A method and device for detecting butt weld of a fully multi-layer high-pressure hydrogen storage container

Abstract

The present invention relates to a method and device for detecting welds of a multi-layer high-pressure container. The purpose is to propose a method and device for detecting butt welds of a multi-layer high-pressure hydrogen storage container head based on a planar array fully focused ultrasonic phased array. The technical solution is: a device for detecting butt welds of a multi-layer high-pressure hydrogen storage container head based on a planar array fully focused ultrasonic phased array, characterized in that the device comprises a sleeve with an axial through hole and one end of the through hole is detachably connected to a pipe forging, an outer bearing box that can be inserted into the other end of the through hole and can be moved along the axial direction of the sleeve through a sliding pair, a rotating shaft rotatably positioned in the middle of the outer bearing box, a planar array phased array probe fixed at one end of the rotating shaft to extend into the pipe forging to detect welds, a plurality of thin water pipes fixed on the side of the planar array phased array probe and evenly distributed with a plurality of small holes, a hand wheel fixed at the other end of the rotating shaft, a rotary encoder sleeved on the rotating shaft, an ultrasonic detector and a water spraying device.

Description

Technical Field

[0001] The present invention relates to a method and a device for detecting welds of a multi-layer high-pressure container, and in particular to a method and a device for detecting butt welds of a multi-layer high-pressure hydrogen storage container head based on a planar fully focused ultrasonic phased array. Background Art

[0002] The fully multi-layer high-pressure hydrogen storage container is a product independently developed and designed by my country. It has the advantages of large volume, high pressure bearing capacity, and online monitoring of hydrogen leakage. It is an important equipment for high-pressure hydrogen storage and has been widely used in hydrogen refueling stations. The fully multi-layer high-pressure hydrogen storage container is a staggered steel belt container with a complex structure, so it is difficult to perform non-destructive testing. Due to the special structure of the butt weld and heat-affected zone between the pipe forging and the double-layer hemispherical head, the existing X-ray detection, magnetic particle detection, penetration detection and corresponding detection equipment are difficult to effectively detect defects generated during the manufacturing process and use. At present, there are few reports on successful detection of such welds at home and abroad. The weld area has a single-layer structure, which is different from other parts of the container (double-layer or multi-layer). Once the defect expands, it may cause the container to rupture, which will seriously threaten the safety of equipment and personnel, and may even cause catastrophic accidents.

[0003] Since conventional external inspections cannot obtain effective results, internal inspection may become a research direction for the inspection of such containers. There is an opening with a narrow inner diameter on the top of the head of a fully multi-layer high-pressure hydrogen storage container, and conventional inspection equipment cannot enter it. Ultrasonic testing has the advantages of convenient operation, high resolution, low cost, wide adaptability, and high sensitivity for detecting area defects in thick-walled containers. However, for the internal inspection of such small holes, ultrasonic testing has the following difficulties: 1) The aperture is small, and it is difficult for conventional phased array probes to enter; 2) The inner wall surface is concave, and the radius of curvature is small, so the ultrasonic propagation energy loss at the interface is large; 3) From the inner wall of the inspection hole to the heat-affected zone outside the weld, the sound path exceeds 120mm, and the commonly used ultrasonic focusing technology is difficult to meet the requirements; 4) The welding structure is complex, with double-layer ferritic steel on one side and single-layer austenitic stainless steel on the other side. It is difficult to judge the waveform, and the welding section is thick, so it is difficult to fully cover the inspection thickness range with a single scan; 5) The weld is austenitic stainless steel with coarse grains and anisotropy, so the acoustic energy attenuation is large and the scattering is serious. Conventional phased array detection has a limited number of focus points, with good imaging near the focus but low resolution at other locations. Due to the superposition of the above multiple difficulties, it is difficult for existing phased array technology to achieve satisfactory results for weld inspection of fixed high-pressure hydrogen storage steel strip staggered containers. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and propose a method and device for detecting butt welds of multi-layer high-pressure hydrogen storage container heads based on a planar fully focused ultrasonic phased array.

