A method for predicting performance of a welded joint of a polyethylene pipeline and determining a safe pressure
By collecting data on polyethylene pipelines and designing orthogonal experiments and performance models, the problem of unsatisfactory performance prediction of welded joints in polyethylene pipelines was solved. This enabled accurate prediction of cold welding and over-welding defects and determination of safe pressure, thus ensuring the safe operation of the pipelines.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA NAT PETROLEUM CORP
- Filing Date
- 2024-12-12
- Publication Date
- 2026-06-12
AI Technical Summary
The performance prediction of welded joints in polyethylene pipes using existing technologies is not ideal, especially since cold welding and over-welding defects are difficult to identify, affecting the safety and pressure-bearing capacity of the pipes.
By collecting data on polyethylene pipes, normal welding process parameters were determined, orthogonal experiments on cold welding and over-welded joints were designed, performance tests were conducted, a joint performance model was established, and the safe pressure was determined through the safety factor.
It improves the accuracy of performance prediction for welded joints in polyethylene pipes, enables timely detection and handling of potential defects, ensures safe pipeline operation, and enhances operational safety and reliability.
Smart Images
Figure CN122200834A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of pipeline safety evaluation technology, and relates to a method for predicting the performance of welded joints in polyethylene pipelines and determining the safe pressure. Background Technology
[0002] Currently, the gas pipeline industry is entering a complex and critical period of transformation, facing multiple challenges such as aging pipeline infrastructure, increasing potential safety hazards, and the rapid expansion of new pipeline networks. With the acceleration of urbanization and the continuous improvement of residents' living standards, the safety of gas, as an important energy supply method, is directly related to the safety of life and property of countless households and the overall social stability. However, due to factors such as the long history of urban gas pipelines, the difficulty of maintenance and management, and complex and variable environmental conditions, safety management is exceptionally challenging. In recent years, gas leaks and explosions have occurred frequently, causing not only serious casualties and property losses but also widespread public concern and deep anxiety about gas safety. Against this backdrop, polyethylene pipes (PE pipes), with their excellent flexibility, superior corrosion resistance, convenient weldability, and relatively low cost, have gradually become the preferred material in gas pipeline engineering, effectively replacing traditional steel and cast iron pipes. This trend of "replacing steel with plastic" has not only driven innovation in pipeline material technology but also significantly improved the efficiency of gas pipeline construction and maintenance. According to statistics, PE pipes account for more than 70% of the newly built, renovated and expanded gas pipeline projects, becoming the mainstream choice in the pipeline field.
[0003] However, quality control of welded joints in polyethylene pipes remains a significant technical challenge. While hot-melt welding and electrofusion welding are two main methods for welding PE pipes, and are technically mature, they are prone to defects such as cold welding and over-welding during the welding process. These defects not only reduce the mechanical strength and sealing performance of the joints but also pose a serious threat to the overall safety and reliability of the pipeline. Particularly problematic is that some polyethylene pipe joints containing cold welding or over-welding defects often appear identical to normal joints, making them difficult to identify effectively with the naked eye or conventional inspection methods. If these potential defects are not detected and addressed in a timely manner, the performance of the welded joint will significantly deteriorate, thereby affecting the pipeline's pressure-bearing capacity and safe operation.
[0004] Currently, although non-destructive testing technologies such as radiographic testing, ultrasonic testing, and ultrasonic phased array testing are widely used in metal pipeline inspection, these technologies still face many challenges in inspecting polyethylene pipe joints with cold welding or over-welding defects, and the inspection results are not ideal. While new welding machines can automatically record welding process parameters, providing some support for quality control during the welding process, they are inadequate for predicting changes in joint performance. Therefore, establishing a scientific, accurate, and efficient method for predicting the performance of polyethylene pipe welded joints and determining safe pressure based on existing technologies has become a key technical problem urgently needing to be solved in the gas pipeline industry. Summary of the Invention
[0005] The purpose of this invention is to solve the technical problem that the performance prediction of polyethylene pipe welded joints is not ideal in the prior art, and to provide a method for predicting the performance of polyethylene pipe welded joints and determining the safe pressure.
