JP2010286330A - Method for inspecting thickness reduction of pipe, and inspection device used in the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify a thickness-reduced section of a pipe due to liquid drop collision erosion, produced at a curved part of a pipe through which steam flows. <P>SOLUTION: A method for inspecting reduction in the thickness of a pipe A due to liquid drop collision erosion 11 produced at a curved part 2 of the pipe 1, through which steam flows by collision of liquid drops in the steam to the inner surface of the pipe includes measuring of pressure fluctuation, based on propagation of sound waves generated by the liquid drop collision erosion 11 in the steam, by using sensors 3, 4, 5, 6 provided at positions upstream and downstream of the curving part 2 of the pipe 1 with intervals; determining the propagation rates of the sound waves propagating in the steam upstream and downstream separately by using the measured results of these; and specifying the production location of the liquid drop collision erosion 11 by the sonar principle, by using the determined propagation rates of the sound wave upstream and downstream and the time difference between the time of the sound waves that has reached the sensor upstream of the curved part 2 and the time of the sound waves that has reached the sensor downstream. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pipe thinning inspection method used in various plants and an inspection apparatus used in the method.

  In a bent portion of a pipe through which water vapor flows installed in various plants, the wall thickness of the pipe due to droplet collision erosion may be reduced. Therefore, it is necessary for equipment maintenance to inspect and find the thinned portion.

  Conventionally, when inspecting a thinned portion of a pipe, as disclosed in Patent Document 1 below, after receiving an ultrasonic pulse from the outside of the pipe, a reflected pulse is received after a lapse of a certain time, and pipe thinning is performed. Measure. Alternatively, as disclosed in Patent Document 2 below, an ultrasonic wave generated by the flow of fluid inside the pipe is measured from the outside of the pipe, and pipe thinning is measured based on the measured ultrasonic wave.

  However, since a heat insulating material is often wound around a pipe or the like, it is necessary to remove all of the heat insulating material at the site to be inspected in the above measurement method, and the work efficiency is poor. As a method for inspecting piping and the like without removing all the heat insulating materials, for example, Patent Document 3 below discloses a method by an acoustic emission method.

JP-A-7-198362 JP 2007-170968 A Japanese Patent Application Laid-Open No. 2003-232728

The sound generated by the interference between the pipe wall of the pipe and the droplets propagates through the wall surface as a Lamb wave due to interference between the longitudinal wave and the transverse wave. If you want to use the acoustic emission method to use the Lamb wave, install a sensor at multiple locations on the pipe, and use the Lamb wave phase difference measured by each sensor and the Lamb wave propagation speed as a sound source pipe. It is conceivable to calculate the distance to the defective part and identify the defective part of the pipe by the principle of sonar.
However, the Lamb wave to be used in the acoustic emission method is a noise with a messy waveform, and at the same time, the propagation speed has frequency dependence. A complex frequency analysis that does not lose information is required.

  On the other hand, the sound wave propagating through the fluid in the pipe flowing through the pipe has no frequency dependence of the propagation velocity like Lamb wave, so without using complicated frequency analysis that does not lose time axis information, It has been found that it is possible to easily identify a piping defect site by the sonar principle using a plurality of sensors.

For example, a _first sensor is provided on the upstream side away from L _{1 and} a second sensor is provided on the downstream side away from L ₂ from a thinned part that is a defective part of a pipe serving as a sound source, and the fluid in the pipe is propagated. Sound waves are measured by the first and second sensors. If the time difference Δt of the sound wave at each sensor is known from the time axis waveform of the sound wave detected by each sensor, the difference ΔL = L ₁ −L ₂ between the sound source and each sensor from the sound wave propagation velocity c is ΔL = It can be calculated by cΔt.

Since the distance L = L ₁ + L ₂ between the sensors can be measured, by subtracting the distance difference ΔL from the sound source to each sensor from the distance L between the sensors, the distance from each sensor to the sound source, L ₁ and L ₂ can be calculated, and the defective portion of the pipe serving as the sound source can be specified.

