JP2013083545A - Method and apparatus for detecting boundary surface states of multilayer pipeline by ultrasonic attenuation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detailedly and quickly determine mutual boundary surface states of a steel pipe 10 and resin lining 9 constituting multilayer pipeline at a plurality of parts thereof using difference in acoustic impedance densities for every steel pipe 10 and resin lining 9.SOLUTION: The apparatus for detecting boundary surface states of multilayer pipeline: applies ultrasonic waves to the surface of a steel pipe 10 the inner face of which is treated by resin lining 9; detects reflection light corresponding to ultrasonic waves reflected from their boundary with an ultrasonic detector 6 by advancement of ultrasonic waves excited at the surface of the steel pipe 10, to the inside of the steel pipe 10 and the resin lining 9; causes an arithmetic processing unit 8 to collect an attenuated waveform of the acoustic impedance density for every virtual lattice point on the steel pipe 10; and visualizes physical defect information generated on the boundary surface from the comparison results of integrated values, convergence widths and the like of exponential and approximation curves of attenuation waveforms at τ time.

Description

  The present invention relates to a method for detecting an interface state of a multilayer pipe by an ultrasonic attenuation method for detecting a defect generated at an interface between a steel pipe constituting the multilayer pipe and a resin lining coated on the inner surface of the steel pipe in a manufacturing process of the multilayer pipe. And an interface state detection device.

    In distribution pipes, especially steel pipes, corrosion of the inner surface has progressed due to water flow for many years, and various problems such as generation of red water and muddy water or adhesion of scale have occurred. For this reason, today, from the viewpoint of emphasizing environmental resistance, the spread of multilayer piping excellent in durability and corrosion resistance has been achieved. The multilayer pipe has a resin lining configuration in which, for example, hard vinyl chloride or polyethylene is coated (lining) on the inner surface of a steel pipe.

    The resin lining is obtained by press-fitting a hard vinyl chloride pipe or polyethylene pipe into the inner surface of a steel pipe in a multilayer pipe production line, and further heat-sealing, and these adhesion strengths become a quality factor as a pipe material. Yes. Therefore, if there is a gap between them, it becomes a serious problem in terms of quality maintenance. That is, in order to maintain the desired corrosion resistance and durability over a long period of time, quality control of the adhesive strength and thickness after the heat fusion becomes important. In quality control so far, an arbitrary number of multilayer pipes are extracted from the production line of multilayer pipes, and tests of the adhesiveness, adhesion and interface state of the resin lining to the steel pipe are carried out using various methods.

    However, when the quality of the resin lining for the steel pipe is determined by extracting the multilayer pipe as described above, the production line must be temporarily stopped and the film thickness of the resin lining must be measured with an electromagnetic film thickness meter. In addition, since it is necessary to perform such measurement over the entire length of the multilayer pipe, the measurement time and the number of measurement steps are increased, resulting in a disadvantage that the production efficiency of the multilayer pipe decreases.

  On the other hand, a defect inspection method for generating an elastic wave in a pipe-like object using a pulsed signal as an excitation source, detecting a reflected wave from the defect portion, and specifying the position of the defect on the pipe-like object Is known (see, for example, Patent Document 1). In addition, an ultrasonic reflection method that transmits ultrasonic waves, captures reflected waves from the tube material, and detects the thickness, defect, damage, etc. of the tube material in a non-contact manner has been proposed.

JP 2006-058291 A

  However, this defect inspection method can only detect defects directly under the excitation source, and it takes a lot of time to inspect the entire multi-layer piping, and there is a high possibility of overlooking the defects. There is an inconvenience that it is difficult to capture defect information according to the properties of the material.

  The present invention has been made in view of the above-described circumstances, and the purpose thereof is to utilize the attenuation waveform of the acoustic impedance for each steel pipe and resin lining constituting the multilayer pipe, and the adhesion state between the steel pipe and the resin lining, It is an object of the present invention to provide an interface state detection method and an interface state detection device for multilayer pipes by an ultrasonic attenuation method capable of discriminating the close state and the interface state in detail and quickly with respect to these plural parts.

