Full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants

Abstract

This paper presents a full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants. [Solution] The method includes: performing a defect inspection on a steel lining weld using a low-frequency magnetic inspection method to determine the defect depth, simultaneously determining the inspectable thickness range of the low-frequency magnetic inspection method using a general-purpose calibration test block in the calibration comparison test block, and if the inspectable thickness range covers the thickness of the steel lining to be inspected, the weld inspection work is completed, and if it does not cover the thickness, proceeding to the next step; pre-treating the surface of the steel lining weld to be inspected and the adjacent base material surface to produce a metallic luster; reconfirming the thickness of the steel lining; and inspecting the area of ​​the steel lining weld that has not been inspected by the low-frequency magnetic inspection method using a transverse wave ultrasonic inspection method.

Description

Technical Field

[0001] The present invention belongs to the technical field of compressed air energy storage, and relates to a full-coverage non-destructive inspection method for the welded joints of the steel lining of an underground cavity in a compressed air energy storage power plant.

Background Art

[0002] With the promotion of the construction of China's new power system, the energy storage industry has been growing rapidly. Among them, compressed air energy storage is suitable for large-scale energy storage, so it is widely applied in energy storage on the grid side, power source side and user side, and can play roles such as peak shifting, frequency adjustment, capacity reserve, reactive power compensation, and black start. Currently, the construction of compressed air energy storage power plants mainly concentrates in areas rich in salt cave resources such as Jintan City, Jiangsu Province, Yingcheng City, Hubei Province, and Feicheng City, Shandong Province. By utilizing the existing salt cave resources, the construction cost can be significantly reduced and the economic efficiency of the project can be improved. On the other hand, geographical constraints limit the development of compressed air energy storage and cannot meet the energy storage development needs of other regions. To solve this problem, the use of artificial underground gas storage (underground cavity) is becoming a mainstream option for large-scale compressed air energy storage power plants.

[0003] The steel flexible sealing layer (steel lining) is a crucial component of underground cavities. Located inside the cavity, it contains compressed air, while the exterior is surrounded by a secondary concrete lining, primary support, and surrounding rock. The steel lining plays a vital role in cavity sealing and the transmission of structural stresses. Therefore, the structural integrity and long-term operational reliability of the steel lining are extremely important. The steel lining of underground cavities in compressed air energy storage power plants is typically formed by assembling and welding numerous thin, curved steel plates on-site. Generally, high-strength carbon steel or low-alloy steel with excellent fatigue resistance is selected, and depending on the capacity of the gas storage facility, the length of the welded section can reach several thousand or even tens of thousands of meters. Due to the structural constraints of the underground cavity, the steel lining must be formed on both sides by single-sided welding from the inside, and multiple welding positions such as downward, vertical, and upward welding are present. This presents certain difficulties in on-site welding and control of welding quality, and also introduces new challenges to the inspection of the steel lining. Furthermore, energy storage systems have high requirements for the cleanliness of compressed air in the gas storage facility and the steel lining. Failure to meet the required cleanliness can adversely affect equipment such as expansion devices during the energy release phase due to expansion. Therefore, inspection of the steel lining must not generate new impurities that are difficult to treat and must not cause secondary contamination.

[0004] Currently, researchers have not yet proposed a specialized and systematic inspection method for steel-lined welds in underground cavities of compressed air energy storage power plants. Because the structure is similar to the welds of butt-jointed plate structures, it is easy to conceive of using the same inspection methods as for butt-jointed plate welds, and generally, surface magnetic particle or penetrant testing and internal ultrasonic testing methods are used. However, conventional surface inspection techniques such as magnetic particle and penetrant testing can intuitively visualize surface defects, but they are limited to inspecting defects that open to the surface or embedded defects up to about 1 mm below the surface. In addition, reagents such as contrast enhancers, magnetic suspensions, penetrants, and cleaning agents used in the inspection may cause secondary contamination and are not suitable for direct application to the inspection of steel linings. Furthermore, the existing ultrasonic inspection standard (NB / T47013.3-2015) stipulates that ultrasonic inspection is only applicable to plate materials with a thickness of 6 mm or more. However, the steel lining of the underground cavities of the compressed air energy storage power plant currently in use is only 4 mm thick, making the existing standard inapplicable. In addition, conventional ultrasonic inspection often uses oil-based binders, which similarly leads to the problem of secondary contamination. As described above, conventional methods have a blind spot in the inspection of welds on thin steel plates less than 6 mm thick (the standard cannot be applied), and on the other hand, they may cause secondary contamination. Therefore, research into new inspection methods is urgently needed. [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to solve the problem of inspecting the structural integrity of steel-lined welds in underground cavities of compressed air energy storage power plants, and to provide a full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants that has the characteristics of intuitive inspection results and high inspection sensitivity, and can realize highly sensitive and full-coverage inspection of welds. [Means for solving the problem]

[0006] The technical solution employed in this invention is a full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants, specifically, Step 1 involves using a low-frequency magnetic testing method to inspect defects in steel-lined welds and determine the defect depth. Simultaneously, the inspectable thickness range of the low-frequency magnetic testing method is determined using a general-purpose calibration test block in the calibration comparison test block. If the inspectable thickness range covers the thickness of the steel lining being inspected, the weld inspection is completed; otherwise, the process proceeds to Step 2. Step 2 involves pre-treating the surface of the steel-lined weld to be inspected and the adjacent base material surface to produce a metallic luster, Step 3 involves reconfirming the thickness of the steel lining, The procedure is carried out according to step 4, which involves using transverse wave ultrasonic testing to inspect the steel-lined weld area that was not inspected in step 1 using the low-frequency magnetic testing method.

