water pressure was loaded inside the cast iron pipe P for generation | occurrence | production of AE, it is not limited to a water pressure, Other stresses, such as the compressive force to the axial direction of the cast iron pipe P, are not limited. May be generated. The inspection object is not necessarily a cast iron pipe, and may be another pipe.

P Cast iron pipe L Lid N AE occurrence position n Defect J Total number of measurements M Total number of judgment points E Position information data R Binary data 1, 2, 3 AE sensor 5 Defect inspection device 7 Pump 10 Arithmetic device 50 Generation position specifying unit 60 Defect Detector 70 Display device

Claims (6)

A pipe defect inspection device for detecting the presence or absence of a pipe defect,
Difference in stress loading means for generating acoustic emission by applying stress to the pipe, detection means for detecting the acoustic emission arranged in the axial direction of the pipe, and the time at which the acoustic emission was detected by each detection means A generation position specifying means for specifying the generation position of the acoustic emission from
If a series of processes for detecting stress on the pipe, detecting acoustic emission, and specifying the position where the acoustic emission occurs are repeated multiple times, and the specified acoustic emission generation position overlaps multiple times, this overlap A defect inspection device for a pipe, comprising defect detection means for determining that there is a defect at a position where the generated acoustic emission occurs.   2. The pipe defect inspection apparatus according to claim 1, wherein the stress load means applies a water pressure to the inside of the pipe.   The generation position specifying unit includes a filter unit that removes a predetermined frequency component from the signal transmitted by the detection unit that has detected acoustic emission, and a calculation unit that calculates the generation position of the acoustic emission based on the signal that has passed through the filter unit. The tube defect inspection apparatus according to claim 1 or 2, characterized by comprising: The acoustic emission is generated by the stress applied to the pipe, the above-mentioned acoustic emission is detected by a plurality of detection means arranged in the axial direction of the pipe, and the acoustic emission is detected from the difference in time at which each detection means detects the acoustic emission. Identify the location of
If a series of processes for detecting stress on the pipe, detecting acoustic emission, and specifying the position where the acoustic emission occurs are repeated multiple times, and the specified acoustic emission generation position overlaps multiple times, this overlap A defect inspection method for a pipe, characterized in that it is determined that there is a defect at a position where the generated acoustic emission occurs.   5. The method for inspecting a defect of a pipe according to claim 4, wherein the stress load on the pipe is a water pressure load on the inside of the pipe. 6. The method for inspecting a defect of a pipe according to claim 5, wherein when the water pressure is applied to the inside of the pipe, the leaking water leaking to the outside of the pipe is inspected simultaneously.

Images