Electric melting pipe fitting and preparation and monitoring method thereof

Abstract

The invention relates to the technical field of nonmetal pipelines and pipe fittings, and discloses an electric melting pipe fitting and a preparation and monitoring method thereof, the electric melting pipe fitting comprises a base layer, a first inner layer, a first resistance wire, a second resistance wire, a first binding post, a second binding post, a third binding post and a fourth binding post; the base layer is formed by uniformly distributing a conductive material in a polymer matrix; the first inner layer is attached to the side wall of the base layer and is formed by an insulating material; the first resistance wire and the second resistance wire are annularly and alternately wound in the axial direction of the first inner layer and embedded in the inner wall of the first inner layer, the first resistance wire is provided with a first end and a second end, and the second resistance wire is provided with a third end and a fourth end; the first binding post penetrates through the base layer and is connected with the first end, and the second binding post penetrates through the base layer and is connected with the second end; the third binding post penetrates through the base layer and is connected with the third end, and the fourth binding post penetrates through the base layer and is connected with the fourth end. According to the electric smelting pipe fitting, the reliability is improved.

Description

Technical Field

[0001] This application relates to the technical field of non-metallic pipes and pipe fittings, and particularly to an electrofusion pipe fitting and its preparation and monitoring methods. Background Art

[0002] Compared with traditional metal pipes, non-metallic pipes such as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) are recognized as "green" pipes due to their excellent corrosion resistance, ease of welding, long service life, good toughness, and economic and environmental protection characteristics. They have been widely used in key national projects such as gas, hydrogen, hydrogen-blended natural gas, oil and gas, and important water conveyance in nuclear power plants. In recent years, both the production and usage of non-metallic pipes have shown a rapid growth trend, gradually replacing traditional metal pipes in many fields and achieving the transformation of "replacing steel with plastics".

[0003] For thermoplastic non-metallic pipes such as polyethylene (PE), electrofusion welding methods (such as electrofusion joints, electrofusion elbows, etc.) are mainly used to connect non-metallic pipes. With the progress of manufacturing technology, the research and application of steel-plastic composite pipes, aluminum-plastic composite pipes, and fiber-wound composite pipes have significantly improved the structural strength and load-bearing capacity of non-metallic pipes. However, the reinforcement methods of electrofusion joints are limited, which leads to the failure of electrofusion joints in non-metallic systems from time to time. Therefore, how to improve the reliability of electrofusion joints is a technical problem that urgently needs to be solved today. Summary of the Invention

[0004] This application provides an electrofusion pipe fitting and its preparation and monitoring methods, which improve the reliability of the electrofusion pipe fitting.

[0005] To achieve the above object, the main technical solutions adopted in this application include:

[0006] In a first aspect, an embodiment of this application provides an electrofusion pipe fitting, which includes a base layer, a first inner layer, a first resistance wire, a second resistance wire, a first terminal, a second terminal, a third terminal, and a fourth terminal; the base layer has a hollow structure and is formed by uniformly distributing a conductive material in a polymer matrix; the first inner layer is attached to the inner wall of the base layer and is formed of an insulating material; the first resistance wire and the second resistance wire are alternately wound axially and circumferentially along the inner wall of the first inner layer and are embedded in the inner wall of the first inner layer. The first resistance wire and the second resistance wire are not connected to each other. Along the length direction of the first resistance wire, the first resistance wire has a first end and a second end. Along the length direction of the second resistance wire, the second resistance wire has a third end and a fourth end; the first terminal passes through the base layer and is connected to the first end, the second terminal passes through the base layer and is connected to the second end; the third terminal passes through the base layer and is connected to the third end, and the fourth terminal passes through the base layer and is connected to the fourth end.

[0007] The electrofusion fitting proposed in the embodiment of the present application has the effect of suppressing crack initiation in the stress concentration area on the inner wall surface of the electrofusion fitting, so that the base layer will not fail prematurely due to crack initiation, which helps to improve the strength of the base layer and enhances the overall strength of the electrofusion fitting. Along the length direction of the first resistance wire, the first resistance wire has a first end and a second end. Along the length direction of the second resistance wire, the second resistance wire has a third end and a fourth end. That is to say, the first resistance wire and the second resistance wire each have two extended ends and are respectively connected to the corresponding terminal posts through the base layer. Such a setting can not only enhance the overall strength of the electrofusion fitting but also endow the electrofusion fitting with a self-sensing function.

[0008] Optionally, along the axial direction of the base layer, the first terminal post and the third terminal post are located at the same end of the base layer in the same direction, and the second terminal post and the fourth terminal post are located at the other end of the base layer in the same direction.

[0009] In the above solution, the first terminal post and the third terminal post are located at the same end of the base layer in the same direction. That is to say, the first end of the first resistance wire and the third end of the second resistance wire are located at the same end of the base layer in the same direction, and the second end of the first resistance wire and the fourth end of the second resistance wire are located at the same end of the base layer in the same direction. Such a setting enables the positive and negative electrodes of the power supply to be connected to the first resistance wire or the second resistance wire through the terminal posts respectively to achieve heating and welding. When the positive and negative electrodes of the power supply are connected to the first resistance wire and the second resistance wire through the terminal posts respectively, the electrical parameters of the electrofusion base material between the corresponding terminal posts of the first resistance wire and the second resistance wire under the action of load can be measured.

[0010] Optionally, the electrofusion fitting further includes a first outer layer, which is attached to the outer wall of the base layer. Both the first terminal post and the second terminal post pass through and extend out of the first outer layer, and both the third terminal post and the fourth terminal post pass through and extend out of the first outer layer.

[0011] In the above solution, the first outer layer serves as an external protective layer and can bear the load acting on the fitting due to internal pressure. When the fitting bears internal pressure, the load first acts on the first inner layer and then is transmitted to the first outer layer through the base layer. The first outer layer and the first inner layer jointly bear the load. At the same time, the first outer layer can also prevent the base layer and the internal resistance wires from being eroded by moisture, chemical corrosion or external pollution, prolonging the service life. The outer layer can also provide additional impact resistance and abrasion resistance for the base layer, especially in buried pipelines or complex working conditions, reducing the risk of damage caused by external forces during construction or operation, and further enhancing the overall strength of the electrofusion fitting.

[0012] Optionally, the first outer layer is formed by uniformly distributing fibers in a polymer matrix, and the structural strength of the first outer layer is greater than that of the first inner layer.

[0013] In the above solution, the first outer layer serves as the outermost protective layer and is formed from a fiber-reinforced polymer material, thereby obtaining a higher strength than the first inner layer, enabling it to better withstand the load exerted by the internal pressure on the pipe fitting, further enhancing the reliability of the entire pipe fitting. Meanwhile, the first outer layer can also bear external mechanical stresses, such as impacts during installation, soil pressure (if it is an underground pipeline), or collisions during transportation. In addition, the first inner layer has a higher plasticity than the first outer layer, reducing the probability of cracks caused by stress concentration on the inner wall surface.

[0014] Optionally, the polymer matrix of the first outer layer is filled with a conductive material.

