JP3715177B2 - Evaluation method of circular pipe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for evaluating a circular tube, and in particular, the thickness, presence / absence or size of a circular tube and a cylindrical container (in the present specification, these are collectively referred to simply as a circular tube) using ultrasonic waves. The present invention also relates to a method for detecting the presence or absence or size of a lining defect on the inner and outer surfaces of a circular tube, and the type and / or state of a liquid or high-pressure gas (hereinafter referred to as fluid) inside the circular tube.
[0002]
[Prior art]
In order to measure the wall thickness distribution and the average wall thickness along the circumferential direction of the circular tube, since the pulse echo type ultrasonic thickness meter that is generally used is used in contact with the position to be measured, It requires measurement at a very large number of points. Further, there is a disadvantage that the defect cannot be detected at a position away from the defect.
[0003]
In addition to the above-mentioned pulse echo type ultrasonic thickness gauge, a method of measuring the thickness of a circular tube using a plate wave propagating along the wall of a thin circular tube is also known. However, this method requires special analysis to identify the waves of multiple modes.
[0004]
Due to the problems in the above prior art, a method for easily measuring the thickness of a circular tube has been desired. In addition, the soundness of the lining formed in the circular pipe, the presence or absence and size of defects on the inner and outer surfaces of the circular pipe, and the type and state of the fluid inside the circular pipe can be easily determined. Or a method of evaluation is desired.
[0005]
[Problems to be solved by the invention]
The present invention relates to the average thickness of a circular tube containing fluid, the presence or absence and size of defects on the inner surface of the circular tube, defects in the lining of the inner surface of the circular tube, and the type of fluid in the circular tube, Provided is a method for evaluating a circular tube, which is suitable for inspecting a state.
[0006]
[Means for Solving the Problems]
In a preferred embodiment of the method for evaluating a circular tube according to the present invention, an ultrasonic wave is incident on the circular tube by an ultrasonic sensor, and the ultrasonic wave is propagated along the circumferential direction of the circular tube. Ultrasound is observed at a specific position, and the first wave propagating in the tube wall while being reflected multiple times on the inner and outer surfaces of the tube, propagating in the tube wall, and then fluid in the tube at the first predetermined position A second wave that enters the inside of the tube wall again after entering the inside, and propagates through the inside of the tube wall and then enters the fluid inside the tube at a second predetermined position. The third wave that is reflected by the inner surface of the tube at a predetermined position and then enters the tube wall again is stored in the digital memory after the waveform is synchronously added multiple times, and the waveform data is digitally processed. Calculate the propagation time and amplitude of each wave. Based on the calculated propagation time and amplitude, the propagation path of each wave is analyzed, the average thickness of the tube, the defects existing on the inner and outer surfaces of the tube, the lining defects of the lined tube, and the inside of the tube Any one or more of the types and / or states of the liquid is determined.
[0007]
The transverse wave incident in the circumferential direction of the circular tube containing the fluid propagates in the circumferential direction while repeatedly reflecting on the inner and outer surfaces of the circular tube. When the fluid or solid is in contact with the inside of the circular tube without a gap, part of the energy of the wave reflected on the inner surface of the circular tube is transmitted to the fluid or solid that is in contact with the inner surface of the circular tube. As a result, a wave propagating only in the wall of the circular tube and a wave propagating in the circular tube wall and then passing through the fluid or solid in contact with the inner surface of the circular tube and incident on the circular tube wall are propagated. Received by sonic sensor. The latter includes a plurality of waves that pass through different paths, and their propagation time is different from the waves that propagate to each other and only within the tube wall. It is possible to evaluate the fluid inside the tube and / or the circular tube.
[0008]
If there is a defect on the inner surface and / or the outer surface (inner / outer surface) of the circular tube, the wave is irregularly reflected, so that the reception amplitude decreases. When the inner surface of the circular pipe is lined, ultrasonic waves generally do not pass through an incomplete joint between the lining and the inner surface of the circular pipe. By analyzing the arrival time and amplitude of each wave of the received waveform, the propagation path of each wave can be determined. Here, if the acoustic characteristics of the circular tube, the lining material, and the internal fluid are known, the thickness of the circular tube and the thickness of the lining can be obtained from the difference in propagation time. The defect position is obtained from the propagation time of the scattered wave from the defect.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail based on embodiments of the present invention with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a circular pipe showing the principle of a circular pipe evaluation method by a circular pipe soundness evaluation apparatus according to an embodiment of the present invention.
