Polyethylene pipeline hot melting joint welding defect ultrasonic phased array detection method and system

Abstract

The invention belongs to the technical field of pipeline welding nondestructive testing, and discloses an ultrasonic phased array detection method and system for welding defects of a polyethylene pipeline hot-melting joint, and the method comprises the following steps: firstly, preparing a welded polyethylene pipeline hot-melting joint and a polyethylene pipeline hot-melting joint containing the welding defects; detecting the polyethylene pipeline hot melting joints at different welding temperatures based on an ultrasonic phased array technology to obtain an ultrasonic phased array detection result; the maximum echo coverage angle range of the tangent plane at different welding temperatures is judged, and the relation between the maximum echo coverage angle range and the welding temperatures is determined; and obtaining an evaluation result of the to-be-evaluated polyethylene pipeline hot-melt joint by combining the relationship between the maximum echo start-end angle difference of the tangent plane and the welding temperature, and determining whether the to-be-evaluated polyethylene pipeline hot-melt joint contains the welding defect or not. According to the method, the welding quality of the polyethylene pipeline hot-melting joint can be more quickly represented by using an ultrasonic phased array detection result, whether the polyethylene pipeline hot-melting joint contains cold welding and over-welding defects or not is judged, the method is convenient and quick, and the cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of nondestructive testing of pipeline welding, and in particular relates to an ultrasonic phased array detection method and system for welding defects in polyethylene pipeline hot-melt joints. Background Art

[0002] Polyethylene has the advantages of wear resistance, corrosion resistance, impact resistance, and good chemical stability. It is widely used in the pipeline manufacturing industry such as gas pipes and water pipes. Pipeline construction usually exists in the form of a pipe network. For large-scale polyethylene pipeline laying, pipeline connection is usually involved. Hot melt welding is the main method of connecting polyethylene pipes. This method has the characteristics of low cost and easy operation. However, due to operational errors and improper selection of process parameters, defects may occur at the hot melt welding joints, affecting the performance and service life of the pipeline. As an important carrier for gas transportation, polyethylene pipes are very likely to cause explosions and fires once they fail and leak, seriously affecting people's lives and property safety.

[0003] According to the causes of the defects, the defect types of polyethylene pipe hot-melt welded joints can be divided into two categories: process defects and structural defects. Process defects refer to defects in hot-melt welded joints caused by improper selection of welding process parameters, mainly including cold welding, over-welding, undervoltage, overvoltage, and misalignment. Structural defects refer to defects in hot-melt joints caused by improper operation of welding operators, working conditions, pipeline quality, and welding environment, mainly holes, cracks, inclusions, etc. In order to further improve the reliability and safety of polyethylene pipeline systems, non-destructive testing is carried out on the basis of appearance inspection, which can effectively make up for the shortcomings of appearance inspection and reduce pipeline operation risks. The current ultrasonic phased array detection technology can accurately detect structural defects such as holes, cracks, inclusions, etc., but cannot detect process defects such as cold welding and over-welding. Therefore, the present invention proposes a method for detecting cold welding defects of polyethylene pipeline hot-melt joints based on ultrasonic phased array detection technology, which can effectively detect cold welding defects of hot-melt joints.

[0004] Through the above analysis, the problems and defects of the existing technology are: the current polyethylene pipe system cannot detect cold welding and over-welding defects of polyethylene pipe hot-melt joints using ultrasonic phased array detection technology. Summary of the Invention

[0005] To overcome the problems existing in the related art, the embodiments disclosed in the present invention provide an ultrasonic phased array detection method and system for welding defects in polyethylene pipe hot melt joints. The technical solution is as follows:

[0006] The present invention is implemented as follows: a method for ultrasonic phased array detection of welding defects in polyethylene pipe hot melt joints comprises the following steps:

[0007] S1, based on the polyethylene pipe hot-melt welding process, preparing welded polyethylene pipe hot-melt joints and polyethylene pipe hot-melt joints with welding defect types;

[0008] S2, based on ultrasonic phased array technology, detects polyethylene pipe hot-melt joints at different welding temperatures and obtains corresponding ultrasonic phased array test results;

[0009] S3, based on the ultrasonic phased array test results, determine the maximum echo coverage angle range of the cross-section at different welding temperatures, and determine the relationship between the maximum echo coverage angle range and the welding temperature;

[0010] S4, based on the maximum echo coverage angle range data of the polyethylene pipe hot-melt joint of the defect type to be evaluated, combined with the relationship between the start and end angle difference of the maximum echo of the section and the welding temperature, obtain the evaluation result of the polyethylene pipe hot-melt joint to be evaluated, and determine whether the polyethylene pipe hot-melt joint to be evaluated contains welding defects.

[0011] In step S1, a welded polyethylene pipe hot melt joint is prepared, comprising:

[0012] Select a clamping tool that matches the pipe size and fix the pipe to be welded; use a milling cutter to cut the welded surfaces at both ends of the pipe, controlling the cutting pressure within 0.5 MPa;

[0013] After cutting, align, check and adjust the pipe position, and use non-woven cloth to clean the pipe surface and heating plate; set the heating plate to the normal welding temperature of 220℃, and perform welding operations after the temperature stabilizes;

[0014] Place the heating plate between the ends of the pipes to be welded, and push the push rod of the welding device to make the pipes contact the heating plate; maintain the applied pressure at 0.5MPa when the pipes are butt-jointed, and use a stopwatch to determine the heat absorption time;

[0015] After the heat absorption is completed, remove the heating plate and align the pipes to be welded. The butt pressure is consistent with the welding pressure. After cooling under pressure on the hot melt welding machine, a normally welded polyethylene pipe hot melt joint is obtained.