[0015] In the above solution, the first outer layer and the base layer adopt the same polymer matrix + conductive material formula (such as carbon fiber, metal powder), enabling the first outer layer and the base layer to be integrated, combining the functions of structural enhancement and electrical sensing, and reducing the process complexity. When the first outer layer uses a material cheaper than that used for the base layer, the cost can be reduced and the economy can be improved.

[0016] Optionally, a first friction part is provided between the base layer and the first inner layer to increase the friction force between the base layer and the first inner layer, and a second friction part is provided between the base layer and the first outer layer to increase the friction force between the base layer and the first outer layer.

[0017] In the above solution, the friction part helps with interlayer bonding, reducing the probability of delamination or sliding, thereby enhancing the structural stability, increasing the interlayer friction force and interface strength, and significantly improving the bonding strength between the base layer and the first inner layer or the first outer layer.

[0018] Optionally, the first friction part is configured as a first groove or a first protrusion formed between the inner side surface of the base layer and the outer side surface of the first inner layer, and the second friction part is configured as a second groove or a second protrusion formed between the outer side surface of the base layer and the inner side surface of the first outer layer.

[0019] In the above solution, the first friction part and the second friction part help with interlayer bonding, reducing the occurrence probability of delamination or sliding, thereby enhancing the structural stability, increasing the interlayer friction force and interface strength. Compared with the traditional planar friction interface, the contact area is increased, the interlayer biting force is increased, the interlayer shear strength is improved, and the interlayer peeling risk is reduced.

[0020] Optionally, the electrofusion pipe fitting includes a first conductive spiral and a second conductive spiral. The first conductive spiral is connected to the first resistance wire and is at least partially disposed in the base layer, and the second conductive spiral is connected to the second resistance wire and is at least partially disposed in the base layer. Along the axial direction of the base layer, the first conductive spiral and the second conductive spiral are spaced apart.

[0021] In the above solution, the first conductive helix and the second conductive helix are arranged at intervals, making it easier for the electrical measurement device to obtain electrical parameters at different positions, thereby realizing the monitoring of different parts of the electrofusion fitting.

[0022] Optionally, the first resistance wire includes a first part and a second part. Both the first part and the second part are wound axially and circumferentially in an alternating manner along the inner wall of the first inner layer and embedded in the inner wall of the first inner layer. One end of the first part far from the second part is connected to the first terminal, and one end of the second part far from the first part is connected to the second terminal. The first conductive helix connects the ends of the first part and the second part close to each other;

[0023] The second resistance wire includes a third part and a fourth part. Both the third part and the fourth part are wound axially and circumferentially in an alternating manner along the inner wall of the first inner layer and involved in the inner wall of the first inner layer. One end of the third part far from the fourth part is connected to the third terminal, and one end of the fourth part far from the third part is connected to the fourth terminal. The second conductive helix connects the ends of the third part and the fourth part close to each other.

[0024] In the above solution, the first conductive helix is located between the first part and the second part, and the second conductive helix is located between the third part and the fourth part, realizing the monitoring of specific positions of the electrofusion fitting, making it easier for the electrical measurement device to obtain electrical parameters at different positions, thereby realizing the monitoring of specific parts of the electrofusion fitting.

[0025] In a second aspect, an embodiment of the present application provides a method for manufacturing an electrofusion fitting as described in the above embodiment, including the following steps:

[0026] An insulating material is used as the polymer material for injection molding to obtain the first inner layer;

[0027] A polymer matrix filled with a conductive material is injection molded on the outer wall of the first inner layer to form a base layer;

[0028] A polymer matrix filled with a fiber material is injection molded on the outer wall of the base layer to form a first outer layer;

[0029] The first resistance wire and the second resistance wire are buried on the inner wall of the first inner layer. The first resistance wire and the second resistance wire are not connected to each other. The two ends of the first resistance wire in the length direction are respectively connected to the corresponding terminals passing through the base layer and the first outer layer, and the two ends of the second resistance wire in the length direction are respectively connected to the corresponding terminals passing through the base layer and the first outer layer.

[0030] The manufacturing method proposed in the embodiment of the present application. The injection molding process can realize the integrated manufacturing of complex structures, especially suitable for manufacturing special-shaped pipe fittings such as those with socket and spigot joints and variable diameter structures. The conductive material filling technology can flexibly adjust the conductivity to meet different voltage levels and power requirements, and improve the reliability of the electrofusion fitting.

[0031] In a third aspect, an embodiment of the present application provides a method for manufacturing an electrofusion fitting as described in the above embodiment, including the following steps:

[0032] Plasticize a polymer material of an insulating material as the first inner layer, a polymer material of a polymer matrix filled with a conductive material as the base layer, and a polymer material of a polymer matrix filled with a fiber material as the first outer layer;

[0033] Introduce the polymer material of the first inner layer, the polymer material of the base layer, and the polymer material of the first outer layer into a composite joint for extrusion molding to obtain a cylindrical body with a multi-layer structure;

[0034] Cut the cylindrical body according to the required size to obtain an electrofusion fitting.

[0035] The manufacturing method proposed in the embodiment of the present application prepares a multi-layer electrofusion fitting through a multi-layer co-extrusion process. On the one hand, it improves the bonding strength of the multi-layer structure, reduces the risk of interface delamination, and improves the overall structural strength. On the other hand, it can also improve the production efficiency of the multi-layer electrofusion fitting.

[0036] In a fourth aspect, an embodiment of the present application provides a monitoring method for an electrofusion fitting, which is applied to the electrofusion fitting described in the above embodiment. The monitoring method includes:

[0037] Electrically connect a first terminal and a fourth terminal spaced apart on the axis of the base layer to the positive and negative electrodes of a measuring device respectively. When the electrofusion fitting is subjected to a load, the measuring device acquires the curve of the change in the electrical parameters of the electrofusion fitting.

[0038] The monitoring method proposed in the embodiment of the present application does not require additional embedding of strain gauges or fiber optic sensors, and directly uses the conductive matrix of the base layer as a sensing element, reducing the manufacturing cost and structural complexity. Description of the Drawings

[0039] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0040] Figure 1 It is a schematic structural diagram of an electrofusion fitting according to some embodiments of the present application;

[0041] Figure 2 It is a schematic structural diagram of an electrofusion fitting and an electrical measurement device according to some embodiments of the present application;

[0042] Figure 3Schematic diagram of the structure of electrofusion fittings according to other embodiments of the present application;

[0043] Figure 4 Schematic diagram of the structure of electrofusion fittings according to other embodiments of the present application;

[0044] Figure 5 Schematic diagram of the structure of electrofusion fittings according to other embodiments of the present application;

[0045] Figure 6 is Figure 5 Partial enlarged schematic diagram of part A in

[0046]

Explanation of reference numerals

[0047] 1000: electrofusion fitting;

[0048] 100: first inner layer;

[0049] 200: base layer;

[0050] 300: first outer layer;

[0051] 400: first resistance wire; 410: first end; 420: second end; 430: first terminal; 440: second terminal; 450: first part; 460: second part;

[0052] 500: second resistance wire; 510: third end; 520: fourth end; 530: third terminal; 540: fourth terminal; 550: third part; 560: fourth part;

[0053] 600: first conductive spiral; 700: second conductive spiral;

[0054] 800: electrical measurement device. Detailed implementation manners

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0056] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used in the description of this application in the specification are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the description and claims of this application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the description and claims of this application or the above drawings are used to distinguish different objects and not to describe a specific order or primary-secondary relationship.

