A pipe corrosion simulation thinning contrast sample for digital radiographic inspection
By setting a semi-annular thinning area and identification code on the tubular sample body, the problem of insufficient simulation of existing flat plate test blocks is solved, realizing high-precision quantitative assessment of corrosion defects in digital X-ray inspection, and improving the accuracy and efficiency of inspection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- TONGLING SPECIAL EQUIP SUPERVISION & INSPECTION CENT
- Filing Date
- 2026-06-10
- Publication Date
- 2026-07-21
Smart Images
Figure CN224535565U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of nondestructive testing technology, and in particular to a comparative sample for simulating thinning of pipe corrosion for digital radiographic testing. Background Technology
[0002] Organic heat carrier boilers (also known as thermal oil boilers) use organic heat carriers as the heat transfer medium, achieving heating temperatures above 300℃ at relatively low pressures. These systems offer high thermal efficiency and low operational safety risks, making them widely used in industrial heating sectors such as petrochemicals and textile printing and dyeing. Their pressure pipelines, as critical heat transfer components, operate under high temperature and pressure conditions for extended periods. Due to corrosion, erosion, and high-temperature oxidation, the pipe walls gradually thin. Regular non-destructive testing of pressure pipeline corrosion is essential to ensure safe equipment operation.
[0003] Digital radiography (DR) technology, with its advantages of high dynamic range, rapid imaging, and digital quantitative processing, has become an important tool for the non-destructive evaluation of pressure equipment in service. Currently, the calibration of the correspondence between image grayscale and penetration thickness in DR testing mainly relies on general-purpose flat stepped test blocks. However, corrosion thinning in actual in-service pipelines occurs on curved pipe walls and often exhibits a gradually changing sloping transition morphology in the axial or circumferential directions. There is a fundamental difference between existing flat stepped test blocks and the actual geometric morphology of pipeline corrosion.
[0004] The existing calibration system based on flat stepped test blocks has the following technical defects:
[0005] First, the simulation of curved surface morphology is lacking. Flat plate test blocks cannot reflect the influence of the circumferential curvature of the pipe on the attenuation path and scattering distribution of rays. The geometric shape of the calibration benchmark is mismatched with that of the actual test object, which means that the actual attenuation law of rays passing through the curved pipe wall cannot be reproduced by flat plate test blocks, and there is geometric distortion in the calibration basis.
[0006] Second, the transition features of defect edges are lost. The abrupt thickness boundary of the existing flat stepped test block cannot simulate the gradually changing slope transition zone commonly seen in actual corrosion thinning. This results in a lack of reference benchmarks for the gray-scale gradient features of defect edges in DR images, which seriously affects the accurate identification and determination of the corrosion boundary range.
[0007] Third, there are systematic errors in quantitative inversion. The image grayscale-wall thickness correspondence established based on the flat plate test block deviates from the actual imaging response of the curved surface thinning. When directly used for inversion of the remaining wall thickness of the pipeline, the calibration curve does not match the actual measurement conditions, resulting in insufficient accuracy in the quantitative assessment of corrosion depth and failing to meet the requirements of high-precision and quantitative DR detection.
[0008] In summary, existing general-purpose flat stepped test blocks cannot accurately simulate the corrosion morphology and gradual transition characteristics of pipeline surfaces, and their calibration systems are insufficient to meet the accuracy requirements for quantitative corrosion detection in in-service pipelines. There is an urgent need for a dedicated comparative specimen that can realistically reproduce the geometric morphology and multi-stage thinning characteristics of pipeline surface corrosion, providing a direct and reliable measurement benchmark for digital radiographic testing. Utility Model Content
[0009] This utility model provides a pipeline corrosion simulation thinning comparison sample for digital radiographic testing, which solves the technical problem that the existing general-purpose flat stepped test block cannot truly simulate the corrosion morphology and gradual transition characteristics of pipeline curved surfaces, resulting in distortion of grayscale and wall thickness calibration in digital radiographic testing and insufficient accuracy in quantitative assessment of corrosion defects.
[0010] In view of the above technical problems, this utility model provides a pipe corrosion simulation thinning comparison specimen for digital radiographic inspection, including a tubular specimen body. Multiple semi-annular thinning regions with different thinning depths are machined along the axial direction on the pipe wall of the specimen body. Each semi-annular thinning region includes a flat bottom area with a constant depth in the middle and a sloping transition area on both sides of the flat bottom area. The specimen body is also provided with an identification code corresponding to the position of each semi-annular thinning region and which can be developed in the radiographic image.
