An evaluation model and design method for nondestructive testing of polyethylene hot melt joints

Abstract

The present application relates to the technical field of town gas pipeline detection, in particular to a kind of polyethylene hot melt joint nondestructive testing evaluation model and design method.The design method includes: by evaluating the influence of different factors of polyethylene gas pipe on welding forming, using the advance and retreat method in combination optimization algorithm, the mechanical property evaluation of polyethylene pipeline non-fusion defect sample formed by different combination modes is carried out, the combination mode of optimal mechanical property test scheme is obtained, and the nondestructive testing evaluation model of polyethylene hot melt joint is obtained with optimal combination mode and hot melt process parameters as standard.The design method not only greatly improves the application effect of nondestructive testing method in the quality control of gas polyethylene hot melt joint, but also provides a new way to solve the problem of non-fusion defect production of current gas polyethylene pipe hot melt joint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of urban gas pipeline detection, in particular to a polyethylene hot melt joint nondestructive detection evaluation model and design method. BACKGROUND

[0002] Polyethylene (PE) pipelines have been widely used in gas transmission systems due to their excellent corrosion resistance, high toughness, and long service life. However, the quality control of polyethylene pipeline hot melt joints has always been a technical challenge in the industry. Although existing construction specifications, such as CJJ 63-2018 "Polyethylene Gas Pipeline Engineering Technical Standards", have made clear requirements for the acceptance of hot melt joints and the testing of pipeline engineering, including edge symmetry inspection, joint alignment inspection, partial joint edge cutting inspection, and pipeline purging, strength testing, and tightness testing, these methods mainly focus on the appearance of the joint and the overall performance of the pipeline, and cannot effectively probe the welding quality inside the hot melt joint.

[0003] The welding quality of polyethylene pipeline hot melt joints directly affects the safety of gas pipeline systems. In actual applications, due to improper welding process control, such as uneven cooling of the joint after welding, oil contamination into the fusion surface during welding, and other factors, un-melted defects may occur inside the joint. These defects may not be detected under existing acceptance standards, but once they expand during use, they will pose a serious threat to the safe operation of gas pipelines, leading to serious accidents such as gas leaks.

[0004] Nondestructive testing technology, as a non-destructive detection method, can effectively identify welding defects inside the joint and avoid safety risks caused by defect expansion. However, due to the significant differences in material and fusion methods between polyethylene pipelines and metal pipelines, traditional metal pipeline nondestructive testing methods cannot be directly applied to polyethylene hot melt joints. Therefore, it is necessary to develop suitable nondestructive testing methods and testing processes based on the structural characteristics, main defect types, and failure modes of polyethylene hot melt joints.

[0005] Currently, the main method for producing polyethylene pipeline un-melted defect samples relies on manual defect production techniques such as drilling and slotting. These methods not only fail to accurately simulate the un-melted defects produced during actual welding, but also lack standardization and systematization, making it difficult for nondestructive testing personnel to provide effective reference maps. This greatly limits the application of nondestructive testing technology in the quality control of polyethylene hot melt joints, making it difficult to detect and evaluate un-melted defects.

[0006] In view of the above problems, the present application provides a multi-factor unfused defect sample design method for non-destructive testing of polyethylene hot melt joints. The method aims to simulate unfused defects under different welding conditions, evaluate the influence of different factors on the unfused weld, and realize the standardized production method of unfused defects considering the combined influence of multiple factors. This innovation not only solves the problem of unfused defect sample production of gas polyethylene pipe hot melt joints, but also provides a reliable basis for the effective application of non-destructive testing technology, and meets the urgent needs of comprehensive testing and evaluation of gas polyethylene pipe hot melt joints. SUMMARY

[0007] The purpose of the present application is to provide a design method for non-destructive testing evaluation model of polyethylene hot melt joints, which greatly improves the application effect of non-destructive testing method in quality control of gas polyethylene hot melt joints, and provides a new idea for solving the problem of unfused defect production of current gas polyethylene pipe hot melt joints.

[0008] In the first aspect, the present application provides a design method for non-destructive testing evaluation model of polyethylene hot melt joints, comprising the following steps:

[0009] By evaluating the influence of different factors of polyethylene gas pipe on the welding formation, using the retreat method in the combination optimization algorithm, i.e. approaching the optimal solution by gradually adjusting the search interval, the mechanical properties of the polyethylene pipe unfused defect samples formed by different combination methods are evaluated, and the combination method of the optimal mechanical property test scheme is obtained. With the optimal combination method and the hot melt process parameters as the standard, the non-destructive testing evaluation model of polyethylene hot melt joints is obtained.