[0057] Reference to "embodiments" in this application means that specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase does not necessarily refer to the same embodiment when it appears in various places in the specification, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0058] In the description of this application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected to", and "attached" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0059] The term "and / or" in this application is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally represents an "or" relationship between the associated objects before and after.

[0060] The "plurality" mentioned in this application refers to two or more (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to two or more pieces (including two pieces).

[0061] In view of this, in order to improve the reliability of the electrofusion fitting, an electrofusion fitting 1000 is proposed in an embodiment of this application. Please refer to Figure 1 , which includes a base layer 200, a first inner layer 100, a first resistance wire 400, a second resistance wire 500, a first terminal 430, a second terminal 440, a third terminal 530, and a fourth terminal 540.

[0062] The base layer 200 has a hollow structure and is formed by uniformly distributing a conductive material in a polymer matrix. It can be understood that the base layer 200 is injection-molded from a polymer filled with a conductive material. That is to say, the conductive material is uniformly distributed in the polymer matrix to form a conductive network. Among them, the conductive material is carbon fiber, and the polymer matrix is a thermoplastic material. The specific filling amount of the conductive material can be comprehensively determined according to the mechanical strengthening effect of the conductive material and the material monitoring sensitivity. This application does not limit this.

[0063] It should be understood that the electrofusion fitting 1000 can be a straight-through fitting or any one of 45°, 60°, and 90° elbow fittings, which can be determined according to the specific usage situation.

[0064] As an example, the conductive filler includes at least one or more of conductive fillers such as carbon nanotubes, carbon nanofibers, carbon fibers, metal fibers, metal-coated glass fibers, graphene, and carbon black; the polymer includes at least one or more of polymers such as polyethylene, polypropylene, and polyvinyl chloride. This application does not limit this.

[0065] On the one hand, the conductive filler can improve the structural strength of the base layer 200 for strengthening the fitting structure, and on the other hand, the conductive filler can improve the conductivity of the base layer 200 for electrical monitoring of the electrofusion fitting 1000.

[0066] The first inner layer 100 fits on the inner side wall of the base layer 200 and is formed of an insulating material. Compared with the electrofusion fitting 1000 made only of a conductive composite material, the first inner layer 100 has the effect of suppressing crack initiation in the stress concentration area on the inner wall surface of the electrofusion fitting 1000, so that the base layer 200 will not fail prematurely due to crack initiation, and the overall strength of the electrofusion fitting 1000 is improved.

[0067] In addition, the base layer 200 is composed of a conductive material and a polymer matrix, and the first inner layer 100 is formed of an insulating material (such as a high-temperature resistant plastic), which can avoid direct contact between the resistance wire and the conductive body, realize electrical insulation between the internal resistance wire of the fitting and the composite material base layer 200, and prevent current leakage or short circuit.

[0068] The first resistance wire 400 and the second resistance wire 500 are respectively wound axially and circumferentially along the inner wall of the first inner layer 100 and embedded in the inner wall of the first inner layer 100, and the first resistance wire 400 and the second resistance wire 500 are not connected to each other.

[0069] It should be understood that the helical lines wound by the first resistance wire 400 and the second resistance wire 500 on the inner wall of the first inner layer 100 can be parallel to each other or not parallel, as long as it is ensured that the first resistance wire 400 and the second resistance wire 500 do not cross and are not connected to each other in the first inner layer 100.

[0070] As an example, the first resistance wire 400 and the second resistance wire 500 are used as heating elements during the welding of the electrofusion fitting 1000. After the first resistance wire 400 and the second resistance wire 500 are energized, heat is generated for the connection between the electrofusion fitting 1000 and the pipe.

[0071] Along the length direction of the first resistance wire 400, the first resistance wire 400 has a first end 410 and a second end 420. Along the length direction of the second resistance wire 500, the second resistance wire 500 has a third end 510 and a fourth end 520. The first terminal 430 passes through the base layer 200 and is connected to the first end 410, and the second terminal 440 passes through the base layer 200 and is connected to the second end 420. The third terminal 530 passes through the base layer 200 and is connected to the third end 510, and the fourth terminal 540 passes through the base layer 200 and is connected to the fourth end 520.

[0072] That is to say, the first resistance wire 400 and the second resistance wire 500 each have two extended ends and are respectively connected to the corresponding terminals passing through the base layer 200. Such a setting not only helps to enhance the overall strength of the electrofusion fitting 1000 but also enables the electrofusion fitting 1000 to have a self-sensing function.

[0073] In some other embodiments, please refer to Figure 1 , along the axial direction of the base layer 200, the first terminal 430 and the third terminal 530 are located at the same end of the base layer 200 in the same direction, and the second terminal 440 and the fourth terminal 540 are located at the other end of the base layer 200 in the same direction.

[0074] That is to say, the first end 410 of the first resistance wire 400 and the third end 510 of the second resistance wire 500 are located at the same end of the base layer 200 in the same direction, and the second end 420 of the first resistance wire 400 and the fourth end 520 of the second resistance wire 500 are located at the same end of the base layer 200 in the same direction. Such a setting enables heating and welding to be achieved when the positive and negative poles of the power supply are respectively connected to the first resistance wire 400 or the second resistance wire 500 through the terminals, and the electrical parameters of the body material of the electrofusion fitting 1000 between the two terminals under the action of load can be measured when the positive and negative poles of the power supply are respectively connected to the two terminals.

[0075] Specifically, the first terminal 430 and the second terminal 440 are respectively connected to the positive and negative electrodes of the power supply, and the third terminal 530 and the fourth terminal 540 are respectively connected to the positive and negative electrodes of the power supply, so that the first resistance wire 400 and the second resistance wire 500 can self-induce heat, thereby being used for the connection between the pipes in the electrofusion fitting 1000. During the service stage of the electrofusion fitting 1000, the first terminal 430 and the fourth terminal 540 are respectively connected to the electrical measurement device 800 as detection electrodes, or the second terminal 440 and the third terminal 530 are respectively connected to the electrical measurement device 800 as detection electrodes, which are used to measure the electrical parameters of the base layer 200 of the electrofusion fitting 1000 under the action of load. The electrical parameters can be one or more of the resistance, capacitance, impedance spectrum, current, and inductance of the base layer 200, and the present application does not limit this.

[0076] In some other embodiments, please refer to Figure 1 , the electrofusion fitting 1000 further includes a first outer layer 300, the first outer layer 300 fits on the outer wall of the base layer 200, and both the first terminal 430 and the second terminal 440 pass through and extend out of the first outer layer 300, and both the third terminal 530 and the fourth terminal 540 pass through and extend out of the first outer layer 300.

