JP2006322902A - Method for measuring thickness of deposit layer on inner surface of tubular body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure thickness of a deposit layer deposited on the inside of a tubular body by using a plate wave, particularly a Lamb wave, as an ultrasonic wave propagated by the tubular body. <P>SOLUTION: One probe contactor 2 of a pair of probe contactors 2, 3 is fixed to the outer surface of the tubular body to be inspected. The other probe contactor 3 is installed so as to be freely moved on the outer surface of the tubular body 1 to be inspected. The Lamb wave is propagated by the tubular body by the transmission and reception of the ultrasonic wave between both the probe contactors while moving the other probe contactor. The propagation time and the amplitude of the ultrasonic wave received by the probe contactor are measured with respect to the transmitted frequency. By at least three relationships selected from the propagation distance, amplitude, frequency, and propagation time, an estimation value is obtained about the thickness of the deposit layer on the inner surface of the tubular body. The method is used for measuring the thickness of the deposit layer of the tubular body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to the thickness of an inner surface adhesion layer of a cylindrical body for measuring the thickness of an adhesion layer such as dirt adhered to the inside of a cylindrical body such as a pipe, tank, reactor, drum, etc. It relates to a measurement method.

  In general, chemical plants and other industrial facilities are provided with a large number of tubular bodies such as pipes that are connected to heat exchangers, distillation towers, etc., and these tubular bodies pass inside when used. Depending on the substance, various stains adhere.

  If the raw material fluid adheres to a cylindrical body such as the above-mentioned pipe until it is solidified by crystallization or the like to form a laminated state, the flow resistance increases and the production efficiency decreases, or safety due to an increase in the pressure in the cylindrical body There is a concern of causing various problems such as problems and a decrease in product purity.

  In order not to cause such a problem, the cylindrical body is periodically cleaned. However, this cleaning operation requires a temporary stop of the manufacturing process, and the manufacturing time is delayed by the operation, and the economic loss is great. Even if there is not much dirt and there is no need for cleaning, a cleaning operation may be performed.

  By the way, as a method of confirming the state of dirt inside the cylindrical body, a method of visually confirming the inside by removing the piping, a method of visually confirming the interior by opening the lid of the reactor, drum, etc. A method for visually confirming the inside of the cylindrical body is mentioned. However, this method requires operations such as removal of the pipe and opening of the lid, and furthermore, since there are blind spots, it is not always possible to completely check visually. For this reason, it is difficult to grasp the degree of dirt on the inner surface of the cylindrical body, and it is difficult to reliably check the degree of dirt adhesion in a wide range.

  On the other hand, as another method for measuring the amount of dirt adhered inside the cylindrical body, an ultrasonic wave is vertically incident on the outer peripheral surface from the outside of the cylindrical body, and the internal adhesion layer is reflected from the reflected wave on the surface of the adhesion layer. A so-called vertical method for measuring the thickness of the film is known.

  Further, as an ultrasonic flaw detection method for a thin plate having a plate thickness change such as a steel plate having a welded portion, a transmission method using a plate wave by ultrasonic waves (see Patent Document 1) is known.

JP 11-118771 A (Claims)

  However, in the method for measuring the thickness of the adhering layer in the cylindrical body by the above vertical method, particularly when the cylindrical body is thin and the thickness of the adhering layer is thin, it is difficult to separate the reflected waves from both. In addition, when the thickness of the adhesion layer is large, attenuation of the reflected wave by the adhesion layer is large, and it may be difficult to measure the thickness.

  Furthermore, since a dirt adhesion layer is not always uniformly formed inside the cylindrical body, even if only a part of the cylindrical body to be inspected is measured by the vertical method, There is a need for a method for measuring the thickness of a cylindrical body inner surface adhesion layer that cannot grasp the degree of adhesion and can grasp the degree of formation of the cylindrical body adhesion layer over a wide range.

  On the other hand, the ultrasonic flaw detection method described above has not been adopted as a method for measuring the amount of dirt adhered in the cylindrical body. In addition, this method can detect changes in plate thickness due to ultrasonic waves, but since longitudinal waves are used, the components of the liquid part and the solid part are the same when applied to an actual pipe or tank. Therefore, even if there is no clear boundary in density, and there is no liquid on the adhesion layer, the reflected wave from the surface of the adhesion layer tends to attenuate and decrease in amplitude. There is a tendency that it is difficult to obtain a reflected wave in the shape.