[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention discloses a method for predicting the performance of welded joints in polyethylene pipes, comprising: Collect data on polyethylene pipes and determine the normal process parameters for welding polyethylene pipes based on the data. Based on the normal welding process parameters, an orthogonal experiment was designed to test cold welded joints and over-welded joints. Based on the orthogonal experiment, cold welded joints, normal welded joints and over-welded joints were prepared. Performance tests were conducted on the cold-welded joints, normal-welded joints, and over-welded joints to obtain performance test data. The performance test data were analyzed and fitted to establish a joint performance model. The actual welding process parameters of the polyethylene pipe are input into the joint performance model to obtain the predicted mechanical properties of the welded joint, thus completing the performance prediction of the polyethylene pipe welded joint.
[0007] Further improvements are made in the following aspects: The data for the polyethylene pipe includes the pipe's material, diameter, wall thickness, raw materials, and joint type.
[0008] The orthogonal tests include orthogonal tests for thermofusion joints and orthogonal tests for electrofusion joints.
[0009] The orthogonal test for the hot melt joint specifically includes: For hot melt joints, while ensuring that the edge rolling pressure, edge rolling height, heat absorption pressure, cooling pressure and cooling time remain constant, orthogonal experiments are designed around the welding temperature and heat absorption time. Based on normal process parameters, welding temperature and heat absorption time are increased or decreased at equal intervals to design cold welding and over-welded joint tests respectively.
[0010] The orthogonal test for the electrofusion joint specifically includes: For electrofusion joints, while ensuring that the cooling time remains constant, orthogonal experiments are designed around the welding voltage and welding time. Cold welding and over-welded joint tests are designed by increasing or decreasing the welding voltage and welding time at equal intervals based on normal process parameters.
[0011] The performance tests on the cold-welded joints, normal-welded joints, and over-welded joints specifically include: The cold-welded joints, normal-welded joints, and over-welded joints all include hot-melt joints and electrofusion joints; tensile tests are performed on the hot-melt joints.
[0012] The cold-welded joints, normal welded joints, and over-welded joints all include hot-melt joints and electrofusion joints; tensile peel tests are performed on the electrofusion joints.
[0013] The specific steps for analyzing and fitting the performance test data to establish a joint performance model include: The performance test data were analyzed, and models of welded joint performance and process parameters under different process conditions were established.
[0014] Secondly, this invention discloses a method for determining the safety pressure of a polyethylene pipe welded joint based on the above method, specifically as follows: Safe pressure = Design pressure × Safety factor.
[0015] The safety factor = predicted mechanical properties of the welded joint / normal mechanical properties of the welded joint.
[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for predicting the performance and determining the safe pressure of welded joints in polyethylene pipelines. The proposed method for predicting the performance of welded joints in polyethylene pipelines involves accurately collecting data from the polyethylene pipeline and determining normal welding process parameters based on this data, ensuring the accuracy and reliability of the foundational data for subsequent experiments and model establishment. This significantly improves the accuracy of joint performance prediction and provides strong support for the safe operation of polyethylene pipelines. The method not only considers normal welded joints but also designs orthogonal experiments for cold-welded and over-welded joints, and prepares corresponding welded joints for performance testing. This comprehensively reflects the impact of different welding defects on joint performance, making the prediction results more comprehensive and accurate. Through analysis and fitting of performance test data, this invention establishes a joint performance model. This model reflects the complex relationship between welding process parameters and joint performance, providing a scientific basis for optimizing actual welding process parameters. Inputting the actual welding process parameters of the polyethylene pipeline into the joint performance model yields the predicted mechanical properties of the welded joint. This enables real-time prediction and management of joint performance, helping to promptly detect and address potential welding defects, ensuring the safe operation of polyethylene pipelines. By using the pipeline welded joint performance prediction method and process provided in this invention, the performance of in-service polyethylene pipeline joints with cold-welded and over-welded defects can be effectively predicted. This helps to promptly detect and address situations where joint performance deteriorates or safety hazards exist, thereby preventing accidents and improving the operational safety of polyethylene pipelines. By using the pipeline welded joint performance prediction method and process provided in this invention, the performance of in-service polyethylene pipeline joints with defects such as cold welding and over-welding can be effectively predicted, achieving safe operation management of polyethylene pipeline welded joints.