[0010] As a preferred technical solution of the present application, the following steps are included:

[0011] S1, according to the forming factors of polyethylene hot melt joint unfused defects, design combination schemes of different factors;

[0012] S2, according to the combination scheme of step S1, prepare polyethylene hot melt joint unfused defect samples with different combined factors;

[0013] S3, test the mechanical properties of the polyethylene hot melt joint unfused defect samples prepared in step S2, and obtain the main factors affecting the polyethylene hot melt joint unfused defects;

[0014] S4, combine the multiple main factors obtained in step S3 to prepare a multi-factor polyethylene hot melt joint unfused defect sample, and compare the mechanical properties of different multi-factor polyethylene hot melt joint unfused defect samples to obtain the combination method of the optimal mechanical property test scheme;

[0015] S5, the combination of the optimal mechanical performance test scheme and the hot melt process parameters as the standard, the nondestructive testing evaluation model of the polyethylene hot melt joint is obtained.

[0016] As the preferred technical solution, in step S1, the forming factors include end face unmilling, uneven cooling, end face inclusion and end face shape, feed amount, welding temperature and time, welding pressure and raw material quality.

[0017] As the preferred technical solution, in step S2, when the polyethylene hot melt joint non-fusion defect sample of different combination factors is made, the parameters of the hot melt welding machine remain unchanged.

[0018] As the preferred technical solution, in step S3, the mechanical property test includes tensile strength test and failure mode test.

[0019] As the preferred technical solution, in step 4, the parameters of the hot melt process are: the temperature of the heating plate is 200-240℃, and preferably 220℃, the heat absorption pressure is 0.1-0.3MPa, and preferably 0.2MPa, and the heat absorption time is the wall thickness of the welded pipe x 10s.

[0020] As the preferred technical solution, the uneven cooling includes different cooling rates.

[0021] As the preferred technical solution, the nondestructive testing method of the polyethylene hot melt joint includes ultrasonic testing method and microwave scanning method.

[0022] As the preferred technical solution, the nominal outer diameter of the polyethylene gas pipe fitting is ≥63mm, and the nominal wall thickness is 6-30mm.

[0023] In the second aspect, the nondestructive testing evaluation model of the polyethylene hot melt joint obtained by the above design method also belongs to the protection scope of the present application.

[0024] The design method of the nondestructive testing evaluation model of the polyethylene hot melt joint has at least the following

[0025] Advantages:

[0026] In the design method of the polyethylene hot melt joint nondestructive testing evaluation model, firstly, the main causes of the polyethylene hot melt joint unmelted defects are considered, such as end face unmilling, uneven cooling, oil mixing on the fusion surface and the shape of the prefabricated pipe end and the like. Through the identification of these factors, a list containing different factors and their possible combinations is designed to systematically explore and identify which factors have a significant impact on the formation of unmelted defects; then, the polyethylene hot melt butt welding machine is used to make polyethylene hot melt joint unmelted defect samples containing different combined factors. Further, the tensile strength and failure mode of these samples are determined by tensile test to quantify the influence of different factors on the mechanical properties of the unmelted defects, so as to determine which is the main influencing factor. Finally, after determining the main influencing factors, different combinations of factors are made to produce multi-factor polyethylene unmelted defect samples, and by comparing the mechanical property curves of different schemes, the optimal tensile test scheme combination method is found, that is, the polyethylene hot melt joint nondestructive testing evaluation model is obtained.

[0027] The polyethylene hot melt joint unmelted defect factor evaluation model and sample design method provided by the present application provides a scientific and reliable means to determine the defect tolerance of the hot melt joint, and accordingly forms a strict nondestructive testing acceptance standard. Not only greatly improves the application effect of the nondestructive testing method in the quality control of the gas polyethylene hot melt joint, but also provides a new way of thinking for solving the problem of the current gas polyethylene pipe hot melt joint unmelted defect production.

[0028] More worth mentioning is that the design method of the polyethylene hot melt joint nondestructive testing evaluation model is simple to operate, easy to implement, and low in economic cost, and has high reliability. This makes it not only meet the comprehensive detection and evaluation needs of the gas polyethylene pipeline hot melt joint, but also plays a crucial role in ensuring the safe operation of the gas pipeline and preventing leakage failure accidents. Effectively avoids potential personnel casualties and property losses caused by the lack of nondestructive testing quality control means, and brings significant economic and social benefits to the society.

[0029] In addition, the design method has strong universality, which can be widely used in the welding process of polyethylene hot melt joints of urban gas, oilfield gathering and transportation pipe network and the like, and is expected to be expanded to more fields in the future, providing strong technical support for the quality control of hot melt joints of various types of plastic pipelines.