[0010]
The soundness evaluation apparatus generates ultrasonic waves in the ultrasonic sensor 11 including a pair of ultrasonic probes 21 and 22 disposed in contact with the outer surface of the circular tube 10 and in one probe 21 of the ultrasonic sensor 11. For transmitting and receiving the ultrasonic electrical signal received by the other probe 22 of the ultrasonic sensor 11, and digital recording for recording the signal received by the pulse transceiver 12 It comprises a device 13 and a digital waveform processing device 14 for analyzing the recorded signal and evaluating the circular tube. Inside the circular tube 10, high-pressure gas or various liquids are accommodated.
[0011]
In the soundness evaluation apparatus of the present embodiment, a transverse wave that propagates in the circumferential direction from one position on the outer periphery of the circular tube 10 (the top in the drawing) using one probe 21 of the ultrasonic sensor 11. And the propagating wave is detected using the other probe 22 of the ultrasonic receiving sensor 11. The pulse receiver 12 receives this signal in synchronization with the transmitted ultrasonic wave and records it in the digital waveform recording device 13. The digital waveform processing device 14 configured as a personal computer quantitatively analyzes and calculates the propagation time and amplitude of the ultrasonic wave from the recorded waveform.
[0012]
FIG. 2 shows that a waveform corresponding to each propagation path is included in the recorded ultrasonic wave received at the same position as the transmission position of the ultrasonic wave. The waveform in FIG. 6A is obtained when the inside of the circular tube is air, and FIG. 5B is obtained when the inside of the circular tube is water. 2 (a) and 2 (b), the leftmost wave W1 is a transmitted wave, the right W2 is a wave that directly reaches an adjacent probe, and the wave W3 is 1 in the wall of the circular tube. Each wave traveling around is shown. In FIG. 5B, it can be understood that a wave packet including waves W4 and W5 having different paths is detected adjacent to W3, and ultrasonic waves that pass through a liquid such as water can be detected effectively. .
[0013]
There are three typical propagation paths of ultrasonic waves. That is, as shown in FIG. 3, with the point P as the incident point of the ultrasonic wave, the wave W3 that passes only within the circular tube wall passes through the circular tube wall via the arc PB, Next, the fluid passes through the fluid in the circular pipe through the chord BC and again passes through the circular pipe wall through the second path along which the wave W4 that enters the circular pipe wall at the point C and the arc PA. Then, the third path follows the wave W5 that passes through the fluid in the circular tube via the strings AB and BC and enters the circular tube wall again at the point C.
[0014]
When the transverse wave velocity in the circular tube wall is V _T and the longitudinal wave velocity in the fluid is V _L , the propagation time of each path is given by the following equation.
The propagation time t ₀ of the wave W3 propagating through the first path is
t ₀ = C · π · (dt) / V _T (1)
The propagation time t ₁ of the wave W4 propagating through the second path is
t ₁ = L / V _L + t ₀ · (2π−∠COB) / 2π (2)
Propagation time t ₂ of the wave W5 propagating the third path,
t ₂ = 2L / V _L + t ₀ · (2π−∠COA) / 2π (3)
It is.
[0015]
In the above formulas (1) to (3), C is a correction coefficient depending on the outer shape and thickness of the circular tube, d is the outer diameter of the circular tube, t is its thickness, and L is the length of the strings AB and BC. is there. The central angles of the strings AB and BC (∠AOB and ∠COB) are geometrically determined by the angle of the transmitting / receiving ultrasonic sensor, the inner diameter of the circular tube, and Snell's law (sound wave velocity of the tube, longitudinal velocity of the fluid). Determined.
[0016]
When the transverse sound velocity V _T inside the circular tube and the outer diameter d of the circular tube are known, the wall thickness t of the circular tube is obtained from the equation (1) by actually measuring the propagation time t ₀ of the wave W3.
[0017]
When fluid is present inside the tube or when its density is higher, the component of the wave that passes through the fluid increases, so it is possible to determine whether there is fluid inside and to detect the state of the fluid inside. Is also possible. If the transverse wave sound velocity V _T , outer diameter d and thickness t of the circular tube are known, the longitudinal wave sound velocity in the fluid is obtained by repeated calculation from the measured arrival times t ₀ , t ₁ and t _{2 of} each wave. Can do. As a result, the type and density of the fluid can be estimated.