  Accordingly, an object of the present invention is to measure the thickness of an adhesion layer attached to the inside of a cylindrical body by using a plate wave, particularly a Lamb wave, as an ultrasonic wave propagated through the cylindrical body.

  According to the present invention, one of the pair of probes is fixed to the outer surface of the cylindrical body to be inspected, and the other probe is movable on the outer surface of the cylindrical body to be inspected. Install and move the other probe while transmitting and receiving ultrasonic waves, particularly burst waves, between the two probes to propagate Lamb waves to the cylindrical body, The propagation time and amplitude of the ultrasonic wave received by the probe are measured, and the thickness of the adhesion layer adhered to the inner surface of the cylindrical body from at least three relationships selected from the propagation distance, amplitude, frequency and propagation time. The above-mentioned problem has been solved by using the method for measuring the thickness of the inner surface adhesion layer of the cylindrical body for obtaining the estimated value of the thickness.

  When an ultrasonic wave is incident on the constituent member of the cylindrical body to be inspected, a plate wave, which is a kind of surface wave among the ultrasonic waves, propagates in the constituent member of the cylindrical body. Of these plate waves, Lamb waves are reflected on the outer surface of the cylindrical member, the inner surface, and the surface of the layer composed of deposits adhering to the inner surface. A phenomenon in which waves and shear waves are generated occurs. For this reason, as the propagation of Lamb waves progresses, many modes are mixed.

  In the present invention, since the other probe is movably installed on the outer surface of the cylindrical body, the propagation distance can be changed between one probe and the other probe. The number of Lamb wave modes varies depending on the propagation distance, and the propagation time and amplitude of the Lamb wave in the receiving probe change.

  Therefore, by measuring the propagation time and amplitude while changing the propagation distance, and further taking the data by changing the frequency of the ultrasonic wave, the four factors of propagation distance, propagation time, frequency and amplitude can be obtained. Changed data can be taken, and from these, relational data indicating a relation such as a three-dimensional diagram can be obtained from at least three relations. For example, by paying attention to a predetermined frequency, relational data such as a three-dimensional diagram of propagation distance, amplitude, and propagation time can be obtained. Further, by paying attention to a predetermined propagation time, relational data such as a three-dimensional diagram of propagation distance, amplitude and frequency can be obtained. Furthermore, since the propagation speed can be derived from the propagation distance and propagation time, relational data such as a three-dimensional diagram of propagation speed, frequency and amplitude can be obtained from each of the above data.

  By comparing the relational data such as these three-dimensional diagrams with a three-dimensional diagram obtained by the same method by attaching a deposit of a specific thickness to the inner peripheral surface of the cylindrical body to be inspected, The thickness of the adhesion layer can be estimated.

  According to the method for measuring the thickness of the cylindrical body inner surface adhesion layer according to the present invention, a pair of probes are installed on the outer surface of a cylindrical body to be inspected, and one of the probes is fixed and the other probe is fixed. In this method, the thickness of the adhesion layer adhering to the inner surface of the cylindrical body is measured by allowing the probe to move and transmitting and receiving ultrasonic waves with the pair of probes.

  That is, as shown in FIG. 1, a pair of transmitting probe 2 and receiving probe are formed on the outer surface of a cylindrical body 1 to be inspected (the figure shows a partial cross section of the cylindrical body). 3, and transmitting and receiving ultrasonic waves between the probes 2 and 3, the plate wave 4 is propagated through the tubular body 1. Then, either one of the transmission side probe 2 and the reception side probe 3 is fixed to the outer surface of the cylindrical body 1, and the other is installed so as to be movable on the outer surface of the cylindrical body 1. In this specification, the transmitter probe 2 is described as a fixed probe and the receiver probe 3 is described as a movable probe. However, a probe with the receiver probe 3 fixed is described. Even if the probe is a probe and the transmitter probe 2 is a movable probe, the same operation and effect can be obtained.