[0005] To solve this technical problem, the solution provided by the present invention is

[0006] A fully multi-layer high-pressure hydrogen storage container head butt weld detection device based on a planar array fully focused ultrasonic phased array, characterized in that: the device includes a sleeve with an axially through-hole and one end of the through-hole is detachably connected to a pipe forging, an outer bearing box that can be inserted into the other end of the through-hole and can move along the axial direction of the sleeve through a sliding pair, a rotating shaft with a middle portion rotatably positioned in the outer bearing box, a planar array phased array probe fixed at one end of the rotating shaft to extend into the pipe forging to detect the weld, a plurality of fine water pipes fixed to the side of the planar array phased array probe and evenly distributed with a plurality of small holes for spraying water on the weld, a hand wheel fixed at the other end of the rotating shaft to facilitate manual rotation of the rotating shaft, a rotary encoder sleeved on the rotating shaft to detect the rotation angle of the rotating shaft, an ultrasonic detector electrically connected to the planar array phased array probe through a wire, and a water spraying device connected to the plurality of fine water pipes.

[0007] The outer surface of the rotating shaft is provided with a mounting groove arranged in a direction parallel to the axis; the mounting groove extends from one end close to the ultrasonic phased array probe to the other end and passes through the outer bearing box; the wire and a plurality of thin water pipes are positioned in the mounting groove.

[0008] The sliding pair comprises a sliding block arranged outside the outer bearing box and a sliding groove opened on the inner wall of the through hole and slidably matched with the sliding block to limit the circumferential rotation of the outer bearing box.

[0009] A method for detecting butt welds of a multi-layer high-pressure hydrogen storage container head based on a fully focused ultrasonic phased array, comprising the following steps:

[0010] (1) Water spraying, using water as a coupling agent for ultrasonic phased array testing;

[0011] (2) controlling the probe clamping device to extend the phased array probe into the pipe at the top of the end cap, and placing the phased array probe at the end of the pipe according to the structural dimensions of the probe clamping device and the container;

[0012] (3) Start the ultrasonic detector and adjust the parameters so that the phased array array performs linear or fan-shaped deflection focusing scanning and focuses the focal area on the butt weld of the end cap; rotate the phased array probe by the rotating handle to perform circumferential scanning inside the opening; and perform axial scanning of the ultrasonic phased array by controlling the phased array probe to move forward and backward in the opening;

[0013] The main acoustic beam excited by all array elements in the phased array probe is focused on a focal point in the object to be tested. F The position of the array element is determined by the following formula:

[0014]

[0015] Where: It is i The horizontal inclination angle of the array element is It is i The distance between the center of each element and the center line OF, r is the inner diameter of the hole where the probe is located, is the sound velocity of the probe's acoustic matching layer or protective film (the sound velocity of both), c is the sound velocity of the object to be measured, It is i The refraction angle of the main sound beam of each array element in the object to be measured is is the focal length of the focus within the object to be measured, is half the width of the array element, i It is i The incident angle of the main sound beam of each array element;

[0016] (4) During the scanning process, observe the displayed image on the ultrasonic detector. If any suspected defects are found, re-inspect the corresponding area.

[0017] The focusing method to determine the focusing area of ​​the fully focusing phased array is:

[0018] An area at a certain distance in front of the probe is set as the target area, which contains several focus points; the received echo signal is focused and superimposed on each point. I ( x , z ) is calculated according to formula (1):

[0019] (1)

[0020] In the formula, e xi,xj ( t i,j ( x , z ))for i Array element launch, j The ultrasonic signal received by the array element is superimposed on ( x , z ) position;

[0021] x i and x j are the coordinates of the array element, i and j The range is [1, N ], x and z are the coordinates of the virtual focal point;

[0022] ti,j ( x , z ) is the sound wave from the array element i Emit to the focal point ( x , z ) and returns from this point to the array element j The desired delay time.

[0023] The method to determine the delay time is:

[0024] According to the following formula (2), the point ( x , z ) corresponding to the delay time, where c is the longitudinal wave velocity of the ultrasonic wave propagating in the test block.