[0011] Optionally, the semi-annular thinning region is divided into two groups and arranged symmetrically about the midpoint of the central axis of the tubular sample body. Each group includes a first thinning region, a second thinning region, a third thinning region and a fourth thinning region sequentially provided from the end face of the tubular sample body.
[0012] The thinning depths of the first thinning zone, the second thinning zone, the third thinning zone, and the fourth thinning zone vary in a stepwise manner along the axial direction of the sample body.
[0013] Optionally, the thinning amounts of the first thinning zone, the second thinning zone, the third thinning zone, and the fourth thinning zone are 8%-10%, 18%-20%, 28%-30%, and 38%-40% of the nominal wall thickness of the sample body, respectively.
[0014] Optionally, the nominal wall thickness of the sample body is 4-4.5 mm.
[0015] Optionally, the identification code is a lead character pasted on the corresponding position on the surface of the sample body.
[0016] Optionally, the width of the flat bottom area is 13-15 mm, the length of the slope transition area of the first thinning area near the end face of the sample body is 23-25 mm, and the length of the slope transition areas of the second thinning area, the third thinning area, and the fourth thinning area is 9-10 mm.
[0017] Optionally, the sample body is made of carbon steel, and the nominal size of the sample body is consistent with the size of the actual pipe to be inspected.
[0018] Optionally, the distance between the first thinning zone and the end face of the sample body is set to 100 mm.
[0019] This invention effectively solves the problem of mismatch between existing flat stepped test blocks and the geometric shape of the pipe surface by using a tubular sample body and processing a semi-annular thinning region on its wall. Since the nominal dimensions and carbon steel material of the sample body are consistent with the actual pipe to be inspected, the ray attenuation path, scattering distribution, and surface penetration thickness variation all match the actual testing conditions, eliminating the geometric distortion caused by flat test blocks and providing a physical calibration benchmark consistent with the surface characteristics of in-service pipes for DR testing. By setting a flat-bottom area and sloping transition areas on both sides within the semi-annular thinning region, the gradual transition morphology of actual corrosion defects is realistically reproduced. The flat-bottom area provides a stable grayscale response area with a constant thinning depth, while the sloping transition area provides the grayscale gradient characteristics of the defect edge; the combination of these two provides a reference benchmark for the transition morphology of corrosion boundaries in DR images, significantly improving the accuracy of corrosion boundary range identification and judgment, and overcoming the defect that existing flat test blocks cannot simulate gradual transition areas due to abrupt thickness changes.
[0020] In this invention, by setting up four thinning zones with stepped thinning depths—a first, second, third, and fourth—and attaching corresponding identification codes that can be developed in X-ray images, a multi-level, locatable grayscale-wall thickness correspondence is established. The different thinning amounts in the four zones, combined with the flat-bottomed area, allow for the acquisition of multiple sets of calibration data points on a single sample. This enables the fitting of a quantitative inversion calibration curve suitable for pipes of the same specifications, eliminating systematic errors between existing flat plate calibration systems and the actual imaging response of curved surface thinning, significantly improving the accuracy of quantitative corrosion depth assessment. Two sets of semi-annular thinning regions symmetrically arranged about the midpoint of the central axis on the sample body allow for simultaneous provision of thinning image references for both the inner and outer pipe walls in a single exposure. Inspectors can obtain multi-directional calibration data without flipping the sample, simplifying the inspection process and improving calibration efficiency. Simultaneously, this symmetrical layout facilitates the comparison of imaging responses under different X-ray incident conditions, providing convenience for the systematic optimization of inspection process parameters.
[0021] In summary, this invention integrates multiple levels of semi-annular thinning regions, flat-bottomed regions, sloping transition regions, and lead-based identification codes onto a tubular curved surface, forming a set of calibrable and comparable dedicated standards. This provides a direct and reliable basis for calibrating the correspondence between image grayscale and wall thickness, quantitatively inverting defects, and optimizing detection process parameters. It effectively solves the problem of defect identification and quantitative assessment caused by calibration benchmark distortion in digital radiographic testing of in-service pipelines, and helps to improve the standardization level and evaluation reliability of pipeline corrosion DR detection. Attached Figure Description
[0022] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 This is a schematic diagram of the cross-sectional structure of a pipe corrosion simulation thinning comparison sample used for digital X-ray inspection in one embodiment of this utility model;
[0024] Figure 2 This is a schematic diagram of the overall structure of a pipe corrosion simulation thinning comparison sample used for digital X-ray inspection in one embodiment of this utility model.
