An electrically fused joint for a double-layer non-metal composite heat-insulating pipe

Abstract

The utility model discloses a kind of electric fusion joint for double-layer non-metal composite heat preservation pipe, it is related to pipe fitting technical field, including first pipe fitting, the left and right ends of first pipe fitting are respectively provided with two second pipe fittings integrally formed with it and coaxially arranged, second pipe fitting inner diameter is same with first pipe fitting inner diameter, second pipe fitting outer diameter is greater than first pipe fitting outer diameter, the free end of two second pipe fittings is equipped with annular mounting groove, resistance wire layer is uniformly arranged on the inner wall of first pipe fitting and second pipe fitting, first pipe fitting and the outer side of two second pipe fittings are equipped with a group of terminal stud electrically connected with the resistance wire layer arranged in its inner wall;The utility model shortens assembly process, can complete the butt joint of pipe fitting and heat preservation pipe once, improves construction efficiency, while greatly improves the sealing performance of heat preservation material.

Description

Technical Field

[0001] This utility model relates to the field of pipe fittings technology, specifically to an electrofusion joint for double-layer non-metallic composite insulation pipes. Background Technology

[0002] Electrofusion joints are key components that use electric current to generate heat to melt the ends of plastic pipes, thereby achieving a sealed connection. They are widely used in the connection of double-layer composite insulation pipes.

[0003] Existing technologies, such as Chinese patent CN223242405U, disclose a high-density polyethylene vacuum insulation pipe. This insulation pipe includes an outer pipe and an inner pipe coaxial with the outer pipe. An annular insulation cavity is provided between the inner and outer pipes, and heat insulation material is injected into the annular insulation cavity to form an insulation layer to ensure insulation performance. In terms of connection method, this patent uses an annular hot-melt joint to connect the outer pipes of two vacuum insulation pipes, and strengthens the connection part by an electrofusion sleeve set on the outside, thereby realizing the connection of the two insulation pipes. To a certain extent, it takes into account both connection strength and insulation effect. However, this structure has the following shortcomings. On the one hand, its connection structure is composed of an annular hot-melt joint and an independent electrofusion sleeve. The overall number of components is large, and the assembly process is relatively complex. This not only increases the cumbersomeness of construction operations, but may also affect the stability of the connection due to the accuracy of the multi-component matching.

[0004] Furthermore, the resistance wire of this connection structure is only laid on the inner wall of the electrofusion sleeve, and the heating area is relatively concentrated on the outer side of the outer pipe joint section. For the key sealing parts where the joint contacts the pipe, the heating uniformity is insufficient, which may lead to insufficient melting in some areas, affecting the sealing performance of the joint, and thus reducing the overall insulation effect and service life of the insulation pipe. Therefore, there is an urgent need for an electrofusion joint with a simpler structure and better sealing performance for double-layer composite insulation pipes to solve the problems existing in the prior art. Utility Model Content

[0005] The purpose of this utility model is to provide an electrofusion joint for double-layer non-metallic composite insulation pipes, aiming to solve the problems of cumbersome construction operations and poor sealing performance in the above-mentioned background technology.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an electrofusion joint for a double-layer non-metallic composite insulation pipe, the electrofusion joint comprising a first pipe fitting, two second pipe fittings integrally formed and coaxially arranged at the left and right ends of the first pipe fitting, the inner diameter of the second pipe fitting being the same as the inner diameter of the first pipe fitting, the outer diameter of the second pipe fitting being larger than the outer diameter of the first pipe fitting, annular mounting grooves provided at the free ends of the two second pipe fittings, resistance wire layers evenly distributed on the inner walls of the first and second pipe fittings, and a set of terminals electrically connected to the resistance wire layers distributed on the inner walls of the first pipe fitting and the two second pipe fittings being provided on the outer sides of the first pipe fitting and the two second pipe fittings.

[0007] Furthermore, the electrofusion joint is made of PE or PE-RT material.

