Butt welding connection structure of steel-plastic composite pipe

Abstract

The utility model discloses a butt welding connection structure of a steel-plastic composite pipe, relates to the technical field of composite pipe butt joint structures, and is mainly used for solving the problem that leakage risks exist in common steel-plastic composite pipe connection modes. According to the main structure, adjacent outer-layer steel pipes are connected in a butt welding mode through radial flaring sections which are arranged at the ends of the outer-layer steel pipes and are of an integrated structure with the outer-layer steel pipes; the end parts of the adjacent inner-layer plastic pipes are connected, a filler cavity is formed between the end parts of the adjacent inner-layer plastic pipes and the radial flaring sections which are in butt welding connection, and threaded holes communicated with the filler cavity are formed in the radial flaring sections. The utility model provides a butt welding connection structure of a steel-plastic composite pipe, which can ensure the loading capacity and the connection reliability of a connection part while completely preventing a medium in an inner-layer plastic pipe from being in contact with an outer-layer steel pipe, avoids the leakage of the medium, and enlarges the applicable working condition range of the product.

Description

Technical Field

[0001] The utility model relates to the technical field of composite pipe butt-welding structures, in particular to a butt-welding connection structure of a steel-plastic composite pipe. Background Art

[0002] Steel-plastic composite pipes are made from a steel pipe base, with an outer steel pipe and an inner plastic pipe bonded together using a hot-melt adhesive layer. The outer steel pipe ensures pressure resistance, while the inner plastic pipe provides corrosion protection. The complementary advantages of these two materials contribute to the product's excellent performance. However, it's important to note that the rationality and reliability of the connection method for steel-plastic composite pipes are crucial to their effectiveness. Common connection methods for steel-plastic composite pipes today include threaded, grooved, butt-welded stainless steel fittings, and flanged connections.

[0003] However, these common steel-plastic composite pipe connection methods all have certain defects, specifically:

[0004] (1) Threaded connection, groove connection and stainless steel joint butt welding connection only realize the mechanical connection between the outer steel pipes, but do not realize the connection between the inner lining plastic pipes. Therefore, it is difficult to avoid the contact between the conveying medium and the end of the outer steel pipe; when the conveying medium of the steel-plastic composite pipe is corrosive, it may cause rapid corrosion to the end of the outer steel pipe, causing leakage, and then leading to failure of the pipeline system.

[0005] (2) Flange-connected steel-plastic composite pipes are not suitable for burial in the design specifications, which limits their operating conditions. On the other hand, during use, the plastic layer covering the flange sealing surface is prone to sealing failure due to uneven force, stress loss, deformation, aging, etc., which can also cause leakage and lead to failure of the pipeline system.

[0006] Therefore, there is an urgent need for a new butt-welding connection structure of steel-plastic composite pipes that can solve the above problems. Utility Model Content

[0007] The purpose of the utility model is to provide a butt-welding connection structure for steel-plastic composite pipes, which can completely prevent the medium in the inner plastic pipe from contacting the outer steel pipe while ensuring the pressure bearing capacity and connection reliability of the connection part, avoiding medium leakage while also increasing the applicable working range of this product.

[0008] The technical solution of the utility model for solving the above technical problems is: a butt-welding connection structure of a steel-plastic composite pipe, comprising at least two coaxially arranged steel-plastic composite pipes, wherein the steel-plastic composite pipe comprises an outer steel pipe, a hot-melt adhesive layer and an inner plastic pipe arranged in sequence along the radial direction, the adjacent outer steel pipes are butt-welded by radial flaring sections arranged at their ends, and the radial flaring sections and the outer steel pipes are an integrated structure; the ends of the adjacent inner plastic pipes are connected and a filling cavity is formed between the radial flaring sections connected with the butt-welding connection, and the radial flaring sections are all provided with threaded holes connected to the filling cavity; the radial flaring section of the outer steel pipe is trumpet-shaped.

[0009] As a further improvement of the present invention, filling material is injected into the filler cavity through the threaded hole.

[0010] As a further improvement of the present invention, a blocking bolt that matches the thread of the threaded hole is installed on the threaded hole.