[0016] Furthermore, the heat absorption time is 110 s and the pressure holding cooling time is 14 min.

[0017] Furthermore, based on the normal welding process, by adjusting the preset temperature of the heating plate during the welding process, polyethylene pipe hot melt joints containing cold welding defects and over-welding defects are prepared; wherein, the welding temperature of the polyethylene pipe hot melt joints containing cold welding defects is lower than 220°C, and the welding temperature of the polyethylene pipe hot melt joints containing over-welding defects is higher than 220°C.

[0018] In step S2, before detecting polyethylene pipe hot-melt joints at different welding temperatures based on ultrasonic phased array technology, the method further includes:

[0019] Cut the welded polyethylene pipe at 25mm on both ends of the center of the hot melt joint;

[0020] Select ultrasonic probes, wedges, standard test blocks, encoders and ultrasonic testing devices that are compatible with polyethylene pipes, and use coupling agents to fill the gaps between the probe and the wedge, and between the wedge and the material to be tested;

[0021] The ultrasonic phased array equipment was calibrated for sound velocity, delay, sensitivity, and TCG using a calibration block made of the same material as the polyethylene pipe to be tested.

[0022] In step S2, ultrasonic phased array detection includes:

[0023] Before scanning begins, mark the scanning starting point and scanning direction on the pipe; install the ultrasonic phased array wedge on the encoder, and use the encoder to fix the hot-melt joint of the polyethylene pipe to be tested;

[0024] The encoder is moved along the circumference of the pipe to scan the entire polyethylene pipe heat-melt joint, and the ultrasonic phased array inspection results of heat-melt welded joints with and without welding defects are obtained.

[0025] In step S3, based on the ultrasonic phased array detection results, the maximum echo coverage angle range of the cross-section at different welding temperatures is determined, and the relationship between the maximum echo coverage angle range and the welding temperature is determined, including:

[0026] Cutting polyethylene pipe hot-melt joints, determining the location of the cut surface in the ultrasonic phased array test results, analyzing the ultrasonic phased array test images, and extracting the A-scan and S-scan data corresponding to the maximum echo at that location;

[0027] Based on the analysis of ultrasonic phased array detection results, the maximum echo coverage angle range of the cross-section at different welding temperatures was determined, and the relationship between the start and end angle difference of the maximum echo of the cross-section and different welding temperatures was obtained.

[0028] Furthermore, the maximum echo coverage angle range of the slice is determined based on:

[0029] In the A-scan results, the area where the maximum echo signal amplitude exceeds 10% is taken as the location of the maximum echo of the section. The position of the A-scan line in the S-scan diagram is adjusted to determine the angular coverage range of the maximum echo signal of the section, and to determine the starting and ending angles of the maximum echo of the polyethylene pipe hot-melt joint section.

[0030] In step S4, determining whether the polyethylene pipe hot-melt joint to be evaluated contains welding defects includes:

[0031] The ultrasonic phased array inspection image of a normal welded joint at 220°C is used to determine the start and end angles of the maximum echo on the cross-section, and to determine the difference in the start and end angles of the maximum echo on the cross-section of the normal welded joint.

[0032] The maximum echo start and end angle difference of the cross section of the joint with cold welding defects is smaller than that of the cross section of the normal welding joint;

[0033] The maximum echo start and end angle difference of the cross-section of the joint with over-welding defects is greater than that of the cross-section of the normal welded joint.

[0034] Another object of the present invention is to provide an ultrasonic phased array detection system for polyethylene pipe hot-melt joint welding defects, the system being used to control the ultrasonic phased array detection method for polyethylene pipe hot-melt joint welding defects, the system comprising:

[0035] Joint preparation module, used to prepare welded polyethylene pipe hot-melt joints and polyethylene pipe hot-melt joints with welding defects based on the polyethylene pipe hot-melt welding process;

[0036] Ultrasonic phased array inspection module, used to inspect polyethylene pipe hot-melt joints at different welding temperatures based on ultrasonic phased array technology and obtain corresponding ultrasonic phased array inspection results;

[0037] A data extraction module is used to determine the maximum echo coverage angle range of the cross-section at different welding temperatures based on the ultrasonic phased array detection results, and to determine the relationship between the maximum echo coverage angle range and the welding temperature;

[0038] The defect type evaluation module is used to obtain the evaluation results of the polyethylene pipe hot-melt joint to be evaluated based on the maximum echo coverage angle range data of the defect type polyethylene pipe hot-melt joint to be evaluated, combined with the relationship between the start and end angle difference of the maximum echo of the section and the welding temperature, and determine whether the polyethylene pipe hot-melt joint to be evaluated contains welding defects.