[0007] In the present invention, further, Step 1 specifically involves: Step 1.1 involves determining the inspectable thickness range of the low-frequency magnetic inspection method using a general-purpose calibration test block from the calibration comparison test block, We perform defect inspections using a low-frequency magnetic flaw detection device, specifically, Steps 1 and 2 involve attaching a defect indicator film to the inner surface of the area to be inspected on the steel lining, positioning a yoke across both sides of the weld, performing inspections sequentially using the cross-crossing method, ensuring that the coverage area of ​​the two inspections (front and back) overlaps by at least 10% during movement to prevent any missed inspections, applying electricity to magnetize the film, and continuously observing any changes on the indicator film. Step 1.3 involves, after the magnetic particle pattern appears on the defect indicator film, changing the magnetic field application angle in at least two ways, selecting the angle at which the defect indication becomes more pronounced, taking and saving a photograph on-site, and marking the position of the magnetic particle pattern. Step 1.4 involves quantifying the defect depth using the depth comparison test block within the calibration comparison test block, The process is characterized by being carried out in accordance with step 1.5, which involves evaluating the grade of the inspection results for steel-lined welds.

[0008] Regarding the specific structure of the calibration comparison test block, The calibration comparison test block includes one set of general-purpose calibration test blocks and one depth comparison test block. The general-purpose calibration test block consists of 15 test pieces with a thickness interval of 1 mm, the thinnest test piece being 1 mm thick and the thickest test piece being 15 mm thick. The surface of the test pieces is provided with three circular grooves of different depths and three cross-shaped grooves of different depths, the depths of the circular grooves being 7 μm, 15 μm, and 30 μm, respectively, and the lengths of the two straight lines of the cross-shaped grooves being 6 mm each, with groove depths of 7 μm, 15 μm, and 30 μm, respectively. The depth comparison test block is an oblique wedge-shaped test block, 150 mm long and 15 mm thick, with a flat top and a sloped bottom, a 150 mm scale engraved on the edge of the flat top, and three straight grooves of different depths uniformly provided on the sloped bottom, with groove depths of 7 μm, 15 μm, and 30 μm, respectively.

[0009] In step 1.1, the specific step of determining the inspectable thickness range of the low-frequency magnetic inspection method using a general-purpose calibration test block is: Select one test piece from the general calibration test block, and the thickness of the test piece is the same as that of the thin-walled steel member to be measured, or the thickness is as close as possible to that of the thin-walled steel member and greater than that of the thin-walled steel member, and then attach the defect indicator film to the grooveless surface of the test piece. Adjust the pulse frequency of the yoke-type low-frequency magnetic flaw detector to 50Hz, place the yoke on a grooveless surface, and start the flaw detector. If the pulse frequency value can be adjusted until a magnetic particle pattern appears on the display film on the calibration test piece, it indicates that the inspectable thickness range of the low-frequency magnetic inspection covers the thickness of the steel lining being inspected. If the magnetic particle pattern does not appear at all, the test may be performed sequentially using other calibration test pieces thinner than the thickness of the steel lining being measured, in an order of decreasing thickness, until the magnetic particle pattern appears. The maximum thickness D of the test piece that can display the magnetic particle pattern may then be set as the maximum inspection depth for the low-frequency magnetic test.

[0010] In step 1.4, the specific step of quantifying the defect depth using the depth comparison test block is: After determining the location of the defective magnetic particle pattern, the pulse frequency of the low-frequency magnetic flaw detector may be gradually increased until the defective magnetic particle pattern disappears, the parameters of the instrument may be locked at this time, the defect indicator film may be attached to the grooveless surface of the depth comparison test block, the yoke may be placed on the grooveless surface, the inspection device may be restarted, the length of the indicated magnetic particle pattern on the surface may be observed, and the corresponding defect depth may be read by comparing it with the scale to determine the depth of the inspected defect.

[0011] Step 4 specifically involves: Using the CSK-IA test block, and according to the ultrasound equipment's specific adjustment program, in the first step, the highest reflected waves of Φ50mm and Φ100mm arcs are simultaneously found, the distance to the leading edge of the probe is measured, and then input into the instrument. Step 4.1 involves finding the highest wave in a Φ50mm stepped hole with a depth of 30mm, inputting it into the instrument, and determining the actual K value of the probe. Step 4.2 involves drawing a DAC curve using an ultrasound comparative test block and creating a reference point or reference line, Step 4.3 involves adding water as a binder to the polishing areas on both sides of the weld to be inspected, selecting the DAC curve created in the first channel, applying a 4dB bonding correction, adjusting the reflection amplitude of the 2mm deep transverse through hole to more than 80% of the entire screen, placing the ultrasonic probe on the polishing area and performing a zigzag scan, with a scan speed of 150mm / s or less, monitoring the waveform changes on the oscilloscope screen in real time during the scan, focusing on observing one or three reflection echoes in the TD range at the root of the weld, and repeating the scan on the opposite side after the scan on one side is completed to ensure full coverage inspection of the weld. If it is detected that the reflected echo exceeds the DAC curve, the location information of the defect is reconfirmed from multiple angles on at least both sides of the weld. If the defect is inside the weld joint, the length is measured using the -6dB method, and the information from the longer side is recorded. The depth, length, location, and amplitude of the defect are recorded. Step 4.4 involves marking the location on the surface of the joint, and if the inspected defect is located within the root of the weld, calling up the reference point or reference line of the second channel, comparing the waveform and reflected equivalent, and determining the nature and size of the defect. Step 4.5, which involves performing inspection grade evaluation and quality evaluation on steel-lined welds, may also be carried out in accordance with this procedure.

