CN113466341B - Radial crack creeping wave detection method for outer wall of steam-water pipeline tube seat open hole - Google Patents
Radial crack creeping wave detection method for outer wall of steam-water pipeline tube seat open hole Download PDFInfo
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
- G01N29/0609—Display arrangements, e.g. colour displays
- G01N29/0645—Display representation or displayed parameters, e.g. A-, B- or C-Scan
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
- G01N29/0654—Imaging
- G01N29/069—Defect imaging, localisation and sizing using, e.g. time of flight diffraction [TOFD], synthetic aperture focusing technique [SAFT], Amplituden-Laufzeit-Ortskurven [ALOK] technique
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/26—Arrangements for orientation or scanning by relative movement of the head and the sensor
- G01N29/265—Arrangements for orientation or scanning by relative movement of the head and the sensor by moving the sensor relative to a stationary material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/30—Arrangements for calibrating or comparing, e.g. with standard objects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
- G01N29/4454—Signal recognition, e.g. specific values or portions, signal events, signatures
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
- G01N29/4463—Signal correction, e.g. distance amplitude correction [DAC], distance gain size [DGS], noise filtering
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
- G01N29/48—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by amplitude comparison
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/023—Solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/0289—Internal structure, e.g. defects, grain size, texture
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/26—Scanned objects
- G01N2291/267—Welds
- G01N2291/2675—Seam, butt welding
Abstract
The invention relates to a radial crack creeping wave detection method for the perforated outer wall of a steam-water pipeline tube seat, which adopts the technical scheme that a scanning path is determined according to the characteristic of radial cracks on the perforated outer wall of the steam-water pipeline tube seat, a distance-amplitude curve is drawn for evaluating the equivalent size of defects by monitoring on a standard test block with simulated cracks, finally 360-degree circumferential scanning is carried out on a detected steam-water pipeline tube along the scanning path, and finally defect identification is carried out on the basis of the distance-amplitude curve to obtain the amplitude, the position and the length of the defects, thereby solving the problem of nondestructive detection of radial cracks on the perforated surface of a large-diameter steam-water pipeline of a thermal power unit, preventing the occurrence of pipeline leakage accidents caused by perforation crack expansion, realizing the effective detection of radial cracks on the perforated outer wall of the steam-water pipeline tube seat by practical application, and achieving the accuracy of more than 99.9 percent.
Description
Technical Field
The invention belongs to the technical field of nondestructive detection of steam-water pipelines of thermal power generating units, and particularly relates to a radial crack creeping wave detection method for an outer wall of an opening of a steam-water pipeline tube seat.
Background
The main steam-water pipeline of the thermal power plant, such as main steam, reheat heat section steam, reheat cold section steam, extraction steam and other pipelines, are connected with a plurality of small pipes outside the machine furnace, such as an air discharge pipe, a pressure sampling pipe, a steam sampling pipe, a water drain pipe and the like. In the running process of the unit, the condition that saturated water flows back to the main pipeline can occur due to the design of an outer pipe pipeline of the machine furnace, leakage of a valve and the like, and as the running time of the unit increases, the number of times of saturated water flow back increases, cracks are gradually initiated around the open holes and gradually extend and increase, and finally leakage occurs at pipe holes. For radial cracks of the pipeline opening along the inner wall, defects can be generally found by ultrasonic transverse wave detection, but for radial cracks of the pipeline opening along the outer wall (shown in fig. 1), the existing nondestructive detection method is difficult to detect the defects, and once the crack propagates, the pipeline leaks, so that unplanned shutdown of a unit can be caused, and even high-temperature steam leakage hurts people accidents can occur. Nondestructive detection of radial cracks on the surface of a large-diameter steam-water pipeline opening of an in-service thermal power generating unit becomes a problem to be solved urgently by those skilled in the art.
Disclosure of Invention
Aiming at the situation, the invention aims to overcome the defects of the prior art, and the invention aims to provide the radial crack creeping wave detection method for the outer wall of the opening of the steam-water pipeline tube seat, which can effectively solve the problem of nondestructive detection of radial cracks on the surface of the opening of the large-diameter steam-water pipeline of an in-service thermal power generating unit so as to prevent pipeline leakage accidents caused by expansion of the opening cracks.