[0039] In combination with all the above technical solutions, the beneficial effects of the present invention are as follows:

[0040] First, the present invention analyzes ultrasonic phased array test results at different welding temperatures, obtains corresponding ultrasonic phased array test results, and determines the relationship between the maximum echo coverage angle range of the section and the welding temperature. Based on the maximum echo coverage angle range data for the polyethylene pipe hot-melt joint, a defect type to be evaluated, and combined with the relationship between the start and end angle difference of the maximum echo of the section and the welding temperature, the evaluation result of the polyethylene pipe hot-melt joint to be evaluated is obtained, namely, whether it contains cold weld (over-weld) defects. This invention can more quickly characterize the welding quality of polyethylene pipe hot-melt joints using ultrasonic phased array test results, and use them to determine whether polyethylene pipe hot-melt joints contain cold weld or over-weld defects. This is more convenient and rapid, significantly reducing costs and improving detection efficiency and reliability.

[0041] Second, based on ultrasonic phased array testing, the present invention obtains the relationship between the maximum echo start and end angle difference based on the cross-section and the welding temperature, and obtains an empirical relationship between the maximum echo start and end angle difference and the welding temperature, achieving the goal of promoting the application of ultrasonic phased array technology in practical engineering applications.

[0042] Third, by establishing a correlation between ultrasonic phased array detection results and welding temperature, the present invention can significantly reduce the quality assessment cost of polyethylene pipe hot-melt joints. In addition, this technology can be integrated into existing detection equipment to form a new type of intelligent detection equipment with significant industrialization prospects. The present invention establishes for the first time a quantitative relationship between the ultrasonic phased array characteristic parameters (maximum echo coverage angle range) and welding temperature of polyethylene pipe hot-melt joints, filling the international technical gap in non-destructive assessment of welding quality. After verification, there are currently no public technical solutions at home and abroad that use ultrasonic phased array echo angle characteristics to determine polyethylene welding temperature and cold welding / over-welding defects.

[0043] Fourth, the present invention successfully overcomes the technical bottlenecks of large signal attenuation and difficult feature extraction in ultrasonic testing of polyethylene materials. Due to the acoustic impedance characteristics of polyethylene materials, traditional methods cannot accurately identify welding temperature differences, resulting in the inability to determine cold welds and over-weld defects in non-destructive testing results. The present invention solves the problem of cold weld and over-weld defect identification by innovatively using ultrasonic characteristic parameters as a characterization method. The present invention breaks through the traditional perception that "cold welds and over-weld defects in polyethylene pipe hot-melt joints are not suitable for quantitative detection by ultrasonic phased arrays." It is generally believed in the industry that the high acoustic attenuation characteristics of polyethylene will cause the ultrasonic signal signal-to-noise ratio to be too low, making it difficult to use for accurate evaluation of cold welds and over-weld defects in polyethylene pipe hot-melt joints. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure;

[0045] Figure 1 This is a flow chart of an ultrasonic phased array detection method for polyethylene pipe hot-melt welding defects provided by an embodiment of the present invention;

[0046] Figure 2 This is a diagram showing the ultrasonic testing results of a cross section of a 220°C hot-melt welded joint provided by an embodiment of the present invention;

[0047] Figure 3 Schematic diagram of the starting angle position of the maximum echo of a cross-section of a 220°C hot-melt welded joint provided by an embodiment of the present invention;

[0048] Figure 4 Schematic diagram of the maximum echo termination angle position of a cross section of a 220°C hot-melt welded joint provided by an embodiment of the present invention;

[0049] Figure 5 Schematic diagram of the relationship between the maximum echo start and end angle difference of the cross-section and different welding temperatures provided by an embodiment of the present invention;

[0050] Figure 6 This is the normal welding joint detection result of the experiment conducted by the present invention based on the technical solution;

[0051] Figure 7 These are the test results of other hot melt welding joints conducted in the present invention based on the technical solution. DETAILED DESCRIPTION

[0052] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0053] The innovation of the present invention lies in that it innovatively proposes the coverage angle range of the curling signal as a key parameter in ultrasonic phased array detection to judge whether the joint contains cold welding or over-welding defects, filling the gap in this technology in detecting such defects.

[0054] In Example 1, a cold weld defect detection system for polyethylene pipe hot melt joints based on ultrasonic phased array is provided in an embodiment of the present invention, comprising:

[0055] The preparation and testing module is used to prepare polyethylene pipe hot-melt joints with cold welding defects based on the polyethylene pipe hot-melt welding process, that is, the welding temperature is lower than the normal welding temperature of 220°C, and to test the hot-melt joints of polyethylene pipes that are normally welded, that is, the welding temperature is 220°C, using ultrasonic phased array technology to obtain the corresponding ultrasonic phased array test results.

[0056] A data extraction module is used to determine the maximum echo coverage angle range of the cross-section at different welding temperatures based on the ultrasonic phased array detection results, and to determine the relationship between the maximum echo coverage angle range and the welding temperature;

[0057] The evaluation module is used to obtain the evaluation result of the polyethylene pipe hot-melt joint to be evaluated, that is, whether it contains cold welding defects, based on the maximum echo coverage angle range data of the polyethylene pipe hot-melt joint of the defect type to be evaluated, combined with the relationship between the start and end angle difference of the maximum echo of the section and the welding temperature.

[0058] like Figure 1 As shown, the polyethylene pipe hot melt joint cold weld defect evaluation method based on ultrasonic phased array implemented by the present invention using the above polyethylene pipe hot melt joint cold weld defect detection system includes:

[0059] Based on the polyethylene pipe hot-melt welding process, a polyethylene pipe hot-melt joint with a cold weld defect, i.e., a welding temperature lower than the normal welding temperature of 220°C, and a normally welded polyethylene pipe hot-melt joint, i.e., a welding temperature of 220°C, were prepared. The hot-melt joints at different welding temperatures were inspected using ultrasonic phased array technology to obtain the corresponding ultrasonic phased array inspection results.