[0012] In Step 4.2, the specific structure of the ultrasound comparative test block is described below. The ultrasound comparative test block consists of three parts: a transverse through-hole region located in the middle, a first stepped groove region located at both ends, and a second stepped groove region. In the transverse through-hole region, six transverse through-holes are distributed sequentially from top to bottom. The horizontal spacing between each transverse through-hole is ≥15 mm, and the vertical spacing is 3 mm. The distance between the uppermost transverse through-hole and the top surface of the ultrasound comparison test block is 3 mm, and the distance between the lowermost transverse through-hole and the bottom surface of the ultrasound comparison test block is 2 mm. The first stepped groove region contains six steps, with the height of each step varying by 3 mm sequentially, and the step at the outermost end being 3 mm high. The stepped groove area with a difference in the second paragraph includes seven steps, and the height of each step difference is different by 3 mm in order. The height of the step located at the outermost end is 2 mm. At the center of the step, a groove with a width of 0.1 mm and a depth of 1 mm may be provided in the width direction of the ultrasonic inspection comparison test block.

[0013] Step 4.2 is specifically Select the first channel by the adjustment program inherent in the ultrasonic inspection device, and select all the through holes with a depth greater than the thickness of the steel lining and closest to the thickness of the steel lining according to the thickness of the steel lining, and create a DAC curve. Use the DAC curve as the comparison curve. Select the second channel separately, and it may also be to select based on the groove depth equal to the thickness of the steel lining to be inspected or the two groove depths closest to the groove depth, and create a reference point or reference line.

[0014] In step 4.4, the specific grade evaluation criteria are 1) When it is qualitatively judged that the nature of the defect is a crack, poor fusion, or incomplete penetration, it is judged as unqualified. 2) When the reflection equivalent of the defect exceeds the DAC curve, it is a defect exceeding the standard and is judged as unqualified, and When the reflection equivalent of the defect does not exceed the DAC curve a. When the length of a single defect ≧ the plate thickness, it is judged as unqualified. b. When the length of a single defect < the plate thickness, it may be judged as a defect to be recorded and judged as qualified.

[0015] Regarding the beneficial effects of the present invention The method of the present invention is applicable to the steel lining in the underground cavity of a compressed air energy storage power plant, corresponding to features and requirements such as a thin thickness of the steel plate, an invisible outer wall, a long length of the welded joint, and no generation of contamination during inspection. Furthermore, it fully considers factors such as efficiency, sensitivity, and economy in non-destructive inspection. In the method of the present invention, the welded joint of the steel lining is inspected by adopting a low-frequency magnetic inspection method, and in the inspection process, a self-made calibration comparison test block is adopted to perform calibration and determination of the defect depth. Thus, a full-coverage inspection for a thin-walled (generally less than 8 mm) steel lining can be realized. The inspection procedure is simple, the inspection results can be intuitively grasped. In the case of a relatively thick thin-walled steel lining (greater than 8 mm), based on low-frequency magnetic inspection and using transverse wave ultrasonic inspection as an auxiliary means, a full-coverage inspection of the welded joint is realized. The method of the present invention makes full use of the features and advantages of the above two inspection methods, has high process compatibility, high sensitivity, good inspection effect, can fully ensure the welding quality of the steel lining, and does not generate contamination throughout the entire inspection process.

Brief Description of the Drawings

[0016] [Figure 1] It is a flowchart of the method of the present invention. [Figure 2] It is a structural schematic diagram of a single general calibration test piece in the calibration comparison test block used in the method of the present invention. [Figure 3] It is a top view of the depth comparison test block in the calibration comparison test block used in the method of the present invention. [Figure 4] It is a side view of the depth comparison test block in the calibration comparison test block used in the method of the present invention. [Figure 5] It is a structural schematic diagram of the groove on the inclined surface of the depth comparison test block in the calibration comparison test block used in the method of the present invention. [Figure 6] It is a structural schematic diagram of the ultrasonic inspection comparison test block used in the method of the present invention. [Figure 7]This is a top view of the ultrasound examination comparison test block used in the method of the present invention. [Modes for carrying out the invention]

[0017] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0018] [Embodiment 1] The present invention provides a full-coverage (overall) non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants, which is specifically carried out according to the following steps 1 to 4, as shown in Figure 1.

[0019] Step 1: Use a low-frequency magnetic testing method to inspect for defects in the steel-lined welds and determine the defect depth.

[0020] The principle of low-frequency magnetic testing is as follows: Low-frequency magnetic flaw detection devices magnetize the yoke by employing the principle of phase adjustment and frequency conversion of DC pulsed current. Because it is driven by DC pulsed current, the instantaneous start shock and magnetization current are large, and the generated magnetic flux is more than ten times that of conventional commercial frequency (50Hz) AC magnetic field flaw detection devices. By generating different pulse widths at different magnetization frequencies, the power consumption of the equipment is kept to a minimum when the flaw detection sensitivity is at its highest.

[0021] The flaw detection will be performed using a low-frequency magnetic flaw detection device, and the specific process parameter requirements are as follows:

[0022] (1) Magnetization method: Yoke method, magnetic pole spacing range: 75~200mm. (2) Type and parameters of magnetization current: DC pulse current, pulse frequency range: 0 <f≦50Hz。 (3) Lifting force: ≥ 177N. (4) Test block type: A self-made calibration comparison test block for low-frequency magnetic testing. (5) Display medium for magnetic powder patterns: Defect indicator film. (6) Magnetization time: 1~3s.