  In order to achieve the above-described object, the interface state detection apparatus for multilayer piping by the ultrasonic attenuation method according to the present invention irradiates the surface of the steel pipe with the resin lining on the inner surface, and excites the surface of the steel pipe. An ultrasonic ultrasonic detector for detecting reflected light corresponding to ultrasonic waves reflected from the interface of the steel pipe and the resin lining and the inner surface of the resin lining as a result of the generated ultrasonic waves traveling into the steel pipe and the resin lining, The attenuation waveform due to the acoustic impedance density for each virtual lattice point set on the steel pipe obtained by the ultrasonic detector is collected, and from the comparison result of exponential approximation curves of the attenuation waveform, the steel pipe and And an arithmetic processing unit that visualizes physical defect information generated at the interface with the resin lining.

  With the above-described configuration, the ultrasonic waves collected on the surface of the steel pipe constituting the multi-layer pipe locally raise the temperature in the vicinity of the light collecting portion and cause volume expansion. For this reason, ultrasonic waves are excited on the surface of the steel pipe, the ultrasonic waves propagate so as to diffuse inside, and are attenuated while being repeatedly reflected at the interface between the steel pipe and the resin lining and the inner surface of the resin lining. The attenuation waveform of each reflected wave is observed using an ultrasonic detector.

  The observation information is an acoustic impedance density represented by the product of the density and sound velocity of each of the steel pipe and the resin lining. Therefore, by collecting the decay time and reflected output in which the reflected wave is attenuated by this acoustic impedance, that is, the decay waveform, comparing and verifying the exponential approximation curves with the decay time τ, the degree of adhesion between the steel pipe and the resin lining, It is possible to accurately determine the closeness and the interface state.

In the method for detecting an interface state of a multilayer pipe by the ultrasonic attenuation method according to the present invention, ultrasonic waves are excited on the surface of a steel pipe whose inner surface is resin-lined, and the ultrasonic waves proceed into the steel pipe and the resin lining. Thus, the vibration of the sound wave attenuated by the acoustic impedance peculiar to the material is applied to exp ^−βx (β is an attenuation constant), and the integrated value up to the attenuation time γ between the exponential approximation curves of the attenuation waveform and the convergence width Φ And the like, and the physical defect information generated at the interface between the steel pipe and the resin lining is visualized.

As a result, the physical state such as the bonding degree, adhesion degree and interface state between the steel pipe and the resin lining constituting the multilayer pipe, the attenuation waveform due to the acoustic impedance at the virtual lattice point in the steel pipe, the attenuation time τ between the exponential approximation curves Can be accurately estimated by comparing the integral value and convergence widths Φ ₁ , Φ _2, etc., and can be carried out with high accuracy and efficiency in a non-contact, non-destructive manner without stopping the production line for multilayer piping. To.

  ADVANTAGE OF THE INVENTION According to this invention, the interface state between a steel pipe and resin lining can be test | inspected in detail and rapidly about each pipe material using the attenuation waveform of the acoustic impedance density observed in the multiple places of multilayer piping.

  The present invention has been briefly described above. Further, the best mode for carrying out the invention described below will be described in detail with reference to the accompanying drawings.

