JP2001324483A - Evaluation method of pipe - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To easily evaluate the average thickness of a circular pipe, the presence or absence of a defect, or the fluid in the circular pipe by ultrasonic waves propagating in the circular pipe in the circumferential direction. SOLUTION: An ultrasonic wave is incident on the inside of a wall of a circular tube 10 and propagates in the wall of the circular tube while undergoing multiple reflections on the inner and outer surfaces of the circular tube 10. The propagation time and / or amplitude is measured for each of the waves propagating through a plurality of paths that enter the inside of the pipe wall again after being incident on the fluid, and the average wall thickness of the pipe, presence or absence of defects inside the pipe, The presence / absence of a lining defect and the presence / absence and type of fluid inside the circular pipe are determined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a circular tube, and more particularly to a method for evaluating the thickness of a circular tube and a cylindrical container (these are collectively referred to simply as a circular tube in this specification) using ultrasonic waves. To detect the presence or size of a defect, the presence 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 a high-pressure gas (hereinafter referred to as a fluid) inside the circular tube. About the method.

[0002]

2. Description of the Related Art In general, a pulse echo type ultrasonic thickness gauge is used in contact with a position to be measured, so that a thickness distribution and an average thickness along a circumferential direction of a circular pipe are measured. Measurement 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.

In addition to the above-described pulse-echo 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 scheme requires a special analysis to identify the waves of many modes.

[0004] Because of the above-mentioned problems in the prior art, a method for simply measuring the thickness of a circular tube has been desired.
In addition, evaluation of the soundness of the lining formed on the circular pipe,
There is a need for a method for easily determining or evaluating the presence or absence and size of defects on the inner and outer surfaces of a circular tube, and also the type and state of a fluid inside the circular tube.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to an average thickness of a circular pipe containing a fluid therein, the presence or absence of a defect on the inner and outer surfaces of the circular pipe, a defect of a lining on the inner and outer surfaces of the circular pipe, and furthermore, The present invention provides a method for evaluating a circular pipe, which is suitable for inspecting the type and state of a fluid in the circular pipe.

[0006]

According to a preferred embodiment of the method for evaluating a circular tube according to the present invention, an ultrasonic wave is applied to the inside of the circular tube by an ultrasonic sensor and is superposed along a circumferential direction of the circular tube. The first wave propagating in the wall of the circular tube while propagating the sound wave and observing the ultrasonic wave at a specific position on the outer periphery of the circular tube while being reflected multiple times on the inner and outer surfaces of the circular tube, propagates in the wall of the circular tube, and then the first wave. A second wave that is incident on the fluid inside the pipe at a predetermined position, and then re-enters the pipe wall, and propagates through the pipe wall and then
The third wave incident on the fluid inside the circular tube at the predetermined position, and further reflected on the inner surface of the circular tube at the first predetermined position and then incident again on the wall of the circular tube, are stored in the digital memory, respectively. The waveforms are stored after being synchronously added a plurality of times, and the waveform data is digitally processed to calculate the propagation time and amplitude of each wave. The propagation path of each wave is analyzed based on the calculated propagation time and amplitude, and the average wall thickness of the circular pipe, defects existing on the inner and outer surfaces of the circular pipe, defects in the lining of the lined circular pipe, and the inside of the circular pipe Any one or more of the type and / or state of the liquid is determined.

A transverse wave incident in the circumferential direction of a circular tube containing a fluid therein propagates in the circumferential direction while being repeatedly reflected on the inner and outer surfaces of the circular tube. When a fluid or solid is in contact with the inside of the circular tube without any gap, a part of the energy of the wave reflected on the inner surface of the circular tube is transmitted to the fluid or solid in contact with the inner surface of the circular tube. As a result, waves propagating only in the wall of the pipe and waves propagating in the wall of the pipe and then passing through a fluid or solid in contact with the inner surface of the pipe and entering the wall of the pipe and propagating are super- Received by the acoustic sensor. The latter includes a plurality of waves passing through different paths, and their propagation times are different from the waves propagating mutually and only within the wall of the pipe. It is possible to evaluate the fluid inside the tube and / or the circular tube.