[0023] The structure of the self-made calibration comparison test block for low-frequency magnetic testing, as shown in Figures 2 to 5, includes one set of general-purpose calibration test blocks and one depth comparison test block. The general-purpose calibration test block consists of 15 test pieces of varying thicknesses, with a thickness range of 1 to 15 mm and a thickness interval of 1 mm. As shown in Figure 2, each test piece is machined with three circular grooves 1 and three cross-shaped grooves 2. The depths of the three circular grooves 1 are 7 μm, 15 μm, and 30 μm, respectively. The lengths of the two straight lines of the three cross-shaped grooves 2 are all 6 mm, and the groove depths are 7 μm, 15 μm, and 30 μm, respectively. Furthermore, the diameters of the three circular grooves 1 may be 10 mm, 25 mm, and 40 mm, respectively, and as shown in Figure 2, the smaller diameter circular grooves can be placed within the larger diameter grooves. The test specimen may also be a square specimen with a side length of 60 mm, and in terms of the diameter, side length dimensions, and arrangement of the circular grooves, the diagonal of the test specimen is slightly larger than the spacing of the yokes, just meeting the usage requirements and representing the minimum dimensional scheme.

[0024] As shown in Figures 3 to 5, the depth comparison test block is a diagonally wedge-shaped test block with a flat top and a sloped bottom. The test block is 150 mm long, 15 mm thick, and ≥ 100 mm wide. A 150 mm scale is engraved on the edge of the flat top of the test block, and three straight grooves 3 with depths of 7 μm, 15 μm, and 30 μm are uniformly provided on the sloped bottom, and marks indicating the groove depths are provided on the side of the test block.

[0025] The material of the calibration comparison test block is the same as the material of the steel lining being inspected, or 45# steel, and its main chemical composition conforms to GB699 "Steel Grades and General Technical Conditions for Superior Carbon Structural Steel". After annealing, the grain size should reach grade 7 or higher, and there should be no groove defects larger than 1 μm in any direction on the interior or surface. The surface roughness of the test block should be Ra ≤ 0.4 μm on each surface, and the parallelism of the end faces should be ≤ 5 μm. The outer surface should be free from obvious scratches, dents, rust, or other defects.

[0026] The inspection steps are as follows:

[0027] Step 1.1: Calibrate and adjust the inspection capability of the low-frequency magnetic inspection device using the general-purpose calibration test block in the above calibration comparison test block.

[0028] Select a calibration test piece whose thickness is equal to or slightly greater than the thin-walled steel lining being measured (for example, if the thickness of the steel lining is 4.5 mm, select a test piece with a thickness of 5 mm), attach the defect indicator film to the grooveless surface of the test piece, adjust the pulse frequency of the yoke-type low-frequency magnetic flaw detector to 50 Hz, place the yoke on the grooveless surface, start the flaw detector, and adjust the pulse frequency value until a magnetic particle pattern appears on the indicator film on the calibration test piece. If this can be adjusted, it indicates that the inspection of the steel lining weld can be completed using only low-frequency magnetic testing. Once step 1 is complete, the entire inspection process is finished. If no magnetic particle pattern appears at all, test using other calibration test pieces thinner than the thickness of the steel lining being measured in decreasing order until a magnetic particle pattern appears, and record the maximum thickness D of the test piece that can display a magnetic particle pattern. In this way, the maximum inspection depth of the low-frequency magnetic testing is determined, and after step 1 is completed, steps 2 to 4 are performed continuously. The parameters of the device used when displaying magnetic powder patterns are locked as inspection parameters.

[0029] Step 1.2: Conduct on-site inspections A defect indicator film is attached to the inner surface of the area to be inspected on the steel lining, and a yoke is positioned to straddle both sides of the weld. Inspections are performed sequentially using the cross-crossing method, and the coverage area of ​​the two inspections (front and back) overlaps by at least 10% during movement to ensure that no inspections are missed. The film is then magnetized by applying electricity, and changes on the indicator film are continuously observed.

[0030] Step 1.3: Defect Record After the magnetic particle pattern appears on the defect indicator film, at least two different magnetic field application angles are changed, and a photograph is taken on-site and saved at the angle in which the defect is more pronounced. The position of the magnetic particle pattern is then marked, and when the inspection work is completed, the indicator film in that area is cut and saved.

[0031] Step 1.4: Quantify the defect depth using the depth comparison test block in the calibration comparison test block described above.

[0032] After determining the location of the defective magnetic particle pattern, the pulse frequency of the low-frequency magnetic flaw detector is gradually increased until the defective magnetic particle pattern disappears, and the parameters of the instrument are locked at this time. The defect indicator film is attached to the grooveless surface of the depth comparison test block, the yoke is placed on the grooveless surface, and the inspection device is restarted. The indicated length of the magnetic particle pattern on the surface is observed and compared with the scale to read the corresponding defect depth (for a ratio of 10:1, if the defect length is 50 mm, the corresponding depth is 5 mm), and in this way the depth of the inspected defect is determined.