[0017] Furthermore, by introducing orthogonal experiments for thermofusion and electrofusion joints, a comprehensive evaluation of the performance of welded joints in polyethylene pipes was achieved. This feature ensures that key parameters in the welding process of both thermofusion and electrofusion joints can be fully examined and optimized, thereby improving the accuracy and applicability of the prediction method. In the orthogonal experiment for thermofusion joints, this invention focuses on adjusting the welding temperature and endothermic time while keeping other parameters constant, designing cold welding and over-welded joint tests by increasing or decreasing these parameters at equal intervals. This precise control method allows us to more accurately evaluate the impact of welding temperature and endothermic time on joint performance, thereby optimizing the welding process and improving the quality and reliability of the joint. For electrofusion joints, this invention designs orthogonal experiments around welding voltage and welding time while keeping the cooling time constant. This design not only considers key parameters in the electrofusion welding process but also evaluates the joint performance by simulating actual welding conditions. This method not only improves the accuracy of prediction but also provides valuable reference and guidance for electrofusion welding processes in actual production, demonstrating significant practicality.
[0018] This invention also discloses a method for determining the safe operating pressure of welded joints in polyethylene pipes. By comprehensively considering the relationship between the actual and predicted performance of the welded joint, the safe operating pressure of the pipeline can be accurately determined. This method not only considers the design pressure as a fundamental factor but also introduces a safety factor as an important adjustment factor, thereby ensuring the comprehensiveness and accuracy of the safe pressure determination. In calculating the safety factor, this invention uses the ratio of the predicted mechanical properties of the welded joint to the mechanical properties of the normal welded joint. This calculation method fully considers the performance changes of the welded joint under different process conditions, as well as the impact of defects such as cold welding and over-welding on the joint performance. By comparing the predicted performance with the actual performance, the safety factor can be determined more scientifically and rationally, thereby ensuring the accuracy and reliability of the safe pressure. Attached Figure Description
[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a flowchart of a method for predicting the performance of welded joints in polyethylene pipes according to the present invention; Figure 2 This is a model diagram of the tensile strength and welding temperature of the welded joint in this invention. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0024] The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 1 This invention discloses a method for predicting the performance of welded joints in polyethylene pipes, characterized by comprising: Step 1: Collect data on the polyethylene pipe and determine the normal process parameters for welding the polyethylene pipe based on the data; determine the normal process parameters for welding the polyethylene pipe according to Appendix A of TSG D2002 "Technical Rules for Welding Polyethylene Pipes for Gas".
[0025] The data for the polyethylene pipe includes the pipe's material, diameter, wall thickness, raw materials, and joint type.
[0026] Step 2: Design orthogonal experiments for cold welding and over-welded joints based on the normal welding process parameters, and prepare cold welding joints, normal welding joints and over-welded joints based on the orthogonal experiments; The orthogonal tests include orthogonal tests for hot-melt joints and orthogonal tests for electrofusion joints. For hot-melt joints, while ensuring that the edge rolling pressure, edge rolling height, heat absorption pressure, cooling pressure, and cooling time remain constant, orthogonal tests are designed around the welding temperature and heat absorption time. Based on normal process parameters, cold welding and over-welded joint tests are designed by increasing or decreasing the welding temperature and heat absorption time at equal intervals.