[0025] Figure 3 yes Figure 2 Schematic diagram of the outer thinning zone;
[0026] Figure 4 This is a schematic diagram of the inner thinning zone;
[0027] Figure 5 This is a schematic diagram of the inversion data of the same-amplitude step interpolation method A and the in-situ calibration method B of the equivalent attenuation model; where (a) represents the inversion residual thickness distribution of algorithm A and algorithm B; and (b) represents the residual distribution of algorithm A and algorithm B.
[0028] The reference numerals in the accompanying drawings are as follows:
[0029] 1-Sample body, 2-Semi-annular thinning region, 21-First thinning region, 22-Second thinning region, 23-Third thinning region, 24-Fourth thinning region, 3-Flat bottom region, 4-Sloping transition region. Detailed Implementation
[0030] To make the technical problems solved, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.
[0031] In the description of this utility model, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.
[0032] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0033] like Figures 1 to 4 As shown, one embodiment of this utility model provides a pipe corrosion simulation thinning comparison sample for digital radiographic inspection, including a tubular sample body 1. Multiple semi-annular thinning regions 2 with different thinning depths are machined along the axial direction on the pipe wall of the sample body 1. Each semi-annular thinning region 2 includes a flat bottom region 3 with a constant depth in the middle and a sloping transition region 4 located on both sides of the flat bottom region 3. The sample body 1 is also provided with an identification code (not shown) that corresponds to the position of each semi-annular thinning region 2 and can be developed in the radiographic image.
[0034] In one embodiment, such as Figure 1 As shown, the semi-annular thinning region 2 is divided into two groups and is symmetrically arranged about the midpoint of the central axis of the tubular sample body 1. Each group includes a first thinning region 21, a second thinning region 22, a third thinning region 23 and a fourth thinning region 24 arranged sequentially from the end face of the tubular sample body 1.
[0035] The thinning depths of the first thinning region 21, the second thinning region 22, the third thinning region 23, and the fourth thinning region 24 vary in a stepped manner along the axial direction of the sample body 1.
[0036] In one embodiment, such as Figure 1 As shown, the thinning amounts of the first thinning region 21, the second thinning region 22, the third thinning region 23 and the fourth thinning region 24 are 8%-10%, 18%-20%, 28%-30% and 38%-40% of the nominal wall thickness of the sample body 1, respectively.
[0037] In one embodiment, such as Figure 1 As shown, the nominal wall thickness of the sample body 1 is 4-4.5 mm.
[0038] In one embodiment, such as Figure 1 As shown, the identification code is a lead character affixed to the corresponding position on the surface of the sample body 1. The lead characters are coded from 1 to 4, corresponding one-to-one with the four thinning zones.
[0039] In one embodiment, such as Figure 1 As shown, the width of the flat bottom area 3 is 13-15mm, the length of the slope transition area 4 of the first thinning area 21 near the end face of the sample body 1 is 23-25mm, and the length of the slope transition area 4 of the second thinning area 22, the third thinning area 23 and the fourth thinning area 24 is 9-10mm.
[0040] In one embodiment, such as Figure 1 As shown, the sample body 1 is made of carbon steel, and the nominal size of the sample body 1 is consistent with the size of the actual pipe to be inspected. Understandably, for example, if the nominal size of the actual pipe to be inspected is Φ89mm×4mm and the length is 510mm, then the nominal size of the sample body 1 is consistent with the size of the actual pipe to be inspected.
[0041] In one embodiment, such as Figure 1 As shown, the distance between the first thinning zone 21 and the end face of the sample body 1 is set to 100mm.
[0042] In this invention, the process of using the pipeline corrosion simulation thinning comparison sample for digital X-ray inspection is as follows:
[0043] S1. Sample installation and positioning: Fix the sample body 1 horizontally or vertically on the support device of the DR detection system, adjust the relative positions of the X-ray source, the sample body 1 and the detector so that the center of the X-ray beam passes vertically through the axis of the sample body 1 and covers all the semi-annular thinning areas 2 and the identification code; place the identification code facing the detector to ensure clear imaging of the identification.
