JP2009098031A - Detecting apparatus and detecting method for interfacial condition of multilayered tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect, with high accuracy and efficiency, the condition of adherence of resin linings to steel tubes as well as physical (interfacial condition) defects such as the presence or absence of pinholes in the resin linings, in a non-contact and non-destructive manner. <P>SOLUTION: An ultrasonic wave that is excited at a surface of a steel tube 14a by receiving a laser beam from a laser oscillator 1 is advanced into the inside of the steel tube 14a and the resin lining 14b to detect reflective lights corresponding to each ultrasonic waves, which are reflected from an interface P between the steel tube 14a and the resin lining 14b and from an inner surface of the resin liming 14b, with a laser interferometer 8. Based on the information on each of the detected reflective lights, an arithmetic processing unit 11 processes the information on defects at the interface P between the steel tube 14a and the resin lining 14b. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an interface state detection device and an interface state detection method for a multilayer pipe that detect defects occurring at the interface between a steel pipe constituting the multilayer pipe and a resin lining coated on the inner surface of the steel pipe in a multilayer pipe manufacturing process. About.

  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, multilayer pipes having excellent durability and corrosion resistance have been widely used. The multilayer pipe has a resin lining structure in which, for example, the inner surface of a steel pipe is coated with hard vinyl chloride or polyethylene.

  The resin lining is produced by heat-sealing the hard vinyl chloride or the like on the inner surface of a steel pipe in a multilayer pipe production line, and in order to maintain the initial corrosion resistance and durability over a long period of time, Quality control of adhesive strength and film thickness after heat fusion becomes important. Up to now, an arbitrary number of multilayer pipes have been extracted from the multilayer pipe production line, and the test of the adhesiveness of the resin lining to the steel pipe has been carried out using various methods.

  However, when the quality of the resin lining for the steel pipe is judged 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 micrometer.

  In addition, since it is necessary to perform such measurement over the entire length of the multilayer tube, there is a disadvantage that the measurement time and the number of measurement steps are increased, and as a result, the production efficiency of the multilayer tube is lowered.

  The present invention has been made paying attention to the above-mentioned conventional problems, and without stopping the production line, non-contact, non-destructive state of the resin lining adhesion to the steel pipe, the presence or absence of pinholes in the resin lining, etc. An object of the present invention is to provide an interface state detecting device for a multilayer tube that can detect a physical (interface state) defect of the multilayer tube with high accuracy and efficiency.

  To achieve the above object, an apparatus for detecting an interface state of a multilayer pipe according to the present invention includes a laser oscillator for irradiating a surface of a steel pipe whose inner surface is resin-lined with a laser beam, and a surface of the steel pipe that receives the laser beam. Laser that optically detects reflected light corresponding to ultrasonic waves reflected from the interface between the steel pipe and the resin lining and the inner surface of the resin lining by the ultrasonic wave excited in the steel pipe and the resin lining. An interferometer, and based on the information of each reflected light obtained by the laser interferometer, the arithmetic processing unit detects physical defect information generated at the interface between the steel pipe and the resin lining by calculation. It is a configuration.

  With the above-described configuration, the laser beam focused on the surface of the steel pipe constituting the multilayer tube locally raises the temperature in the vicinity of the focused portion and causes volume expansion. Therefore, ultrasonic waves are excited on the surface of the steel pipe, the ultrasonic waves propagate so as to diffuse inside, and are reflected at the interface between the steel pipe and the resin lining and the inner surface of the resin lining. Observed using an interferometer.

  The observation information is information including the delay time of the reflected wave, the detected amplitude, the normality of the waveform, etc., and when these information cannot be obtained or is below a predetermined threshold level, the interface between the steel pipe and the resin lining. It is possible to detect the occurrence of voids or the occurrence of pinholes in the resin lining. In addition, an alarm can be generated at the time of defect determination.

  According to the present invention, when a reflected wave of ultrasonic waves is not detected from a multilayer pipe or is below a predetermined level, there are physical defects such as voids generated at the interface between the steel pipe and the resin lining and pinholes generated in the resin lining. It is possible to obtain an effect that automatic measurement can be performed quickly with high accuracy without stopping the production line.