[0025] (2)

[0026] The steps of the re-examination are:

[0027] Record the bottom wave echo position of the acoustically transparent wedge during the scanning process, remove the probe, replace the phased array probe with a phased array probe containing wedges of different thicknesses, perform ultrasonic testing again according to the steps described in steps (3) and (4), and then merge the test results. Usually, after replacing the phased array probe containing wedges of different thicknesses 1 to 2 times, the merged result can solve the problem of missed detection caused by the overlap of the wedge bottom wave echo and the defect echo. If there is still an echo overlap area, replace the probe again until the influence of the wedge bottom wave echo on the defect echo is eliminated.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The detection system provided by the invention is fast and reliable, has stronger acoustic field response and higher sensitivity; and the detection method is simple. The detection device provided has a simple structure, large internal detection support force, good coupling effect, low production requirements and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the head structure of the high-pressure hydrogen storage container in the present invention.

[0031] Figure 2 This is the focusing diagram of the fully focused ultrasonic phased array in the present invention.

[0032] Figure 3-1 It is a schematic diagram of the arrangement of probe array elements distributed along the circumferential direction in the present invention.

[0033] Figure 3-2 It is a schematic diagram of the arrangement of probe array elements distributed along the axial direction in the present invention.

[0034] Figure 4-1It is a schematic diagram of positioning the i-th array element on the left side of the center line of the present invention.

[0035] Figure 4-2 for Figure 4-1 A local enlarged schematic diagram of the .

[0036] Figure 5 It is a schematic diagram of the butt weld detection device for the head of a fully multi-layer high-pressure hydrogen storage container in the present invention.

[0037] Figure 6 It is a schematic diagram of the structure of the probe clamping device in the present invention.

[0038] Figure 7 It is a schematic diagram of the structure of the phased array probe and the probe clamping device in the present invention. DETAILED DESCRIPTION

[0039] The following is a further description with reference to the embodiments shown in the accompanying drawings.

[0040] The fully multi-layer high-pressure hydrogen storage container head butt weld detection device based on the area array fully focused ultrasonic phased array shown in the accompanying drawings includes an area array phased array probe 18 (electrically connected to the ultrasonic detector 17 when in use), a water spray device 16, a rotating shaft 20, a bearing 4, a retaining ring 10, an outer bearing box 5, a hand wheel 8 and a hollow encoder 14, etc.; the area array phased array probe is composed of array elements of the area array, an acoustic matching layer, a protective film, a damping block 22, a wire 15, etc.

[0041] like Figure 5 As shown, an axial through hole is provided in the middle of the sleeve 3, and one end of the through hole (shown as the left end of the through hole in the figure) is detachably connected to the pipe forging 1 (preferably, an internal thread is provided on the inner wall of the through hole, and the sleeve and the outer periphery of the pipe forging are connected through a threaded pair). The outer bearing box shown can be extended to the other end of the through hole (shown as the right end of the through hole in the figure), and the outer bearing box can be moved along the axial direction of the sleeve through a sliding pair to adjust the axial detection position of the ultrasonic phased array probe. The sliding pair includes a slider (not shown in the figure) arranged on the outside of the outer bearing box and a slide groove (not shown in the figure) provided on the inner wall of the through hole and slidingly matched with the slider; when the outer bearing box moves along the slide groove in the through hole, the slide groove can limit the circumferential rotation of the outer bearing box, thereby ensuring the accurate positioning of the ultrasonic phased array probe.

[0042] The wire 15 and the thin water pipe 2 are installed from the end of the rotating shaft 20 with a square groove. The two thin water pipes 2 with several small holes evenly distributed at the head end are respectively fixed in the through holes of the connecting plate 24 and are closely attached to the left and right sides of the ultrasonic phased array probe 18. The water spray device (existing technology) 16 can ensure that water flows out of the thin water pipe 2 to ensure the smooth progress of ultrasonic scanning.