[0060] Based on the ultrasonic phased array test results, the maximum echo coverage angle range of the cross-section at different welding temperatures is determined, and the relationship between the maximum echo coverage angle range and the welding temperature is determined;

[0061] Based on the maximum echo coverage angle range data of the polyethylene pipe hot-melt joint of the defect type to be evaluated, combined with the relationship between the start and end angle difference of the maximum echo of the section and the welding temperature, the evaluation result of the polyethylene pipe hot-melt joint to be evaluated is obtained, that is, whether the polyethylene pipe hot-melt joint contains cold welding defects.

[0062] In Example 1 of the present invention, obtaining ultrasonic phased array data of polyethylene pipe hot-melt joints at different welding temperatures includes:

[0063] Using a semi-automatic hot-melt welding machine, hot-melt welding tests were conducted on polyethylene pipes to obtain hot-melt welded joints with and without cold-weld defects.

[0064] Ultrasonic phased array testing equipment was used to perform ultrasonic phased array testing on polyethylene hot-melt welded joints after welding, and ultrasonic phased array testing results of hot-melt welded joints with and without cold welding defects were obtained.

[0065] The cold welding defect evaluation method of polyethylene pipe hot melt joints based on ultrasonic phased array of the present invention specifically includes:

[0066] Step (1): Select a polyethylene pipe with a diameter of 110 mm, a standard dimension ratio (SDR) of 11, and a material of PE100 for hot melt welding;

[0067] Step (2): Select a clamping tool that matches the pipe size and fix the pipe to be welded;

[0068] Step (3): Use a milling cutter to cut the surfaces to be welded at both ends of the pipe, ensuring that the cutting is smooth;

[0069] Step (4): Control the cutting pressure within 0.5 MPa to avoid excessive pressure causing pipe deformation;

[0070] Step (5): After cutting, align, check and adjust the position of the pipe to avoid misalignment of the end faces to be welded;

[0071] Step (6): Use non-woven cloth to clean the pipe surface and heating plate to avoid affecting the welding quality;

[0072] Step (7): The normal welding temperature is 220°C. Set the heating plate to this temperature and perform the welding operation after the temperature stabilizes.

[0073] Step (8): placing the heating plate between the end faces of the pipe to be welded, and pushing the push rod of the welding device to make the pipe and the heating plate in close contact;

[0074] Step (9): When the pipes are docked, the applied pressure is maintained at 0.5 MPa, and a stopwatch is used to determine that the heat absorption time is 110 s;

[0075] Step (10): After the heat absorption is completed, the heating plate is quickly removed and the pipe to be welded is connected. The connection pressure is kept consistent with the welding pressure. The time for removing the heating plate and the connection pressure increase operation time are controlled within 10 seconds to avoid premature cooling of the pipe molten zone.

[0076] Step (11): After cooling under pressure for 14 minutes on a hot melt welding machine, a hot melt joint corresponding to the welding temperature in step (7) is obtained;

[0077] Step (12): Repeat steps (1) to (11), and change the temperature of the heating plate in step (7) to 150° C., 170° C., and 190° C. to obtain a polyethylene pipe hot-melt joint containing cold welding defects;

[0078] Step (13): cutting the polyethylene pipe welded in step (11), with the cutting position being 25 mm from both ends of the center of the hot melt joint;

[0079] Step (14): Select an ultrasonic probe, a wedge, a standard test block, an encoder, and an ultrasonic detection device that are compatible with the pipeline, and use a suitable coupling agent to fill the gaps between the probe and the wedge, and between the wedge and the material to be tested. The purpose is to improve the acoustic wave transmission efficiency between the ultrasonic probe and the wedge, and between the wedge and the pipeline to be tested, and to avoid signal attenuation or distortion.

[0080] Step (15): Use a calibration block made of the same material as the pipeline to be tested to calibrate the ultrasonic phased array device for sound velocity, delay, sensitivity, and TCG;

[0081] Step (16): Ultrasonic phased array detection, first install the ultrasonic phased array wedge on the encoder, then fix the polyethylene pipe hot melt joint to be tested, and finally fix the encoder on the polyethylene pipe hot melt joint to be tested; move the encoder by manually dragging it so that it moves circumferentially along the pipe to achieve an overall scan of the polyethylene pipe hot melt joint; before the scan begins, the scanning starting point and scanning direction should be clearly marked on the pipe, which will help in the subsequent comparative analysis and evaluation of the ultrasonic phased array detection images on both sides of the hot melt joint.

[0082] In Example 1 of the present invention, obtaining ultrasonic phased array data of a polyethylene pipe heat-melt joint includes:

[0083] Based on the ultrasonic phased array test results, determine the maximum echo coverage angle range of the cross-section at different welding temperatures and determine the relationship between the angle range and welding temperature. Specifically, the following are performed:

[0084] Step (17): Analyze the ultrasonic phased array detection image and extract the A-scan and S-scan data corresponding to the maximum echo position of the pipeline section;

[0085] Step (18): In the A-scan result, the area where the maximum echo signal amplitude exceeds 10% is taken as the location of the maximum echo of the section, and the position of the A-scan line in the S-scan diagram is adjusted to determine the angular coverage range of the maximum echo signal of the section, and the starting and ending angles of the maximum echo are determined;

[0086] Step (19): Using the judgment method of step (18), the ultrasonic phased array detection image of the normal welded joint at 220°C is used to judge the starting and ending angles of the maximum echo of the cross section. Figure 2 The ultrasonic test results of the cross-section of a 220°C hot-melt welded joint are shown. The left side shows the A-scan image, and the right side shows the S-scan image. In the S-scan image on the right, the green line is the A-scan line, and the red area is the location of the maximum echo on the cross-section.