[0018]
The amplitude of each wave is maximum when there are no defects on the inner and outer surfaces of the circular tube. In the ultrasonic transverse wave traveling inside the circular tube wall, if there is a defect in the circumferential position on the inner and outer surfaces of the circular tube, the wave undergoes irregular reflection, and the wave propagates other than the path shown in FIG. For this reason, the reception amplitude of the wave corresponding to the path shown in FIG. 3 decreases. Therefore, by comparing the amplitudes of the waves with each other, the presence / absence and size of a defect at a specific position can be estimated. By sequentially changing (scanning) the position of the ultrasonic sensor on the incident side in the circumferential direction, the reflection position on the inner and outer surfaces of the circular tube shown in FIG. 3 changes. Can be detected. Even when the lining is present on the inner surface or the outer surface of the circular tube, an incomplete portion of the lining can be detected by the same concept.
[0019]
For example, if there is a thinning as a defect in a circular tube, t ₁ obtained by Equation (2) is different from the actually measured propagation time of the wave W4. Further, when the shape of the inner surface changes due to a defect and irregular reflection occurs, the observed amplitude changes. Further, the defect on the outer surface of the circular pipe can be determined by the actually measured value of the propagation time t _{0 in} the equation (1). In this case, the propagation time t ₁ in equation (2) also changes.
[0020]
When the length L of the strings AB and BC is known and the wall thickness is sound, the type of fluid is determined from the difference between the propagation times t ₁ and t ₂ obtained by the calculation and the actually measured values. Can be determined. In this case, if the density of the fluid is large, the point B is shifted away from the point A, and the propagation time is shortened.
[0021]
【Example】
The calculation was performed for the case where the steel-side refraction angle on the surface of the steel circular tube was 70 degrees, the transmission / reception ultrasonic probe was disposed at the same position, and the frequency was 5 MHz. In a steel tube with an outer diameter of 60 mm, a thickness of 3 mm, and a shear wave velocity of 3250 m / s, when there is no fluid inside, only the waves that have made a round around the wall of the tube are effectively observed. Is done. The arrival time (propagation time) of the ultrasonic wave is 63 μs in the calculation. When this circular tube is filled with water, two waves that arrive at an equal time difference are observed in addition to this wave. The arrival time difference is about 12 μs.
[0022]
FIG. 4 shows the result of calculating the propagation path in a steel circular pipe having an outer diameter of 60 mm, a thickness of 3 mm, and a transverse wave speed of 3250 m / s. Here, the incident point A from the steel to water, the reflection point B, and the incident point C from the steel to water at the boundary surface of the steel and water in the third path are respectively the ultrasonic incident point P. The 0-degree position is about 90 degrees, 218 degrees, and 346 degrees counterclockwise. The reflection point B is also an incident point from steel to water in the second path.
[0023]
Actually, since the ultrasonic wave propagating in the tube wall has an extent of about 60 to 90 degrees from the perpendicular line standing on the circumference at the incident point from the ultrasonic probe, FIG. As shown, the ultrasonic wave becomes a band-like wave. Since the longitudinal acoustic velocity of water is 1500 m / s, according to Snell's law, when the steel-side refraction angle is 70 degrees, the water-side refraction angle is about 26 degrees.
[0024]
Various materials were prepared by attaching a vinyl chloride sheet having a thickness of 2 mm to the inner surface of the circular tube having the above structure. Ultrasonic waves cannot penetrate this thickness of vinyl chloride sheet. The vinyl chloride sheet was affixed to the entire inner surface of the circular tube, the item was not affixed at all, and the inner surface was divided into 12 equal parts in the circumferential direction. Various steel circular pipes with open windows are manufactured, and the wave propagation path from the steel side to the water side or from the water side to the steel side is cut off / opened, so that It was decided to confirm the propagation path of the sound wave.
[0025]
FIG. 6 shows a comparison of received waves from the one without the vinyl sheet 15 (FIG. 6A) and the one attached to the entire surface (FIG. 6B). In the circular pipe with vinyl chloride 15 affixed to the entire inner surface, only a wave propagating inside the circular pipe wall was observed, as shown in FIG. As shown in (a), three types of waves were observed.