[0043] The ultrasonic phased array probe 18 and the wire 15 pass through the holes of the bearing end cover 13, the shaft elastic retaining ring 11, the retaining ring 10, the bearing 4 and the outer bearing box 5 in sequence. Then the ultrasonic phased array probe 18 and the damping block 22 are installed (fixed with countersunk screws 23) on the connecting plate 24 on the rotating shaft 20 and fixed with countersunk screws 23. The ultrasonic phased array probe is connected to the ultrasonic detector through the wire 15 so as to transmit the detection signal to the ultrasonic detector for processing and forming an image.

[0044] The rotating shaft 20 is provided with a bearing 4 and a retaining ring 10, and is limited by an elastic retaining ring 11 to ensure stable rotation. A hand wheel 8 is fixed by a screw 9 at the end of the rotating shaft 20 to facilitate rotating the ultrasonic phased array probe 18 for one circle for detection.

[0045] A hollow encoder 14 is installed on the rotating shaft, and an encoder fixing frame 6 is fixed to the hollow encoder 14 with screws 7, and the other end is installed on the bearing end cover 13 with screws 12, so that when the shaft hole of the hollow encoder 14 rotates with the rotating shaft 20, its shell remains stationary.

[0046] like Figure 7 As shown: a universal ball device 19 is installed on the left, right and lower sides of the connecting plate 24 on the rotating shaft 20; a spring 25 is also installed between the ultrasonic phased array probe 18 and the universal ball device 19 on its lower side to ensure that the damping block 22 is in close contact with the part to be detected.

[0047] The surface array phased array probe has multiple array elements; taking 64 array elements as an example (such as Figure 3-1 , Figure 3-2 As shown in the figure, 4 array elements (chips) are arranged circumferentially along the rotation axis, and 16 array elements (chips) are arranged axially along the rotation axis to form a 4×16 array. The array elements are installed on the rotation axis (probe base), and the outer surface of the array elements is coated with an acoustic matching layer coating (existing technology), and a replaceable protective film is covered on the outside of the acoustic matching layer, and the curvature of the protective film matches the coupling surface.

[0048] 1) Focusing method to determine the focusing area of ​​the full-focus phased array

[0049] To detect the weld defects of multi-layer high pressure vessels (such as Figure 1 As shown in the figure, the weld and heat affected zone to be inspected are set as a target area, with 1mm×1mm as the pixel point. Figure 2 Assuming the size in the x direction is 120 mm and the size in the z direction is 50 mm, the number of pixels on the cross section is 6000. If 10 pixels are set in the circumferential direction, the number of pixels in the entire three-dimensional target area is 60,000, that is, 60,000 focus points.

[0050] First, the first array element of the probe is excited to emit ultrasonic waves, and all array elements receive and save ultrasonic echo signals; then other array elements are excited in turn to emit ultrasonic waves, and all array elements receive echoes and store them in turn, until the last array element is excited and all array elements receive signals, a data set of 64×64=4096 A-scan signals is obtained. The received 4096 A-scan echo signals are focused and superimposed-averaged for each focal point, and the sound field amplitude at each focal point is calculated by formula (1): I ( x , z ) and image processing is performed. When all the focus points are calculated and processed, the target area image is formed.

[0051] (1)

[0052] In the formula, e xi,xj ( t i,j ( x , z ))for i Array element launch, j The ultrasonic signal received by the array element is superimposed on ( x , z ) position;

[0053] x i and x j are the coordinates of the array element, i and j The range is [1, N ], x and z are the coordinates of the virtual focal point, N The value is 64;

[0054] t i,j ( x , z ) is the sound wave from the array element i Emit to the focal point ( x , z ) and returns from this point to the array element j The desired delay time.

[0055] For curved surfaces, when the probe array element size is much smaller than the diameter of the curved surface, its curved surface focusing can be approximately treated as plane focusing.

[0056] 2) Delay time formula

[0057] According to formula (2), the point ( x ,z ) The corresponding delay time is as follows, where c The longitudinal wave velocity of ultrasonic wave propagating in the test block.