[0008] If a defect exists on the inner surface and / or outer surface (inner and outer surfaces) of the circular tube, the waves are irregularly reflected, so that the reception amplitude decreases. Further, when the inner surface of the circular tube is lined, the ultrasonic waves generally do not pass through the imperfect joint between the lining and the inner surface of the circular tube. 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 properties of the circular pipe, the lining material, and the internal fluid are known, the wall thickness of the circular pipe and the thickness of the lining can be obtained from the propagation time difference. Is obtained from the propagation time of the scattered wave from the defect.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings based on embodiments of the present invention. FIG.
1 is a schematic cross-sectional view of a circular pipe showing the principle of a method for evaluating a circular pipe by a circular pipe soundness evaluation apparatus according to an embodiment of the present invention.

The soundness evaluation device includes an ultrasonic sensor 11 comprising a pair of ultrasonic probes 21 and 22 arranged in contact with the outer surface of a circular tube 10, and one probe 2 of the ultrasonic sensor 11.
1, a pulse transceiver 12 that transmits a pulse for generating an ultrasonic wave and receives an ultrasonic electric signal received by the other probe 22 of the ultrasonic sensor 11;
The digital recording device 13 includes a digital recording device 13 that records the signal received in step 2, and a digital waveform processing device 14 that analyzes the recorded signal and evaluates the circular tube. High pressure gas or various liquids are accommodated in the inside of the circular tube 10.

In the soundness evaluation apparatus of the present embodiment, one probe 21 of the ultrasonic sensor 11 is used in a circumferential direction from an arbitrary position (the top in the drawing) of the outer periphery of the circular tube 10. A propagating transverse wave is incident, and the propagating wave is detected using the other probe 22 of the ultrasonic receiving sensor 11.
The pulse receiver 12 receives the signal in synchronization with the transmitted ultrasonic wave, and records the signal 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.

FIG. 2 shows that the recorded wave of the ultrasonic wave received at the same position as the transmission position of the ultrasonic wave includes a waveform corresponding to each propagation path. The waveform in FIG. 3A is obtained when the inside of the circular tube is air, and the waveform in FIG. 3B is obtained when the inside of the circular tube is water. In both FIGS. 2A and 2B, the leftmost wave W1 represents the transmission wave and the rightmost W1.
Numeral 2 indicates a wave that reaches the adjacent probe directly, and wave W3 indicates a wave that propagates around the wall of the circular tube. In FIG. 5B, a wave packet including waves W4 and W5 adjacent to W3 and having different paths from the wave packet W3 is detected, and it can be understood that ultrasonic waves transmitted through a liquid such as water can be effectively detected. .

[0013] There are three typical propagation paths of ultrasonic waves. In other words, as shown in FIG. 3, the point P is set as the point of incidence of the ultrasonic wave, passes through the inside of the tube wall via the arc PB, the first path followed by the wave W3 passing only inside the tube wall,
Next, the wave W4 that passes through the fluid in the pipe via the chord BC and enters the pipe wall at the point C again follows the second path, and passes through the pipe wall via the arc PA. And then string A
This is a third path along which the wave W5 that passes through the fluid in the circular pipe via B and the chord BC and then enters the circular pipe wall at the point C again.

Assuming that the velocity of the transverse wave in the pipe wall is V _T and the velocity of the longitudinal wave in the fluid is _VL , the propagation time of each path is given by the following equation. Propagation time t _{0 of} wave W3 propagating in the first path
Is: t ₀ = C · π · (dt) / V _T (1) The propagation time t ₁ of the wave W4 propagating in the second path is t ₁ = L / V _L + t ₀ · (2π−∠ (COB) / 2π (2) The propagation time t ₂ of the wave W5 propagating in the third path is t ₂ = 2L / V _L + t ₀ · (2π−∠COA) / 2π (3)

In the above equations (1) to (3), C is a correction coefficient depending on the outer shape and thickness of the circular pipe, d is the outer diameter of the circular pipe, t is its thickness, and L is the chord AB and BC. Length. String AB and String B
The central angle of C (∠AOB and ∠COB) is geometrically determined by the angle of the transmitting and receiving ultrasonic sensor, the inner diameter of the circular tube, and Snell's law (transverse sound speed of the circular tube, longitudinal wave speed of the fluid).