The technical scheme of the invention is as follows:
a radial crack creeping wave detection method for an outer wall of an opening of a steam-water pipeline tube seat comprises the following steps:
step one, determining a scanning path
The method comprises the steps of using the outer wall of a parent pipeline around a pipe seat fillet weld as a detection surface, establishing a two-dimensional graph of a top view of an opening of a pipe seat of a steam-water pipeline to be detected, and carrying out n radial simulated crack defects Q which are evenly distributed along the circumferential direction of the opening on the two-dimensional graph n Where n=1, 2,3,4, …, each simulate a crack defect Q n Is 5mm long and 0.2mm wide and 3mm deep, to simulate each crack defect Q n A vertical line L is formed at the center point along the length direction n Each probe placement position Z n Located at each corresponding vertical line L n On each probe placement position Z n The following conditions are specifically satisfied: is positioned at the probe placement position Z n The front edge of the probe is opposite to the corresponding simulated crack defect, and the minimum distance S between the probe and the fillet weld of the tube seat is more than or equal to 1mm and less than or equal to 5mm;
place all probes in position Z n (Z 1 、Z 2 …Z n ) The method is characterized in that a section of smooth transition curve is formed in sequence, namely a scanning path of radial cracks of the pipe seat opening of the outer wall of the steam-water pipeline is a concentric circle taking the pipe seat opening as a circle center, and the radius of the pipe seat opening is r, so that the vertical central line of the front edge of the probe is always tangent to a circle taking the pipe seat opening as the center and having the radius of r+2.5mm in the moving process of the probe;
step two, instrument and equipment selection and parameter setting
The scanning instrument adopts an A-type pulse reflection ultrasonic detector, and a probe selects a long-focus creeping wave twin-crystal parallel probe;
performing performance test on the A-type pulse reflection ultrasonic detector and the probe, setting basic parameters, and preparing a DAC curve by matching with a standard test block BZSK-1, wherein the standard test block BZSK-1 is provided with simulation cracks, and the specific steps of preparing the DAC curve are as follows: placing a probe on a standard test block BZSK-1, simulating cracks at the front edge distance of the probe by 10mm, measuring the strongest reflected wave, adjusting an A-type pulse reflection ultrasonic detector to 80% of screen height, sequentially measuring the simulated crack wave heights at the positions, 20mm, 30mm, 40mm and 50mm, of the front edge distance of the probe, and drawing a distance-amplitude curve on a oscillographic screen, wherein the distance-amplitude curve is a DAC curve, and the DAC curve is used for evaluating the equivalent size of a defect;
step three, scanning
The probe is arranged near the fillet weld of the tube seat of the steam-water pipeline to be detected, the minimum distance between the front end of the probe and the fillet weld of the tube seat is less than or equal to 1mm and less than or equal to 5mm, the probe is kept in stable contact with the workpiece to be detected, 360-degree circular scanning is carried out along a scanning path, the front edge vertical central line of the probe is ensured to be always tangent to a circle with the radius of r+2.5mm by taking the tube seat opening as the center, and the scanning speed is not more than 150mm/S;
step four, defect identification
Scanning according to the fourth step, quantifying the defects and measuring the positions of the defects to obtain the maximum reflected wave amplitude and the indication length, and judging that all the reflected waves exceeding the height of the distance-amplitude curve obtained in the second step are defect waves;
measurement of defect amplitude: the difference delta between the maximum reflection amplitude of the defect and the height of the distance-amplitude curve is the defect amplitude and is marked as SL (+ -) delta dB;
determination of the position of the defect: determining the position of the defect around the tube hole according to the position of the probe on the detection surface and the horizontal position of the highest reflected wave on the oscillography screen, and recording;
determination of defect length: the indication length is measured by a single-side half wave height method (6 dB method), and the specific method is as follows: and (3) moving the probe to find the strongest reflected wave of the defect, adjusting the wave height to 80% of the screen height, and moving the probe to the outside, wherein when the wave height is reduced to 40% of the screen height, marks are made on the position corresponding to the central line of the probe, and the distance from the marks to the edge of the hole is the indication length of the defect.