  However, the fluid flowing in the pipe is steam, and the droplet contained in the steam collides with the pipe wall surface at the inspection site where the steam can change the flow direction, for example, the bent portion of the flow path. When such a collision occurs, droplet collision erosion that promotes thinning of the pipe occurs.

  When the droplet collision erosion occurs, the amount of droplets in the steam decreases from the vapor after the droplet collision due to the droplet collision, so that the physical properties of the fluid on the upstream and downstream sides of the droplet collision erosion occurrence point The sound velocity c of the sound wave that changes and propagates the fluid in the pipe is different between the upstream side and the downstream side.

  For this reason, there has been a problem that the method based on the principle of sonar cannot be applied to the evaluation for specifying the pipe thinning portion caused by the droplet collision erosion.

  Accordingly, an object of the present invention is to provide an inspection method for identifying a site where droplet collision erosion occurs under a situation where the propagation speed of a sound wave changes before and after an inspection unit, and an inspection apparatus used for the inspection method. is there.

  The inspection method for achieving the object of the present invention is characterized in that the bent portion of the sound wave generated by the collision between the droplet generated when the steam flows in the pipeline having the bent portion and the inner wall surface of the pipeline. The propagation velocity in the steam is determined for each of the upstream side and the downstream side of the flow, the difference between the detection times of the sound waves detected on the upstream side and the downstream side of the flow of the bent portion is determined, and the detection time of the sound waves is calculated. This is a pipe thinning inspection method that identifies the sound source part of the sound wave based on the difference and the propagation speed of the sound wave.

  Preferably, the propagation speed of the sound wave is calculated from a difference in time when vibrations due to the sound wave are received at a plurality of detection positions set at intervals in the flow direction, and a distance between the plurality of detection positions. It is characterized by seeking.

  More preferably, the difference between the detection times of the sound waves detected on the upstream side and the downstream side of the flow of the bent portion is the time axis waveform of the sound waves detected on the upstream side of the flow of the bent portion, and It is obtained by comparing with a time axis waveform of the sound wave detected on the downstream side of the flow of the bent portion.

  The inspection apparatus for achieving the object of the present invention is characterized in that the steam flows in the direction of the steam in a portion of the pipe located upstream of the steam flow, with the bend of the pipe flowing the steam as a boundary. A plurality of sensors that are installed at intervals and convert pressure fluctuations in the pipeline into electrical signals, and the bent portion of the pipeline through which the steam flows are the boundary, and are located downstream of the steam flow. A plurality of sensors that are installed at intervals in the direction of the flow of the steam at the site of the pipeline, and that convert pressure fluctuations in the pipeline into electrical signals; electrically connected to each of the sensors; An inspection apparatus for pipe thinning comprising an information converter for converting a sent electric signal into pressure fluctuation data and a display device for displaying the pressure fluctuation data generated by the information converter as a time axis waveform.

  Preferably, the pipe thinning inspection apparatus further includes a recording device for recording the pressure fluctuation data generated by the information converter.

  In the pipe thinning inspection method according to the present invention, when the bent part of the steam pipe is used as the inspection part, the sound wave in the fluid on the upstream side and the downstream side of the inspection part with respect to the sound wave emitted from the inspection part. The sound wave generation location can be identified as the droplet collision erosion generation site even under the situation where the sound wave propagation velocity changes between the upstream side and the downstream side of the inspection section.

  In addition, since the sound velocity and detection time of the sound wave propagating through the fluid in the pipe line is detected and specified as the occurrence site of the droplet collision erosion, it is not necessary to remove all the heat insulating material wound around the detection location, Inspection work efficiency is good.

  In the pipe thinning inspection apparatus according to the present invention, the generation location of the sound wave can be identified as the generation site of the droplet collision erosion even under the situation where the propagation speed of the sound wave changes between the upstream side and the downstream side of the inspection unit. In addition, it is possible to provide an inspection apparatus suitable for carrying out the pipe thinning inspection method that improves the inspection work efficiency.