  Hereinafter, an interface state detection apparatus for a multilayer tube according to an embodiment of the present invention will be described in detail with reference to the drawings.

  The multilayer pipe interface state detection apparatus according to the embodiment of the present invention is basically excited by irradiating the surface of a steel pipe having a resin resin lining on the inner surface with a laser beam from a laser oscillator. Ultrasonic wave travels into the steel pipe and the resin lining, so that the reflected light corresponding to the ultrasonic wave reflected from the interface of the steel pipe and the resin lining and the inner surface of the resin lining is optically detected by a laser interferometer, Based on the detected information of each reflected light, the calculation processing unit calculates defect information at the interface between the steel pipe and the resin lining.

  With the above configuration, it is possible to detect the physical state such as the resin lining adhesion to the steel pipe and the presence or absence of pinholes in the resin lining with high accuracy and efficiency without stopping the multilayer pipe production line. Yes.

  FIG. 1 is a block diagram showing an interface state detection device for a multilayer tube according to this embodiment, FIG. 2 is an explanatory diagram showing the progress of ultrasonic waves measured in this embodiment, and FIG. 3 is measured in this embodiment. FIG. 4 is a logical configuration diagram used for determining an abnormality of the reflected wave in the present embodiment, and FIG. 5 is a signal determination flowchart.

  As shown in FIG. 1, the multilayer tube interface state detection device according to the present embodiment includes a laser oscillator, a light projecting side condensing lens 2, a light projecting reflecting prism 3, a light receiving reflecting prism 4, From the light-receiving side condenser lens 5, reflecting mirrors 6 and 7, laser interferometer 8, amplifier 9, waveform drawing unit 10, arithmetic processing unit (CPU) 11, half mirror 12, and photodiode 13. Become.

  Among these, the laser oscillator 1 generates laser light as a pulse laser. The condensing lens 2 functions to increase the energy density of the light by condensing the laser light from the laser oscillator 1. The reflecting prism or mirror 3 (hereinafter simply referred to as “reflecting prism 3”) irradiates the surface of a multi-layered tube, specifically, a steel tube whose inner surface is resin-lined, as a subject with the focused laser beam. To function.

  The reflection prism or mirror 4 (hereinafter simply referred to as “reflection prism 4”) receives ultrasonic information generated on the surface of the multilayer tube as optical information. The condensing lens 5 condenses the laser beam reflected by the reflecting prism 4 and functions to input the laser beam to the laser interferometer 8 through the reflecting mirrors 6 and 7.

  The laser interferometer 8 irradiates the surface of the multilayer tube 14 through the reflected light based on the reflected wave that has entered through the reflecting prism 4, the condensing lens 5, and the reflecting mirrors 6 and 7. By mixing the irradiation light, an interference signal between the reflected light and the diffracted light is obtained. The laser output of the laser interferometer on the surface of the steel pipe 14 is 100 mW or less, and the spot diameter is about 2 mm.

  The waveform drawing unit 10 functions to draw and display the reflected wave, the interference signal waveform, and the like measured by a laser interferometer. The microcomputer 11 as an arithmetic processing unit detects a change in the reflected waveform input to the laser interferometer 8, and a steel pipe 14a and a hard vinyl chloride pipe 14b which is a resin lining applied to the inner surface of the steel pipe 14a; The physical state abnormalities (defects) such as the air gap P generated at the interface of the metal and the pinhole generated in the hard vinyl chloride tube 14b itself are detected.

  When the air gap or pinhole is present, the ultrasonic wave is not propagated due to air resistance or is difficult to propagate. Therefore, the reflected waveform level from the inner wall of the hard vinyl chloride tube 14b becomes extremely small or almost no. No longer appears.

  Therefore, the microcomputer 11 outputs, for example, a signal “1” when the reflected wave is normal, and a signal “0” when the reflected wave is abnormal (defective). Shall. When the reflected wave is equal to or higher than a preset threshold level, it is determined that the reflected wave is substantially normal, and the signal “1” is output, whereby the normal allowable limit can be extended.