[0044] Understandably, the above positioning ensures that the rays penetrate the tube wall of the sample body 1 perpendicularly, so that the first thinning area 21, the second thinning area 22, the third thinning area 23 and the fourth thinning area 24 in the semi-annular thinning area 2 are all fully projected onto the detector receiving surface, providing a complete field of view for subsequent grayscale extraction.
[0045] S2. Setting of detection process parameters: Based on the material and nominal wall thickness of the sample body 1, set the detection process parameters such as tube voltage, tube current, focal length and integration time.
[0046] Understandably, the parameter settings need to match the carbon steel material and 4-4.5mm nominal wall thickness of the sample body 1 to ensure that the DR image has sufficient contrast and signal-to-noise ratio, so that the semi-annular thinning region 2 with different thinning depths forms a distinguishable grayscale difference in the image.
[0047] S3. Digital X-ray Exposure and Image Acquisition: Start the DR system to perform exposure and acquire a digital X-ray image of the sample body 1.
[0048] Understandably, in the obtained image, the four semi-annular thinning regions 2 will appear as alternating light and dark image bands, with their gray levels transitioning sequentially from the deepest thinning region 21 to the shallowest thinning region 24; in each semi-annular thinning region 2, the flat bottom region 3 exhibits a uniform gray level distribution, and the sloping transition regions 4 on both sides exhibit a gray level gradient feature; the identification code is superimposed as a high-contrast black number on the corresponding thinning band image to achieve region positioning.
[0049] S4. Gray-scale extraction and calibration curve establishment: Using image analysis software, the average gray-scale value is extracted from the center of the flat bottom area 3 indicated by each of the identification codes, and the gray-scale change gradient of each of the slope transition areas 4 is measured to establish a quantitative relationship between the nominal remaining wall thickness and the average gray-scale of the image, thus forming a calibration curve.
[0050] Understandably, by extracting the center grayscale of the flat bottom area 3 corresponding to the first thinning area 21 to the fourth thinning area 24, grayscale-wall thickness data points corresponding to 8%-10%, 18%-20%, 28%-30%, and 38%-40% of the nominal wall thickness can be obtained, and then a quantitative inversion calibration curve suitable for pipes of the same specification can be fitted.
[0051] S5. Calibration of the detection system and evaluation of unknown pipelines: The detection system is calibrated based on the calibration curve, and the corrosion degree of the unknown pipeline area under inspection is evaluated based on this. Alternatively, it can be used for system comparison and optimization of different DR detection process parameters, as well as operation training and skills assessment for inspection personnel.
[0052] Understandably, since the nominal dimensions of the sample body 1 are consistent with the actual pipeline to be inspected, and the semi-annular thinning region 2 realistically simulates the morphology of the flat bottom region 3 and the sloping transition region 4 of the pipeline's curved surface corrosion, this calibration curve can be directly transferred to the DR inspection of in-service pipelines, eliminating the systematic errors caused by the flat plate test block and achieving accurate quantitative assessment of corrosion defects. Furthermore, under the same digital radiography inspection process parameters, by first comparing the grayscale values of different thinning regions of the simulated sample through radiography, a thickness-grayscale mapping relationship is established. Then, the actual workpiece is radiographed, and the grayscale values within the region of interest are analyzed to infer the pipeline corrosion situation.
[0053] In one specific embodiment, under double-wall single-shadow illumination conditions, the ray needs to penetrate two layers of the tube wall. Two technical approaches can be compared: one is the same-amplitude step interpolation method A, and the other is the in-situ calibration method B based on the equivalent attenuation model. Using these two inversion methods, the remaining wall thickness of the inner and outer thinned areas under different geometric distances D is calculated. To visually present the variation of inversion accuracy with spatial location, comparative data and residuals under three illumination distances are extracted and analyzed sequentially. Under the optimal illumination condition where the detector is close to the thinned side (D=5mm), geometric unsharpenedness is suppressed to a minimum. The inversion data and corresponding residual distributions of the two methods are shown in Table 1.1. Figure 5 As shown.
[0054] Table 1.1 shows the inversion of residual thickness and residual using methods A and B when D=5mm.