[0011] As a further improvement of the present invention, the ends of adjacent inner plastic tubes are connected by hot melt.

[0012] As a further improvement of the present invention, a socket connecting pipe is provided between the ends of adjacent inner plastic pipes, and the two ends of the connecting pipe are respectively sleeved on the outer sides of the ends of the two inner plastic pipes.

[0013] As a further improvement of the present invention, a hot melt adhesive layer is also provided between the inner wall of the socket connection pipe and the outer wall of the inner plastic pipe.

[0014] As a further improvement of the present invention, the socket-and-spigot connection pipe is a plastic pipe.

[0015] Beneficial effects

[0016] Compared with the prior art, the advantages of the butt-welding connection structure of a steel-plastic composite pipe of the utility model are:

[0017] 1. When two pipes with this connection structure are connected, since the inner plastic pipes are connected as a whole, the transported medium can only contact the inner plastic pipe, and the medium is completely prevented from contacting the outer steel pipe, thereby solving the problem of corrosion of the outer steel pipe and avoiding the problem of leakage of the medium due to pipeline corrosion; at the same time, since the adjacent outer steel pipes are connected by butt welding through the radial expansion section set at their ends, and the radial expansion section and the outer steel pipe are an integrated structure, the pressure bearing capacity and connection reliability of the connection part can be better guaranteed compared with the flange connection, and the applicable working condition range of the product can be increased; in addition, in the process of welding the adjacent outer steel pipes, the coolant inlet pipe / output pipe can be connected to the radial expansion section by threaded connection, so that coolant can be injected into the filler cavity during the welding process, thereby effectively avoiding the damage to the inner plastic pipe caused by the high temperature generated when the outer steel pipes are butt welded.

[0018] The present invention will become more clear through the following description in conjunction with the accompanying drawings, which are used to explain embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a cross-sectional view of Example 1 of the present utility model;

[0021] Figure 2 This is a cross-sectional view of Example 2 of the present utility model;

[0022] Figure 3 It is a partial structural diagram of the radial expansion section of the present utility model.

[0023] Among them: 1-steel-plastic composite pipe; 2-outer steel pipe; 3-hot melt adhesive layer; 4-inner plastic pipe; 5-radial expansion section; 6-filling cavity; 7-threaded hole; 8-socket connection pipe. DETAILED DESCRIPTION

[0024] To make the purpose, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described herein are merely a portion of the embodiments of the present invention, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0025] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; of course, they can also refer to mechanical connections or electrical connections; in addition, they can also refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. For those skilled in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0026] Embodiments of the present invention will now be described with reference to the accompanying drawings.

[0027] Example 1

[0028] The specific embodiments of the present invention are as follows Figure 1 As shown, a butt-welding connection structure of a steel-plastic composite pipe and a connection method thereof include at least two coaxially arranged and sequentially connected steel-plastic composite pipes 1. The steel-plastic composite pipe 1 includes an outer steel pipe 2, a hot melt adhesive layer 3, and an inner plastic pipe 4 arranged sequentially from the outside to the inside along its radial direction. Among them, adjacent outer steel pipes 2 are butt-welded via a radial flaring section 5 provided at the end of the outer steel pipe 2, and the radial flaring section 5 and the outer steel pipe 2 are an integral structure. At the same time, the ends of adjacent inner plastic pipes 4 are connected and a stuffing cavity 6 is formed between the radial flaring sections 5 connected by butt welding. In addition, threaded holes 7 communicating with the stuffing cavity 6 are provided on the radial flaring sections 5. In this embodiment, the radial flaring section 5 of the outer steel pipe 2 is trumpet-shaped, and the inner wall of the radial flaring section 5 does not contact the inner plastic pipe 4.