The generation of ultrasonic creeping wave is a waveform conversion by ultrasonic wave propagation to two hetero interfaces, as shown in FIG. 2, if the incident wave velocity and the refracted wave velocity satisfy the following relationship C L1 ＜C S2 ＜C L2 Time (wherein, C L1 C is the longitudinal wave sound velocity of the incident sound wave in the first medium L2 C is the longitudinal wave sound velocity of the incident sound wave in the second medium S2 For the transverse wave sound velocity of the incident sound wave in the second medium), when the incident angle α=arc sin (C L1 /C L2 ) When the refraction angle of the longitudinal wave is equal to 90 °, a creeping wave is excited in the second medium, which is theoretically a longitudinal wave propagating parallel to the surface. The creeping wave detection has the following characteristics: 1) The creeping wave is suitable for detecting defects in the near surface of a workpiece with rough surface or in a thin piece, and the influence of a tube seat fillet weld and a tube seat per se can be avoided when the creeping wave is used for detecting the outer wall of a tube seat opening; 2) The creeping wave probe can change the sensitivity degree of the defect near the surface by selecting proper f.D value (f is the probe frequency and D is the wafer diameter); 3) The creeping wave is only sensitive to the region with the depth of a few millimeters on the surface layer, and the general range is 1 mm-9 mm; 4) The attenuation of the creeping wave is serious, the sound path is short, and the effective sound path is not more than 50mm.
The ultrasonic creeping wave detection technology adopts a wedge block with a large incidence angle, so that after the sound wave enters a workpiece, longitudinal surface creeping waves, longitudinal waves in the volume and transverse waves of two types can be generated. The angle of the primary creeping wave is 75-83 degrees and is almost perpendicular to the thickness direction of the detected workpiece, and the angle is close to 90 degrees with the crack in the vertical direction in the workpiece, so that the detection sensitivity to the vertical crack is better. Meanwhile, the creeping wave detection is less interfered by the surface nicks, the unevenness, the pits and the like of the workpiece, so that the creeping wave detection technology is widely applied to crack detection of the near surface. Therefore, the ultrasonic creeping wave detection technology is adopted to detect radial cracks on the outer wall of the opening of the steam-water pipeline tube seat, and the method has high feasibility.
According to the invention, a scanning path is determined through the characteristics of radial cracks on the open pore outer wall of the steam-water pipeline tube seat, a distance-amplitude curve is drawn through monitoring on a standard test block with simulated cracks and used for evaluating the equivalent size of defects, finally 360-degree circumferential scanning is carried out on the inspected steam-water pipeline tube along the scanning path, and finally defect identification is carried out on the basis of the distance-amplitude curve, so that the amplitude, the position and the length of the defects are obtained, the problem of nondestructive detection of the radial cracks on the open pore surface of the large-diameter steam-water pipeline of an in-service thermal power generating unit is solved, the occurrence of pipeline leakage accidents caused by the expansion of the open pore cracks is prevented, and the accuracy reaches more than 99.9% through practical application, so that the effective detection of the radial cracks on the open pore outer wall of the steam-water pipeline tube seat is realized, and good social and economic benefits are achieved.
Drawings
FIG. 1 is a schematic view of radial cracks on the outer wall of an opening of a steam-water pipeline tube seat.
FIG. 2 is a cross-sectional view of a steam-water pipe socket.
FIG. 3 is a two-dimensional graph of a top view of an opening of a steam-water pipeline tube seat to be detected.
Fig. 4 is a perspective view of the probe wedge of the present invention.
Fig. 5 is a front view of the probe wedge of the present invention.
Fig. 6 is a side view of the probe wedge of the present invention.
Fig. 7 is a front view of the standard test block BZSK-1 of the present invention.
Fig. 8 is a side view of the area of the standard block BZSK-1A of the present invention.
Fig. 9 is a side view of the area BZSK-1B of the standard test block of the present invention.
Fig. 10-13 are schematic top views of the pipe socket open radial crack reference blocks DBSK 1-DBSK 4 of the present invention.
Fig. 14 is a schematic diagram of waveform conversion at different interfaces of the ultrasonic creeping wave detection technique.
Detailed Description
The following describes the embodiments of the present invention in further detail with reference to the drawings.