It is a block connection diagram showing an interface state detection device for multilayer piping by an ultrasonic attenuation method according to an embodiment of the present invention. It is a longitudinal cross-sectional view which shows an example of the multilayer piping of FIG. It is a longitudinal cross-sectional view which shows the other example of multilayer piping. It is explanatory drawing which shows the control system of an ultrasonic device. FIG. 5 is an impulse response characteristic diagram of the control system shown in FIG. 4. It is an attenuation waveform figure of the reflected wave of the part where the interlayer of multilayer piping is sound. It is an attenuation waveform figure of a reflected wave when there is exfoliation between layers of multilayer piping. FIG. 7 is an exponential approximation curve of a reflection wave attenuation waveform when the layers of the multilayer pipe shown in FIG. 6 are healthy. FIG. 8 is an exponential approximation curve of an attenuation waveform diagram of a reflected wave when there is separation between layers of the multilayer pipe shown in FIG. 7. It is an exponential approximation curve obtained at a virtual lattice point on a steel pipe. It is explanatory drawing which shows the example of a setting of the virtual lattice point on a steel pipe. It is explanatory drawing which shows the example which also makes judgment about the area | region where the acoustic impedance density of a, b, and c differs on a steel pipe. It is a truth table which logically constitutes defect information of each mesh point of multilayer piping in this embodiment with an AND circuit.

  Hereinafter, an interface state detection device for multilayer piping by an ultrasonic attenuation method according to an embodiment of the present invention will be described with reference to the drawings.

An apparatus for detecting an interface state of a multilayered pipe by an ultrasonic attenuation method according to the present embodiment includes an ultrasonic oscillator that irradiates ultrasonic waves on the surface of a steel pipe whose inner surface is resin-lined, and the surface of the steel pipe that receives the ultrasonic waves. Ultrasonic detection that optically detects reflected light corresponding to ultrasonic waves reflected from the interface of the steel pipe and the resin lining and the inner surface of the resin lining as the excited ultrasonic waves travel into the steel pipe and the resin lining. For each virtual lattice point set on the vessel and the steel pipe, an attenuation waveform of the acoustic impedance density is sampled, and an integrated value at a time τ between the exponential approximation curves of the attenuation waveform, a convergence width Φ ₁ <Φ ₂ or An arithmetic processing unit that makes it possible to visualize physical defect information generated at the interface between the steel pipe and the resin lining based on a comparison result such as Φ ₁ > Φ _2. The

With this configuration, the physical state of the steel pipe and the resin lining, such as the degree of adhesion, adhesion, and interface state, is collected, and the attenuation waveform of the acoustic impedance density at multiple virtual lattice points in the steel pipe is collected. A normal determination output can be obtained by comparing the integral values at the time τ, the convergence widths Φ ₁ , Φ _{2, and the} like.

  As shown in FIG. 1, an apparatus for detecting an interface state of a multilayer pipe by an ultrasonic attenuation method according to the present embodiment includes an ultrasonic oscillator 1, a reflecting mirror 2 for projecting light, a light condensing lens 3 on a light projecting side, and light receiving. It comprises a side condenser lens 4, a light receiving reflection mirror 5, an ultrasonic detector 6, a waveform drawing unit 7, and an arithmetic processing unit (CPU) 8.

  Among these, the ultrasonic oscillator 1 generates ultrasonic waves. The reflection mirror 2 is a multi-layer pipe as shown in FIG. 2 using ultrasonic waves from the ultrasonic oscillator 1 as an object, specifically, a steel pipe having a resin lining 9 such as hard vinyl chloride on the inner peripheral surface. It functions to irradiate 10. The condenser lens 3 increases the energy level of the ultrasonic wave reflected by the reflection mirror 2 and irradiates the surface of the steel pipe 10. The outer peripheral surface of the steel pipe 10 is rust-proofed by the galvanized layer 11. As another multilayer pipe, as shown in FIG. 3, there is one in which a resin lining 9 such as hard vinyl chloride is applied to both an inner peripheral surface and an outer peripheral surface of a steel pipe (carbon steel) 10. Multi-layer piping having such a three-layer structure can also be an inspection target for physical states such as the degree of bonding, the degree of adhesion, and the interface state according to the present invention.

The condensing lens 4 condenses ultrasonic information generated on the surface of the steel pipe 10 by irradiation of ultrasonic waves as optical information, and the reflection mirror 5 receives the light of the optical information, and It functions to input to the sound wave detector 6.