[0029] When assembling a long conveying pipeline through the steel-plastic composite pipe 1, first connect the ends of the coaxially arranged adjacent inner plastic pipes 4 together; then, connect the coolant inlet pipe and the coolant outlet pipe respectively through the threaded holes 7 on the two radial flared sections 5 to be butt-welded; after that, use welding equipment to butt-weld the radial flared sections 5 of the adjacent outer steel pipes 2, and during the butt-welding process, the coolant inlet pipe and the coolant outlet pipe are opened at the same time to form a coolant circulation between the stuffing chamber 6, the coolant inlet pipe and the coolant outlet pipe; finally, when the radial flared sections 5 are butt-welded, it is only necessary to drain the coolant in the stuffing chamber 6 to complete the connection of the adjacent steel-plastic composite pipes 1.

[0030] When two steel-plastic composite pipes 1 are connected using this connection structure, the inner plastic pipes 4 are integrally connected, so the transported medium can only come into contact with the inner plastic pipe 4, completely preventing contact between the medium and the outer steel pipe 2. This solves the problem of corrosion of the outer steel pipe 2 and avoids leakage of the medium due to pipeline corrosion. Furthermore, since adjacent outer steel pipes 2 are butt-welded via radially flared sections 5 disposed at their ends, and the radially flared sections 5 and the outer steel pipes 2 are integrally formed, this connection structure not only reduces the number of parts compared to flange connections, but also better ensures the pressure-bearing capacity and connection reliability of the connection, and also expands the product's applicable operating range. Furthermore, during the welding process of adjacent outer steel pipes 2, the coolant inlet / outlet pipes can be connected to the radially flared sections 5 via threaded connections, allowing coolant to be injected into the filler cavity 6 during the welding process, effectively preventing damage to the inner plastic pipe 4 from the high temperatures generated during the butt welding of the outer steel pipes 2.

[0031] In this connection structure, a filling material is injected into the filling cavity 6 through the threaded hole 7. The filling material is a solidified, wrapped thermal insulation material. The filling material can transmit the pressure of the conveying medium on the inner plastic tube 4 to the outer steel tube 2. That is, it can ensure the tensile strength of the connection between the steel-plastic composite tube 1 and the medium in the direction of medium conveyance, and can also ensure the high-pressure strength of the connection between the steel-plastic composite tube 1 and the steel-plastic composite tube 1 in the radial direction, thereby ensuring the strength of the connection between the steel-plastic composite tube 1 and the steel-plastic composite tube 1 when the pipeline is conveying high-pressure media. In this embodiment, in order to prevent the filling material 7 from leaking during the filling process and subsequent use, a sealing bolt that matches its thread is installed on the threaded hole 7.

[0032] In this embodiment, in order to achieve the connection between adjacent inner plastic tubes 4, the ends of adjacent inner plastic tubes 4 are connected by hot melting.

[0033] In this embodiment, the manufacturing process of the steel-plastic composite pipe 1 includes the following steps:

[0034] S1', expanding the ends of the carbon steel base pipe to form a radial expansion section 5, or welding the expanded expansion section short pipe to the end of the carbon steel base pipe, and processing the butt welding groove on the end face of the radial expansion section 5, and processing the threaded hole 7 on the side wall of the radial expansion section 5 to complete the production of the outer steel pipe 2;

[0035] S2', the inner lining layer composed of the inner plastic tube 4 and the hot melt adhesive layer 3 is formed by double-layer co-extrusion to form a double-layer structure in which the outer layer is the hot melt adhesive layer 3 and the inner layer is the inner plastic tube 4 of a polymer material such as polyethylene or polypropylene;

[0036] S3', insert the inner lining layer into the outer steel pipe 2 after the expansion process through the pipe-threading equipment; then clamp the inflatable clamps at both ends of the semi-finished steel-plastic composite pipe 1, and pressurize the pipe to expand the inner lining layer outward; at the same time, the hot melt adhesive layer 3 is heated by electromagnetic induction to reach the bonding temperature, so that the inner lining layer and the outer steel pipe 2 are bonded and fused into one;

[0037] S4', through the processing of the flat port equipment, the extended sections of the inner lining of the two ports are made flat and reach the required length for installation.