  As an apparatus for fixing the transmitting probe 2 and making the receiving probe 3 movable, as shown in FIG. 2, the transmitting probe 2 is fixed to a guide 6 and a fixing member 7 is used. And a device in which the receiving probe 3 is attached to a slide member 8 that is movable along the rail 5 provided on the guide 6. When this apparatus is used, the receiving side probe 3 can move in the direction along the rail 5. When this apparatus is used, the receiving side probe 3 is moved linearly in the axial direction of the cylindrical body 1 by installing the guide 6 in the axial direction of the cylindrical body 1 to be inspected. It becomes possible.

  Said apparatus is connected to the cylindrical body 1 using the connection members 9 and 10 of the both ends of a guide. At this time, when the cylindrical body 1 is made of a material attached to a magnet such as steel, it is preferable to use a magnet as the connecting members 9 and 10 because the apparatus can be easily attached to and detached from the cylindrical body 1.

  The cylindrical body 1 is a pipe, a tank, a reactor, a drum, or the like, and a part of an apparatus or facility in which a main part is formed in a cylindrical shape so that a substance can be stored or passed inside or a part thereof. It refers to the whole and does not mean only a particularly limited form.

  Moreover, the deposit | attachment in this invention is a substance which consists of the substance stored or passed inside this cylindrical body 1, or that substance origin, and is generally solid form or a gel form.

  Next, the ultrasonic wave transmitted from the transmission side probe 2 has a frequency within a predetermined range, and is incident on the constituent member of the cylindrical body 1 at a predetermined incident angle θ as shown in FIG. Among the incident ultrasonic waves, a plate wave propagates in the constituent members of the cylindrical body 1. The plate wave is an elastic wave that propagates along a plate having a finite thickness and an infinite width under ideal conditions. This plate wave is divided into two modes, a Lamb wave and an SH wave. Of these, the SH wave has particles in the medium parallel to the plane on which the ultrasonic wave is incident and perpendicular to the propagation direction. A wave that vibrates in a direction. The Lamb wave is a wave that propagates in a solid plate having a sufficient width with respect to the thickness in which a longitudinal wave and a transverse wave are mixed and integrated. This transverse wave is called an SV wave. The SV wave is a wave transmitted by particles in a medium oscillating in a direction perpendicular to the plane on which the ultrasonic wave is incident and perpendicular to the wave propagation direction. .

  When ultrasonic waves are incident on the constituent members of the cylindrical body 1 obliquely, as shown in FIG. 3, among the ultrasonic plate waves, a transverse wave (dotted arrow in FIG. 3) and a longitudinal wave (in FIG. 3). A Lamb wave having a solid line arrow) is reflected by the inner surface of the constituent member of the cylindrical body 1, and a longitudinal wave and a transverse wave are generated upon reflection. Next, these transverse waves and longitudinal waves are reflected by the outer surface of the constituent member of the cylindrical body 1, and further longitudinal waves and transverse waves are generated. Such a phenomenon is called mode conversion. Since the Lamb wave repeats mode conversion indefinitely, when the propagation distance becomes longer, a longitudinal wave and a transverse wave of a plurality of modes are mixed and integrated into a wave that propagates.

  By the way, the vibration of the Lamb wave appears as vibration between the inner surface and the outer surface of the constituent member of the cylindrical body 1 when one point of the constituent member of the cylindrical body 1 is viewed. As shown in FIG. 4, the A mode (asymmetric mode, see FIG. 4A) in which the phases of the inner surface and the outer surface are the same, and the S mode (symmetric mode, in which the phases of the inner surface and the outer surface are opposite to each other. 4 (b)). In this case, when viewed from an intermediate surface between the inner surface and the outer surface, in the A mode, vibration is also generated in the intermediate surface, but in the S mode, vibration is not generated in the intermediate surface.

  In general, when an ultrasonic wave is incident from one side of a plate member such as the constituent member of the cylindrical body 1, the A mode is more likely to be generated. On the other hand, if the ultrasonic wave is simultaneously incident from both sides of the plate member, the S mode is likely to be generated. Become. In the measurement of the present invention, since ultrasonic waves are incident only from the outer surface, an asymmetric A mode is more likely to occur preferentially among Lamb waves, and it is desirable to use the A mode. It should be noted that the judgment of whether the predetermined wave is the A mode or the S mode is based on the relationship between the frequency of the received plate wave × the plate thickness and the phase velocity when there is no adhesion layer. Can be determined.