  The ultrasonic detector 6 mixes the reflected light having the optical information incident through the condenser lens 4 and the reflection mirror 5 and the irradiation light irradiated on the surface of the steel pipe 10 through these. Diffracted light is generated by, and an interference signal between the reflected light and the diffracted light is obtained as optical information. The output of the ultrasonic detector 6 on the surface of the steel pipe 10 is 100 mW or less, the spot diameter is about 2 mm, and the waveform drawing unit 7 is used for the reflected wave and interference signal waveform measured by the ultrasonic detector 6. Function to draw and display.

The arithmetic processing unit 8 collects an attenuation waveform of the acoustic impedance density for each virtual lattice point provided in advance on the steel pipe 10, and an integrated value in the exponential approximation curve at the time τ between the exponential approximation curves of the attenuation waveform, From the comparison results such as the convergence widths Φ ₁ and Φ ₂ , it is possible to visualize physical defect information such as voids generated at the interface between the steel pipe 10 and the resin lining 9 and pinholes generated in the resin lining. When the voids and pinholes are present, only the attenuation waveform of the surface wave (interface) and the bottom wave (inner surface) with the steel pipe appears. That is, the ultrasonic wave is not propagated due to the air resistance or becomes difficult to propagate. Therefore, the level of the reflected waveform from the inner wall of the resin lining 9 becomes extremely small or hardly appears.

In general, when ultrasonic waves are incident perpendicularly from the surface of a multi-layered structure composed of different materials, even if the materials are different, the ultrasonic waves pass through the interface at the interlayer surface between materials with the same acoustic impedance. End up. A plurality of layers composed of layers of acoustic impedances Z ₁ and Z ₂ of materials having different acoustic impedances Z (expressed by a product of density ρ (g / cm ³ ) and sound velocity C (m / sec)) When an ultrasonic wave is incident on the object or an object having a gap between layers, a part of the ultrasonic wave is reflected at the interface by the reflectivity r = Z ₂ −Z ₁ / Z ₂ + Z _{1 at} the boundary surface. In other words, the acoustic energy is consumed by the acoustic impedance density which is the resistance force of the viscosity density of the material proportional to the speed, and the damped vibration is attenuated in proportion to exp- ^βx (β is a damping constant) with time.

Now, when the ultrasonic apparatus is viewed as a control system for input / output information as shown in FIG. 4, an impulse that takes a damped oscillation having a transfer function g (t) that converts the signal input x (t) into another signal and sends it out. A response y (t) can be assumed. In FIG. 5, it is assumed that the transmission waveform is given a unit impulse of a minute time Δt at a height x (t) at an arbitrary time t. This strength can be set to x (t) Δ (t). If the response observed at time t is y (t), then y (t) = ∫ ₀ ^X g (t−τ) x (t) dt, and information on the value of time t is for the control area sum (integral value). Can be obtained in half. Here, τ <t.

Since the impulse response can be handled assuming that it is an exponential function approximation, the relationship between the attenuation of the multi-reflection ultrasonic wave is expressed by the voltage (for each acoustic characteristic unique to each lattice point in the fine mesh on the steel pipe 10 as shown in FIG. mv) and time (μs) are used as information up to a certain time τ to measure attenuation of sound waves. This result can be obtained by an empirical formula.
FIG. 6 shows the attenuation characteristic of the reflected output when no gap (separation) occurs between the layers, and FIG. 7 shows the attenuation characteristic of the reflected output when the gap (separation) occurs between the layers. In FIG. 6, the amplitude of the waveform of the reflected output substantially converges to about 1/15 from 10 μs, and the convergence width becomes Φ ₁ at time τ, and the joining state between the steel pipe 10 and the resin lining 9 in FIG. 11 is complete. On the other hand, in FIG. 7, the amplitude of the waveform of the reflected output converges to about 1/6 of the maximum amplitude (near 6 μs), and the convergence width becomes Φ ₂ at time τ. Therefore, it is possible to determine the presence or absence of an interlayer gap (peeling) from the comparison result of the convergence states of these waveforms.