The invention provides a method for detecting radial cracks on the outer wall of a perforated hole of a steam-water pipeline tube seat, which takes the radial cracks on the outer wall of the perforated hole of the steam-water pipeline tube seat as a detection object, as shown in fig. 2, the tube seat is fixed on the outer side of the perforated hole of a main pipe through a tube seat fillet weld, the radius of the main pipe is R, the distance from the edge of the tube seat fillet weld to the center of the perforated hole of the main pipe is D, the radius R of the main pipe is more than or equal to 150mm, and the distance D from the edge of the tube seat fillet weld to the center of the perforated hole of the main pipe is less than or equal to 50mm, and the method is suitable for nondestructive detection of the radial cracks on the outer wall of the perforated hole of the steam-water pipeline, and comprises the following steps:
step one, determining a scanning path
Taking the outer wall of a parent pipeline around the fillet weld of the pipe seat as a detection surface, establishing a two-dimensional graph of the top view of the opening of the pipe seat of the steam-water pipeline to be detected, and as shown in fig. 3, performing n radial simulation crack defects Q distributed evenly along the circumferential direction of the opening on the two-dimensional graph n Where n=1, 2,3,4, …, each simulate a crack defect Q n Is 5mm long and 0.2mm wide and 3mm deep, to simulate each crack defect Q n A vertical line L is formed at the center point along the length direction n Each probe placement position Z n Located at each corresponding vertical line L n On each probe placement position Z n The following conditions are specifically satisfied: is positioned at the probe placement position Z n The front edge of the probe is opposite to the corresponding simulated crack defect, and the minimum distance S between the probe and the fillet weld of the tube seat is more than or equal to 1mm and less than or equal to 5mm;
place all probes in position Z n (Z 1 、Z 2 …Z n ) The method is characterized in that a section of smooth transition curve is formed in sequence, namely a scanning path of radial cracks of the pipe seat opening of the outer wall of the steam-water pipeline is a concentric circle taking the pipe seat opening as a circle center, and the radius of the pipe seat opening is r, so that the vertical central line of the front edge of the probe is always tangent to a circle taking the pipe seat opening as the center and having the radius of r+2.5mm in the moving process of the probe;
step two, instrument and equipment selection and parameter setting
The scanning instrument adopts an A-type pulse reflection ultrasonic detector, and a probe selects a long-focus creeping wave twin-crystal parallel probe;
the parameter requirements of the long-focus creeping wave twin-crystal parallel probe are as follows: the specific scanning sound Cheng Yiban from the tube seat fillet weld edge to the tube hole center point is larger than 20mm, so that a long-focus creeping wave probe with a focal point horizontal distance of 20mm is selected; the probe frequency is 5MHz, the area of a single wafer is 6mm multiplied by 8mm, and the sensitivity of crack defects near the surface layer is met.
As shown in fig. 4, the length l=20mm and the width d=8mm of the probe wedge block, because the detected steam-water pipeline detection surface is a curved surface, the contact part of the detected workpiece and the probe detection surface is a curved surface which is continuously changed in the process of scanning a path, and in order to ensure the coupling effect of the probe detection surface and the detected workpiece, a certain radian (the radius of the curved surface is a concave surface of r=500 mm) is preset in the direction of the length (l=20mm) of the probe wedge block as shown in fig. 5; the ultrasonic beam does not pass through the part of the probe wedge with the width of 1.5mm at the rear side in the width direction, as shown in fig. 6, and a certain radian (a concave surface with the curved surface radius of r=50 mm is shown in the figure) is preset at the part along the length (l=20mm) direction, so that the coupling effect is further enhanced.
The performance requirements of the A-type pulse reflection ultrasonic detector are as follows: testing the vertical linearity and the horizontal linearity of the A-type pulse reflection ultrasonic detector, wherein the vertical linearity error of the A-type pulse reflection ultrasonic detector is required to be not more than 4 percent, and the horizontal linearity error is required to be not more than 1 percent;
the performance requirements of the creeping wave twin-crystal parallel probe are as follows: the creeping wave twin-crystal parallel probe is tested, the horizontal deflection angle of the sound beam axis is not more than 2 degrees, the signal to noise ratio at the position with the maximum detection distance of 50mm is more than 6dB, and the vertical deflection of the main sound beam has no obvious double peaks.