  Therefore, the higher the threshold level, the stricter the accuracy of normal reflected wave inspection, and the more reliable the detection data.

  Next, the operation will be described. First, the interface state detection device of the present embodiment is installed at a predetermined portion in the production line of the multilayer tube 14. Next, the surface of the multilayer tube 14 is irradiated with the laser beam from the laser oscillator 1 through the condenser lens 2 and the reflecting prism 3. In this embodiment, as shown in FIG. 2, the multilayer pipe 14 has a two-layer structure in which a hard vinyl chloride pipe 14b is resin-lined on the inner peripheral surface of the steel pipe 14a.

  The laser beam that has passed through the reflecting prism 3 irradiates the surface of the multilayer tube 14 perpendicularly. In the portion irradiated with the laser beam, the energy density on the surface of the steel pipe 14a is increased, and a rapid temperature rise is locally induced. For this reason, explosive volume expansion occurs in the steel pipe 14a in the vicinity of the laser beam irradiation site.

  As the volume expands, energy is converted from light to pressure (sound waves), and ultrasonic waves are excited on the surface and inside of the steel pipe 14a by the laser beam.

  The ultrasonic wave travels so as to diffuse further from the surface of the steel pipe 14a. That is, it proceeds with a predetermined incident angle and further propagates into the multilayer tube 14. In addition, the ultrasonic wave obliquely entered the interface (boundary surface) P (hereinafter simply referred to as “interface P”) between the steel pipe 14a and the hard vinyl chloride tube 14b having different sound speeds according to Snell's refraction law is refracted, and the traveling direction. change. The progress of this ultrasonic wave is as shown in FIG.

  FIG. 2 shows how the ultrasonic waves A, B, and C travel through the steel pipe 14a and the hard vinyl chloride pipe 14b at different angles.

  Each of the ultrasonic waves A and B is reflected at the interface P between the steel pipe 14a and the hard vinyl chloride 14b, and proceeds toward the surface of the steel pipe 14a as an interface first reflected wave and an interface second reflected wave. The ultrasonic wave C passes through the interface P, is reflected by the back surface (inner surface) of the hard vinyl chloride 14b, and travels toward the surface of the steel pipe 14a.

  Therefore, if the steel pipe 14a and the hard vinyl chloride pipe 14b are in close contact with each other, the structure of the multilayer pipe 14 is normal without any defects, and the time required for these three reflected waves to reach the surface of the steel pipe 14a is constant. A time lag will occur. FIG. 3 is a timing chart of an ultrasonic signal including three reflected waves with this shift.

  On the other hand, the three reflected waves are converted into changes in the laser beam irradiated from the laser interferometer 8 onto the surface of the steel pipe 14a (the laser beam is modulated by the reflected waves), and the reflecting prism 4, the condensing lens 5, and enters the laser interferometer 8 through the reflecting mirrors 6 and 7. As the laser interferometer 8, for example, a two-wave mixing interferometer is used. The laser interferometer 8 can obtain interference signals of reflected light and irradiation light corresponding to the ultrasonic waves A, B, and C, respectively.

  Next, the arithmetic processing unit 11 determines whether the reflected light corresponding to each reflected wave is normal “1” or abnormal “0” with respect to the delay time, detection amplitude, and waveform information of the reflected waveform. To do. For example, when the reflected light corresponding to all of the reflected waves A, B, and C is “1”, it is determined that there is no defect such as the gap or pinhole. In addition, when there are a plurality of reflected wave numbers, the abnormality determination can be made stricter or relaxed by adjusting the ratio of normal “1” and abnormal “0”.

The reflected wave A, B, C, ‥‥ are analog output wave, when the i is defined as the beat signal, since the reflected waves A from the time axis is a first reflected wave interface, the reflected wave A i _1, the reflected wave B _{i 2,} the reflected wave C _{i 3,} the ‥‥ reflected wave n and _{i n,} thereby respectively.