[0026]
Similarly, a circular pipe (FIG. 7 (a)) in which the vinyl chloride 15 is not attached at an angle of 210 ° to 240 ° and an angle of 330 ° to 360 ° and thus the path BC is opened by the window 16 (FIG. 7A), In addition, the circular pipe 15 (b) and the circular pipe (b) in which the chloride building 15 is not attached at an angle of 90 ° to 120 ° and therefore the path AB and BC are opened by the window 16 is shown. Three kinds of circular tubes (FIGS. (C) to (e)) in which any one of the open windows 16 is slightly shifted were prepared, and ultrasonic waves propagating through the respective circular tubes were observed.
[0027]
In FIG. 7A, the waves W3 and W4 of the first and second paths were observed, and in FIG. 7B, all of the waves W3, W4 and W5 of the first to third paths were observed. In FIG. 4C, only the first and second waves W3 and W4 are observed by blocking the incident point A from the steel to the water. In FIG. 4D, the first path is blocked by blocking the reflection point B. Only the first wave W3 was observed in the same manner as shown in FIG. 2E due to the interception of the incident point C from the water to the steel. From these observation results, it can be determined that the wave propagation path obtained by the calculation is correct.
[0028]
As mentioned above, although this invention was demonstrated based on the suitable embodiment example, the evaluation method of the circular pipe of this invention is not limited only to the structure of the said embodiment example, From the structure of the said embodiment example. Various modifications and changes are also included in the scope of the present invention.
[0029]
【The invention's effect】
As described above, according to the method for evaluating a circular tube according to the present invention, the inside of the circular tube and / or the circular tube is measured by a very simple method of measuring the propagation time and / or amplitude of the ultrasonic wave incident on the circular tube. It is possible to evaluate the fluid.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of a soundness evaluation apparatus for implementing an evaluation method of the present invention.
FIG. 2 is a graph showing waveforms observed by the evaluation apparatus of FIG.
FIG. 3 is a cross-sectional view of a circular tube showing a propagation path of a wave passing through the inside of the circular tube.
FIG. 4 is a cross-sectional view of a circular tube showing a propagation path of a wave in calculation.
FIG. 5 is a cross-sectional view of a circular tube showing a propagation path of a calculated wave packet.
FIGS. 6A and 6B are a cross-sectional view of a circular tube measured in an example and a graph showing an observed waveform, respectively.
7A to 7E are cross-sectional views of various circular tubes measured in Examples and graphs showing observed waveforms, respectively.
[Explanation of symbols]
10: Circular tube 11: Ultrasonic sensor 12: Pulse transceiver 13: Digital waveform recording device 14: Digital waveform processing device 15: Lining sheet 16: Open window 21, 22: Ultrasonic probe

Claims (5)

Detecting the ultrasonic wave at a specific position on the outer periphery of the circular tube while propagating the ultrasonic wave along the circumferential direction of the circular tube or cylindrical container (hereinafter referred to as a circular tube),
A first wave propagating in the tube wall and then entering the fluid inside the tube at a first predetermined position and then entering the tube wall again; and a second wave propagating in the tube wall and then the second wave Propagation time and at least one of the second waves incident on the fluid inside the circular tube at a predetermined position and reflected on the inner surface of the circular tube at the first predetermined position and then incident on the circular tube wall again. / Or measure amplitude,
An evaluation method for a circular pipe, comprising: evaluating a circular pipe and / or a fluid in the circular pipe from the measurement result. The method for evaluating a circular pipe according to claim 1, wherein the presence / absence or size of a defect on the inner surface of the circular pipe is obtained based on at least the measured amplitude.   The method for evaluating a circular tube according to claim 1, wherein the type and / or state of the fluid is determined from the measured propagation time. The method for evaluating a circular pipe according to claim 1, wherein the soundness of the lining on the inner surface of the circular pipe is evaluated based on the measured amplitude.   Detecting the ultrasonic wave at a specific position on the outer periphery of the circular tube while propagating the ultrasonic wave along the circumferential direction of the circular tube or cylindrical container (hereinafter referred to as a circular tube),
  Measure the propagation time of ultrasonic waves propagating in the fluid inside the tube wall and inside the tube,
  A method for evaluating a circular tube, comprising: obtaining an average thickness of the circular tube based on the measured propagation time of the ultrasonic wave.

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