[0033] Step 1.5: Inspection Grade Evaluation and Quality Evaluation In accordance with the requirements of the Steel Lining Inspection Standard (see NB / T47013.4-2015), the inspection results of the welded joints are graded. If the length of the linear magnetic particle pattern is ≤ 1.5 mm, it is graded as Grade I. If the diameter of the circular defect magnetic particle pattern is ≤ 2.0 mm and the number within the evaluation frame (the dimensions of the evaluation frame are 35 mm x 100 mm) is 1 or less, it is also graded as Grade I. If it exceeds Grade I, it is graded as Grade II. The weld is then judged to be acceptable or not in light of the Steel Lining Quality Standard and the provisions of the contract.

[0034] [Embodiment 2] Based on Embodiment 1, the following steps are performed.

[0035] In step 1.1, if a magnetic particle pattern can be displayed on a test piece equal to the thickness of the steel lining, and the entire inspection process is completed, and no magnetic particle pattern is displayed on the test piece equal to the thickness of the steel lining, the maximum inspection depth D for the low-frequency magnetic inspection is determined, and the process proceeds to step 2.

[0036] Step 2: Surface preparation of the weld and adjacent base metal The steel lining is mechanically polished using equipment such as an angle grinder until a metallic luster appears, with the polishing area being 2KT each for the surface of the weld and the base material on both sides, where K represents the K value of the probe in the transverse wave ultrasonic inspection in step 4, T represents the thickness of the steel lining, and the polishing width on one side is 50 mm or more.

[0037] Step 3: Reconfirm the thickness of the steel lining. Using instruments such as ultrasonic thickness gauges, the thickness of the base material adjacent to the weld is measured, and the thickness is determined to be greater than or equal to the theoretical minimum design thickness of the steel lining.

[0038] Step 4: Inspect the steel-lined weld using transverse wave ultrasonic testing.

[0039] For steel linings that are somewhat thick and cannot be fully covered by low-frequency magnetic testing, in Step 1, the maximum inspection depth D for low-frequency magnetic testing is determined, and then, for the remaining areas that cannot be inspected, transverse wave ultrasound, which is applicable to the inspection of welds in thick steel linings, is used to achieve full coverage inspection of the welds.

[0040] In principle, ultrasonic testing is a non-destructive testing method that inspects internal defects in materials by utilizing the energy changes in the reflection of the ultrasonic wave propagation waveform caused by differences in the acoustic properties of the material and its defects. The pulse reflection method uses transverse waves during angled flaw detection, and on the waveform display screen of the ultrasonic equipment, the horizontal coordinate indicates the propagation time of the sound wave, and the vertical coordinate indicates the amplitude of the echo signal. In the case of a uniform medium, the propagation time of the pulse wave is proportional to the sound path length, so the presence of a defect can be determined by the appearance of a defect echo signal. Furthermore, the distance from the defect to the detection surface can be determined by the position where the echo signal appears, enabling the localization of the defect, and the equivalent size of the defect can be determined by the echo amplitude.

[0041] Equipment process parameters: (1) Examination method: Pulse reflection ultrasound (A-mode ultrasound). (2) Probe parameters: K2-K5, frequency range: 3≦f≦5MHz. (4) Binding method: water. (5) Test block type: CSK-IA, a proprietary ultrasound comparative test block. (6) Scanning method: Zigzag scan.

[0042] The structure of the self-made ultrasonic testing comparison block, as shown in Figures 6 and 7, is a solid structure with a length of ≥310 mm, a thickness of ≥40 mm, and a height of 20 mm. Both ends in the longitudinal direction have a stepped structure, and the whole consists of three parts: a transverse through-hole region 4 located in the middle, a first stepped groove region 5 located at both ends, and a second stepped groove region 6. The first stepped groove region 5 contains six layers of steps 7, with the height of each layer of steps differing by 3 mm sequentially, and the height of the step at the outermost end being 3 mm. The width of each groove platform (i.e., step) is ≥15 mm, and a groove 8 with a width of 0.1 mm and a depth of 1 mm is machined in the center of the groove platform of each layer in the width direction of the ultrasonic testing comparison block to simulate vertical cracks at the root of the weld. When using the ultrasound comparative test block, the probe is obliquely incident on the groove from the underside of the ultrasound comparative test block to form an echo. If the groove root (i.e., the surface of the groove platform) is taken as the groove depth value, the simulated depths in that groove region (from the end to the middle) are 3 mm, 6 mm, 9 mm, 12 mm, 15 mm, and 18 mm, respectively.

[0043] The second stepped groove region 6 includes seven steps 7, with the height of each step differing by 3 mm sequentially, and the height of the step at the outermost end being 2 mm. The width of each groove platform (i.e., step) is ≥ 15 mm, and a groove 8 with a width of 0.1 mm and a depth of 1 mm is machined in the center of each groove platform in the width direction of the ultrasonic testing comparison block to simulate vertical cracks at the root of the weld. When using the ultrasonic testing comparison block, the probe is obliquely incident on the groove from the top surface of the ultrasonic testing comparison block to form an echo. If the groove root (i.e., the surface of the groove platform) is taken as the groove depth value, the simulated depths (from the end to the middle) in the groove region on that side are 2 mm, 5 mm, 8 mm, 11 mm, 14 mm, 17 mm, and 20 mm, respectively (located on the bottom surface of the ultrasonic testing comparison block).

[0044] The stepped slopes formed sequentially by six steps 7 within the first stepped groove region 5 and the stepped slopes formed sequentially by seven steps 8 within the second stepped groove region 6 are arranged parallel to each other and face each other, and can function as a base for joining ultrasonic testing comparison test blocks of steel-lined welds in underground cavities of compressed air energy storage power plants. The side view of the ultrasonic testing comparison test block of the steel-lined welds in underground cavities of compressed air energy storage power plants is approximately parallelogram-shaped.