It is the schematic for demonstrating the inspection method of piping concerning one Embodiment of this invention. It is a flowchart which shows the inspection method of piping concerning one Embodiment of this invention. It is a figure for demonstrating the process of calculating the propagation speed of the sound wave of the upstream and downstream from the test | inspection part in one Embodiment of this invention. It is a figure for demonstrating the process of specifying the generation | occurrence | production site | part of a droplet collision erosion from the time difference of the sound wave of the upstream and downstream from the test | inspection part in one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  In various plants, as shown in FIG. 1, there is a pipe line by a pipe 1 through which steam flows as a fluid. The pipe line has a bent portion 2 due to the arrangement plan of the pipe 1. The bent portion 2 is configured by bending the pipe 1 or by connecting a straight pipe to an elbow employed in the bent portion. In the present embodiment, the bent portion 2 is formed by bending the pipe 1 as shown in FIG. 1, but the following description is the same even if the bent portion is formed using an elbow as described.

  The pipe inspection apparatus according to the present embodiment is arranged along the direction in which the steam flows for each part before and after the bent part 2 of the pipe 1, that is, the upstream and downstream parts as viewed from the bent part 2 of the steam flow. Two sensors 3, 4, 5, and 6 are provided at intervals. Sensors 3, 4, 5, and 6 are sensors that measure pressure fluctuations in the pipe 1 as electrical signals. An information converter 7 that converts electrical signals sent from the sensors 3, 4, 5, and 6 into pressure fluctuation data, a recording device 8 that records the data, and a display device 9 that displays the pressure fluctuation data. Are electrically connected to form a pipe inspection apparatus.

  The display device 9 has a function of displaying the pressure fluctuation data obtained by the sensors 3, 4, 5, 6 as the time axis waveform of the sound wave of FIGS. 3 and 4. The recording device 8 also records the pressure fluctuation data obtained by the sensors 3, 4, 5, 6 for each time, and generates data necessary for generating the time axis waveform of the sound wave of FIGS. 3 and 4. Has a function to record. The display device 9 may have a function of displaying the time axis waveform of the sound wave shown in FIGS. 3 and 4 using the data in the recording device once recorded.

  In the present embodiment, the vicinity of the bent portion 2 of the pipe 1 is an inspection site, and the sound wave generated by the droplet collision erosion generated in the vicinity of the bent portion 2 propagates the fluid flowing in the pipe 1 and the sensors 3 and 4. , 5 and 6. As the sensors 3, 4, 5, and 6, a pressure sensor, a strain rate sensor, or the like is used to measure the pressure fluctuation of the flow in the pipe 1.

  FIG. 2 is a flowchart of the pipe inspection method of this embodiment. In the pipe inspection according to the present embodiment, first, sensors 3 and 4 are arranged at an interval d on the upstream side of the bent portion 2 of the pipe 1 where occurrence of droplet collision erosion is assumed, and the sensor 5 is provided on the downstream side of the bent portion 2 of the pipe. , 6 are installed at intervals d. At this time, if a heat insulating material is applied to the pipe 1, a part of the heat insulating material is removed so that a pipe portion to which the sensor is attached is exposed, and the sensor is installed. After the inspection, remove the heat insulating material that has been removed.

  Next, the propagation velocity of the sound wave propagating upstream is calculated from the upstream sensors 3 and 4, and the propagation velocity of the sound wave propagating downstream is calculated from the downstream sensors 5 and 6. This step will be described in detail with reference to FIG. FIG. 3A is a cross-sectional view of the upstream side of the pipe bending portion. Sound waves generated by the droplet collision erosion 11 near the bent portion 2 of the pipe 1 propagate to the upstream side and the downstream side of the bent portion 2 of the pipe 1 as shown in FIG.

As shown in FIG. 3A, when the sound wave 10 propagating to the upstream side of the bent portion 2 of the pipe 1 at the speed c ₁ reaches the installation position of the sensors 3 and 4, the sound wave 10 is detected by the sensors 3 and 4. The FIG. 3B is an example of a time axis waveform of a sound wave detected by the sensor 3, and FIG. 3C is an example of a time axis waveform of a sound wave detected by the sensor 4. Since the sensors 3 and 4 are installed at the interval d, the time axis waveform of the sound wave 10 is detected with a certain time difference Δt ₁ . If attention is paid to sound waves having the same amplitude, the time difference Δt ₁ of the sound waves 10 can be detected from the time-axis waveform data.