[0008] This utility model has the following beneficial effects: This invention provides an electrofusion joint for double-layer non-metallic composite insulation pipes. Compared with the combined structure of annular hot-melt joint and electrofusion sleeve, this invention uses an integrated molding structure, eliminating the need for additional electrofusion sleeve assembly, shortening the assembly process, and enabling one-time connection between the pipe fitting and the insulation pipe. This reduces the complexity of construction operations, improves construction efficiency, and covers all key sealing areas in contact with the inner and outer pipes of the insulation pipe, significantly improving the sealing performance of the insulation material and effectively preventing the medium from leaking into the insulation layer and causing a decrease in insulation performance. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a cross-sectional view of the structure of this utility model; In the diagram: 1. First fitting; 2. Second fitting; 3. Annular mounting groove; 4. Resistance wire layer; 5. Terminal. Detailed Implementation

[0010] like Figures 1 to 2 As shown, in this embodiment, the electrofusion joint is made of PE-RT heat-resistant polyethylene material, which has excellent heat resistance and chemical stability, and meets the requirements for pipeline corrosion resistance and aging resistance.

[0011] The first fitting 1 serves as the main connecting section of the electrofusion joint. Its inner diameter is consistent with that of the inner pipe of the insulation pipe, ensuring that there is no obstruction to the flow of the medium during transportation and maintaining the effective passage ratio of the pipeline cross-section. The outer diameter of the first fitting 1 is designed to be 80mm, and the outer wall adopts a smooth surface design, which facilitates subsequent docking and positioning with the outer pipe of the insulation pipe.

[0012] The second fitting 2 is integrally formed with the first fitting 1 and is coaxially arranged. There are two of them, located at the left and right ends of the first fitting 1 respectively. Their inner diameter is the same as that of the first fitting 1 to ensure the continuity of media transportation. The outer diameter is designed to be 100mm, which can realize the tight fit between the second fitting 2 and the outer pipe. Each second fitting 2 has an annular mounting groove 3 at the end away from the first fitting 1. Its size is precisely matched with the end size of the outer pipe of the double-layer composite insulation pipe. The groove depth is 50mm, which is used to lock the end of the outer pipe of the double-layer composite insulation pipe. The inner wall of the mounting groove can play a radial limiting role on the outer pipe of the insulation pipe, ensuring that the insulation pipe and the electrofusion joint are coaxially arranged and avoiding misalignment during the docking process.

[0013] A sealing ring is installed inside the annular insulation cavity of the double-layer composite insulation pipe. After being embedded, the sealing ring can completely fit the inner wall of the annular insulation cavity and the end of the embedded part of the second pipe fitting 2, forming an additional sealing barrier between the joint and the insulation pipe. Before the hot-melt heating, the sealing ring can initially block external dust and impurities from entering the joint gap, avoiding affecting the fusion quality; it effectively prevents the medium inside the pipe from leaking into the insulation layer, and together with the fusion layer, it forms a double sealing structure, improving the sealing reliability.

[0014] The resistance wire layer 4 uses 0.8mm diameter nickel-chromium alloy resistance wire, which is evenly distributed on the inner wall of the first pipe fitting 1 and the second pipe fitting 2 through an embedded injection molding process. The resistance wire on the inner wall of the first pipe fitting 1 is spirally wound with a pitch of 5-8mm, covering the entire inner wall area of ​​the electrofusion joint, with a focus on covering the sealing section in contact with the outer pipe of the insulation pipe. The resistance wire on the inner wall of the second pipe fitting 2 is arranged with a spiral pitch of 3-5mm, focusing on covering the sealing section in contact with the outer pipe of the insulation pipe. The density of the resistance wire layer 4 is precisely calculated to ensure that when the power is applied for heating, the contact area between the first pipe fitting 1 and the inner pipe of the insulation pipe, and the contact area between the second pipe fitting 2 and the outer pipe of the insulation pipe, can achieve uniform heating, avoiding problems such as local overheating or insufficient melting.

[0015] The terminal block 5 is made of brass, which has good conductivity and oxidation resistance. It is divided into three groups and is set on the outer middle of the first pipe 1 and the outer side of the second pipe 2 near the first pipe 1. Each group of terminal blocks 5 contains two terminals, and each terminal is reliably electrically connected to the resistance wire layer in the corresponding area through an internal wire. The outer side of the terminal block 5 is equipped with an insulating protective sleeve made of high temperature resistant silicone to prevent leakage risk during construction and facilitate the connection of an external power cord to provide a stable current input to the resistance wire layer 4.

[0016] The specific operation process of this utility model is as follows: The ends of the two double-layer composite insulation pipes to be connected (hereinafter referred to as the pipes to be connected) are pre-treated. A special pipe cutting machine is used to cut the end faces of the outer and inner pipes of the pipes to be connected flat, ensuring that the end faces are perpendicular to the pipe axis. Then, the burrs on the inner wall of the inner pipe and the inner wall of the outer pipe are sanded with sandpaper and wiped clean with alcohol to remove oil, dust and other impurities, so as to prevent affecting the heat fusion sealing effect.