[0058] (2)

[0059] 3) By calculating the arrangement and angle of each array element, the main sound beams of all chips can be focused in the specified area, further improving the focusing effect of the fully focused phased array. Figure 3-1 , Figure 3-2 As shown, one dimension of the planar phased array probe is arranged along the axial direction, and the other dimension is arranged along the circumferential direction. Each circumferentially arranged array element has its own positioning (position and angle), and the array elements in the same row along the axis are positioned consistently.

[0060] The arrangement direction of the circumferentially arranged array elements can make the sound beam excited by each array element point to a specific position in the detection area. In order to focus the main sound beam excited by all array elements at the F focus in the object to be tested, the array element positioning is calculated by the following formula:

[0061]

[0062] As shown in formulas (3) to (5) and Figure 4-1 , Figure 4-2 As shown, It is i The horizontal inclination angle of the array element is It is i The distance between the center of each element and the center line OF, r is the inner diameter of the hole where the probe is located, is the sound velocity of the probe's acoustic matching layer and protective film (the sound velocities of the two are the same), c is the sound velocity of the object to be measured, It is i The refraction angle of the main sound beam of each array element in the object to be measured is is the focal length of the focus within the object to be measured, is half the width of the array element, It is i The incident angle of the main sound beam of each array element is, h iL The left side of the center line i The distance between the left end point of an array element and the circle in the radial direction, h iR is the corresponding distance of the right endpoint.

[0063] h iL The left side of the center line i The distance between the left end point of an array element and the circle in the radial direction, h iR is the corresponding distance of the right endpoint. The total number of array elements on the probe is 2 Nc , symmetrically distributed along the center line (i.e. OF) (see Figure 4-1 , Figure 4-2 ), where the left array element is the one closest to the center line as element 1, and from right to left are 1, 2, 3… N c , i As the array element number, the range is [1, N c ]. h iR and h iL Represents the total thickness of the probe acoustic matching layer and the protective film. The minimum value of both is 0.1mm.

[0064] In this case, the number of circumferential array elements of the probe is 4, which are symmetrically distributed along the center line (OF), with 2 elements on the left and 2 elements on the right. Starting from the left element No. 1, h 1L Take 0.1mm, according to the known , i 、r、 , , , calculated to obtain , then use the left end point of element 1 as the right end point of element 2 to calculate , by adjusting the h 2R and h 2L , so that the minimum value of both is 0.1mm, and the positioning parameters and matching layer and protective film thickness of the two array elements on the left are determined. The two array elements on the right are symmetrically distributed with the left side.

[0065] By combining the above surface-coupled full-focusing function and the focusing method within the specified area, as well as conventional full-focusing phased array detection parameters, a full-focusing ultrasonic phased array detection method based on the 4×16 array was established.

[0066] Before testing, the sleeve 3 is threadedly connected to the single-layer pipe forging 1. The outer bearing box 5 is installed in the sleeve 3.

[0067] During the inspection, the ultrasonic detector 17 is turned on, and the instrument is set according to the process parameters determined by the test. The rotating shaft 20 is rotated by the hand wheel 8 to ensure that the position of the surface array probe chip is against the weld. The weld to be inspected is sprayed with water through the water spray device 16 and the thin water pipe 2 to keep the surface array probe 18 in a wet state. At the same time, the ultrasonic detector 17 is started to start scanning.

[0068] During the scanning process, the displayed image on the ultrasonic detector 17 is observed, and the obtained scanning result image is analyzed. If a suspected defect is found, the corresponding area is re-inspected. Through the above method, volume defects, area defects and longitudinal defects in the weld and heat-affected zone can be basically detected.

[0069] After the inspection is completed, the outer bearing box 5 is taken out from the sleeve 3, and then the sleeve 3 is unscrewed from the single-layer pipe forging 1.