[0027] For electrofusion joints, while ensuring that the cooling time remains constant, orthogonal experiments are designed around the welding voltage and welding time. Cold welding and over-welded joint tests are designed by increasing or decreasing the welding voltage and welding time at equal intervals based on normal process parameters.
[0028] By introducing orthogonal experiments for thermofusion and electrofusion joints, a comprehensive evaluation of the performance of welded joints in polyethylene pipes was achieved. This feature ensures that key parameters in the welding process of both thermofusion and electrofusion joints can be fully examined and optimized, thereby improving the accuracy and applicability of the prediction method. In the orthogonal experiment for thermofusion joints, this invention focuses on adjusting the welding temperature and endothermic time while keeping other parameters constant. Cold welding and over-welded joint tests are designed by increasing or decreasing these parameters at equal intervals. This precise control method allows us to more accurately evaluate the impact of welding temperature and endothermic time on joint performance, thereby optimizing the welding process and improving the quality and reliability of the joint. For electrofusion joints, this invention designs orthogonal experiments around welding voltage and welding time while keeping the cooling time constant. This design not only considers key parameters in the electrofusion welding process but also evaluates the joint performance by simulating actual welding conditions. This method not only improves the accuracy of predictions but also provides valuable reference and guidance for electrofusion welding processes in actual production, demonstrating significant practicality.
[0029] Step 3: Conduct performance tests on the cold-welded joints, normal welded joints, and over-welded joints to obtain performance test data; For the hot-melt joints, specimens were prepared in accordance with GB / T 19810 "Determination of tensile strength and failure mode of hot-melt butt joints of polyethylene (PE) pipes and fittings" and tensile tests were carried out.
[0030] For electrofusion joints, specimens were prepared in accordance with GB / T 19808 "Plastic pipes and fittings - tensile peel test of polyethylene electrofusion assemblies with a nominal outer diameter greater than or equal to 90 mm" and tensile peel tests were carried out.
[0031] Step four: Analyze and fit the performance test data to establish a joint performance model; Step 5: Input the actual welding process parameters of the polyethylene pipe into the joint performance model to obtain the predicted mechanical properties of the welded joint, thus completing the performance prediction of the polyethylene pipe welded joint.
[0032] Tensile or tensile peel test data of welded joints with normal process, cold welding, and over-welding defects were analyzed, and models of welded joint performance and process parameters under different process conditions were established.
[0033] This invention discloses a method for predicting the performance and determining the safe pressure of welded joints in polyethylene pipelines. The proposed method for predicting the performance of welded joints in polyethylene pipelines involves accurately collecting data from the polyethylene pipeline and determining normal welding process parameters based on this data, ensuring the accuracy and reliability of the foundational data for subsequent experiments and model establishment. This significantly improves the accuracy of joint performance prediction and provides strong support for the safe operation of polyethylene pipelines. The method not only considers normal welded joints but also designs orthogonal experiments for cold-welded and over-welded joints, and prepares corresponding welded joints for performance testing. This comprehensively reflects the impact of different welding defects on joint performance, making the prediction results more comprehensive and accurate. Through analysis and fitting of performance test data, this invention establishes a joint performance model. This model reflects the complex relationship between welding process parameters and joint performance, providing a scientific basis for optimizing actual welding process parameters. Inputting the actual welding process parameters of the polyethylene pipeline into the joint performance model yields the predicted mechanical properties of the welded joint. This enables real-time prediction and management of joint performance, helping to promptly detect and address potential welding defects, ensuring the safe operation of polyethylene pipelines. By using the pipeline welded joint performance prediction method and process provided in this invention, the performance of in-service polyethylene pipeline joints with cold-welded and over-welded defects can be effectively predicted. This helps to promptly detect and address situations where joint performance deteriorates or safety hazards exist, thereby preventing accidents and improving the operational safety of polyethylene pipelines. By using the pipeline welded joint performance prediction method and process provided in this invention, the performance of in-service polyethylene pipeline joints with defects such as cold welding and over-welding can be effectively predicted, achieving safe operation management of polyethylene pipeline welded joints.