From the detected time difference Δt ₁ and the distance d between the sensors 3 and 4, the propagation velocity c ₁ of the sound wave 10 propagating upstream of the pipe can be calculated by c ₁ = d / Δt ₁ . Similarly, regarding the propagation velocity c ₂ of the sound wave propagating downstream of the pipe, c ₂ = d / Δt from the time difference Δt ₂ of the time axis waveform of the sound wave detected by the sensors 5 and 6 and the interval d between the sensors 5 and 6. ₂ can be calculated.

  In the pipe inspection of the present embodiment, next, the time difference between the sound waves detected by the sensor installed on the upstream side of the bent portion 2 and the sensor installed on the downstream side, the propagation speed of the sound wave on the upstream side, The generation site of the droplet collision erosion 11 is specified from the propagation speed of the sound wave. This step will be described in detail with reference to FIG.

FIG. 4A is a cross-sectional view including the bent portion 2 of the pipe 1. The sound wave generated by the droplet collision erosion 11 near the bent portion 2 of the pipe 1 propagates upstream at the velocity c ₁ and downstream at the velocity c ₂ . The sound wave propagated upstream is detected by the sensor 4, and the sound wave propagated downstream is detected by the sensor 5.

  4B is an example of a time axis waveform of a sound wave detected by the sensor 4, and FIG. 4C is an example of a time axis waveform of a sound wave detected by the sensor 5. The time axis waveform of the sound wave detected by the sensors 4 and 5 is that the distance from the sound source of the droplet collision erosion 11 to the sensor 4 is different from the distance from the same sound source to the sensor 5, and the upstream side of the bent portion 2 of the pipe 1. Is detected at a certain time difference Δt.

  If attention is paid to sound waves having the same amplitude in the time axis waveforms of the sound waves in FIGS. 4B and 4C, the time difference Δt between the sound waves detected by the sensor 4 and the sensor 5 can be detected from the time axis waveform data. It is.

The distance L ₁ from the droplet collision erosion 11 serving as the sound source to the sensor 4, the distance L ₂ from the sensor 5, the propagation velocity c ₁ of the sound wave to the upstream side, the propagation velocity c ₂ of the sound wave to the downstream side, A relationship of Δt = L ₁ / c ₁ −L ₂ / c ₂ is established between the time differences Δt of the sound waves detected by the sensor 5. Since the distance L ₁ + L ₂ between the sensor 4 and the sensor 5 can be measured, the distance L ₁ from the droplet collision erosion 11 serving as the sound source to the sensor 4 is L ₁ = c ₁ (L ₁ + L ₂ ) / ( c ₁ + c ₂ ) + c ₁ c ₂ Δt / (c ₁ + c ₂ ), and the distance L ₂ from the droplet collision erosion 11 to the sensor 5 is L ₂ = c ₂ (L ₁ + L ₂ ) / ( c ₁ + c ₂ ) −c ₁ c ₂ Δt / (c ₁ + c ₂ ).

The occurrence location of the droplet collision erosion 11 can be specified from the calculated L ₁ or L ₂ and the installation position of the sensors 4 and 5. Then, the occurrence location of the droplet collision erosion 11 is evaluated as a pipe thinning occurrence site or a pipe thinning occurrence candidate site due to the droplet collision erosion 11.

  As described above, in this embodiment, in the pipe thinning inspection method by the droplet collision erosion 11 generated in the pipe 1 having the bent portion 2 through which the vapor fluid containing droplets flows, before and after the upstream portion (upstream side) of the bent portion 2 of the pipe 1. And the downstream side), the propagation speed of the sound wave propagating the vapor fluid in the pipe 1 from the generation site of the droplet collision erosion 11 is obtained, and the obtained sound wave propagation speed and the sound wave before and after the bent portion 2 of the pipe 1 are obtained. It is characterized in that the generation site of the droplet collision erosion 11 is specified by the sonar principle from the time difference.