The basic parameters of the A-type pulse reflection ultrasonic detector and the probe are set as follows: the receiving and transmitting mode selects a bicrystal mode, the probe angle is selected to be 82-85 degrees, the calibrated sound velocity is set to be 5900mm/s, and the front edge is set to be 8mm.
Performing performance test on the A-type pulse reflection ultrasonic detector and the probe, setting basic parameters, and preparing a DAC curve by matching with a standard test block BZSK-1, wherein the standard test block BZSK-1 is provided with simulation cracks, and the specific steps of preparing the DAC curve are as follows: placing a probe on a standard test block BZSK-1, simulating cracks at the front edge distance of the probe by 10mm, measuring the strongest reflected wave, adjusting an A-type pulse reflection ultrasonic detector to 80% of screen height, sequentially measuring the simulated crack wave heights at the positions, 20mm, 30mm, 40mm and 50mm, of the front edge distance of the probe, and drawing a distance-amplitude curve on a oscillographic screen, wherein the distance-amplitude curve is a DAC curve, and the DAC curve is used for evaluating the equivalent size of a defect;
as shown in FIGS. 7-9, the standard test block BZSK-1 has a length of 200mm, a width of 50mm and a height of 50mm, is divided into A, B two areas along the central line, the four sides of the A, B two areas are curved surfaces, and the curved surfaces of the A, B two areas are respectively provided with a depth of 3mm and a width of 0.2 along the circumferential directionSimulated cracks formed by mm through grooves, wherein the curvature radius R of 4 curved surfaces in the area A is R respectively A1 ＝150mm、R A2 ＝200mm、R A3 ＝250mm、R A4 The radii of curvature of the 4 faces of the b region are R B1 ＝350mm、R B2 ＝400mm、R B3 ＝450mm、R B4 ＝500mm。
When a distance-amplitude curve is manufactured, the surface of the probe placed on the standard test block BZSK-1 is selected to be a curved surface similar to the curvature of the detected main pipeline, and the specific principle is as follows:
when the curvature radius of the main pipeline is 150mm or less than R Mother and mother Less than 175mm, selecting a radius of curvature R A1 Curved surface=150 mm; when the curvature radius of the main pipeline is 175mm or less than R Mother and mother Less than 225mm, radius of curvature R is selected A2 Curved surface=200 mm; when the curvature radius of the main pipeline is 225mm or less than R Mother and mother Less than 275mm, selecting a radius of curvature R A3 Curved surface=250 mm; when the curvature radius of the main pipeline is 275mm or less than R Mother and mother Less than 325mm, selecting a radius of curvature R A4 Curved surface=300 mm; when the curvature radius of the main pipeline is 325mm less than or equal to R Mother and mother Less than 375mm, select radius of curvature R B1 Curved surface=350 mm; when the curvature radius of the main pipeline is 375mm or less than R Mother and mother Less than 425mm, radius of curvature R is selected B2 Curved surface=400 mm; when the curvature radius of the main pipeline is 425mm or less than R Mother and mother Less than 475mm, selecting a radius of curvature R B3 Curved surface=450 mm; when the curvature radius R of the main pipeline Mother and mother Not less than 475mm, selecting curvature radius R B4 Curved surface=500 mm.
The method for determining the scanning sensitivity during scanning comprises the following steps: and placing the probe on a test block, finding out the strongest reflected wave of the simulated crack with the depth of 3mm and 10mm from the front edge of the probe, and adjusting the reflected wave to 80% of the screen height to serve as the reference sensitivity. The gain 6dB is increased as the scanning sensitivity based on the reference sensitivity.