[0077] It can be understood that the first outer layer 300 is composed of a fiber-reinforced polymer and is used for the structural reinforcement of the electrofusion fitting 1000. Since the first outer layer 300 uses a reinforced polymer to achieve the structural reinforcement of the base layer 200, the structural strength and electrical sensing performance of the electrofusion fitting 1000 can be adjusted according to the materials and thicknesses of the first inner layer 100, the base layer 200, and the first outer layer 300. Different thickness combinations can enable the electrofusion fitting 1000 to meet the requirements of different application scenarios, and the present application does not limit this.

[0078] In addition, since the first inner layer 100 has the effect of suppressing the crack initiation in the stress concentration area on the inner wall surface of the electrofusion fitting 1000, the first outer layer 300 will not fail prematurely due to crack initiation, thereby improving the overall strength of the electrofusion fitting 1000.

[0079] As an example, the first outer layer 300 is a reinforced polymer composite material, and the filler therein may include at least one or more of fibers such as glass fiber, natural fiber, and aramid fiber. The matrix polymer of the first outer layer 300 composite material includes at least one or more of polymers such as polyethylene, polypropylene, and polyvinyl chloride, and the present application does not limit this.

[0080] In the above solution, the first outer layer 300 serves as an external protective layer and can bear the load acting on the pipe fitting due to internal pressure. When the pipe fitting bears internal pressure, the load first acts on the first inner layer 100 and then is transmitted to the first outer layer 300 through the base layer 200. The first outer layer 300 and the first inner layer 100 jointly bear the load, preventing the base layer 200 and the internal resistance wire from being eroded by moisture, chemical corrosion or external pollution, prolonging the service life. The first outer layer 300 can also provide additional impact resistance and abrasion resistance for the base layer 200. Especially in buried pipelines or complex working conditions, it reduces the risk of damage caused by external forces during construction or operation, further enhancing the overall strength of the electrofusion pipe fitting 1000.

[0081] In some other embodiments, the first outer layer 300 is formed by uniformly distributing fibers in a polymer matrix, and the structural strength of the first outer layer 300 is greater than that of the first inner layer 100.

[0082] In the above solution, as the outermost protective layer, the first outer layer 300 needs to bear external mechanical stresses, such as impacts during installation, soil pressure (if it is an underground pipeline) or collisions during transportation. The first outer layer 300 is filled with fiber materials to achieve structural enhancement. With higher strength, the first outer layer 300 can protect the internal structure from being damaged and improve the reliability of the entire pipe fitting.

[0083] As the outermost protective layer, the first outer layer 300 is formed by using a fiber-reinforced polymer material, thereby obtaining a higher strength than the first inner layer 100, so that it can better bear the load acting on the pipe fitting due to internal pressure, and further improve the reliability of the entire pipe fitting.

[0084] In addition, the first inner layer 100 has higher plasticity relative to the first outer layer 300, reducing the probability of crack generation due to stress concentration on the inner wall surface.

[0085] The first outer layer 300 can maintain a stable shape during pipe installation or fusion, avoiding deformation of the base layer 200 or the first inner layer 100 due to external forces, thereby protecting the integrity of the internal resistance wire and the circuit.

[0086] The first outer layer 300 is usually selected from engineering plastics, glass fiber reinforced materials, etc., and has excellent ultraviolet resistance, acid and alkali resistance and corrosion protection properties, and is suitable for harsh environments (such as chemical pipelines, offshore engineering).

[0087] As an example, the fibers filled in the first outer layer 300 include at least one or more of fibers such as glass fibers, natural fibers, aramid fibers, etc., and the matrix polymers of the first outer layer 300 include at least one or more of polymers such as polyethylene, polypropylene, polyvinyl chloride, etc. The present application does not limit this.

[0088] As an example, the material of the first outer layer 300 is a fiber - reinforced polymer, and the reinforcement methods include various methods such as short - fiber filling and fiber winding, which are not limited in this application.

[0089] In some other embodiments, please refer to Figure 4 , the polymer matrix of the first outer layer 300 is filled with a conductive material.

[0090] In the above - mentioned solution, the first outer layer 300 and the base layer 200 adopt the same formula of polymer matrix plus conductive materials (such as carbon fiber, metal powder), so that the first outer layer 300 and the base layer 200 can be used as one layer, with both the functions of structural reinforcement and electrical sensing, and the process complexity is reduced. Thus, the electrical parameters of the first outer layer 300 can also be detected by the electrical measurement device 800. For example, it can be one or more of the resistance, capacitance, impedance spectrum, current, and inductance of the first outer layer 300, which are not limited in this application.

[0091] As an example, the first outer layer 300 can also adopt a formula of polymer matrix plus conductive material different from that of the base layer 200. For example, a material cheaper than that of the base layer 200 is selected. In this way, on the one hand, the first outer layer 300 can have both electrical conductivity and strength, and on the other hand, the cost of the first outer layer 300 can be reduced, improving the economy of the product.

[0092] In some other embodiments, a first friction part is provided between the base layer 200 and the first inner layer 100 to increase the friction force between the base layer 200 and the first inner layer 100, and a second friction part is provided between the base layer 200 and the first outer layer 300 to increase the friction force between the base layer 200 and the first outer layer 300.

[0093] In the above - mentioned solution, the friction part helps the inter - layer bonding, reduces the probability of delamination or sliding, thereby improving the structural stability, increasing the inter - layer friction force and interface strength, and significantly improving the bonding strength between the base layer 200 and the first inner layer 100 or the first outer layer 300.

[0094] It can be understood that the friction part can transfer the external load more evenly to each functional layer, avoiding cracking of the inner insulating material or fatigue damage of the outer conductive matrix caused by local stress concentration. Under sudden impact loads, the non - linear friction behavior of the friction interface can absorb part of the impact energy and reduce the overall deformation of the pipe fitting.

[0095] At the same time, when the pipe fitting bears axial tensile or torsional loads, the friction part effectively inhibits inter - layer slip by increasing the interface friction resistance, avoiding the overall structural failure caused by delamination.

[0096] As an example, the friction part can be tooth - shaped, convex - concave structure, etc., which are not limited in this application.

[0097] In some other embodiments, the first friction portion is configured to be a first groove or a first protrusion formed between the inner side surface of the base layer 200 and the outer side surface of the first inner layer 100, and the second friction portion is configured to be a second groove or a second protrusion formed between the outer side surface of the base layer 200 and the inner side surface of the first outer layer 300.

[0098] In the above solution, the first friction portion can be disposed on the inner side surface of the base layer 200, the outer side surface of the first inner layer 100, or on both of the above side surfaces simultaneously. The first groove and the first protrusion can be configured as trapezoidal teeth, triangular teeth, irregular protrusions, etc., and the present application does not limit this.

[0099] The second friction portion can be disposed on the outer side surface of the base layer 200, the inner side surface of the first outer layer 300, or on both of the above side surfaces simultaneously. The second groove and the second protrusion can be configured as trapezoidal teeth, triangular teeth, irregular protrusions, etc., and the present application does not limit this.

[0100] In addition, only the first friction portion or the second friction portion can be arranged, or both the first friction portion and the second friction portion are arranged simultaneously.