[0087] Step (20): The result obtained in step (19) is that when the A scan line angle is 57°, it is the starting angle of the maximum echo of the section ( Figure 3 ), when the A scan line angle is 71°, it is the end angle of the maximum echo of the section ( Figure 4 ), that is, the maximum echo start and end angle difference of the welded joint section with a welding temperature of 220°C is 14°;

[0088] Step (21): Repeat steps (17) to (20) for other welding temperatures (150°C, 170°C, 190°C) of the hot melt joints, and obtain the maximum echo start and end angle differences corresponding to different welding temperatures as 10°, 10.5°, and 13°. The relationship between the maximum echo start and end angle difference of the cross section and the welding temperature is as follows: Figure 5 shown.

[0089] Step (22): According to the results of step (20) and step (21), it is found that the maximum echo start and end angle difference of the cross section of the joint containing the cold welding defect is smaller than the maximum echo start and end angle difference of the cross section of the normal welding joint.

[0090] The quality of hot-melt welded joints of polyethylene pipes of the same model on site was evaluated. The relationship between the obtained welding temperature and the start and end angle difference of the maximum echo of the section was used to determine whether the hot-melt joint of the pipe to be inspected contained cold weld defects. When the angle difference was less than 14°, the welded joint could be judged to be a cold weld defect.

[0091] In Example 2, the present invention provides a polyethylene pipe hot melt joint over-welding defect detection system based on ultrasonic phased array, which includes:

[0092] The preparation and detection module is used to prepare polyethylene pipe hot-melt joints with over-welding defects based on the polyethylene pipe hot-melt welding process, that is, the welding temperature is higher than the normal welding temperature (220°C), and to detect the hot-melt joints of polyethylene pipes that are normally welded, that is, the welding temperature is 220°C, using ultrasonic phased array technology to obtain corresponding ultrasonic phased array detection results.

[0093] A data extraction module is used to determine the maximum echo coverage angle range of the cross-section at different welding temperatures based on the ultrasonic phased array detection results, and to determine the relationship between the maximum echo coverage angle range and the welding temperature;

[0094] The evaluation module is used to obtain the evaluation result of the polyethylene pipe hot-melt joint to be evaluated, that is, whether it contains over-welding defects, based on the maximum echo coverage angle range data of the polyethylene pipe hot-melt joint of the defect type to be evaluated, combined with the relationship between the start and end angle difference of the maximum echo of the cross-section and the welding temperature.

[0095] like Figure 1 As shown, the present invention utilizes the above-mentioned polyethylene pipe hot melt joint over-weld defect detection to implement the polyethylene pipe hot melt joint over-weld defect evaluation method based on ultrasonic phased array, which includes:

[0096] S1, based on the polyethylene pipe hot-melt welding process, preparing welded polyethylene pipe hot-melt joints and polyethylene pipe hot-melt joints with welding defect types;

[0097] Preparation of polyethylene pipe hot melt joints with over-welding defects, i.e., the welding temperature is higher than the normal welding temperature of 220°C, and normally welded polyethylene pipe hot melt joints, i.e., the welding temperature is 220°C;

[0098] S2, based on ultrasonic phased array technology, detects polyethylene pipe hot-melt joints at different welding temperatures and obtains corresponding ultrasonic phased array test results;

[0099] S3, based on the ultrasonic phased array test results, determine the maximum echo coverage angle range of the cross-section at different welding temperatures, and determine the relationship between the maximum echo coverage angle range and the welding temperature;

[0100] S4, based on the maximum echo coverage angle range data of the polyethylene pipe hot-melt joint of the defect type to be evaluated, combined with the relationship between the start and end angle difference of the maximum echo of the section and the welding temperature, obtain the evaluation result of the polyethylene pipe hot-melt joint to be evaluated, and determine whether the polyethylene pipe hot-melt joint to be evaluated contains welding defects.

[0101] In Example 2 of the present invention, obtaining ultrasonic phased array data of polyethylene pipe hot-melt joints at different welding temperatures includes:

[0102] Use a semi-automatic hot melt welding machine to perform hot melt welding on polyethylene pipes to obtain hot melt welded joints with or without over-welding defects;

[0103] Ultrasonic phased array testing equipment was used to perform ultrasonic phased array testing on polyethylene hot-melt welded joints after welding, and ultrasonic phased array testing results of hot-melt welded joints with and without over-welding defects were obtained.

[0104] The ultrasonic phased array-based method for evaluating over-welding defects in polyethylene pipe hot-melt joints of the present invention specifically includes:

[0105] Step (1): Select a polyethylene pipe with a diameter of 110 mm, a standard dimension ratio (SDR) of 11, and a material of PE100 for hot melt welding;

[0106] Step (2): Select a clamping tool that matches the pipe size and fix the pipe to be welded;

[0107] Step (3): Use a milling cutter to cut the surfaces to be welded at both ends of the pipe, ensuring that the cutting is smooth;

[0108] Step (4): Control the cutting pressure within 0.5 MPa to avoid excessive pressure causing pipe deformation;

[0109] Step (5): After cutting, align, check and adjust the position of the pipe to avoid misalignment of the end faces to be welded;

[0110] Step (6): Use a clean non-woven cloth to clean the pipe surface and heating plate to avoid affecting the welding quality;

[0111] Step (7): The normal welding temperature is 220°C. Set the heating plate to this temperature and perform the welding operation after the temperature stabilizes.