  At this time, when the reflected wave corresponding to the reflected wave C is “0”, the abnormality is determined as being defective. The logical configuration diagram in this case is as shown in FIG.

  If the analog signals corresponding to the reflected waves A, B, C,... Are defined as β, and the entire bit signal corresponding to the reflected waves A, B, C,. As shown.

  Here, the total number of bits converted from the analog output wave of each reflected wave A, B, C,... Into a bit signal is set as a threshold value. If there is even one “0” signal, it is determined that the steel pipe 14a is defective, and an abnormality is determined.

  Further, by performing the arithmetic processing of the logical configuration diagram (FIG. 4), it becomes possible to carry out stricter quality control. When the abnormality is determined, an alarm is generated by voice, image, text, or the like using alarm means (not shown). A buzzer can be used for voice.

  As described above, in the present embodiment, the surface of the steel pipe 14a whose inner surface is resin-lined is irradiated with the laser beam from the laser oscillator 1, and the ultrasonic waves excited on the surface of the steel pipe 14a are transmitted to the steel pipe 14a and the resin. By proceeding into the lining 14b, the reflected light corresponding to the ultrasonic waves reflected from the interface P between the steel pipe 14a and the resin lining 14b and the inner surface of the resin lining 14b is optically detected by the laser interferometer 8, respectively. Based on the detected information of each reflected light, the calculation processing unit 6 calculates the defect information at the interface P between the steel pipe 14a and the resin lining 14b.

  As a result, the laser beam condensed on the surface of the metal tube 14a constituting the multilayer tube 14 can locally raise the temperature in the vicinity of the condensing portion and cause volume expansion. For this reason, ultrasonic waves are excited on the surface and inside of the metal tube 14a, and this ultrasonic wave propagates so as to diffuse inside, from the interface P between the steel tube 14a and the resin lining 14b and the inner surface of the resin lining 14b. Each reflected wave can be observed accurately and quickly using the laser interferometer 8.

  The present invention can accurately and efficiently detect physical (interface state) defects such as the state of adhesion of a resin lining to a steel pipe and the presence or absence of pinholes in the resin lining without stopping the production line. The present invention is useful for an interface state detection device for a multilayer pipe that detects defects and the like occurring at the interface between a steel pipe constituting the multilayer pipe and a resin lining coated on the inner surface of the steel pipe.

1 is a block diagram showing an apparatus for detecting an interface state of a multilayer tube according to an embodiment of the present invention. It is explanatory drawing which shows the advancing condition of the ultrasonic wave measured by this embodiment, and a two-layered tube structure. It is a measurement waveform figure of the reflected wave measured by this embodiment. It is a logic block diagram utilized by abnormality determination of the reflected wave in this embodiment. It is a flowchart of the signal determination in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser oscillator 2, 5 Condensing lens 3, 4 Reflection prism or mirror 6, 7 Reflection mirror 8 Laser interferometer 9 Amplifier 10 Waveform drawing part 11 Arithmetic processing part (microcomputer)

Claims (2)

A laser oscillator for irradiating a surface of a steel pipe with a resin lining on the inner surface, and an ultrasonic wave excited on the surface of the steel pipe upon receiving the laser beam proceeds into the steel pipe and the resin lining. A laser interferometer that optically detects reflected light corresponding to ultrasonic waves reflected from the interface between the steel pipe and the resin lining and the inner surface of the resin lining, and based on the information of each reflected light obtained by the laser interferometer And a calculation processing unit for detecting physical defect information generated at the interface between the steel pipe and the resin lining by calculation. A laser beam output from a laser oscillator is irradiated onto the surface of a steel pipe whose inner surface is resin-lined, and is excited on the surface of the steel pipe by the laser beam and travels into the steel pipe and the resin lining. And a reflected wave reflected by the resin lining interface and the resin lining inner surface using a laser interferometer as reflected light corresponding to the reflected wave, and based on the information of each reflected light detected by the laser interferometer A method of detecting an interface state of a multilayer pipe, wherein the arithmetic processing unit detects physical defect information generated at the interface between the steel pipe and the resin lining by calculation.

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