[0101] It can be understood that the first friction portion and the second friction portion contribute to the interlayer bonding, reduce the probability of delamination or sliding, thereby improving the structural stability, increasing the interlayer friction force and the interface strength. Compared with the traditional planar friction interface, the contact area is increased, the interlayer biting force is increased, the interlayer shear strength is improved, and the interlayer peeling risk is reduced.

[0102] When the pipe fitting bears a dynamic load, the protrusion or the groove can lock the adjacent layers, effectively suppressing the interface fatigue damage under the alternating load.

[0103] In some other embodiments, please refer to Figure 5 and Figure 6 , the electrofusion pipe fitting 1000 includes a first conductive helix 600 and a second conductive helix 700. The first conductive helix 600 is connected to the first resistance wire 400 and is at least partially disposed in the base layer 200. The second conductive helix 700 is connected to the second resistance wire 500 and is at least partially disposed in the base layer 200. Along the axial direction of the base layer 200, the first conductive helix 600 and the second conductive helix 700 are arranged at intervals.

[0104] In the above solution, the arrangement of the first conductive helix 600 and the second conductive helix 700 at intervals makes it easier for the electrical measurement device 800 to obtain the electrical parameters of a specific position (along the axial direction of the base layer 200, the portion of the base layer 200 located between the first conductive helix 600 and the second conductive helix 700), so as to realize the monitoring of a specific part of the electrofusion pipe fitting 1000.

[0105] Specifically, since the first conductive helix 600 and the second conductive helix 700 extend into the base layer 200, the first terminal 430 and the fourth terminal 540 can be respectively connected to the electrical measurement device 800. Although the base layer 200 has conductivity, because the resistance of the base layer 200 is greater than the resistance of the first resistance wire 400 and the second resistance wire 500, the detection current of the electrical measurement device 800 will pass through the first terminal 430, the part between the first end 410 of the first resistance wire 400 and the first conductive helix 600, the first conductive helix 600, the part of the base layer 200 between the first conductive helix 600 and the second conductive helix 700, the second conductive helix 700, the part between the fourth end 520 of the second resistance wire 500 and the second conductive helix 700, and the fourth terminal 540, so as to realize the detection of specific positions of the electrofusion fitting 1000.

[0106] As an example, the first conductive helix 600 can be a part of the first resistance wire 400, and the second conductive helix 700 can be a part of the second resistance wire 500. That is to say, at least one turn of the helix of each of the first resistance wire 400 and the second resistance wire 500 is laid on the base layer 200, and the remaining helices of the first resistance wire 400 and the second resistance wire 500 are laid on the first inner layer 100. The part of the resistance wire laid on the base layer 200 is in direct contact with the composite material of the base layer 200 and can be used as a monitoring electrode to measure the electrical parameters of the body material in a specific area of the electrofusion fitting 1000.

[0107] Thus, by laying part of the helices of the first resistance wire 400 and the second resistance wire 500 on the base layer 200, the position of the monitoring electrode of the electrofusion fitting 1000 can be adjusted, so that the electrical parameter monitoring of different areas of the fitting can be realized, and it is convenient to set the monitoring range of the electrofusion fitting 1000 according to needs.

[0108] In some other embodiments, please refer to Figure 5 , the first resistance wire 400 includes a first part 450 and a second part 460. Both the first part 450 and the second part 460 are wound axially and circumferentially alternately along the inner wall of the first inner layer 100 and are embedded in the inner wall of the first inner layer 100. One end of the first part 450 far from the second part 460 is connected to the first terminal 460, and one end of the second part 460 far from the first part 450 is connected to the second terminal 440. The first conductive helix 600 connects the ends of the first part 450 and the second part 460 close to each other.

[0109] That is to say, the first resistance wire 400 is axially divided into a first part 450 and a second part 460 along the axis of the first inner layer 100. The first conductive helix 600 connects the first part 450 and the second part 460. That is, along the axis of the first inner layer 100, the first part 450, the first conductive helix 600, and the second part 460 are connected in sequence.

[0110] The first part 450 may include a multi-layer spiral structure. The second part 460 may include a multi-layer spiral structure. The first part 450 and the second part 460 are connected by the first conductive helix 600.

[0111] The second resistance wire 500 includes a third part 550 and a fourth part 560. Both the third part 550 and the fourth part 560 are wound circumferentially and alternately along the axis of the first inner layer 100 and are involved in the inner wall of the first inner layer 100. One end of the third part 550 far from the fourth part 560 is connected to the third terminal 530. One end of the fourth part 560 far from the third part 550 is connected to the fourth terminal 540. The second conductive helix 700 connects the third part 550 and the fourth part 560.

[0112] That is to say, the second resistance wire 500 is axially divided into a third part 550 and a fourth part 560 along the axis of the first inner layer 100. The second conductive helix 700 connects the third part 550 and the fourth part 560. That is, along the axis of the first inner layer 100, the third part 550, the second conductive helix 700, and the fourth part 560 are connected in sequence.

[0113] The third part 550 may include a multi-layer spiral structure. The fourth part 560 may include a multi-layer spiral structure. The third part 550 and the fourth part 560 are connected by the first conductive helix 600.

[0114] Specifically, since the first conductive helix 600 and the second conductive helix 700 extend into the base layer 200, the first terminal 430 and the fourth terminal 540 can be respectively connected to the electrical measurement device 800. Although the base layer 200 has conductivity, because the resistance of the base layer 200 is greater than the resistance of the first resistance wire 400 and the second resistance wire 500, the detection current of the electrical measurement device 800 will pass through the first terminal 430, the first part 450, the first conductive helix 600, the part of the base layer 200 between the first conductive helix 600 and the second conductive helix 700, the second conductive helix 700, the fourth part 560, and the fourth terminal 540, so as to realize the detection of a specific position of the electrofusion fitting 1000.

[0115] Thus, the monitoring of a specific position of the electrofusion fitting 1000 is realized, making it easier for the electrical measurement device 800 to obtain the electrical parameters of the specific position, so as to realize the monitoring of different parts of the electrofusion fitting 1000.

[0116] In a second aspect, an embodiment of the present application provides a method for manufacturing the electrofusion fitting 1000 as described in any one of the above embodiments, including the following steps:

[0117] Injecting with an insulating material as the polymer material to obtain the first inner layer 100;

[0118] Injecting a polymer matrix filled with a conductive material on the outer wall of the first inner layer 100 to form the base layer 200;

[0119] Injecting a polymer matrix filled with a fiber material on the outer wall of the base layer 200 to form the first outer layer 300.

[0120] Embedding a first resistance wire 400 and a second resistance wire 500 on the inner wall of the first inner layer 100. The first resistance wire 400 and the second resistance wire 500 are not connected to each other. The two ends of the first resistance wire 400 in the length direction are respectively connected to the corresponding terminal posts passing through the base layer 200 and the first outer layer 300, and the two ends of the second resistance wire 500 in the length direction are respectively connected to the corresponding terminal posts passing through the base layer 200 and the first outer layer 300.

[0121] As an example, first inject the first inner layer 100 with a polymer material, place the formed first inner layer 100 into a secondary molding die and inject the base layer 200 with a polymer composite material filled with a conductive filler, and finally place the formed first inner layer 100 and the base layer 200 into the final fitting die and inject the first outer layer 300 with a fiber-reinforced polymer.