[0112] Step (8): placing the heating plate between the end faces of the pipe to be welded, and pushing the push rod of the welding device to make the pipe and the heating plate in close contact;

[0113] Step (9): When the pipes are docked, the applied pressure is maintained at 0.5 MPa, and a stopwatch is used to determine that the heat absorption time is 110 s;

[0114] Step (10): After the heat absorption is completed, the heating plate is quickly removed and the pipe to be welded is connected. The connection pressure is kept consistent with the welding pressure. The time for removing the heating plate and the connection pressure increase operation time are controlled within 10 seconds to avoid premature cooling of the pipe molten zone.

[0115] Step (11): After cooling under pressure for 14 minutes on a hot melt welding machine, a hot melt joint corresponding to the welding temperature in step (7) is obtained;

[0116] Step (12): Repeat steps (1) to (11), and change the temperature of the heating plate in step (7) to 250° C., 280° C., and 300° C. to obtain a polyethylene pipe hot-melt joint containing over-welding defects;

[0117] Step (13): cutting the polyethylene pipe welded in step (11), with the cutting position being 25 mm from both ends of the center of the hot melt joint;

[0118] Step (14): Select an ultrasonic probe, a wedge, a standard test block, an encoder, and an ultrasonic detection device that are compatible with the pipeline, and use a suitable coupling agent to fill the gaps between the probe and the wedge, and between the wedge and the material to be tested. The purpose is to improve the acoustic wave transmission efficiency between the ultrasonic probe and the wedge, and between the wedge and the pipeline to be tested, and to avoid signal attenuation or distortion.

[0119] Step (15): Use a calibration block made of the same material as the pipeline to be tested to calibrate the ultrasonic phased array device for sound velocity, delay, sensitivity, and TCG;

[0120] Step (16): Ultrasonic phased array detection, first install the ultrasonic phased array wedge on the encoder, then fix the polyethylene pipe hot melt joint to be tested, and finally fix the encoder on the polyethylene pipe hot melt joint to be tested; move the encoder by manually dragging it so that it moves circumferentially along the pipe to achieve an overall scan of the polyethylene pipe hot melt joint; before the scan begins, the scanning starting point and scanning direction should be clearly marked on the pipe, which will help in the subsequent comparative analysis and evaluation of the ultrasonic phased array detection images on both sides of the hot melt joint.

[0121] In Example 2 of the present invention, obtaining ultrasonic phased array data of a polyethylene pipe heat-melt joint includes:

[0122] Based on the ultrasonic phased array test results, determine the maximum echo coverage angle range of the cross-section at different welding temperatures and determine the relationship between the angle range and welding temperature. Specifically, the following are performed:

[0123] Step (17): Analyze the ultrasonic phased array detection image and extract the A-scan and S-scan data corresponding to the maximum echo at the section position;

[0124] Step (18): In the A-scan result, the area where the maximum echo signal amplitude exceeds 10% is taken as the location of the maximum echo of the section, and the position of the A-scan line in the S-scan diagram is adjusted to determine the angular coverage range of the maximum echo signal of the section, and the starting and ending angles of the maximum echo are determined;

[0125] Step (19): Using the judgment method of step (18), the ultrasonic phased array detection image of the normal welded joint at 220°C is used to judge the starting and ending angles of the maximum echo of the cross section. Figure 2 The ultrasonic test results of the cross-section of a 220°C hot-melt welded joint are shown. The left side shows the A-scan image, and the right side shows the S-scan image. In the S-scan image on the right, the green line is the A-scan line, and the red area is the location of the maximum echo on the cross-section.

[0126] Step (20): The result obtained in step (19) is that when the A scan line angle is 57°, it is the starting angle of the maximum echo of the section ( Figure 3 ), when the A scan line angle is 71.0°, it is the end angle of the maximum echo of the section ( Figure 4 ), that is, the maximum echo start and end angle difference of the welded joint section with a welding temperature of 220°C is 14°;

[0127] Step (21): Repeat steps (17) to (20) for other welding temperatures (250°C, 280°C, 300°C) of the hot melt joints, and obtain the maximum echo start and end angle differences corresponding to different welding temperatures as 15.5°, 16°, and 15.5°. The relationship between the maximum echo start and end angle difference of the cross section and the welding temperature is as follows: Figure 5 shown.

[0128] Step (22): According to the results of step (20) and step (21), it is found that the maximum echo start and end angle difference of the cross section of the cold weld defect joint is smaller than the maximum echo start and end angle difference of the cross section of the normal weld joint.

[0129] The quality of hot-melt welded joints of polyethylene pipes of the same model on site was evaluated. The relationship between the obtained welding temperature and the start and end angle difference of the maximum echo of the cross section was used to determine whether the pipeline to be inspected contained over-welding defects. When the angle difference was greater than 14°, the welded joint could be judged to have an over-welding defect.