[0030] In summary, the polyethylene hot melt joint unmelted defect factor evaluation model and sample design method provided by the present application not only solves the current technical problems, but also points out the direction for future pipeline welding quality control work, and has important theoretical and practical value. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative labor based on these drawings also belong to the protection scope of the present application.

[0032] Figure 1 The original polyethylene gas pipe end cross section of the present application is shown in the figure.

[0033] Figure 2 The improved polyethylene gas pipe end cross section of the present application is shown in the figure.

[0034] Figure 3 The design method flow chart of the non-destructive testing evaluation model of the polyethylene hot melt joint of the present application is shown in the figure.

[0035] Figure 4 The tensile strength and failure mode of the DN160x14.6mm polyethylene hot melt joint un-melted defect sample made according to the end face not milled flat of the present application are determined, and it is identified as ductile failure.

[0036] Figure 5 The tensile strength and failure mode of the DN160x14.6mm polyethylene hot melt joint un-melted defect sample made according to the uneven cooling of the present application are determined, and it is identified as ductile failure.

[0037] Figure 6 The tensile strength and failure mode of the DN160x14.6mm polyethylene hot melt joint un-melted defect sample made according to the oil mixing of the fusion surface of the present application are determined, and it is identified as brittle failure. Specific embodiments

[0038] The technical solutions of the present application will be described below in conjunction with the embodiments. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor also belong to the protection scope of the present application.

[0039] In the description of the present application, it is to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0040] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, "a plurality of" means two or more, unless otherwise specifically limited. In addition, the terms "mounting", "connecting", "connecting" should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0041] Embodiment 1

[0042] As Figure 3 shown, the present embodiment provides a design method of a polyethylene hot melt joint nondestructive testing evaluation model, comprising the following steps:

[0043] By evaluating the influence of different factors of polyethylene gas pipe fittings on the welding forming, using the advance and retreat method in the combined optimal algorithm, that is, by gradually adjusting the search interval to approach the optimal solution, the mechanical property evaluation of the polyethylene pipe non-fusion defect sample formed by different combination methods is carried out, and the optimal mechanical property test scheme combination method is obtained. With the optimal combination method and the hot melt process parameters as the standard, the polyethylene hot melt joint nondestructive testing evaluation model is obtained.

[0044] In the design method of the polyethylene hot melt joint nondestructive testing evaluation model, firstly, the main causes of the polyethylene hot melt joint unmelted defects are considered, such as end face unmilling, uneven cooling, oil mixing on the fusion surface, and the shape of the prefabricated pipe end, etc. Through the identification of these factors, a list containing different factors and their possible combinations is designed to systematically explore and identify which factors have a significant impact on the formation of unmelted defects; then, using a polyethylene hot melt butt welding machine, polyethylene hot melt joint unmelted defect samples containing different combined factors are made. Further, the tensile strength and failure mode of these samples are determined by tensile test to quantify the influence of different factors on the mechanical properties of the unmelted defects, so as to determine which are the main influencing factors. Finally, after determining the main influencing factors, different combinations of factors are made to produce multi-factor polyethylene unmelted defect samples, and by comparing the mechanical property curves of different schemes, the optimal tensile test scheme combination method is found, that is, the polyethylene hot melt joint nondestructive testing evaluation model is obtained. The evaluation method not only greatly improves the application effect of the nondestructive testing method in the quality control of the gas polyethylene hot melt joint, but also provides a new way of thinking for solving the current problem of making unmelted defects of the gas polyethylene pipe hot melt joint.

[0045] Further preferably, the method comprises the following steps:

[0046] S1. Designing a combination scheme of different factors according to the formation factors of the polyethylene hot melt joint unmelted defects;

[0047] The formation factors include end face unmilling, uneven cooling, end face inclusion, and end face shape (such as shown in FIG. 1), feed amount, welding temperature and time, welding pressure, and raw material quality. The uneven cooling here includes different cooling rates. Table 1 is a list of different factor combinations. Figures 1-2

[0048] Table 1 Different factor combinations

[0049]

[0050]

[0051] S2. According to the combination scheme of step S1, polyethylene hot melt joint unmelted defect samples with different combined factors are made under the premise that the parameters of the hot melt welding machine remain unchanged, wherein the parameters of the hot melt welding machine process are: the heating plate temperature is 220℃, the heat absorption pressure is 0.2MPa, and the heat absorption time is the wall thickness of the welded pipe x 10s;

[0052] S3. The polyethylene hot melt joint unmelted defect samples prepared in step S2 are tested for tensile strength and failure mode to obtain the main factors affecting the polyethylene hot melt joint unmelted defects.​

[0053] S4, combine the plurality of main factors obtained in step S3 to obtain a multi-factor polyethylene hot melt joint non-fusion defect sample, and obtain the optimal mechanical property test scheme combination mode by comparing the mechanical properties of different multi-factor polyethylene hot melt joint non-fusion defect samples;

[0054] S5, taking the optimal mechanical property test scheme combination mode and the hot melt process parameters as standards, obtain a polyethylene hot melt joint nondestructive testing evaluation model.