Step three, scanning
The probe is arranged near the fillet weld of the tube seat of the steam-water pipeline to be detected, the minimum distance between the front end of the probe and the fillet weld of the tube seat is less than or equal to 1mm and less than or equal to 5mm, the probe is kept in stable contact with the workpiece to be detected, 360-degree circular scanning is carried out along a scanning path, the front edge vertical central line of the probe is ensured to be always tangent to a circle with the radius of r+2.5mm by taking the tube seat opening as the center, and the scanning speed is not more than 150mm/S;
step four, defect identification
Scanning according to the fourth step, quantifying the defects and measuring the positions of the defects to obtain the maximum reflected wave amplitude and the indication length, and judging that all the reflected waves exceeding the height of the distance-amplitude curve obtained in the second step are defect waves;
measurement of defect amplitude: the difference delta between the maximum reflection amplitude of the defect and the height of the distance-amplitude curve is the defect amplitude and is marked as SL (+ -) delta dB;
determination of the position of the defect: determining the position of the defect around the tube hole according to the position of the probe on the detection surface and the horizontal position of the highest reflected wave on the oscillography screen, and recording;
determination of defect length: the indication length is measured by a single-side half wave height method (6 dB method), and the specific method is as follows: and (3) moving the probe to find the strongest reflected wave of the defect, adjusting the wave height to 80% of the screen height, and moving the probe to the outside, wherein when the wave height is reduced to 40% of the screen height, marks are made on the position corresponding to the central line of the probe, and the distance from the marks to the edge of the hole is the indication length of the defect.
And (3) verifying a detection method:
manufacturing radial crack reference blocks DBSK 1-DBSK 4 with holes on a pipe seat, wherein the specification of a main pipe is phi 800mm multiplied by 100mm, the specification of the pipe seat is phi 30mm multiplied by 10mm, 2 artificial defects are processed around the holes on the reference block DBSK1, the length of the defect 1 is 5mm multiplied by the width of the defect 0.2mm multiplied by the depth of the defect 3mm, and the length of the defect 2 is 5mm multiplied by the width of the defect 0.2mm multiplied by the depth of the defect 6mm as shown in figures 9-13; 2 artificial defects are processed around the DBSK2 open hole of the reference block, wherein the defects are 3mm long, 0.2mm wide, 0.2mm deep and 3mm deep, and the defects are 4 mm long, 20mm wide, 0.2mm wide and 3mm deep; 2 artificial defects are processed around the DBSK3 open hole of the reference block, wherein the defects are 5mm long, 10mm wide, 0.2mm deep, 3mm, 6mm long, 0.2mm wide, and 6mm deep; 2 artificial defects are processed around the hole of the reference block DBSK4, wherein the defects are 7mm long by 0.2mm wide by 3mm deep, and the defects are 8mm long by 20mm wide by 0.2mm deep by 3mm. According to the method, the radial cracks of the pipe seat openings are scanned in comparison with the surrounding areas of the test block openings.
The test results are shown in the following table:
| sequence number | Defect numbering | Defect size | Defect location | Maximum wave height | Measured length of defect |
| 1 | Defect 1 | Length 5mm x width 0.2mm x depth 3mm | Axial center line | SL+3.8dB | 6mm |
| 2 | Defect 2 | Length 5mm x width 0.2mm x depth 6mm | Axial center line | SL+5.6dB | 7mm |
| 3 | Defect 3 | 10mm long by 0.2mm wide by 3mm deep | Circumferential center line | SL+5.2dB | 11mm |
| 4 | Defect 4 | 20mm long by 0.2mm wide by 3mm deep | Circumferential center line | SL+6.0dB | 21mm |
| 5 | Defect 5 | 10mm long by 0.2mm wide by 3mm deep | Axial center line | SL+5.5dB | 11mm |
| 6 | Defect 6 | 10mm long by 0.2mm wide by 6mm deep | Axial center line | SL+8.6dB | 12mm |
| 7 | Defect 7 | Length 5mm x width 0.2mm x depth 6mm | Circumferential center line | SL+5.5dB | 6mm |
| 8 | Defect 8 | 20mm long by 0.2mm wide by 6mm deep | Circumferential center line | SL+9.1dB | 22mm |
Through detection, the maximum reflected wave height SL+3.8dB of the defect 1 is detected, and the length measurement value is 6mm; defect 2 maximum reflected wave height sl+5.6db, length measurement 7mm; defect 3 maximum reflected wave height sl+5.2dB, length measurement 11mm; defect 4 maximum reflected wave height sl+6.0dB, length measurement 21mm; defect 5 maximum reflected wave height sl+5.5db, length measurement 11mm; defect 6 maximum reflected wave height sl+8.6db, length measurement 12mm; defect 7 maximum reflected wave height sl+5.5dB, length measurement 6mm; defect 8 maximum reflected wave height SL +9.1dB, length measurement was 22mm.