[0045] In the intermediate section, the transverse through-hole region 4 has six Φ1 transverse through-holes 9 distributed sequentially from top to bottom. The horizontal spacing between each hole is ≥15 mm, the distance between the uppermost hole and the edge of the first stepped groove region 5 is ≥25 mm, the vertical spacing is 3 mm, and the distance between the uppermost hole and the top surface of the test block is 3 mm. Therefore, the depths of the transverse through-holes from top to bottom are 3 mm, 6 mm, 9 mm, 12 mm, 15 mm, and 18 mm, and correspondingly, the depths of the transverse through-holes from bottom to top are 2 mm, 5 mm, 8 mm, 11 mm, 14 mm, and 17 mm, respectively.

[0046] The overall height of the ultrasonic comparative test block is 20 mm, which can cover the thickness range of the steel lining of the current compressed air energy storage underground cavity. The thickness of the test block is ≥ 40 mm, which meets the dimensional requirements for the lateral through-hole required for the ultrasonic test block and better avoids the influence of sidewall echoes. The material of the ultrasonic comparative test block is the same as the material of the steel lining being inspected, or 45# steel, and its main chemical composition conforms to GB699 "Steel Grades and General Technical Conditions for Superior Carbon Structural Steel". After annealing, the grain size reaches grade 7 or higher. Ultrasonic inspection is performed from various directions inside the material, and the ultrasonic reflection signal intensity due to the inspected defects does not exceed the ultrasonic reflection signal intensity generated when a flat-bottom hole with a diameter of 0.5 mm (Φ0.5 mm) is present inside the material. The surface roughness of the test block was Ra ≤ 0.4 μm for each surface and the parallelism of the end faces was ≤ 5 μm. The outer surface was free of obvious scratches, dents, rust, and other defects, and the depth of each stepped groove was marked on the side of the test block.

[0047] The specific inspection steps are as follows:

[0048] Step 4.1: Determining the front edge and K value of the probe Using the CSK-IA test block, and according to the ultrasound equipment's specific adjustment program, in the first step, the highest reflected waves of Φ50mm and Φ100mm arcs are simultaneously found, the distance to the leading edge of the probe is measured, and then input into the instrument. In the second step, the highest wave of a Φ50mm stepped hole with a depth of 30mm is found, input into the instrument, and the actual K value of the probe is determined.

[0049] Step 4.2: Use the above ultrasound examination comparison test block to draw the distance-amplitude correction curve (DAC curve).

[0050] Using the ultrasonic inspection device's specific adjustment program, the first channel is selected, and all lateral through-holes with a depth slightly greater than the thickness of the steel lining are selected to create a DAC curve (for example, if the thickness of the steel lining is 6 mm, lateral through-holes with depths of 2 mm, 3 mm, 5 mm, 6 mm, and 8 mm are selected as lateral through-holes for curve creation), and the creation of a distance-amplitude correction curve is completed and used as the comparison curve. The second channel is selected separately, and groove depths equal to the thickness of the steel lining being inspected, or the two groove depths closest to that groove depth are selected as references (for example, if the thickness of the steel lining is 6 mm, a groove depth of 6 mm is selected, and if the thickness of the steel lining is 7 mm, groove depths of 6 mm and 8 mm are selected), and a reference point or reference line is created.

[0051] The DAC curve (Distance Amplitude Correction Curve) is an important tool in ultrasound imaging to compensate for changes in echo amplitude due to factors such as beam diffusion and material attenuation at different distances. By establishing a correction relationship between distance and echo amplitude, the echo amplitude of defects of the same size at different distances can be accurately evaluated, thereby ensuring the accuracy and reliability of inspection results.

[0052] Step 4.3: Conduct on-site inspections Water is added as a binder to the polishing areas on both sides of the weld to be inspected. The DAC curve created in the first channel is selected, a bonding correction of 4 dB is applied, and the reflection amplitude of the 2 mm deep transverse through hole is adjusted to more than 80% of the entire screen. An ultrasonic probe is placed in the area and a zigzag scan is performed at a scan speed of 150 mm / s or less. The waveform changes on the oscilloscope screen are monitored in real time during the scan, and one or three reflection echoes in the TD range at the root of the weld are observed in detail. After the scan on one side is completed, the scan is repeated on the other side to ensure full coverage inspection of the weld.

[0053] Step 4.4: Defect Record If it is detected that the reflected echo exceeds the DAC curve, information such as the location of the defect is re-examined from multiple angles, at least on both sides of the weld. If the defect is located inside the weld joint, the length is measured using the -6dB method, and the information from the longer side is recorded. The depth, length, location, and amplitude of the defect are recorded, and its location is marked on the surface of the joint. If the detected defect is located at the root of the weld, the reference point or reference line of the second channel is recalled, and the waveform and reflected equivalent are compared to determine the nature and size of the defect.

[0054] Step 4.5: Inspection Grade Evaluation and Quality Evaluation In accordance with the requirements of the Steel Lining Inspection Standard (see NB / T47013.3-2015), the inspection results for welded joints will be graded.

[0055] 1) If the nature of the defect is qualitatively determined to be a crack, poor fusion, or incomplete penetration, it will be judged as unacceptable.

[0056] 2) If the reflected equivalent of a defect exceeds the DAC curve, it is considered an over-standard defect and will be deemed unacceptable.