[0070] Finally, it should be noted that what is listed above is only a specific implementation case of the present invention, and does not limit the present invention in any form. Obviously, the present invention is not limited to the above embodiments, and there may be many variations. For example, other materials with different sound velocity properties and different thicknesses are used to make wedges to stagger the echo of the bottom surface of the wedge and the echo of the weld defect. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field from the content disclosed in the present invention, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fully multi-layer high-pressure hydrogen storage container head butt weld detection device based on a fully focused ultrasonic phased array, characterized in that: The device comprises a sleeve (3) having an axially through-hole and one end of the through-hole detachably connected to the pipe forging, an outer bearing box (5) which can be inserted into the other end of the through-hole and can be moved along the axial direction of the sleeve through a sliding pair, a rotating shaft (20) whose middle part is rotatably positioned in the outer bearing box, a planar array phased array probe (18) fixed to one end of the rotating shaft to be inserted into the pipe forging to detect the weld, a plurality of fine water pipes (2) fixed to the side of the planar array phased array probe and uniformly provided with a plurality of small holes for spraying water on the weld, a hand wheel fixed to the other end of the rotating shaft to facilitate manual rotation of the rotating shaft, a hollow encoder sleeved on the rotating shaft to detect the rotation angle of the rotating shaft, an ultrasonic detector (17) electrically connected to the planar array phased array probe through a wire (15), and a water spraying device (16) connected to the plurality of fine water pipes; The outer surface of the rotating shaft is provided with a mounting groove arranged in a direction parallel to the axis; the mounting groove extends from one end close to the ultrasonic phased array probe to the other end and passes through the outer bearing box; the wire and a plurality of thin water pipes are positioned in the mounting groove; The sliding pair includes a sliding block arranged outside the outer bearing box and a sliding groove opened on the inner wall of the through hole and slidingly matched with the sliding block to limit the circumferential rotation of the outer bearing box; The invention discloses a method for detecting butt welds of a multi-layer high-pressure hydrogen storage container head based on a fully focused ultrasonic phased array, comprising the following steps: 1) Spray water, using water as a coupling agent for ultrasonic phased array testing; 2) Controlling the probe clamping device to extend the phased array probe into the pipe at the top of the end cap, and placing the phased array probe at the end of the pipe according to the structural dimensions of the probe clamping device and the container; 3) Start the ultrasonic detector and adjust the parameters so that the phased array array performs linear or fan-shaped deflection focusing scanning, and focuses the focus area on the butt weld of the head; rotate the phased array probe by rotating the handle to perform circumferential scanning inside the opening; and perform axial scanning of the ultrasonic phased array by controlling the phased array probe to move forward and backward in the opening; The main acoustic beam excited by all array elements in the phased array probe is focused at the focal point in the object to be tested, and the position of the array element is determined by the following formula: Where: It is i The horizontal inclination angle of the array element is It is i The distance from the center of each element to the center line, r is the inner diameter of the hole where the probe is located, is the sound velocity of the probe's acoustic matching layer or protective film, c is the sound velocity of the object to be measured, It is i The refraction angle of the main sound beam of each array element in the object to be measured is is the focal length of the focus within the object to be measured, is half the width of the array element, i It is i The incident angle of the main sound beam of each array element; 4) Observe the displayed image on the ultrasonic detector during the scanning process. If any suspected defects are found, re-inspect the corresponding area; The focusing method to determine the focusing area of ​​the fully focusing phased array is: An area at a certain distance in front of the probe is set as the target area, which includes several focusing points; the received echo signal is focused and superimposed on each point; The sound field amplitude at its location I ( x , z ) is calculated according to formula (1): （1） In the formula, e xi,xj ( t i,j ( x , z ))for i Array element launch, j The ultrasonic signal received by the array element is superimposed on ( x , z ) position; x i and x j are the coordinates of the array element, i and j The range is [1, N ], x and z are the coordinates of the virtual focal point; t i,j ( x , z ) is the sound wave from the array element i Emit to the focal point ( x , z ) and returns from this point to the array element j The required delay time; The method to determine the delay time is: The focus point can be calculated according to the following formula (2): x , z ) corresponding to the delay time, where c is the longitudinal wave velocity of the ultrasonic wave propagating in the test block; （2）。

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