[0130] Example 3: The method for evaluating cold welding and over-welding of polyethylene pipe hot-melt joints provided by the embodiment of the present invention includes:

[0131] Based on the ultrasonic phased array inspection data of polyethylene pipe hot-melt joints, a relationship is established between the difference in the maximum echo start and end angles of the corresponding cross-section of the pipe and the welding temperature.

[0132] Based on the above relationship, the relationship between the cold welding (over-welding) characterization quantity and the welding temperature is determined. The cold welding (over-welding) characterization quantity is the ratio of the start and end angle difference of the maximum echo of the section to the pipe diameter.

[0133] Based on the ultrasonic phased array data of the polyethylene pipe hot-melt joint to be inspected, the relationship between the cold weld (over-weld) characterization quantity and the welding temperature, the welding quality of the polyethylene pipe hot-melt joint to be inspected, that is, whether it contains cold weld (over-weld) defects, is determined.

[0134] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0135] In order to further demonstrate the positive effects of the above embodiment, the present invention conducts the following experiments based on the above technical solution.

[0136] Experimental plan:

[0137] Sample preparation: Prepare seven hot-melt welded joint samples, including one standard welded joint and six welded joints with preset defects (only the inspectors know whether the other six joints contain defects);

[0138] Blind sample numbering: The inspector will randomly number the six defective joints and record the defect types to form a blind sample inspection group;

[0139] Testing process:

[0140] (1) Spectrum analysis method (conventional defect detection method): ultrasonic phased array detection is used to obtain the spectrum of each joint, and the presence of defects is preliminarily determined by comparing the spectrum morphology;

[0141] (2) Characteristic parameter method (technical solution of the present invention): extract the ultrasonic characteristic parameters of each joint, focus on analyzing the angle coverage index, and establish defect judgment criteria;

[0142] Result verification: Compare the defect truth data recorded by the inspectors and calculate the defect detection rates of the two methods.

[0143] Experimental results:

[0144] Spectrum analysis results: The test results of normal welding joints are as follows: Figure 6 As shown, the test results of other hot melt welding joints are as follows Figure 7 shown.

[0145] Through image comparison, it was found that the welding joints numbered 1 and 6 had defects, and the welding joints numbered 2, 3, 4, and 5 could not be accurately judged.

[0146] Characteristic parameter analysis results (as shown in Table 1): Defect judgment criteria: a) Cold welding defect: angle coverage range < standard joint value; b) Over-welding defect: angle coverage range > standard joint value.

[0147] serial number Maximum echo starting angle Maximum echo termination angle Angle coverage normal 57.5 71 13.5 1 59 70 11 2 60.5 76.5 16 3 57.5 72.5 15 4 57.5 70.5 13 5 58.5 75 16.5 6 57.5 69 11.5

[0148] Combined with the angle coverage in the table, it can be found that the joints numbered 1, 2, 3, 4, 5, and 6 have defects. Among them, the angle coverage of joints numbered 1, 4, and 6 is smaller than the angle coverage of normal joints, which are cold welding defects, and the angle range of joints numbered 2, 3, and 5 is larger than the angle coverage of normal joints, which are over-welding defects.

[0149] The defect detection rate is determined by combining the test personnel's record results. The defect detection rate is directly determined to be 33.33% based on the atlas. The defect detection rate of the above technical solution is 100%.

[0150] The present invention establishes a quantitative judgment standard for ultrasonic characteristic parameters (angle coverage range), and through the above experiments it is found that the present invention can significantly increase the defect detection rate from 33.3% of the traditional atlas method to 100%.

[0151] The above description is only a preferred specific implementation method of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. An ultrasonic phased array detection method for welding defects of polyethylene pipe hot melt joints, characterized in that: The method comprises the following steps: S1, based on the polyethylene pipe hot-melt welding process, preparing welded polyethylene pipe hot-melt joints and polyethylene pipe hot-melt joints with welding defect types; S2, based on ultrasonic phased array technology, detects polyethylene pipe hot-melt joints at different welding temperatures and obtains corresponding ultrasonic phased array test results; S3, based on the ultrasonic phased array test results, determine the maximum echo coverage angle range of the cross-section at different welding temperatures, and determine the relationship between the maximum echo coverage angle range and the welding temperature; S4, based on the maximum echo coverage angle range data of the polyethylene pipe hot-melt joint of the defect type to be evaluated, combined with the relationship between the start and end angle difference of the maximum echo of the section and the welding temperature, obtain the evaluation result of the polyethylene pipe hot-melt joint to be evaluated, and determine whether the polyethylene pipe hot-melt joint to be evaluated contains welding defects.

2. The ultrasonic phased array detection method for polyethylene pipe hot melt joint welding defects according to claim 1 is characterized in that: In step S1, a welded polyethylene pipe hot melt joint is prepared, comprising: Select a clamping tool that matches the pipe size and fix the pipe to be welded; use a milling cutter to cut the welded surfaces at both ends of the pipe, controlling the cutting pressure within 0.5 MPa; After cutting, align, check and adjust the pipe position, and use non-woven cloth to clean the pipe surface and heating plate; set the heating plate to the normal welding temperature of 220℃, and perform welding operations after the temperature stabilizes; Place the heating plate between the ends of the pipes to be welded, and push the push rod of the welding device to make the pipes contact the heating plate; maintain the applied pressure at 0.5MPa when the pipes are butt-jointed, and use a stopwatch to determine the heat absorption time; After the heat absorption is completed, remove the heating plate and align the pipes to be welded. The butt pressure is consistent with the welding pressure. After cooling under pressure on the hot melt welding machine, a normally welded polyethylene pipe hot melt joint is obtained.