[0038] In step S1 of the aforementioned manufacturing process, the ratio of the volume of the filling cavity 6 to the weld volume in the welding area is ≥10:1. This ensures that the dimensions of the flared portion meet the requirements for butt welding while also ensuring that the outer dimensions and internal volume of the filling cavity 6 meet the requirements for circulating cooling efficiency. Furthermore, the flared height is 2.5-3 times the wall thickness of the steel pipe, and the flared depth is 4-5 times the wall thickness of the steel pipe. This also ensures the structural strength of this area after filling, thereby ensuring the safety and reliability of the system.

[0039] In this embodiment, the connection process between the steel-plastic composite pipes 1 includes the following steps:

[0040] S1. Perform pretreatment such as flattening and cleaning the inner lining layers at both ends of the steel-plastic composite pipe 1;

[0041] S2. Preheating the end surface of the inner lining layer to be butted by heat fusion;

[0042] S3, the end faces of the inner lining layers at the two ends to be connected are butt-welded, and the end faces of the radially flared sections 5 of the outer steel pipe 2 are butted to the desired position for butt welding;

[0043] S4. Perform a bottom thin weld on the butt weld of the outer steel pipe 2, and respectively install a coolant inlet pipe and a coolant outlet pipe on the threaded holes 7 on both sides to seal the stuffing cavity 6. Then connect a water pump to introduce circulating coolant to circulate the coolant;

[0044] S5, butt welding the butt weld of the outer steel pipe 2, during which the heat generated by welding is removed by circulating coolant;

[0045] S6. After the butt welding is completed, clean and polish the weld, then inject filler into the filler cavity 6 through the threaded hole 7. After the filler solidifies, use sealing bolts to seal the threaded holes 7 on both sides to complete the installation construction.

[0046] In step S5 of the above connection process, a portable temperature measuring instrument is used during the welding process to monitor the temperature of the welding area and adjacent areas to ensure that the inner plastic tube 4 is not damaged by high temperature.

[0047] Example 2

[0048] The difference between this embodiment and embodiment 1 is as follows Figure 2 As shown, in order to realize the connection between adjacent inner plastic pipes 4, a socket connection pipe 8 is further provided between the ends of adjacent inner plastic pipes 4. The two ends of the connection pipe 8 are respectively sleeved on the outer sides of the ends of the two inner plastic pipes 4.

[0049] In this embodiment, a hot melt adhesive layer 3 is also provided between the inner wall of the socket-and-spigot connection pipe 8 and the outer wall of the inner plastic pipe 4. The socket-and-spigot connection pipe 8 is a plastic pipe.

[0050] In this embodiment, the manufacturing process of the steel-plastic composite pipe 1 includes the following steps:

[0051] S1', expanding the ends of the carbon steel base pipe to form a radial expansion section 5, or welding the expanded expansion section short pipe to the end of the carbon steel base pipe, and processing the butt welding groove on the end face of the radial expansion section 5, and processing the threaded hole 7 on the side wall of the radial expansion section 5 to complete the production of the outer steel pipe 2;

[0052] S2', the inner lining layer composed of the inner plastic tube 4 and the hot melt adhesive layer 3 is formed by double-layer co-extrusion to form a double-layer structure in which the outer layer is the hot melt adhesive layer 3 and the inner layer is the inner plastic tube 4 of a polymer material such as polyethylene or polypropylene;

[0053] S3', insert the inner lining layer into the outer steel pipe 2 after the expansion process through the pipe-threading equipment; then clamp the inflatable clamps at both ends of the semi-finished steel-plastic composite pipe 1, and pressurize the pipe to expand the inner lining layer outward; at the same time, the hot melt adhesive layer 3 is heated by electromagnetic induction to reach the bonding temperature, so that the inner lining layer and the outer steel pipe 2 are bonded and fused into one;

[0054] S4', through the processing of the flat port equipment, the extended sections of the inner lining of the two ports are made flat and reach the required length for installation.

[0055] In step S1 of the aforementioned manufacturing process, the ratio of the volume of the filling cavity 6 to the weld volume in the welding area is ≥10:1. This ensures that the dimensions of the flared portion meet the requirements for butt welding while also ensuring that the outer dimensions and internal volume of the filling cavity 6 meet the requirements for circulating cooling efficiency. Furthermore, the flared height is 2.5-3 times the wall thickness of the steel pipe, and the flared depth is 4-5 times the wall thickness of the steel pipe. This also ensures the structural strength of this area after filling, thereby ensuring the safety and reliability of the system.