In the present embodiment, paying attention to the acoustic impedance ρC, the attenuation waveform of the reflected wave from the steel pipe 10 and the resin lining 9 in FIG. 11, that is, the decay time τ (t) and the reflected output C (mv) from the state of the reflected wave, The information is digitized as information captured for each virtual lattice point set on the steel pipe 10 in advance, and the convergence widths Φ ₁ and Φ ₂ are compared. Thereby, the adhesiveness, closeness, and normality of each pipe material which comprises multilayer piping can be estimated. These numerical values are plotted on the coordinates of the reflected output (mV) versus time (τ) as shown in FIG. 10, and an attenuation characteristic curve B of the reflected output as shown in FIG. 10 changing with time (μs) is obtained. At the same time, an approximate curve A of this attenuation characteristic curve B is obtained.

Moreover, FIG. 11 shows what set the mesh pattern which has a grid point of the mesh of a 5-mm space | interval in the xy direction, for example in the xy direction, and FIG. 12 expands and shows a part. The acoustic energy has a loss of propagation energy due to a resistance force proportional to the density ρ (kg / m ² ) of each medium and the particle velocity C (m / s) of the medium, and the steel pipe 10 constituting the multilayer pipe shown in FIG. It attenuates for each lattice point of the resin lining 9. As the temporal attenuation of this propagation energy, the results of the acoustic regions a, b, and c from the exponential approximation curve with the attenuation coefficient β as a parameter are divided into regions on the mesh pattern as shown in FIG. indicate. As a result, visualization becomes possible, and it is possible to estimate the states of adhesion, close contact, and interface between the steel pipe 10 and the resin lining 9 shown in FIG.

Depending on the internal state of the steel pipe 10, if the reflection due to the acoustic impedance density at the lattice point is regarded as a point, and the signal sent as a multiple reflection ultrasonic wave is regarded as an impulse response, how the applied signal is related to the relationship between input and output Whether it is changing or not can be grasped as a surface by measuring the transient response. The state of the boundary surface can be estimated by comparing the individual transfer functions of the actually measured locations on the time axis. Each transfer function is information inside the steel pipe 10 and has an important meaning such as an interface state of the multilayer pipe. Therefore, contour lines can be drawn by approximating with a line connecting grid points (measurement points) for each reflection response time. The multi-reflection echo of the multilayer pipe is attenuated by the sound wave absorption of the vinyl chloride polymer. FIG. 8 (empirical formula y = 13.425e−0.06631x ⁺ 0.6434) and FIG. 9 (experimental formula y = 7.926e− ^0.05017x + 2. 9825), when the time τ approaches ∞ from the empirical formula, it converges with the convergence width Φ ₁ = 0.6434 mv and Φ ₂ = 2.9825 mv, and Φ ₂ > Φ ₁ .

  As described above, in this embodiment, a virtual lattice point is set on the surface of the multilayer pipe, an attenuation waveform of the acoustic impedance density on the lattice point is sampled, and comparison is performed using an exponential approximation curve. Interlayer bonding, adhesion, and interface state are estimated. The ultrasonic wave generating means may be a laser, an EMAT type, a piezoelectric type, or the like, but is not limited to any one of them due to the principle of attenuation.

  As described above, in this embodiment, the ultrasonic wave is applied to the surface of the steel pipe 10 by irradiating the surface of the steel pipe 10 with the resin lining 9 on the inner surface from the ultrasonic oscillator 1 and receiving the ultrasonic wave. Is propagated into the steel pipe 10 and the resin lining 9, and the reflected light corresponding to the ultrasonic waves reflected from the interface of the steel pipe 10 and the resin lining 9 and the inner surface of the resin lining 9 are optically reflected by the ultrasonic detector 6, respectively. An attenuation waveform of the acoustic impedance density is sampled for each virtual lattice point set on the steel pipe 10 by the arithmetic processing unit 8, and an integration value up to the attenuation time τ between the exponential approximation curves of the attenuation waveform and By calculating a comparison result such as the convergence width φ, it is possible to visualize physical defect information generated at the interface between the steel pipe 10 and the resin lining 9.