[0055]
[0056] In Table 1.1, This represents the thickness value obtained by the same-width step interpolation method A inversion. This represents the thickness value retrieved by in-situ calibration method B based on the equivalent attenuation model. This represents the residual, which is the difference between the thickness value retrieved by the same-width step interpolation method A and the nominal thickness value; The residual represents the difference between the thickness value retrieved by the in-situ calibration method based on the equivalent attenuation model B and the nominal thickness value. Figure 5 In the diagram (a), the inversion residual thickness distributions of Algorithm A and Algorithm B are represented. Figure 5 In the diagram (b), the residual distributions of algorithm A and algorithm B are shown, with the residual on the ordinate being... and The term refers to the total number of inverted values. The magnitude of the residual is a key indicator of the error between the inverted value and the nominal value; a smaller residual indicates higher accuracy of the inverted value. From the data in Table 1.1, we can calculate the residuals at positions 1, 2, 3, 4, and 5 in the inner thinning region. The maximum value is 0.354 mm, and the average absolute value is 0.2738 mm. The maximum value is 0.558 mm, and the average absolute value is 0.3446 mm; calculate the difference between the inversion value and the nominal value at positions 1, 2, 3, 4, and 5 in the outer thinning zone. The maximum value is 0.596 mm, and the average absolute value is 0.3992 mm. The maximum value is 0.835 mm, and the average absolute value is 0.4690 mm. This indicates that, regardless of the maximum or average value of the thinning residuals of the inner and outer walls, the residual value of the same-amplitude step interpolation method is relatively small, and its accuracy is significantly superior. This is because the method has the physical advantage of having a synchronous reference from the same source, which effectively offsets the exposure fluctuations and the drift of the scattering baseline. In contrast, the in-situ calibration method based on the equivalent attenuation model is limited by a single global coefficient and cannot fully compensate for the local systematic deviation caused by the spatial non-uniform attenuation caused by the curvature of the tube.
[0057] The above-described embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.
Claims
1. A comparative specimen for simulating thinning of pipe corrosion using digital radiographic testing, characterized in that, The sample includes a tubular sample body (1), and multiple semi-annular thinning regions (2) with different thinning depths are processed along the axial direction on the tube wall of the sample body (1). Each semi-annular thinning region (2) includes a flat bottom region (3) with a constant depth in the middle and a slope transition region (4) located on both sides of the flat bottom region (3). The sample body (1) is also provided with an identification code that corresponds to the position of each semi-annular thinning region (2) and can be developed in X-ray images.
2. The pipe corrosion simulation thinning comparison sample for digital X-ray inspection according to claim 1, characterized in that, The semi-annular thinning region (2) is divided into two groups and is symmetrically arranged about the midpoint of the central axis of the tubular sample body (1). Each group includes a first thinning region (21), a second thinning region (22), a third thinning region (23) and a fourth thinning region (24) arranged sequentially from the end face of the tubular sample body (1). The thinning depths of the first thinning region (21), the second thinning region (22), the third thinning region (23) and the fourth thinning region (24) vary in a stepwise manner along the axial direction of the sample body (1).
3. The pipeline corrosion simulation thinning comparison sample for digital X-ray inspection according to claim 2, characterized in that, The thinning amounts of the first thinning zone (21), the second thinning zone (22), the third thinning zone (23), and the fourth thinning zone (24) are 8%-10%, 18%-20%, 28%-30%, and 38%-40% of the nominal wall thickness of the sample body (1), respectively.
4. The pipeline corrosion simulation thinning comparison sample for digital X-ray inspection according to claim 3, characterized in that, The nominal wall thickness of the sample body (1) is 4-4.5 mm.
5. The pipe corrosion simulation thinning comparison sample for digital X-ray inspection according to claim 4, characterized in that, The identification code is a lead character pasted on the corresponding position on the surface of the sample body (1).
6. The pipeline corrosion simulation thinning comparison specimen for digital X-ray inspection according to claim 4, characterized in that, The width of the flat bottom area (3) is 13-15 mm, the length of the slope transition area (4) of the first thinning area (21) near the end face of the sample body (1) is 23-25 mm, and the length of the slope transition area (4) of the second thinning area (22), the third thinning area (23) and the fourth thinning area (24) is 9-10 mm.
7. The pipeline corrosion simulation thinning comparison sample for digital X-ray inspection according to claim 6, characterized in that, The sample body (1) is made of carbon steel, and the nominal size of the sample body (1) is consistent with the actual size of the pipe to be inspected.
8. The pipe corrosion simulation thinning comparison sample for digital X-ray inspection according to claim 7, characterized in that, The distance between the first thinning zone (21) and the end face of the sample body (1) is set to 100 mm.