  When the deposit adheres to the inner surface of the cylindrical body 1, as shown in FIG. 1, a part of the Lamb wave propagating inside the constituent member of the cylindrical body 1 is the surface of the adhesion layer a, that is, the adhesion layer. Reflection and mode conversion occur at the interface between a and the internal substance b inside the cylindrical body 1 (only reflected waves are shown in FIG. 1). For this reason, the Lamb wave which propagates the inside of the structural member of the cylindrical body 1 and the Lamb wave which reflects and changes its mode on the surface of the adhesion layer a coexist. These Lamb waves are different in phase, and this difference varies depending on the type and thickness of the adhesion layer a.

As a typical method for generating the above plate wave, in particular, the Lamb wave, there is a method of selecting the incident angle θ of the ultrasonic wave to the constituent member of the cylindrical body 1 within a predetermined range. Assuming that the longitudinal wave propagation velocity of the medium (water) is Vw, the phase velocity in the medium (for example, steel) is Vp, and the incident angle is θ, the plate wave mode having the phase velocity Vp is stressed when the following equation is satisfied. Can be generated.
Vp = Vw / sinθ

  As said incident angle (theta), in order to confirm a plate wave clearly, 10-60 degrees is good and 20-40 degrees is preferable.

  When a plate wave is generated, the mode existing in the medium changes with the product of the frequency and the plate thickness as a parameter, but since many waves do not have only a single frequency, the type of the adhesion layer a Even if the thickness is the same, the wave received by the receiving probe 3 may differ depending on the type of ultrasonic wave generation source. Therefore, by using a burst wave having a substantially single frequency as the applied waveform, a specific mode can be generated by adjusting only the angle. In order to make the frequency of the burst wave closer to a single wave, the number of sin waves used for the burst wave may be increased appropriately to increase the duration.

  The burst wave (a) can be created by multiplying a Gaussian function (b) and a continuous sin function (c) as shown in FIG. As a result, the rising and falling amplitudes of the burst wave are reduced, and a single frequency component wave is easily obtained.

  The frequency of the burst wave is preferably 0.1 to 1 MHz, and more preferably 0.2 to 0.7 MHz, in order to make the frequency band in which the number of generated modes does not increase so much.

Next, the procedure of the method for measuring the thickness of the cylindrical body inner surface adhesion layer according to the present invention will be described.
First, the apparatus shown in FIG. 2 is attached to the outer surface of the cylindrical body 1 to be inspected. Next, the transmission side probe 2 is fixed by fixing the water reservoir member 12 to which the transmission side probe 2 is attached to the outer surface of the cylindrical body 1. On the other hand, by installing the water reservoir member 11 to which the receiving side probe 3 is attached at a position away from the transmitting side probe 2 by a predetermined distance, the receiving side probe 3 is set at a predetermined position. Water is put in the water reservoir members 11 and 12 and attenuation of the transmitted ultrasonic waves can be suppressed.

  Although not shown in FIG. 2, as shown in FIG. 6, a burst wave generated by an arbitrary waveform generator and enhanced by a power amplifier is sent to the transmission-side probe 2. Lamb waves propagate through the components and are received by the receiving probe 3. The received wave is checked with an oscilloscope via a pulsar receiver, and the amplitude and propagation time are measured.

  Next, the reception-side probe 3 is moved, the distance between the transmission-side probe 2 and the reception-side probe 3, that is, the propagation distance is changed, and the amplitude and propagation time are similarly measured. Thereby, measurement data on the relationship between the propagation distance, the amplitude, and the propagation time is obtained.

  If necessary, the amplitude and propagation time may be measured in the same manner by changing the frequency of ultrasonic waves such as burst waves before or after the measurement by changing the propagation distance. As a result, measurement data on the relationship between frequency, amplitude, and propagation time is obtained. As a result, in addition to the relationship between propagation distance, amplitude, and propagation time, data on the relationship between propagation time, amplitude, and frequency is obtained. Can do.