The detection result shows that the detection method can effectively detect all artificial simulation defects in the reference block, and the minimum defects which can be detected are 5mm long by 0.2mm wide by 3mm deep; the defect position can be accurately measured; the defect length can be accurately measured, the error is less than or equal to 2mm, and in conclusion, the detection method can effectively detect radial cracks on the outer wall of the opening of the steam-water pipeline tube seat.
Claims (5)
1. The radial crack creeping wave detection method for the outer wall of the opening of the steam-water pipeline tube seat is characterized by comprising the following steps of:
step one, determining a scanning path
The method comprises the steps of using the outer wall of a parent pipeline around a pipe seat fillet weld as a detection surface, establishing a two-dimensional graph of a top view of an opening of a pipe seat of a steam-water pipeline to be detected, and carrying out n radial simulated crack defects Q which are evenly distributed along the circumferential direction of the opening on the two-dimensional graph n Where n=1, 2,3,4, …, each simulate a crack defect Q n Is 5mm long and 0.2mm wide and 3mm deep, to simulate each crack defect Q n A vertical line L is formed at the center point along the length direction n Each probe placement position Z n Located at each corresponding vertical line L n On each probe placement position Z n The following conditions are specifically satisfied: is positioned at the probe placement position Z n Upper probeThe front edge of the head is opposite to the corresponding simulated crack defect, and the minimum distance S between the probe and the fillet weld of the tube seat is more than or equal to 1mm and less than or equal to 5mm;
place all probes in position Z n The method is characterized in that a section of smooth transition curve is formed in sequence, namely a scanning path of radial cracks of the pipe seat opening of the outer wall of the steam-water pipeline is a concentric circle taking the pipe seat opening as a circle center, and the radius of the pipe seat opening is r, so that the vertical central line of the front edge of the probe is always tangent to a circle taking the pipe seat opening as the center and having the radius of r+2.5mm in the moving process of the probe;
step two, instrument and equipment selection and parameter setting
The scanning instrument adopts an A-type pulse reflection ultrasonic detector, and a probe selects a long-focus creeping wave twin-crystal parallel probe;
performing performance test on the A-type pulse reflection ultrasonic detector and the probe, setting basic parameters, and preparing a DAC curve by matching with a standard test block BZSK-1, wherein the standard test block BZSK-1 is provided with simulation cracks, and the specific steps of preparing the DAC curve are as follows: placing a probe on a standard test block BZSK-1, simulating cracks at the front edge distance of the probe by 10mm, measuring the strongest reflected wave, adjusting an A-type pulse reflection ultrasonic detector to 80% of screen height, sequentially measuring the simulated crack wave heights at the positions, 20mm, 30mm, 40mm and 50mm, of the front edge distance of the probe, and drawing a distance-amplitude curve on a oscillographic screen, wherein the distance-amplitude curve is a DAC curve, and the DAC curve is used for evaluating the equivalent size of a defect;
step three, scanning
The probe is arranged near the fillet weld of the tube seat of the steam-water pipeline to be detected, the minimum distance between the front end of the probe and the fillet weld of the tube seat is less than or equal to 1mm and less than or equal to 5mm, the probe is kept in stable contact with the workpiece to be detected, 360-degree circular scanning is carried out along a scanning path, the front edge vertical central line of the probe is ensured to be always tangent to a circle with the radius of r+2.5mm by taking the tube seat opening as the center, and the scanning speed is not more than 150mm/S;
step four, defect identification
Scanning according to the fourth step, quantifying the defects and measuring the positions of the defects to obtain the maximum reflected wave amplitude and the indication length, and judging that all the reflected waves exceeding the height of the distance-amplitude curve obtained in the second step are defect waves;
measurement of defect amplitude: the difference delta between the maximum reflection amplitude of the defect and the height of the distance-amplitude curve is the defect amplitude and is marked as SL (+ -) delta dB;
determination of the position of the defect: determining the position of the defect around the tube hole according to the position of the probe on the detection surface and the horizontal position of the highest reflected wave on the oscillography screen, and recording;
determination of defect length: the indication length is measured by adopting a single-side half wave height method, and the specific method is as follows: and (3) moving the probe to find the strongest reflected wave of the defect, adjusting the wave height to 80% of the screen height, and moving the probe to the outside, wherein when the wave height is reduced to 40% of the screen height, marks are made on the position corresponding to the central line of the probe, and the distance from the marks to the edge of the hole is the indication length of the defect.