[0056] In this embodiment, the connection process between the steel-plastic composite pipes 1 includes the following steps:

[0057] S1. Perform pretreatment such as flattening and cleaning the inner lining layers at both ends of the steel-plastic composite pipe 1;

[0058] S2. Apply cold-setting adhesive or hot-melt preheating treatment to the socket section of the inner lining layer;

[0059] S3, insert the inner lining layers at both ends to be connected into the socket joint pipe 8, and make the end faces of the radial expansion section 5 of the outer steel pipe 2 butt together to reach the required position for butt welding;

[0060] S4. Perform a bottom thin weld on the butt weld of the outer steel pipe 2, and respectively install a coolant inlet pipe and a coolant outlet pipe on the threaded holes 7 on both sides to seal the stuffing cavity 6. Then connect a water pump to introduce circulating coolant to circulate the coolant;

[0061] S5, butt welding the butt weld of the outer steel pipe 2, during which the heat generated by welding is removed by circulating coolant;

[0062] S6. After the butt welding is completed, clean and polish the weld, then inject filler into the filler cavity 6 through the threaded hole 7. After the filler solidifies, use sealing bolts to seal the threaded holes 7 on both sides to complete the installation construction.

[0063] The penetration depth of the hot-melt socket connection of the inner liner is approximately 60% of the wall thickness of the inner plastic pipe 4, and the length of the socket section of the inner liner is ≥ 1 / 2 of the socket depth of the socket connection pipe 8. Furthermore, in step S5 of the above connection process, a portable temperature measuring instrument is used during the welding process to monitor the temperature of the welding process and adjacent areas to ensure that the inner plastic pipe 4 is not damaged by high temperatures.

[0064] The present invention is described above in conjunction with the best embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations based on the essence of the present invention.

Claims

1. A butt-welding connection structure of a steel-plastic composite pipe, comprising at least two coaxially arranged steel-plastic composite pipes (1), wherein the steel-plastic composite pipe (1) comprises an outer steel pipe (2), a hot melt adhesive layer (3) and an inner plastic pipe (4) sequentially arranged along its radial direction, characterized in that: The adjacent outer steel pipes (2) are connected by butt welding through radial expansion sections (5) arranged at their ends, and the radial expansion sections (5) and the outer steel pipes (2) are an integrated structure; the ends of the adjacent inner plastic pipes (4) are connected and a stuffing cavity (6) is formed between the radial expansion sections (5) connected by butt welding, and the radial expansion sections (5) are all provided with threaded holes (7) communicating with the stuffing cavity (6); the radial expansion section (5) of the outer steel pipe (2) is trumpet-shaped.

2. The butt welding connection structure of the steel-plastic composite pipe according to claim 1 is characterized in that: Filling material is injected into the filling cavity (6) through the threaded hole (7).

3. The butt welding connection structure of the steel-plastic composite pipe according to claim 1 or 2, characterized in that: A blocking bolt that matches the threaded hole (7) is installed on the threaded hole (7).

4. The butt welding connection structure of the steel-plastic composite pipe according to claim 1, characterized in that: The ends of adjacent inner plastic tubes (4) are connected by hot melting.

5. The butt welding connection structure of the steel-plastic composite pipe according to claim 1, characterized in that: A socket connection pipe (8) is further provided between the ends of the adjacent inner plastic pipes (4), and the two ends of the connection pipe (8) are respectively sleeved onto the outer sides of the ends of the two inner plastic pipes (4).

6. The butt welding connection structure of the steel-plastic composite pipe according to claim 5, characterized in that: A hot melt adhesive layer (3) is also provided between the inner wall of the socket-and-spigot joint pipe (8) and the outer wall of the inner plastic pipe (4).

7. The butt-welding connection structure of the steel-plastic composite pipe according to claim 5 or 6, characterized in that: The socket-and-spigot connection pipe (8) is a plastic pipe.

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