When the transverse sound velocity V _T inside the pipe and the outer diameter d of the pipe are known, the wall thickness t of the pipe is obtained from equation (1) by actually measuring the propagation time t ₀ of the wave W3. Can be

When a fluid exists inside the circular pipe or when the density of the fluid is higher, the component of the wave passing through the fluid increases, so that it is determined whether or not the fluid exists inside the pipe. State detection is also possible. Transverse sound speed V of circular pipe
_{If T} , the outer diameter d, and the thickness t are known, the longitudinal wave velocity in the fluid can be obtained by repeated calculation from the measured arrival times t ₀ , t ₁ , and t _{2 of} each wave. Thus, the type and density of the fluid can be estimated.

The amplitude of each wave is maximum when there are no defects on the inner and outer surfaces of the tube. In the case of a transverse ultrasonic wave traveling in the wall of a circular tube, if a defect exists in the circumferential direction on the inner and outer surfaces of the circular tube, the wave is irregularly reflected, 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, it is possible to estimate the presence or absence and size of a defect at a specific position. 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 is changed. Can be detected.
Even if there is a lining on the inner or outer surface of the pipe,
With the same concept, an incomplete portion of the lining can be detected.

For example, if there is wall thinning as a defect in a circular pipe,
The time t ₁ obtained by the equation (2) is different from the actually measured propagation time of the wave W4. Also, when the shape of the inner surface changes due to a defect and irregular reflection occurs, the observed amplitude changes. Furthermore,
Defects on the outer surface of the circular tube can be determined from the measured value of the propagation time t _{0 in} equation (1). In this case, the propagation time t ₁ in equation (2) also changes.

The lengths L of the strings AB and BC are known,
In addition, when the wall thickness is sound, the type of fluid can be determined from the difference between the calculated propagation times t ₁ and t ₂ and their measured values. In this case, if the density of the fluid is large, the point B
Shifts away from the point A, and the propagation time is shortened.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A steel tube has a refraction angle of 70 on the steel tube surface.
The calculation was performed for the case where the transmitting and receiving ultrasonic probe was disposed at the same position and the frequency was 5 MHz. Outer diameter 60mm, thickness 3mm, shear wave speed 3250m
/ S, in the case of a steel pipe having no fluid inside, only waves that have made a round in the wall of the pipe are effectively observed. Ultrasonic arrival time (propagation time) is calculated as 63μs
It is. If the inside of this tube is filled with water,
In addition to this wave, two waves arriving at equal time differences are observed. The arrival time difference is about 12 μs.

FIG. 4 shows an outer diameter of 60 mm and a thickness of 3 mm.
The figure shows the result obtained by calculating the propagation path in a steel circular pipe having a shear wave velocity of 3250 m / s. here,
In the third path, the point of incidence A from steel to water at the interface between steel and water, the point of reflection B, and the point of incidence C from steel to water are respectively located at 0 degrees from the point of incidence P of ultrasonic waves. The position is about 90 degrees, 218 degrees, and 346 degrees counterclockwise. Reflection point B
Is also the point of incidence from steel to water in the second path.

In practice, the ultrasonic wave propagating in the wall of the pipe is
At the point of incidence from the ultrasonic probe, the ultrasonic wave has a width of about 60 to 90 degrees from the vertical line formed on the circumference, so that the ultrasonic wave becomes a band-like wave as shown in FIG. Since the longitudinal sound velocity of water is 1500 m / s, the refraction angle on the water side is about 26 degrees according to Snell's law when the steel-side refraction angle is 70 degrees.

Various pipes having a 2 mm thick vinyl chloride sheet attached to the inner surface of a circular tube having the above structure were prepared. Ultrasound cannot penetrate a vinyl chloride sheet of this thickness.
A vinyl chloride sheet attached to the entire inner surface of a circular tube, one not attached at all, and an inner surface divided into 12 equal parts in the circumferential direction, and any one of the divided parts Various types of steel circular pipes with open windows were manufactured, and the wave propagation path from the steel side to the water side or from the water side to the steel side was blocked / opened, so that the above-mentioned steel circular pipes The propagation path of the sound wave was confirmed.

FIGS. 6A and 6B show the case without the vinyl sheet 15 (FIG. 6A) and the one attached to the entire surface (FIG. 6B).
Are shown in comparison. Vinyl chloride 1 on the entire inner circumference
5A, only the wave propagating in the wall of the circular tube was observed in the circular tube to which the vinyl chloride was applied, and in the circular tube to which no vinyl chloride was affixed, as shown in FIG. In addition, three types of waves were observed.