[0057] If the reflected equivalent of a defect does not exceed the DAC curve, a. if the length of a single defect is greater than or equal to the plate thickness, it will be judged as a failure, and b. if the length of a single defect is less than the plate thickness, it will be judged as a recordable defect, judged as a pass, the defect information will be recorded, and monitoring will be strengthened in the future.

[0058] [Embodiment 3] The full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants is, specifically, Step 1 involves performing a defect inspection on the steel lining weld using a low-frequency magnetic testing method to determine the defect depth, and simultaneously determining the inspectable thickness range of the low-frequency magnetic testing method using a general-purpose calibration test block in the calibration comparison test block. If the inspectable thickness range covers the thickness of the steel lining being inspected, the weld inspection is completed; if it does not cover the thickness, the process proceeds to Step 2. Step 2 involves pre-treating the surface of the steel-lined weld to be inspected and the adjacent base material surface to produce a metallic luster, Step 3 involves reconfirming the thickness of the steel lining, The procedure is carried out according to step 4, which involves using transverse wave ultrasonic testing to inspect the steel-lined weld area that was not inspected in step 1 using the low-frequency magnetic testing method. [Explanation of Symbols]

[0059] 1. Circular groove, 2. Cross-shaped groove, 3. Straight groove, 4. Transverse through-hole area, 5. First stepped groove area, 6. Second stepped groove area, 7. Step, 8. Groove, 9. Transverse through-hole.

Claims

1. A full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants, specifically, Step 1 involves performing a defect inspection on the steel lining weld using a low-frequency magnetic testing method to determine the defect depth, and simultaneously determining the inspectable thickness range of the low-frequency magnetic testing method using a general-purpose calibration test block in the calibration comparison test block. If the inspectable thickness range covers the thickness of the steel lining being inspected, the weld inspection is completed; otherwise, the process proceeds to Step 2. Step 2 involves pre-treating the surface of the steel-lined weld to be inspected and the adjacent base material surface to produce a metallic luster, Step 3 involves reconfirming the thickness of the steel lining, A full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants, characterized by being performed according to step 4, which involves inspecting areas of the steel-lined weld that were not inspected by the low-frequency magnetic inspection method in step 1 using a transverse wave ultrasonic inspection method.

2. Step 1 specifically involves: Step 1.1 involves determining the inspectable thickness range of the low-frequency magnetic inspection method using a general-purpose calibration test block from the calibration comparison test block, We perform defect inspections using a low-frequency magnetic flaw detection device, specifically, Steps 1 and 2 involve attaching a defect indicator film to the inner surface of the area to be inspected on the steel lining, positioning a yoke to straddle both sides of the weld, performing inspections sequentially using the cross-crossing method, ensuring that the coverage area of ​​the two inspections during movement overlaps by at least 10%, thereby preventing any missed inspections, and then applying electricity to magnetize the film and continuously observing any changes on the indicator film. Step 1.3 involves, after the magnetic particle pattern appears on the defect indicator film, changing the magnetic field application angle in at least two ways, selecting the angle at which the defect indication becomes more pronounced, taking and saving a photograph on-site, and marking the position of the magnetic particle pattern. Step 1.4 involves quantifying the defect depth using the depth comparison test block within the calibration comparison test block, A full-coverage non-destructive testing method for a steel-lined weld in an underground cavity of a compressed air energy storage power plant, as described in claim 1, characterized in that it is carried out in accordance with step 1.5, which involves evaluating the grade of the inspection results for the steel-lined weld.

3. Regarding the specific structure of the aforementioned calibration comparison test block, The calibration comparison test block comprises one set of general-purpose calibration test blocks and one depth comparison test block. The general-purpose calibration test block consists of 15 test pieces with a thickness interval of 1 mm, the thinnest test piece being 1 mm thick, and the thickest test piece being 15 mm thick. The surface of the test pieces is provided with three circular grooves (1) of different depths and three cross-shaped grooves (2) of different depths. The depths of the circular grooves (1) are 7 μm, 15 μm, and 30 μm, respectively. The lengths of the two straight lines of the cross-shaped grooves (2) are both 6 mm, and the depths of the grooves are 7 μm, 15 μm, and 30 μm, respectively. The depth comparison test block is an oblique wedge-shaped test block, with a length of 150 mm and a thickness of 15 mm, with a flat top and a sloped bottom, a 150 mm scale engraved on the edge of the flat top, and three straight grooves (3) of different depths uniformly provided on the sloped bottom, with groove depths of 7 μm, 15 μm, and 30 μm, respectively, characterized in that it is a full-coverage non-destructive testing method for a steel-lined welded joint in an underground cavity of a compressed air energy storage power plant according to claim 2.

4. In step 1.1, the specific step of determining the inspectable thickness range of the low-frequency magnetic inspection method using a general-purpose calibration test block is: Select one test piece from the general calibration test block, and the thickness of the test piece is the same as that of the thin-walled steel member to be measured, or the thickness is as close as possible to that of the thin-walled steel member and greater than that of the thin-walled steel member, and then attach the defect indicator film to the grooveless surface of the test piece. The pulse frequency of the yoke-type low-frequency magnetic flaw detector is adjusted to 50 Hz, the yoke is placed on a grooveless surface, and the flaw detector is started. If the pulse frequency value can be adjusted until a magnetic particle pattern appears on the display film on the calibration test piece, it indicates that the inspectable thickness range of the low-frequency magnetic inspection covers the thickness of the steel lining being inspected. The full-coverage non-destructive testing method for steel lining welds in underground cavities of compressed air energy storage power plants according to claim 3, characterized in that, if the magnetic particle pattern does not appear at all, tests are performed sequentially using other calibration test pieces thinner than the thickness of the steel lining being measured, in an order of decreasing thickness, until the magnetic particle pattern appears, and the maximum thickness D of the test piece on which the magnetic particle pattern can be displayed is set as the maximum inspection depth for low-frequency magnetic testing.