[0034] This invention also discloses a method for determining the safe pressure of a polyethylene pipe welded joint based on the above method, specifically as follows: Safe pressure = Design pressure × Safety factor. The safety factor = Predicted mechanical properties of the welded joint / Normal mechanical properties of the welded joint.
[0035] This invention also discloses a method for determining the safe operating pressure of welded joints in polyethylene pipes. By comprehensively considering the relationship between the actual and predicted performance of the welded joint, the safe operating pressure of the pipeline can be accurately determined. This method not only considers the design pressure as a fundamental factor but also introduces a safety factor as an important adjustment factor, thereby ensuring the comprehensiveness and accuracy of the safe pressure determination. In calculating the safety factor, this invention uses the ratio of the predicted mechanical properties of the welded joint to the mechanical properties of the normal welded joint. This calculation method fully considers the performance changes of the welded joint under different process conditions, as well as the impact of defects such as cold welding and over-welding on the joint performance. By comparing the predicted performance with the actual performance, the safety factor can be determined more scientifically and rationally, thereby ensuring the accuracy and reliability of the safe pressure.
[0036] Example 1 A polyethylene pipe has an outer diameter of 110mm, is made of PE100 steel, has a wall thickness of 10mm, and a design pressure of 0.8MPa. The application of this invention for this pipeline is as follows: Step 1: Collection of Basic Information on Polyethylene Pipelines Collect basic information such as the material, diameter, and wall thickness of the polyethylene pipe.
[0037]
[0038] Step Two: Determining Normal Process Parameters for Polyethylene Pipe Welding The normal process parameters for welding polyethylene pipes are determined according to Appendix A of TSG D2002 "Technical Rules for Welding Polyethylene Pipelines for Gas".
[0039] Given that the SDR is 11, the normal process parameters for hot melt welding are as follows: Welding temperature 225℃; The rolled edge height is 1.5mm; Heat absorption time: 100s; Cooling time: 14 minutes.
[0040] Step 3: Experimental Design of Welded Joints Based on the normal process parameters for polyethylene pipe welding determined in step 2, for hot melt joints, while ensuring that parameters such as edge height, heat absorption pressure, cooling pressure, and cooling time remain unchanged, orthogonal experiments are designed around welding temperature and heat absorption time. Based on the normal process parameters, welding temperature and heat absorption time are increased or decreased at equal intervals to design cold welding and over-welded joint tests respectively.
[0041] When the heat absorption time remains constant, the welding temperature design is as follows:
[0042] Step 4: Preparation of Welded Joints Cold welded, normal welded, and over-welded hot melt welded joints were prepared respectively.
[0043] Step 5: Performance Test of Welded Joint The hot-melt joint specimens were prepared according to GB / T 19810 "Determination of Tensile Strength and Failure Mode of Hot-Melt Butt Joints of Polyethylene (PE) Pipes and Fittings", and tensile tests were conducted. The test results are as follows.
[0044] Step Six: Establish a performance model for the welded joint A joint performance model was established using Gaussian fitting. ,like Figure 2 As shown, where T represents the tensile strength of the hot melt joint, and T represents the welding temperature.
[0045] Step 7: Acquisition of Welding Parameters for Polyethylene Pipes Based on the automatic acquisition or welding record of the polyethylene pipe welding machine, the process parameters of a certain hot melt welding joint are collected, with a welding temperature of 150℃ and a heat absorption time of 100S.
[0046] Step 8: Performance Prediction of Welded Joints The parameters collected in step seven were substituted into the model in step six, and the predicted mechanical properties of the welded joint were 14.2 MPa.