3. The ultrasonic phased array detection method for welding defects of polyethylene pipe hot melt joints according to claim 2 is characterized in that: The heat absorption time is 110s and the pressure holding cooling time is 14min.

4. The ultrasonic phased array detection method for polyethylene pipe hot melt joint welding defects according to claim 2 is characterized in that: Based on the normal welding process, polyethylene pipe hot-melt joints containing cold welding defects and over-welding defects are prepared by adjusting the preset temperature of the heating plate during the welding process; among them, the welding temperature of the polyethylene pipe hot-melt joints containing cold welding defects is lower than 220°C, and the welding temperature of the polyethylene pipe hot-melt joints containing over-welding defects is higher than 220°C.

5. The ultrasonic phased array detection method for welding defects of polyethylene pipe hot melt joints according to claim 1 is characterized in that: In step S2, before detecting polyethylene pipe hot-melt joints at different welding temperatures based on ultrasonic phased array technology, the method further includes: Cut the welded polyethylene pipe at 25mm on both ends of the center of the hot melt joint; Select ultrasonic probes, wedges, standard test blocks, encoders and ultrasonic testing devices that are compatible with polyethylene pipes, and use coupling agents to fill the gaps between the probe and the wedge, and between the wedge and the material to be tested; The ultrasonic phased array equipment was calibrated for sound velocity, delay, sensitivity, and TCG using a calibration block made of the same material as the polyethylene pipe to be tested.

6. The ultrasonic phased array detection method for polyethylene pipe hot melt joint welding defects according to claim 1 is characterized in that: In step S2, ultrasonic phased array detection includes: Before scanning begins, mark the scanning starting point and scanning direction on the pipe; install the ultrasonic phased array wedge on the encoder, and use the encoder to fix the hot-melt joint of the polyethylene pipe to be tested; The encoder is moved along the circumference of the pipe to scan the entire polyethylene pipe heat-melt joint, and the ultrasonic phased array inspection results of heat-melt welded joints with and without welding defects are obtained.

7. The ultrasonic phased array detection method for welding defects of polyethylene pipe hot melt joints according to claim 1 is characterized in that: In step S3, based on the ultrasonic phased array detection results, the maximum echo coverage angle range of the cross-section at different welding temperatures is determined, and the relationship between the maximum echo coverage angle range and the welding temperature is determined, including: Cutting polyethylene pipe hot-melt joints, determining the location of the cut surface in the ultrasonic phased array test results, analyzing the ultrasonic phased array test images, and extracting the A-scan and S-scan data corresponding to the maximum echo at that location; Based on the analysis of ultrasonic phased array detection results, the maximum echo coverage angle range of the cross-section at different welding temperatures was determined, and the relationship between the start and end angle difference of the maximum echo of the cross-section and different welding temperatures was obtained.

8. The ultrasonic phased array detection method for polyethylene pipe hot melt joint welding defects according to claim 7, characterized in that: The determination basis for the maximum echo coverage angle range of the slice is: In the A-scan results, the area where the maximum echo signal amplitude exceeds 10% is taken as the location of the maximum echo of the section. The position of the A-scan line in the S-scan diagram is adjusted to determine the angular coverage range of the maximum echo signal of the section, and to determine the starting and ending angles of the maximum echo of the polyethylene pipe hot-melt joint section.

9. The ultrasonic phased array detection method for welding defects of polyethylene pipe hot melt joints according to claim 1, characterized in that: In step S4, determining whether the polyethylene pipe hot-melt joint to be evaluated contains welding defects includes: The ultrasonic phased array inspection image of a normal welded joint at 220°C is used to determine the start and end angles of the maximum echo on the cross-section, and to determine the difference in the start and end angles of the maximum echo on the cross-section of the normal welded joint. The maximum echo start and end angle difference of the cross section of the joint with cold welding defects is smaller than that of the cross section of the normal welding joint; The maximum echo start and end angle difference of the cross-section of the joint with over-welding defects is greater than that of the cross-section of the normal welded joint.

10. An ultrasonic phased array detection system for polyethylene pipe hot melt joint welding defects, characterized in that: The system is used to control the ultrasonic phased array detection method for welding defects of polyethylene pipe hot-melt joints according to any one of claims 1 to 9, and the system comprises: Joint preparation module, used to prepare welded polyethylene pipe hot-melt joints and polyethylene pipe hot-melt joints with welding defects based on the polyethylene pipe hot-melt welding process; Ultrasonic phased array inspection module, used to inspect polyethylene pipe hot-melt joints at different welding temperatures based on ultrasonic phased array technology and obtain corresponding ultrasonic phased array inspection results; A data extraction module is used to determine the maximum echo coverage angle range of the cross-section at different welding temperatures based on the ultrasonic phased array detection results, and to determine the relationship between the maximum echo coverage angle range and the welding temperature; The defect type evaluation module is used to obtain the evaluation results of the polyethylene pipe hot-melt joint to be evaluated based on the maximum echo coverage angle range data of the defect type polyethylene pipe hot-melt joint to be evaluated, combined with the relationship between the start and end angle difference of the maximum echo of the section and the welding temperature, and determine whether the polyethylene pipe hot-melt joint to be evaluated contains welding defects.

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