5. In step 1.4, the specific step of quantifying the defect depth using the depth comparison test block is: After determining the location of the defective magnetic particle pattern, the pulse frequency of the low-frequency magnetic flaw detector is gradually increased until the defective magnetic particle pattern completely disappears, and the parameters of the instrument are locked at this time. Attach the defect indicator film to the grooveless surface of the depth comparison test block, place the yoke on the grooveless surface, restart the inspection device, The full-coverage non-destructive testing method for a steel-lined weld in an underground cavity of a compressed air energy storage power plant, according to claim 3, characterized in that the depth of the inspected defect is determined by observing the displayed length of the magnetic particle pattern on the surface and reading the corresponding defect depth by comparing it with a scale.

6. Step 4 specifically involves: Using the CSK-IA test block, and according to the ultrasound equipment's specific adjustment program, in the first step, the highest reflected waves of Φ50 mm and Φ100 mm arcs are simultaneously found, the distance to the leading edge of the probe is measured, and then input into the instrument. Step 4.1 involves finding the highest wave in a Φ50 mm stepped hole with a depth of 30 mm, inputting it into the instrument, and determining the actual K value of the probe. Step 4.2 involves drawing a DAC curve using an ultrasound comparative test block and creating a reference point or reference line, Step 4.3 involves applying water as a binder to the polishing areas on both sides of the weld to be inspected, selecting the DAC curve created in the first channel, applying a 4 dB bonding correction, adjusting the reflection amplitude of the 2 mm deep transverse through hole to 80% or more of the entire screen, placing the ultrasonic probe on the polishing area and performing a zigzag scan, with a scan speed of 150 mm / s or less, monitoring the waveform changes on the oscilloscope screen in real time during the scan, focusing on observing one or three reflection echoes in the T-D range at the root of the weld, and repeating the scan on the opposite side after the scan on one side is completed to ensure full coverage inspection of the weld. If it is detected that the reflected echo exceeds the DAC curve, the location information of the defect is reconfirmed from multiple angles on at least both sides of the weld. If the defect is inside the weld joint, the length is measured using the -6 dB method, and the information from the longer side is recorded. The depth, length, location, and amplitude of the defect are recorded. Step 4.4 involves marking the location on the surface of the joint, and if the inspected defect is located within the root of the weld, recalling the reference point or reference line of the second channel, comparing the waveform and reflected equivalent, and determining the nature and size of the defect. A full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants according to claim 1, characterized in that it is carried out in accordance with step 4.5, which involves performing inspection grade evaluation and quality evaluation on the steel-lined welds.

7. In step 4.2, the specific structure of the ultrasound examination comparison test block is as follows: The aforementioned ultrasonic testing comparison block consists of three parts: a transverse through-hole region (4) located in the middle, a first stepped groove region (5) located at both ends, and a second stepped groove region (6). In the aforementioned transverse through-hole region (4), six transverse through-holes (9) are distributed sequentially from top to bottom, with a horizontal spacing of ≥ 15 mm and a vertical spacing of 3 mm between each transverse through-hole (9). The distance between the uppermost transverse through-hole (9) and the upper surface of the ultrasound inspection comparison test block is 3 mm, and the distance between the lowermost transverse through-hole (9) and the lower surface of the ultrasound inspection comparison test block is 2 mm. The first stepped groove region (5) includes six layers of steps (7), the height of each layer of steps (7) differs by 3 mm in sequence, and the height of the step (7) located at the outermost end is 3 mm. The second stepped groove region (6) includes seven steps (7), the height of each step (7) differs by 3 mm in sequence, and the height of the step (7) located at the outermost end is 2 mm. The full-coverage non-destructive testing method for a steel-lined welded section of an underground cavity of a compressed air energy storage power plant according to claim 6, characterized in that a groove (8) with a width of 0.1 mm and a depth of 1 mm is provided in the width direction of the ultrasonic testing comparison test block at the center of the step (7).

8. Step 4.2 specifically means: Using the ultrasonic testing equipment's specific adjustment program, the first channel is selected, and according to the thickness of the steel lining, all lateral through-holes whose depth is greater than the thickness of the steel lining and closest to the thickness of the steel lining are selected to create a DAC curve, and this DAC curve is used as a comparison curve. The full-coverage non-destructive testing method for steel lining welds in underground cavities of compressed air energy storage power plants according to claim 7, characterized in that a second channel is separately selected, and a reference point or reference line is created by selecting a groove depth equal to the thickness of the steel lining to be inspected or the two groove depths closest to the groove depth.

9. In step 4.4, the specific grade evaluation standard is: 1) If the nature of the defect is qualitatively determined to be a crack, poor fusion, or incomplete penetration, it will be judged as unacceptable. 2) If the reflected equivalent of a defect exceeds the DAC curve, it is considered an over-standard defect and will be judged as unacceptable, and If the reflected equivalent of the defect does not exceed the DAC curve, a. If the length of a single defect is greater than or equal to the plate thickness, it is judged as unacceptable. b. A full-coverage non-destructive testing method for steel-lined welds in underground cavities of compressed air energy storage power plants according to claim 6, characterized in that a single defect length < plate thickness is determined to be a record defect and is judged as acceptable.

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