Similarly, vinyl chloride 15 is not stuck at angles 210 ° to 240 ° and 330 ° to 360 °,
Therefore, the chloride pipe 15 is not stuck at an angle of 90 ° to 120 ° in addition to the above-mentioned circular pipe in which the path BC is opened by the window 16 (FIG. 7A). A circular pipe opened in the window 16 (FIG. (B)), and
(B) Three kinds of circular tubes (FIGS. (C) to (e)) in which one of the open windows 16 of the circular tube is slightly shifted are prepared, and ultrasonic waves propagating in each circular tube are transmitted. Observed.

In FIG. 7A, waves W3 and W4 on the first and second paths are observed, and in FIG. 7B, waves W3, W4 and W5 on the first to third paths are all observed. Was done. In the same figure (c), the first point A due to the interruption of the point of incidence A from the steel to the water.
And only the second waves W3 and W4 are observed. In FIG. 6D, only the wave W3 in the first path is observed due to the interruption of the reflection point B. In FIG. Similarly, only the wave W3 in the first path was observed by blocking the incident point C. From these observation results, it can be determined that the wave propagation path obtained by the above calculation is correct.

Although the present invention has been described based on the preferred embodiment, the method for evaluating a circular tube according to the present invention is not limited to the configuration of the above-described embodiment. Various modifications and changes from the configuration described above are also included in the scope of the present invention.

[0029]

As described above, according to the method for evaluating a circular tube according to the present invention, the circular tube and the ultrasonic wave incident on the circular tube are measured by a very simple method of measuring the propagation time and / or amplitude. And / or there is an effect that the fluid inside the circular pipe can be evaluated.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a soundness evaluation device that performs an evaluation method of the present invention.

FIG. 2 is a graph showing a waveform observed by the evaluation device of FIG. 1;

FIG. 3 is a cross-sectional view of a circular pipe showing a propagation path of a wave passing through the inside of the circular pipe.

FIG. 4 is a cross-sectional view of a circular tube showing a calculated wave propagation path.

FIG. 5 is a cross-sectional view of a circular tube showing a propagation path of a calculated wave packet.

6A and 6B are a cross-sectional view of a circular tube measured in the example and a graph showing an observed waveform, respectively.

7A to 7E are cross-sectional views of various circular tubes measured in the 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

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Junji Miyauchi 1 Sakaide-cho, Sakaide-shi, Kagawa F-term in the Sakaide Works of Mitsubishi Chemical Corporation (reference) 2G047 AB01 AB05 BA02 BC02 BC03 BC07 BC18 GA19

Claims (5)

[Claims] An ultrasonic wave is propagated along a circumferential direction of a circular tube or a cylindrical container (hereinafter referred to as a circular tube) while detecting ultrasonic waves at a specific position on the outer periphery of the circular tube, and multiple reflections are formed on inner and outer surfaces of the circular tube. A first wave propagating in the wall of the tube while propagating in the wall of the tube, a second wave propagating in the wall of the tube and then entering the fluid inside the tube at the first predetermined position and then again entering the wall of the tube And then propagates through the wall of the tube and then enters the fluid inside the tube at the second predetermined position, and further reflects at the inner surface of the tube at the first predetermined position and then re-enters the wall of the tube. For at least one of the incident third waves, the propagation time and / or
Alternatively, a method of evaluating a circular tube, comprising measuring an amplitude and evaluating a circular tube and / or a fluid in the circular tube from the measurement result. 2. The method for evaluating a circular pipe according to claim 1, wherein an average wall thickness of the circular pipe is obtained based on at least a propagation time of the first wave. 3. At least based on the measured amplitude,
To find the presence or size of a defect on the inner or outer surface of the pipe,
The method for evaluating a circular pipe according to claim 1. 4. The method for evaluating a circular pipe according to claim 1, wherein the type and / or state of the fluid is determined from the measured propagation time. 5. The method for evaluating a circular pipe according to claim 1, wherein the evaluation of the soundness of the lining on the inner surface or the outer surface of the circular tube is performed based on the measured amplitude.