[0122] During the multi-layer injection molding process, before each time the cylinder in the intermediate process is placed into the die, the cylinder is pre-heated to 100 °C in advance, so that the temperature difference between the cylinder and the material in the injection molding machine is reduced, which is more conducive to the melting and combination of the materials between the two layers, thereby enhancing the interface combination effect.

[0123] In a third aspect, an embodiment of the present application provides a method for manufacturing an electrofusion fitting 1000, which is applied to the electrofusion fitting 1000 as described in any one of the above embodiments. The manufacturing method includes:

[0124] Using an insulating material as the polymer material of the first inner layer 100, using a polymer matrix filled with a conductive material as the polymer material of the base layer 200, and using a polymer matrix filled with a fiber material as the polymer material of the first outer layer 300 and performing plasticization;

[0125] In the above solution, the plasticization process can make the polymer material reach a suitable processing viscous flow state, reduce the viscosity and hardness of the material, enhance its fluidity and plasticity, facilitate the subsequent extrusion molding operation, and ensure the smooth progress of the molding process.

[0126] During the plasticization process, the materials are fully mixed, enabling the insulating material, conductive material, and fiber material to be evenly distributed in their respective polymer matrices.

[0127] The polymer materials of the first inner layer 100, the base layer 200, and the first outer layer 300 are introduced into a composite joint for extrusion molding to obtain a cylindrical body with a multi-layer structure.

[0128] In the above solution, simultaneous extrusion molding enables the first inner layer 100, the base layer 200, and the first outer layer 300 to be tightly combined during the molding process, forming an integral structure, avoiding problems such as delamination and peeling between the multi-layer structures, and improving the structural integrity and stability of the pipe fitting.

[0129] Compared with the method of separately molding and then assembling, simultaneous extrusion molding can complete the molding of the multi-layer structure in one processing operation, reducing the production process and time, improving production efficiency, and reducing production costs.

[0130] The cylindrical body is cut according to the required size to obtain the electrofusion pipe fitting 1000. That is to say, according to different engineering requirements, the cylindrical body can be cut into different lengths and sizes to meet diverse application scenarios, improving the applicability and market competitiveness of the product.

[0131] As an example, an extruder can also be used to plasticize the polymer of the first inner layer 100 and the polymer composite material filled with conductive filler of the base layer 200 respectively, and then introduce them into a composite joint for extrusion to obtain a cylindrical body with a multi-layer structure, and after cutting, an electrofusion pipe fitting 1000 with a multi-layer structure is obtained.

[0132] In a fourth aspect, an embodiment of the present application provides a monitoring method for the electrofusion pipe fitting 1000, which is applied to the electrofusion pipe fitting 1000 described in any of the above embodiments. The monitoring method includes:

[0133] The first terminal 430 and the fourth terminal 540 spaced apart on the axis of the base layer 200 are respectively electrically connected to the positive and negative electrodes of the electrical measurement device 800. When the electrofusion pipe fitting 1000 is subjected to a load, the electrical measurement device 800 obtains the electrical parameter change curve of the electrofusion pipe fitting 1000.

[0134] Specifically, first, any one of the two terminals of the first resistance wire 400 of the electrofusion pipe fitting 1000 is selected, and any one of the two terminals of the second resistance wire 500 of the electrofusion pipe fitting 1000 is selected, such as selecting the terminals of the first resistance wire 400 and the second resistance wire 500 located at the same end of the base layer 200; or, Figure 2 and Figure 3 , select the terminals of the first resistance wire 400 and the second resistance wire 500 located at both ends of the electrofusion pipe fitting 1000 respectively.

[0135] Then, connect the two terminal posts to the positive and negative electrodes of the electrical measurement device 800 respectively through wires to monitor the electrical parameters of the electrode measurement base layer 200 material. When the electrofusion fitting 1000 is subjected to a load, the electrical parameter change curve of the base layer 200 can be obtained in real time through the electrical measurement device 800.

[0136] Finally, by analyzing the electrical parameter change curve of the base layer 200 material, a qualitative or quantitative judgment is made on the current working state of the electrofusion fitting 1000, thereby realizing the monitoring of the internal pressure, strain and damage of the electrofusion fitting 1000.

[0137] Among them, the electrical parameters of the base layer 200 can be one or more of the resistance, impedance spectrum, capacitance, current, and inductance of the base layer 200; the electrical measurement device 800 can be at least one of a multimeter, an electrochemical workstation, a resistance measuring instrument, a capacitance measuring instrument, or an inductance measuring instrument, and the present application does not limit this.

[0138] This solution does not require additional embedding of strain gauges or fiber optic sensors, and directly uses the conductive matrix of the base layer 200 as the sensing element, reducing the manufacturing cost and structural complexity, and improving the detection convenience.

[0139] During monitoring, please refer to Figure 3 and use wires to connect the negative and positive electrodes of the electrical measurement device 800 to the second terminal post 440 of the first resistance wire 400 and the third terminal post 530 of the second resistance wire 500 of the electrofusion fitting 1000 respectively, as shown by the arrow in Figure 3 . At this time, the monitoring current flows from the positive electrode of the electrical measurement device 800, through the part of the third terminal post 530 that is not buried in the first inner layer 100 and the first outer layer 300, and finally flows back to the negative electrode of the electrical measurement device 800 through the part of the second terminal post 440 that is not buried in the first inner layer 100 and the first outer layer 300 through the axial and circumferential current paths, thereby realizing the measurement of the electrical parameters of the base layer 200 material of the electrofusion fitting 1000 in the area to be measured, that is, the part within the dotted line frame in the figure.

[0140] When the electrofusion fitting 1000 is subjected to a load, the electrical parameter change curve of the base layer 200 of the electrofusion fitting 1000 is obtained in real time through the electrical measurement device 800. Finally, the electrical parameter change curve of the body material of the electrofusion fitting 1000 is analyzed, and a qualitative or quantitative judgment is made on the current working state of the electrofusion fitting 1000, thereby realizing the monitoring of the internal pressure, strain and damage of the electrofusion fitting 1000.

[0141] The following is further illustrated by specific implementation cases of the present invention in actual application scenarios.

[0142] This embodiment discloses a multi-layer electrofusion fitting 1000 with structural enhancement and self-sensing functions. The material of its first inner layer 100 is ultra-high molecular weight polyethylene (UHMWPE), which has good plasticity and toughness and can play a role in crack initiation. For example, the first inner layer 100 is injection-molded into an inner diameter of 111 mm, a wall thickness of 3 mm, and an axial length of 160 mm. Then, the first inner layer 100 is placed into a secondary molding die and injection-molded with a polyethylene composite material uniformly filled with short carbon fibers for the base layer 200. The thickness of the base layer 200 is 3 mm, and the conductivity of the base layer 200 can be controlled by the mass fraction of the filled short carbon fibers. In this example, 10% mass fraction of carbon fibers is used.