[0047] Step 9: Recommended safe operating pressure Safety factor = Predicted mechanical properties of welded joint / Normal mechanical properties of welded joint = 14.2 / 23.2 = 0.61 Recommended safe operating pressure = design pressure * safety factor = 0.8 * 0.61 = 0.488 MPa.
[0048] The working process of this invention is as follows: 1) Collection of basic information on polyethylene pipelines 2) Determination of normal process parameters for polyethylene pipe welding 3) Test design for cold-welded and over-welded joints 4) Preparation of welded joints 5) Performance test of welded joints 6) Establishment of joint performance model 7) Collection of welding parameters for polyethylene pipes 8) Performance prediction of welded joints 9) Recommended safe operating pressure The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for predicting the performance of welded joints in polyethylene pipes, characterized in that, include: Collect data on polyethylene pipes and determine the normal process parameters for welding polyethylene pipes based on the data. Based on the normal welding process parameters, an orthogonal experiment was designed to test cold welded joints and over-welded joints. Based on the orthogonal experiment, cold welded joints, normal welded joints and over-welded joints were prepared. Performance tests were conducted on the cold-welded joints, normal-welded joints, and over-welded joints to obtain performance test data. The performance test data were analyzed and fitted to establish a joint performance model. The actual welding process parameters of the polyethylene pipe are input into the joint performance model to obtain the predicted mechanical properties of the welded joint, thus completing the performance prediction of the polyethylene pipe welded joint.
2. The method for predicting the performance of welded joints in polyethylene pipes according to claim 1, characterized in that, The data for the polyethylene pipe includes the pipe's material, diameter, wall thickness, raw materials, and joint type.
3. The method for predicting the performance of welded joints in polyethylene pipes according to claim 1, characterized in that, The orthogonal tests include orthogonal tests for thermofusion joints and orthogonal tests for electrofusion joints.
4. The method for predicting the performance of welded joints in polyethylene pipes according to claim 3, characterized in that, The orthogonal test for the hot melt joint specifically includes: For hot melt joints, while ensuring that the edge rolling pressure, edge rolling height, heat absorption pressure, cooling pressure and cooling time remain constant, orthogonal experiments are designed around the welding temperature and heat absorption time. Based on normal process parameters, welding temperature and heat absorption time are increased or decreased at equal intervals to design cold welding and over-welded joint tests respectively.
5. The method for predicting the performance of welded joints in polyethylene pipes according to claim 3, characterized in that, The orthogonal test for the electrofusion joint specifically includes: For electrofusion joints, while ensuring that the cooling time remains constant, orthogonal experiments are designed around the welding voltage and welding time. Cold welding and over-welded joint tests are designed by increasing or decreasing the welding voltage and welding time at equal intervals based on normal process parameters.
6. The method for predicting the performance of welded joints in polyethylene pipes according to claim 3, characterized in that, The performance tests on the cold-welded joints, normal-welded joints, and over-welded joints specifically include: The cold-welded joints, normal-welded joints, and over-welded joints all include hot-melt joints and electrofusion joints; tensile tests are performed on the hot-melt joints.
7. The method for predicting the performance of welded joints in polyethylene pipes according to claim 3, characterized in that, The cold-welded joints, normal welded joints, and over-welded joints all include hot-melt joints and electrofusion joints; tensile peel tests are performed on the electrofusion joints.
8. The method for predicting the performance of welded joints in polyethylene pipes according to claim 1, characterized in that, The specific steps for analyzing and fitting the performance test data to establish a joint performance model include: The performance test data were analyzed, and models of welded joint performance and process parameters under different process conditions were established.
9. A method for determining the safe pressure of a polyethylene pipe welded joint based on the method described in any one of claims 1-8, characterized in that, Specifically: Safe pressure = Design pressure × Safety factor.
10. The method for determining the safe pressure of a polyethylene pipe welded joint according to claim 9, characterized in that, The safety factor = predicted mechanical properties of the welded joint / normal mechanical properties of the welded joint.