In this case, in this embodiment, the propagation speed of the sound wave is determined between the two sensors 3 and 4 and two sensors 5 provided at two positions at the front and rear of the bent portion 2 of the pipe 1. , and the time difference Delta] t ₁ of the acoustic waves between 6, and calculates also the distance d between the two sensors.

  Further, the time difference Δt between the sound waves before and after the bent portion 2 of the pipe 1 is detected from the time axis waveform of the sound waves detected by both sensors 4 and 5 installed before and after the bent portion 2 of the pipe 1. .

  According to such a present Example, the propagation speed of the local sound wave is measured in the upstream and downstream of the bending part 2 of the piping 1, and the propagation time of the sound wave from the sound source to each sensor by the droplet collision erosion 11 is measured. Therefore, the generation site of the droplet collision erosion 11 in which the propagation speed of the sound wave changes before and after the bent portion 2 can be specified by the sonar principle.

  In addition, since the method of specifying the generation site of the droplet collision erosion 11 is adopted based on the principle of sonar, it is not necessary to remove all the heat insulating material wound around the pipe 1, and the sensors 3, 4, 5, 6 Since it is only necessary to remove the heat insulating material only at the site to which the is attached, the work efficiency is good.

  Further, since the method of specifying the location where the droplet collision erosion 11 occurs is adopted based on the principle of sonar, the entire surface of the pipe can be inspected without scanning by a dynamic device.

  INDUSTRIAL APPLICABILITY The present invention can be used for an inspection apparatus that identifies a site where droplet collision erosion that occurs in a pipeline through which steam flows is generated.

DESCRIPTION OF SYMBOLS 1 Piping 2 Bending part 3, 4, 5, 6 Sensor 7 Information converter 8 Recording apparatus 9 Display apparatus 10 Sound wave 11 Droplet collision erosion

Claims (5)

Propagation in the steam for each of the upstream side and the downstream side of the flow of the bent portion of the flow of the sound wave generated by the collision between the droplet generated when the steam flows in the pipeline having the bent portion and the inner wall surface of the pipeline. Seeking speed,
Find the difference in detection time of the sound waves detected on the upstream side and downstream side of the flow of the bent portion,
A pipe thinning inspection method for identifying a portion of the sound source of the sound wave based on a difference in detection time of the sound wave and a propagation speed of the sound wave.   2. The propagation speed of the sound wave according to claim 1, wherein the propagation speed of the sound wave is calculated from a difference in time at which the vibration due to the sound wave is received at a plurality of detection positions set at intervals in the flow direction and a distance between the plurality of detection positions. An inspection method for pipe thinning characterized by calculating and obtaining.   The difference in detection time of the sound wave detected between the upstream side and the downstream side of the flow of the bent portion according to claim 2, wherein the time axis waveform of the sound wave detected on the upstream side of the flow of the bent portion, A pipe thinning inspection method, characterized in that it is obtained by comparison with a time axis waveform of the sound wave detected on the downstream side of the flow of the bent portion. Pressure fluctuations in the pipes are installed at intervals in the steam flow direction at portions of the pipes located on the upstream side of the steam flow with a bend of the pipes through which the steam flows. A plurality of sensors that convert electrical signals into electrical signals;
Pressure fluctuations in the pipe line are installed at intervals in the steam flow direction at a part of the pipe line located downstream of the steam flow with a bend of the pipe line through which the steam flows. A plurality of sensors that convert electrical signals into electrical signals;
An information converter electrically connected to each of the sensors and converting an electrical signal sent from the sensor into pressure fluctuation data;
A display device for displaying the pressure fluctuation data generated by the information converter as a time axis waveform;
Pipe thinning inspection device equipped with.   5. The pipe thinning inspection apparatus according to claim 4, further comprising a recording device that records pressure fluctuation data generated by the information converter.

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