[0143] After testing, under this material, when the fiber content is 10%, the sensitivity change of the structure with the internal pressure is greater than 20% / MPa and the strength can be increased by 100%. Finally, the formed first inner layer 100 and the base layer 200 are placed into the final fitting die, and the first outer layer 300 is injection-molded with short glass fiber-reinforced high-density polyethylene. The finally obtained electrofusion fitting 1000 with a multi-layer structure has an inner diameter of 111 mm, a wall thickness of 14 mm, and an axial length of 160 mm.

[0144] After injection molding, a first part of copper-nickel alloy resistance wires with a diameter of 0.8 mm can be buried axially at 15 mm inside the first inner layer 100, with 8 turns and a pitch of 16 mm. On the outer wall of the fitting, there are connection terminals connected to the ends of the resistance wires and tubular sheaths that protect the connection terminals.

[0145] Then, starting from 180° on the opposite side of the starting point of the first resistance wire laying, a second copper-nickel alloy resistance wire is laid in the gap between the helical lines of the first resistance wire. The two resistance wires are independent and non-conductive to each other, forming a double-helix resistance wire structure. Under this size of resistance wire arrangement, the heat distribution inside the fitting during welding can ensure sufficient uniformity.

[0146] In another embodiment, please refer to Figure 3 , this embodiment discloses a multi-layer electrofusion fitting 1000 with structural enhancement and self-sensing functions. The material of its first inner layer 100 is also ultra-high molecular weight polyethylene (UHMWPE). For example, the first inner layer 100 is injection-molded into an inner diameter of 111 mm, a wall thickness of 6 mm, and an axial length of 160 mm.

[0147] The electrofusion fitting 1000 is used for the electrical parameters of the body material of the electrofusion fitting 1000. Except for the parts of the two resistance wires that extend along the wall thickness direction and are connected to the terminal posts, the rest of the resistance wires are buried in the ultra-high molecular weight polyethylene insulated in the first inner layer 100 and the short glass fiber reinforced polyethylene in the first outer layer 300, so as to form electrical insulation with the conductive composite material of the base layer 200. Only the parts of the resistance wires that extend along the wall thickness direction and are connected to the terminal posts are in direct contact with the conductive composite material, and the resistance wires in this local area each form a monitoring electrode.

[0148] Use wires to connect the negative pole and the positive pole of the electrical measurement device 800 to the second terminal post 440 of the first resistance wire 400 and the third terminal post 530 of the second resistance wire 500 of the electrofusion fitting 1000 respectively. At this time, the monitoring current flows from the positive pole of the electrical measurement device 800, through the part of the third terminal post 530 that is not buried in the first inner layer 100 and the first outer layer 300, and finally flows back to the negative pole of the electrical measurement device 800 through the axial and circumferential current paths from the part of the second terminal post 440 that is not buried in the first inner layer 100 and the first outer layer 300, so as to realize the measurement of the electrical parameters of the material of the electrofusion fitting 1000 in the area to be measured, that is, the part within the dotted line frame in the figure.

[0149] When the electrofusion fitting 1000 is subjected to a load, the electrical parameter change curve of the base layer 200 in the electrofusion fitting 1000 is obtained in real time through the electrical measurement device 800. Finally, the electrical parameter change curve of the body material of the electrofusion fitting 1000 is analyzed to qualitatively or quantitatively judge the current working state of the electrofusion fitting 1000, and further realize the internal pressure, strain and damage monitoring of the electrofusion fitting 1000.

[0150] In another specific embodiment, please refer to Figure 4 , the embodiment of the present application is a double-layer structure electrofusion fitting 1000 with structural enhancement and self-monitoring functions. It is a double-layer structure electrofusion fitting 1000 with structural enhancement and self-monitoring functions. The material of its first inner layer 100 is also ultra-high molecular weight polyethylene (UHMWPE), and the first inner layer 100 with an inner diameter of 111 mm, a wall thickness of 6 mm and an axial length of 160 mm is formed by injection molding.

[0151] The difference is that the base layer 200 and the first outer layer 300 adopt the same short fiber reinforced polyethylene composite material, and 10% mass fraction of carbon fiber is used. In this case, the base layer 200 and the first outer layer 300 act as one layer, playing the roles of structural enhancement and electrical sensing at the same time, and the overall barrel of the electrofusion fitting 1000 is a double-layer structure.

[0152] Under this structure, its first inner layer 100 is ultra-high molecular weight polyethylene (UHMWPE) which is the same as that in some other embodiments. It is injection-molded into a first inner layer with an inner diameter of 111 mm, a wall thickness of 3 mm, and an axial length of 160 mm. The first outer layer 300 is a polyethylene composite material uniformly filled with short carbon fibers which is the same as the base layer 200 in some other embodiments. The inner diameter of the barrel of the electrofusion fitting 1000 with a double-layer structure obtained by the second injection molding is 111 mm, the wall thickness is 14 mm, and the axial length is 160 mm. After injection molding, the laying method of the resistance wire of the electrofusion fitting 1000 is the same as that in some other embodiments.

[0153] After welding is completed, the electrofusion fitting 1000 can be used for the electrical parameters of the material of the electrofusion fitting 1000 body. Except for the parts of the two resistance wires that extend out of the first inner layer 100 along the wall thickness direction and are connected to the terminal posts, the rest of the resistance wires are buried in the insulating ultra-high molecular weight polyethylene of the first inner layer 100, so as to form electrical insulation with the conductive composite material of the base layer 200. Only the parts of the resistance wires that extend out of the first inner layer 100 along the wall thickness direction and are connected to the terminal posts are in direct contact with the conductive composite material of the base layer 200, and the resistance wires in this local area each form a monitoring electrode.

[0154] Connect the negative pole and the positive pole of the electrical measurement device 800 to the second terminal post 440 of the first resistance wire 400 and the third terminal post 530 of the second resistance wire 500 of the electrofusion fitting 1000 respectively with wires. At this time, the monitoring current flows from the positive pole of the electrical measurement device 800, through the part of a terminal post that is not buried in the first inner layer 100, and finally flows back to the negative pole of the electrical measurement device 800 through the part of the other terminal post that is not buried in the first inner layer 100 through the axial and circumferential current paths, so as to realize the measurement of the electrical parameters of the material of the base layer 200 of the electrofusion fitting 1000 in the area to be measured, that is, the part within the dotted line frame in the figure.

[0155] Since the base layer 200 has both sensing and strengthening functions at the same time, the state of the base layer 200 determines the overall strength of the electrofusion fitting 1000. When the electrofusion fitting 1000 is subjected to a load, the electrical parameter change curve of the base layer 200 is obtained in real time through the electrical measurement device 800. Finally, the electrical parameter change curve of the material of the electrofusion fitting 1000 body is analyzed to qualitatively or quantitatively judge the current working state of the electrofusion fitting 1000, and further realize the internal pressure, strain and damage monitoring of the electrofusion fitting 1000.

[0156] In another specific embodiment, please refer to Figure 5 and Figure 6, in this embodiment, the multi-layer electrofusion fitting 1000 with structural enhancement and self-monitoring functions is provided. The material of its first inner layer 100 is the same as that in other specific parts of other embodiments, which is also ultra-high molecular weight polyethylene (UHMWPE). The first inner layer is injection-molded into an inner diameter of 111 mm, a wall thickness of 3 mm, and an axial length of 160 mm. The remaining injection steps are the same as those in other embodiments.