[0017] Confirm that the PE-RT material is free of cracks and deformation, the resistance wire layer 4 is free of breakage, the terminal block 5 is not loose, and the annular mounting groove 3 is not blocked; use a multimeter to test the resistance value of the resistance wire circuit to ensure that the heating circuit is conducting normally.

[0018] Embed the matching sealing ring into the annular groove at the ends of the two pipes to be connected, ensuring that the sealing ring fits completely against the inner wall of the mounting groove 3 without any offset or wrinkles. The sealing ring is made of EPDM rubber, which has excellent elasticity and aging resistance, and can improve the sealing performance of the joint. Insert the outer end of one of the pipes to be connected into the annular mounting groove 3. At this time, the inner wall of the second fitting 2 is pressed against the outer wall of the inner pipe of the pipe to be connected. Connect the other pipe to be connected in the same way to ensure that the two pipes to be connected are coaxial and that there is no gap in the contact area between the joint and the insulation pipe.

[0019] Use pipe clamps to secure the two second pipe fittings at the connection points with the outer pipe of the insulation pipe. The clamping force should be moderate to ensure that the joint and the insulation pipe remain relatively stable during the heating process, so as to avoid affecting the connection quality due to displacement and to ensure the formation of a uniform fusion layer.

[0020] Connect the output end of the hot melt welding machine to the three sets of terminals 5 on the electrofusion joint, set the heating parameters: heating temperature is 210℃, heating time is 30s, turn on the hot melt welding machine, the current passes through the resistance wire layer to generate heat, the heat is evenly transferred to the inner wall of the first pipe fitting 1 and the second pipe fitting 2, so that the PE-RT material of the inner wall gradually melts (the thickness of the melt layer is about 1-1.5mm); at the same time, the outer wall of the inner pipe to be connected and the inner wall of the outer pipe also melt synchronously due to the heat conduction with the inner wall of the electrofusion joint, forming a uniform weld layer.

[0021] After heating is complete, turn off the hot melt welding machine, keep the pipe to be connected to the electrofusion joint in a docking state, apply a certain holding pressure to prevent gaps from appearing at the docking part due to thermal expansion and contraction; allow natural cooling to allow the fusion layer to fully solidify and form a tight sealed connection.

[0022] After cooling, a sealing test is performed on the connection. Using the air pressure test method, compressed air is injected into the annular insulation cavity of the insulation pipe and kept for 30 minutes. The pressure gauge reading is then observed to see if it drops. At the same time, soapy water is applied to the joint between the electrofusion joint and the pipe to be connected, and the presence of bubbles is checked. If the pressure does not drop and there are no bubbles, the seal is considered qualified.

[0023] Thermal insulation performance testing involves conducting heat loss tests on the connected pipelines; hot water at 70°C is passed through the pipelines for 24 hours, and an infrared thermometer is used to detect the outer wall temperature of the electrofusion joint to ensure that the thermal insulation performance does not decrease due to the connection.

[0024] After passing the inspection, disconnect the heating equipment connection wires from the terminal block, and put a protective cap on the outside of the terminal block to prevent damage to the terminal block during subsequent use; clean the excess sealant on the outside of the electrofusion joint to keep the pipeline appearance clean.

Claims

1. An electrofusion joint for double-layer non-metallic composite insulation pipes, characterized in that: The electrofusion joint includes a first pipe fitting (1), and two second pipe fittings (2) are provided at the left and right ends of the first pipe fitting (1) respectively. The inner diameter of the second pipe fitting (2) is the same as the inner diameter of the first pipe fitting (1), and the outer diameter of the second pipe fitting (2) is larger than the outer diameter of the first pipe fitting (1). The free ends of the two second pipe fittings (2) are provided with annular mounting grooves (3). Resistance wire layers (4) are evenly distributed on the inner walls of the first pipe fitting (1) and the two second pipe fittings (2). A set of terminals (5) electrically connected to the resistance wire layers distributed on the inner walls of the first pipe fitting (1) and the two second pipe fittings (2) are provided on the outer side of the first pipe fitting (1) and the two second pipe fittings (2).

2. The electrofusion joint according to claim 1, characterized in that, The electrofusion joint is made of PE or PE-RT material.

Images