[0055] The method of the present application is suitable for polyethylene gas pipe fittings with a nominal outer diameter of ≥63 mm and a nominal wall thickness of 6-30 mm.

[0056] Finally, the method of polyethylene hot melt joint nondestructive testing includes ultrasonic testing and microwave scanning, and the present application does not make strict limitations.

[0057] Example 2

[0058] A gas company needs to make a DN160x14.6mm polyethylene hot melt joint non-fusion defect sample to verify the effectiveness of the nondestructive testing method and the defect detection rate, and the non-fusion defect sample for polyethylene hot melt joint nondestructive testing is made by using the design method of the present application.

[0059] Specifically, the following steps are included:

[0060] Step 1: According to the formation factors of polyethylene hot melt joint non-fusion defects, design the combination scheme of different factors according to Table 1;

[0061] Step 2: Select DN160x14.6mm PE100 high-density polyethylene pipe, and cut several pipe sections from the pipe, according to the formation conditions under the influence of each factor, and use a semi-automatic PE hot melt butt welding machine to make polyethylene hot melt joint non-fusion defect samples of different combination factors, wherein the parameters of the hot melt welding machine are: the temperature of the heating plate is 220℃, the heat absorption pressure is 0.2MPa, and the heat absorption time is 146s;

[0062] Step 3: The tensile strength and failure mode of each non-fusion defect sample are determined by tensile test, as shown in Table 2: Figures 4-6

[0063] Step 4: Combine the plurality of main factors obtained in step 3 to obtain a multi-factor polyethylene hot melt joint non-fusion defect sample, and obtain the optimal mechanical property test scheme combination mode by comparing the mechanical properties of different multi-factor polyethylene hot melt joint non-fusion defect samples, which is end face inclusion + end face non-milling flatness.

[0064] ​Step 5: The polyethylene hot melt joint nondestructive detection evaluation model is obtained by taking the end face inclusion + end face unmilling flat combination mode and the hot melting process parameters as the standard.

[0065] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not limited to them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or replace some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for designing a polyethylene hot-plate joint non-destructive evaluation model, characterized in that, The method comprises the following steps: S1, evaluating the influence of different factors on the welding forming of the polyethylene gas pipe, and designing a combination scheme of different factors according to the formation factors of the non-fusion defect of the polyethylene hot melt joint; S2, preparing the polyethylene hot melt joint non-fusion defect sample of different combined factors according to the combination scheme of step S1; S3, using the advance and retreat method in the combination optimization algorithm to approach the optimal solution by gradually adjusting the search interval, and testing the mechanical properties of the polyethylene hot melt joint non-fusion defect sample prepared in step S2 to obtain the main factors affecting the polyethylene hot melt joint non-fusion defect; S4, combining the multiple main factors obtained in step S3 to prepare the multi-factor polyethylene hot melt joint non-fusion defect sample, and obtaining the combination mode of the optimal mechanical property test scheme by comparing the mechanical properties of different multi-factor polyethylene hot melt joint non-fusion defect samples; S5, taking the combination mode of the optimal mechanical property test scheme and the hot melt process parameters as the standard to obtain the non-destructive testing evaluation model of the polyethylene hot melt joint; In step S1, the formation factors include end face unmilling, uneven cooling, end face inclusion and end face shape, feed amount, welding temperature and time, welding pressure and raw material quality.

2. The design method of claim 1, wherein In step S2, when preparing the polyethylene hot melt joint non-fusion defect sample of different combined factors, the parameters of the hot melt welding machine remain unchanged.

3. The method of claim 1, wherein, In step S3, the mechanical property test includes tensile strength test and failure mode test.

4. The method of claim 1, wherein, In step 4, the parameters of the hot melt process are: the heating plate temperature is 200-240℃, the heat absorption pressure is 0.1-0.3MPa, and the heat absorption time is the wall thickness of the welded pipe x 10s.

5. The method of claim 1, wherein, The uneven cooling includes different cooling rates.

6. The method of claim 1, wherein The non-destructive testing method of the polyethylene hot melt joint includes ultrasonic testing method and microwave scanning method.

7. The method of claim 1, wherein The nominal outside diameter of the polyethylene gas pipe is ≥63mm, and the nominal wall thickness is 6-30mm.

8. A polyethylene fusion joint non-destructive testing assessment model, characterized by, The design method is obtained according to any one of claims 1-7.

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