  As described above, the waves received by the receiving probe 3 are integrated with a plurality of mode waves. As described above, the waves inside the constituent members of the cylindrical body 1 are included. And the wave reflected and mode-converted by the surface of the adhesion layer a adhering to the inner surface of the cylindrical body 1. Depending on the type and thickness of the adhesion layer a, the phase and intensity of the wave reflected and mode-converted on the surface of the adhesion layer a change, so that the wave received by the receiving probe 3 is the type of the adhesion layer a. Varies with thickness. Therefore, the obtained measurement data varies depending on the type and thickness of the adhesion layer a.

  This measurement data is attached to the inner peripheral surface of the cylindrical body to be inspected using the same attachment as that constituting the adhesion layer a, thereby forming an adhesion layer having a specific thickness. Is compared with the control data obtained by measuring in the same manner as described above. Since the same data is obtained when the thickness of the adhesion layer a is the same, it is possible to estimate the thickness of the adhesion layer a.

  Specifically, as described above, by changing the two factors of the propagation distance and the frequency, the relational data including the four factors of the propagation distance, the frequency, the amplitude, and the propagation time can be obtained. From these, at least three relationships can be selected, and from these three relationships, relationship data indicating a relationship such as a three-dimensional diagram can be obtained. For example, by paying attention to a predetermined frequency, relational data such as a three-dimensional diagram of propagation distance, amplitude, and propagation time can be obtained. Further, by paying attention to a predetermined propagation time, relational data such as a three-dimensional diagram of propagation distance, amplitude and frequency can be obtained. Furthermore, since the propagation speed can be derived from the propagation distance and propagation time, relational data such as a three-dimensional diagram of propagation speed, frequency and amplitude can be obtained from each of the above data. Furthermore, by picking up the maximum amplitude among the above amplitudes, relational data such as a three-dimensional diagram such as maximum amplitude−propagation distance−frequency can be obtained.

  In addition, since the change in propagation time when the propagation distance is changed corresponds to the phase velocity of the wave, the relationship consisting of the three factors of frequency, amplitude, and phase velocity is obtained from the relationship data consisting of the above four factors. Data is obtained.

  Compare these relationship data such as 3D diagrams with the relationship data such as 3D diagrams obtained in the same way by forming an adhesion layer with a specific thickness on the inner peripheral surface of the cylindrical body to be inspected. By doing so, the thickness of the adhesion layer can be estimated. Of the above four factors, it is preferable to assemble the relational data using the amplitude as an essential factor because the comparison becomes easy.

  In addition, about the deposit | attachment which comprises the said adhesion layer a, although the same thing was used by measurement data and contrast data, this is stored in the inside, when the usage form of an actual cylindrical body is considered. Alternatively, since the substance to be passed is limited to a specific substance, as a result, the kind of deposit is limited to the specific substance, and the measurement side can judge that the substance is something. This is because I thought.

  Further, in the case of alpha olefin, acrylic resin, gypsum, aluminum hydroxide or the like as the deposit constituting the adhesion layer a, the estimated value of the thickness of the adhesion layer on the inner surface of the cylindrical body 1 is obtained by the measurement method described above. It is possible to ask.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
A steel pipe having a thickness of 3.5 mm, an outer diameter of 48.6 mm, and a length of 300 mm was used as a cylindrical body to be inspected using the apparatus shown in FIG.
First, on the inner surface of the steel pipe, alpha olefin (manufactured by Mitsubishi Chemical Co., Ltd .: Dialene 30, component and content: carbon number 30 to 95% (including carbon number 28 or less 5%)) melting point: 75 ° C to 85 ° C , Density: 0.78 to 0.79 g / cm ³ (90 ° C.) was applied to a thickness of 1 mm or 2 mm to form an adhesion layer.
Next, the apparatus shown in FIG. 2 was joined to the steel pipe with the connecting members 9 and 10 made of magnets. And the water reservoir members 11 and 12 were installed on the steel pipe. The apparatus shown in FIG. 6 is connected to the transmitting probe 2 and the receiving probe 3 of the above apparatus so that burst waves can be transmitted and received waves can be analyzed.

Then, 10 burst waves are used as incident waves incident from the transmission side probe 2, and the frequency is changed by 0.05 MHz from 0.25 MHz to 0.55 MHz. Waves were received and amplitude (V) and propagation time were measured. In this case, the received wave was an A mode wave.
Next, the position of the receiving probe 3 was changed little by little to change the propagation distance (mm), and the measurement was performed in the same manner as described above.
About the obtained result, the three-dimensional figure of the relationship of propagation distance (mm)-propagation time (s)-amplitude (V) is shown in FIGS. FIG. 9 shows three-dimensional data of the relationship of propagation distance (mm) −frequency (kHz) −maximum amplitude (V) when the amplitude is maximum.