2. The method for detecting radial crack creeping wave of the outer wall of the opening of the steam-water pipeline tube seat according to claim 1, wherein the parameter requirements of the long-focus creeping wave twin-crystal parallel probe are as follows: the specific scanning sound Cheng Yiban from the tube seat fillet weld edge to the tube hole center point is larger than 20mm, so that a long-focus creeping wave probe with a focal point horizontal distance of 20mm is selected; the probe frequency is 5MHz, the area of a single wafer is 6mm multiplied by 8mm, and the sensitivity of crack defects near the surface layer is met.
3. The method for detecting radial crack creeping wave of the outer wall of the opening of the steam-water pipeline tube seat according to claim 1, wherein the performance requirements of the A-type pulse reflection ultrasonic detector are as follows: testing the vertical linearity and the horizontal linearity of the A-type pulse reflection ultrasonic detector, wherein the vertical linearity error of the A-type pulse reflection ultrasonic detector is required to be not more than 4 percent, and the horizontal linearity error is required to be not more than 1 percent;
the performance requirements of the creeping wave twin-crystal parallel probe are as follows: the creeping wave twin-crystal parallel probe is tested, the horizontal deflection angle of the sound beam axis is not more than 2 degrees, the signal to noise ratio at the position with the maximum detection distance of 50mm is more than 6dB, and the vertical deflection of the main sound beam has no obvious double peaks;
the basic parameters of the A-type pulse reflection ultrasonic detector and the probe are set as follows: the receiving and transmitting mode selects a bicrystal mode, the probe angle is selected to be 82-85 degrees, the calibrated sound velocity is set to be 5900mm/s, and the front edge is set to be 8mm.
4. The method for detecting radial crack creeping wave of the outer wall of a perforated hole of a steam-water pipeline tube seat according to claim 1, wherein the standard test block BZSK-1 is 200mm long, 50mm wide and 50mm high, is divided into A, B areas along a central line, the peripheral side surfaces of the A, B areas are curved surfaces, simulated cracks formed by through grooves with the depth of 3mm and the width of 0.2mm are respectively arranged on the curved surfaces of the A, B areas along the circumferential direction, and the curvature radius R of 4 curved surfaces of the A area is R respectively A1 ＝150mm、R A2 ＝200mm、R A3 ＝250mm、R A4 The radii of curvature of the 4 faces of the b region are R B1 ＝350mm、R B2 ＝400mm、R B3 ＝450mm、R B4 ＝500mm。
5. The method for detecting radial crack creeping wave of the outer wall of the opening of the steam-water pipeline tube seat according to claim 4, wherein when a distance-amplitude curve is manufactured, the surface of the probe placed on the standard test block BZSK-1 is selected to be a curved surface similar to the curvature of the detected main pipeline, and the specific principle is as follows:
when the curvature radius of the main pipeline is 150mm or less than R Mother and mother Less than 175mm, selecting a radius of curvature R A1 Curved surface=150 mm; when the curvature radius of the main pipeline is 175mm or less than R Mother and mother Less than 225mm, radius of curvature R is selected A2 Curved surface=200 mm; when the curvature radius of the main pipeline is 225mm or less than R Mother and mother Less than 275mm, selecting a radius of curvature R A3 Curved surface=250 mm; when the curvature radius of the main pipeline is 275mm or less than R Mother and mother Less than 325mm, selecting a radius of curvature R A4 Curved surface=300 mm; when the curvature radius of the main pipeline is 325mm less than or equal to R Mother and mother Less than 375mm, select radius of curvature R B1 Curved surface=350 mm; when the curvature radius of the main pipeline is 375mm or less than R Mother and mother Less than 425mm, radius of curvature R is selected B2 Curved surface=400 mm; when the curvature radius of the main pipeline is 425mm or less than R Mother and mother Less than 475mm, selecting a radius of curvature R B3 Curved surface=450 mm; when the curvature radius R of the main pipeline Mother and mother Not less than 475mm, selecting curvature radius R B4 Curved surface=500 mm.
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