[0157] However, during the process of laying the resistance wires, the fifth turns of each resistance wire are buried deeper into the wall surface, crossing the insulation layer of the first inner layer 100 and contacting the conductive composite material of the base layer 200, so that the fifth turns of the two resistance wires become two independent monitoring electrodes capable of monitoring the electrical parameters of the base layer 200 in the electrofusion fitting 1000.

[0158] Under the resistance wire pitch of this embodiment, there is a sufficient conductive network between the two resistance wires to ensure the monitoring sensitivity. At the same time, it can cover the damaged parts of the fitting, improving the pertinence of monitoring.

[0159] Similarly, when using wires to connect the positive and negative poles of the electrical measurement device 800 to the terminals of the first resistance wire 400 and the second resistance wire 500 of the electrofusion fitting 1000 respectively, the monitoring current flows from the positive pole of the electrical measurement device 800, enters the first resistance wire 400 through the terminal, flows through the fifth turn of the first resistance wire 400, and finally flows back to the negative pole of the electrical measurement device 800 through the fifth turn of the second resistance wire 500 and the corresponding terminal through the axial current path, realizing the measurement of the electrical parameters of the body material of the electrofusion fitting 1000 in the area to be measured. It can also realize the structural health monitoring of the weak parts of the structure of the electrofusion fitting 1000, and in the actual service process, realize the function of early warning for possible failures.

[0160] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such process, method, commodity or device. Without more limitations, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, commodity or device including the said element.

[0161] Each embodiment in this specification is described in a progressive manner. The same or similar parts between each embodiment can be referred to each other, and the key points of each embodiment are the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0162] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

[0163] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. An electrofusion fitting, characterized in that, Comprising: A base layer, the base layer having a hollow structure and being formed by uniformly distributing a conductive material in a polymer matrix; A first inner layer, attached to the inner wall of the base layer and formed of an insulating material; A first resistance wire and a second resistance wire, the first resistance wire and the second resistance wire being alternately wound axially and circumferentially along the inner wall of the first inner layer and embedded in the inner wall of the first inner layer, the first resistance wire and the second resistance wire being non-connected to each other. Along the length direction of the first resistance wire, the first resistance wire has a first end and a second end. Along the length direction of the second resistance wire, the second resistance wire has a third end and a fourth end; A first terminal and a second terminal, the first terminal passing through the base layer and connected to the first end, and the second terminal passing through the base layer and connected to the second end; A third terminal and a fourth terminal, the third terminal passing through the base layer and connected to the third end, and the fourth terminal passing through the base layer and connected to the fourth end.

2. The electrofusion fitting according to claim 1, characterized in that, Axially along the base layer, the first terminal and the third terminal are located at the same end of the base layer, and the second terminal and the fourth terminal are located at the same end of the base layer in the same direction.

3. The electrofusion fitting according to claim 1, characterized in that, The electrofusion fitting further includes a first outer layer, the first outer layer being attached to the outer wall of the base layer, and the first terminal and the second terminal both passing through and protruding from the first outer layer, and the third terminal and the fourth terminal both passing through and protruding from the first outer layer.

4. The electrofusion fitting according to claim 3, characterized in that, The first outer layer is formed by uniformly distributing fibers in a polymer matrix, and the structural strength of the first outer layer is greater than that of the first inner layer.

5. The electrofusion fitting according to claim 3, characterized in that, The polymer matrix of the first outer layer is filled with a conductive material.

6. The electrofusion fitting according to claim 3, wherein, A first friction portion is provided between the base layer and the first inner layer to increase the friction force between the base layer and the first inner layer, and a second friction portion is provided between the base layer and the first outer layer to increase the friction force between the base layer and the first outer layer.

7. The electrofusion fitting according to claim 6, wherein, The first friction portion is configured as a first groove or a first protrusion formed between the inner side surface of the base layer and the outer side surface of the first inner layer, and the second friction portion is configured as a second groove or a second protrusion formed between the outer side surface of the base layer and the inner side surface of the first outer layer.

8. The electrofusion fitting according to claim 1, wherein, The electrofusion fitting includes a first conductive spiral and a second conductive spiral, the first conductive spiral being connected to the first resistance wire and at least partially disposed in the base layer, and the second conductive spiral being connected to the second resistance wire and at least partially disposed in the base layer. Axially along the base layer, the first conductive spiral and the second conductive spiral are spaced apart.

9. The electrofusion fitting according to claim 8, wherein, The first resistance wire includes a first portion and a second portion, both the first portion and the second portion being alternately wound axially and circumferentially along the inner wall of the first inner layer and embedded in the inner wall of the first inner layer. One end of the first portion away from the second portion is connected to the first terminal, and one end of the second portion away from the first portion is connected to the second terminal. The first conductive spiral connects the ends of the first portion and the second portion close to each other; The second resistance wire includes a third part and a fourth part. Both the third part and the fourth part are wound axially and circumferentially alternately and embedded in the inner wall of the first inner layer. One end of the third part away from the fourth part is connected to the third terminal, and one end of the fourth part away from the third part is connected to the fourth terminal. The second conductive spiral connects the ends of the third part and the fourth part close to each other.

10. A method for preparing an electrofusion pipe fitting according to any one of claims 3 to 7, characterized in that, Comprising the following steps: Injecting with an insulating material as the polymer material to obtain the first inner layer; Injecting a polymer matrix filled with a conductive material on the outer wall of the first inner layer to form a base layer; Injecting a polymer matrix filled with a fiber material on the outer wall of the base layer to form a first outer layer; Embedding a first resistance wire and a second resistance wire on the inner wall of the first inner layer. The first resistance wire and the second resistance wire are not connected to each other. Two ends of the first resistance wire in the length direction are respectively connected to corresponding terminals passing through the base layer and the first outer layer, and two ends of the second resistance wire in the length direction are respectively connected to corresponding terminals passing through the base layer and the first outer layer.

11. A method for preparing an electrofusion pipe fitting according to any one of claims 3 to 7, characterized in that, Comprising the following steps: Using an insulating material as the polymer material of the first inner layer, using a polymer matrix filled with a conductive material as the polymer material of the base layer, using a polymer matrix filled with a fiber material as the polymer material of the first outer layer and plasticizing; Introducing the polymer material of the first inner layer, the polymer material of the base layer and the polymer material of the first outer layer into a composite joint and extrusion molding to obtain a cylinder with a multi-layer structure; Cutting the cylinder according to the required size to obtain the electrofusion fitting.

12. A monitoring method for an electrofusion fitting, which is applied to the electrofusion fitting described in any one of claims 1 to 9, characterized in that, The monitoring method includes: Electrically connecting a first terminal and a fourth terminal spaced apart on the axis of the base layer to the positive pole and the negative pole of a measuring device respectively. When the electrofusion fitting is subjected to a load, the measuring device acquires the change curve of the electrical parameters of the electrofusion fitting.

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