(result)
7 (a) to 7 (g) and FIGS. 8 (a) to 8 (g), the propagation distance-propagation time in the case of an adhesion layer (alpha olefin) having a specific thickness and a predetermined incident wave frequency- A three-dimensional diagram of the amplitude is shown.
As is apparent from FIGS. 7A to 7G and FIGS. 8A to 8G, the shape of the three-dimensional diagram of propagation distance-propagation time-amplitude is completely different depending on the frequency of the incident wave. For this reason, it is possible to select the frequency of the incident wave that can be more easily determined depending on the type of the deposit.

  Further, as is clear from the comparison between FIGS. 7A to 7G and FIGS. 8A to 8G, even if incident waves with the same frequency are used, the propagation distance − The shape of the three-dimensional diagram showing the propagation time-amplitude relationship is completely different. For this reason, from the shape of the three-dimensional diagram of propagation distance-propagation time-amplitude obtained by measuring the cylindrical body in actual use by changing the thickness of the adhesion layer in advance, It is possible to easily estimate the thickness of the adhesion layer.

  Further, FIG. 9 shows a three-dimensional diagram of the relationship of propagation distance-frequency-maximum amplitude. FIG. 9 shows changes in propagation distance and frequency of the maximum amplitude, and it is possible to grasp the change tendency of the amplitude, that is, interference.

(Example 2)
Instead of alpha olefin, gypsum (Wako Pure Chemical Industries, Ltd .: baked gypsum, ingredients and content: calcium sulfate (0.5 water) 97% or more, 2.96 g / cm ³ (20 ° C.) (anhydrous As an example, except that an adhesive layer was formed by applying the material to a thickness of 0 mm, 1 mm, 1.5 mm, 2.5 mm, 3 mm, and 4 mm. A body was prepared.

The plate wave measurement was performed in the same manner as in Example 1 above. Note that the propagation distance was two cases of 100 mm and 150 mm. The phase velocity was calculated from the propagation time difference between the propagation distance of 100 mm and 150 mm.
When there was no adhesion of gypsum, the received plate wave was an A mode wave. The propagation time was the falling edge of the first burst wave (the part where the amplitude was changed from positive to negative).
By the way, when comparing the results, in order to remove the influence due to the difference in the measurement environment, all amplitudes were normalized with reference amplitudes to obtain relative amplitudes. That is, the maximum amplitude (peak-to-peak value) of the response waveform obtained when a wave having a frequency of 0.45 MHz is incident when there is no adhesion layer, is set as 1.
Regarding the obtained results, the relationship diagram between the frequency (MHz) and the phase velocity (km / s) and the relationship diagram between the frequency (MHz) and the relative amplitude at the propagation distance of 150 mm are shown in FIGS. Show.

(result)
10 (b), (c), (e), and (f), when an adhesion layer (gypsum) is present, a sudden change in phase velocity occurs at a specific frequency, and the relative amplitude rapidly attenuates. (Near locations indicated by arrows in FIGS. 10B, 10C, 10E, and 10F). This abrupt change in the phase velocity originates from the generation of plate waves in modes other than the A0 mode used for measurement. At frequencies where other modes occur, a plurality of modes are received at the same time, and the plate waves of each mode interfere with each other, so the amplitude at that time is considered to be greatly attenuated. From this, it can be determined from the frequency-dependent attenuation of the amplitude that a plate wave of another mode is generated.

  As is clear from FIGS. 10A to 10F, the frequency at which the phase velocity changes suddenly varies depending on the thickness of the adhesion layer. From this, it is possible to predict the thickness of the adhesion layer from the value of the frequency at which the phase velocity changes suddenly and the amplitude becomes minimum by taking in advance data when the thickness of the adhesion layer is clear. Become.

  Note that changes in phase velocity and amplitude associated with the generation of this higher-order mode may not always be observed depending on the distance between the transmitter and the receiver (FIGS. 10A, 10D, etc.). By changing the propagation distance little by little, it is good to find a distance that can clearly identify the occurrence of the mode.