  Thus, by utilizing the fact that the acoustic impedance density of the lattice points is different for each of the steel pipe 10 and the resin lining 9 constituting the multi-layer pipe, the interface state between the steel pipe 10 and the resin lining 9 is detailed and rapidly obtained for these plural parts. Can be determined.

Further, when the bit signals [0] and [1] are set for the following determination elements (input signals) i ₁ and i ₂ based on the attenuation waveform at each mesh point (lattice point), the calculation is performed. A truth table as shown in FIG. 13 can be obtained by referring to the bit signal set by calculating defect information at each mesh point by the processing unit 8. In this truth table, _if at least one of i _{1 to} in is a [0] bit signal, the AND circuit performs arithmetic processing, and it is easy to determine an abnormality from this arithmetic result (determination output X of each mesh point). can do. This abnormality determination result can be displayed using a known display means that can be recognized visually or auditorily.

i ₁ : Convergence width φ (mv) ≦ normal convergence width φ (mv) at time τ, that is, [1] when Φ ₁ <Φ ₂ .

i ₂ : integral value ∫ ^z ₀ y (t) dt ≦ normal integral value, that is, when (I) <(II), it corresponds to [1].

i _n : By adding necessary information by adding a logical configuration such as attenuation information of steel pipe joints having different acoustic impedance densities in order to maintain quality, more accurate arithmetic processing can be performed.

  As described above, the present invention detects the reflected light from the interface of the multi-layer pipe based on the ultrasonic irradiation, and differs from the calculation of the detection information, as described above, the material specific to the material based on the ultrasonic irradiation. It is intended to provide an interface state detection method and an interface state detection apparatus for multilayer piping by an ultrasonic attenuation method that collects attenuation waveforms of acoustic impedance densities of the above, and compares and verifies the exponential approximation curves.

  The present invention has an effect that the interface state between a steel pipe and a resin lining can be determined in detail and quickly for these plural parts, and a steel pipe constituting a multilayer pipe and a resin lining coated on the inner surface of the steel pipe, The present invention is useful for an interface state detection method and an interface state detection apparatus for multilayer pipes by an ultrasonic attenuation method for detecting defects generated at the interface of the pipe.

DESCRIPTION OF SYMBOLS 1 Ultrasonic oscillator 2 Reflection mirror 3 Light emission side condensing lens 4 Light reception side condensing lens 5 Reflection mirror 6 Ultrasonic detector 7 Waveform drawing part 8 Arithmetic processing part 9 Resin lining 10 Steel pipe 11 Zinc plating layer

Claims (2)

By irradiating the surface of the steel pipe with the resin lining on the inner surface with ultrasonic waves, and the ultrasonic waves excited on the surface of the steel pipe proceed into the steel pipe and the resin lining, the interface between the steel pipe and the resin lining and the resin lining are obtained. An ultrasonic detector for detecting reflected light corresponding to ultrasonic waves reflected from the inner surface, and attenuation of acoustic impedance density for each virtual lattice point set on the steel pipe obtained by the ultrasonic detector An ultrasonic processing system comprising: an operation processing unit that collects a waveform and visualizes physical defect information generated at an interface between the steel pipe and the resin lining from a comparison result of exponential approximation curves of the attenuation waveform Multi-layer piping interface state detection device using the attenuation method. Ultrasonic waves are excited on the surface of the steel pipe with the resin lining on the inner surface, and the ultrasonic waves travel into the steel pipe and the resin lining, so that the vibration of the sound wave attenuated by the acoustic impedance inherent to the material is ^expressed as exp ^−βx (β Is an attenuation constant), and the integral value up to the decay time τ of the exponential approximation curves of the decay waveform and the convergence width φ are compared by arithmetic processing, and physical defects generated at the interface between the steel pipe and the resin lining A method for detecting an interface state of a multilayer pipe by an ultrasonic attenuation method characterized by visualizing information.

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