  Incidentally, even in the case of FIG. 9, there is a frequency at which the maximum amplitude falls. From this frequency value as well, in the same way as in the case of Example 2, it is considered that the thickness of the adhesion layer can be predicted by taking in advance data when the thickness of the adhesion layer is obvious. .

Explanatory drawing of the thickness measurement method of the cylindrical body inner surface adhesion layer The front view which shows the example of the measuring apparatus of the thickness of a cylindrical body inner surface adhesion layer Explanatory drawing of the incident angle of the probe in the plate wave generation method, and a schematic diagram showing the mode conversion of Lamb waves (A) Explanatory drawing about A wave (b) Explanatory drawing about S wave Illustration of how to create a burst wave Block diagram of the device used to measure the thickness of the adhesion layer on the inner surface of the cylindrical body

Three-dimensional diagram showing the relationship of propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 1 mm and the frequency of the incident wave is 0.25 MHz Three-dimensional diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 1 mm and the frequency of the incident wave is 0.30 MHz 3D diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 1 mm and the frequency of the incident wave is 0.35 MHz Three-dimensional diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 1 mm and the frequency of the incident wave is 0.40 MHz Three-dimensional diagram showing the relationship of propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 1 mm and the frequency of the incident wave is 0.45 MHz Three-dimensional diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 1 mm and the frequency of the incident wave is 0.50 MHz 3D diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 1 mm and the frequency of the incident wave is 0.55 MHz

Three-dimensional diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 2 mm and the frequency of the incident wave is 0.25 MHz Three-dimensional diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 2 mm and the frequency of the incident wave is 0.30 MHz Three-dimensional diagram showing the relationship of propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 2 mm and the frequency of the incident wave is 0.35 MHz Three-dimensional diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 2 mm and the frequency of the incident wave is 0.40 MHz Three-dimensional diagram showing the relationship of propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 2 mm and the frequency of the incident wave is 0.45 MHz Three-dimensional diagram showing the relationship of propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 2 mm and the frequency of the incident wave is 0.50 MHz 3D diagram showing the relationship between propagation distance-propagation time-amplitude when the adhesion layer (alpha olefin) is 2 mm and the frequency of the incident wave is 0.55 MHz Three-dimensional diagram showing the relationship of propagation distance (mm)-frequency (kHz)-maximum amplitude (V)

Relationship diagram of frequency-phase velocity and relationship of frequency-relative amplitude when there is no adhesion layer (gypsum) Relationship diagram of frequency-phase velocity and relationship diagram of frequency-relative amplitude when adhesion layer (gypsum) is 1 mm Relationship diagram of frequency-phase velocity and relationship diagram of frequency-relative amplitude when adhesion layer (gypsum) is 1.5 mm Relationship diagram of frequency-phase velocity and relationship diagram of frequency-relative amplitude when adhesion layer (gypsum) is 2.5 mm Relationship diagram of frequency-phase velocity and relationship diagram of frequency-relative amplitude when adhesion layer (gypsum) is 3.0 mm Relationship diagram of frequency-phase velocity and relationship diagram of frequency-relative amplitude when adhesion layer (gypsum) is 4.0 mm

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical body 2 Transmission side probe 3 Reception side probe 4 Sheet wave 5 Rail 6 Guide 7 Fixing member 8 Slide member 9 Connection member 10 Connection member 11 Water reservoir member 12 Water reservoir member a Adhesion layer b Internal substance

Claims (2)

While fixing one probe of the pair of probes to the outer surface of the cylindrical body to be inspected, the other probe is installed so as to be movable on the outer surface of the cylindrical body to be inspected,
By moving ultrasonic waves between the two probes while moving the other probe, Lamb waves are propagated through the cylindrical body, and the transmitted frequency is received by the probe. Measure the propagation time and amplitude of ultrasound,
A method for measuring the thickness of a cylindrical body inner surface adhesion layer, which obtains an estimated value of the thickness of the adhesion layer adhered to the inner surface of the cylindrical body from at least three relationships selected from the above propagation distance, amplitude, frequency and propagation time. The method for measuring the thickness of the cylindrical body inner surface adhesion layer according to claim 1, wherein the ultrasonic wave is a burst wave.