Large-diameter polyethylene pipeline joint welding process
By using linear high molecular weight polyethylene sheets and heating wires in the welding process of large-diameter polyethylene pipeline joints, combined with the design of the port vertical edge and reinforced ring layer, the problems of welding strength and construction difficulty of super large-diameter pipes are solved, and stable connection and efficient construction are achieved.
Patent Information
- Application Number
- CN202510445062.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2025-05-30
AI Technical Summary
It is difficult to effectively weld ultra-large diameter polyethylene pipelines with a diameter of more than 2 meters. The traditional hot melt welding machine is huge in size, the welding strength is difficult to guarantee, and the construction is difficult.
The welding process of large-diameter polyethylene pipe joints is adopted, including the use of linear high molecular weight polyethylene sheet circumferential welding to make the vertical edge of the port, the saw blade leveling the end face, the welding gun sealing the steel wire, the use of heating wire and nail gun to achieve the melt plasticization of the joint, and the joint strength is enhanced by the external and internal reinforcement of the ring layer.
The stable connection of large-diameter polyethylene pipeline joints is achieved, the connection performance and strength are improved, the construction process is simplified, and the long-lasting problem of traditional welding equipment technology is solved.
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Figure CN120056466A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of pipeline joint welding, and more specifically, to a welding process for large-diameter polyethylene pipeline joints. Background Art
[0002] Welding of large-diameter polyethylene pipeline joints with a diameter of more than 2 meters is currently blank. Due to the too large volume of traditional hot melt welding machines, the lifting time after the heating plate finishes heating the joints is too long, and the end faces of the joints will cool down significantly. The welding strength simply cannot be guaranteed. Moreover, the volume of the welding machine is very large, and the welding construction difficulty is too great. Summary of the Invention
[0003] The purpose of the present invention is to provide a welding process for large-diameter polyethylene pipeline joints, which can achieve stable connection of large-diameter polyethylene pipeline joints, improve the connection performance and strength of pipeline joints, and at the same time the construction is very light and simple. It effectively solves the long-standing difficult problems of the welding equipment process for ultra-large-diameter polyethylene pipelines.
[0004] The technical solution adopted by the present invention to solve its technical problems is: a welding process for large-diameter polyethylene pipe joints, including the following steps: ① At one end of the pipe to be welded, use a linear high-molecular-weight polyethylene sheet to perform circumferential welding at the outer peripheral position of the pipe joint to make the port vertical edge of the pipe joint; ② After the port vertical edge in step ① is made, use a saw blade to level the end face, and then use a welding torch to cover and seal the wire composite cut of the pipe end face to prevent the internal wire from being exposed, completing the processing of a single pipe joint. Subsequently, repeat steps ① and ② to make the pipe joints of another pipe to be welded; ③ After the pipe joints of the two pipes in step ② are made, continuously bend a heating wire into a W shape, use a nail gun to nail the heating wire to the end face of one of the pipes, and closely align the joints of the two pipes; ④ After the joints of the two pipes are closely aligned in step ③, install a clamp at the position of the port vertical edge to clamp and fix the port vertical edges on the two pipes; ⑤ After the clamp is installed in step ④, install a top support inner mold inside the two pipes corresponding to the joint position, and then energize the heating wire to heat it to achieve melting and plasticization between the two pipe joints; ⑥ After the two pipes are connected in step ⑤, remove the clamp, cut off the energized wire of the heating wire, and use a polyethylene welding torch to weld a circle of outer reinforcement ring layer at the outer joint position of the pipe joint; ⑦ After the outer reinforcement ring layer is welded in step ⑥, remove the internal top support inner mold, and use a polyethylene welding torch to weld a circle of inner reinforcement ring layer at the inner joint position of the pipe joint, thus completing the welding of the large-diameter polyethylene pipe joints. The width of the linear high-molecular-weight polyethylene sheet used in step ① is about 80 mm, and the thickness is 10 mm. In step ①, the linear high-molecular-weight polyethylene sheet is circumferentially welded two to three circles at the pipe joint position. The heating wire is evenly arranged on the end face of the pipe, the diameter of the heating wire is 0.8 - 1 mm, the center distance between adjacent bent heating wires is 10 mm, and there is a 5-mm clearance between the heating wire and the inner peripheral surface of the pipe and the outer peripheral surface of the port vertical edge. The clamp is two semi-circular welding molds sleeved up and down at the position of the port vertical edge. After the two semi-circular welding molds are connected and tightened, tighten the U-shaped clips on the semi-circular welding molds to clamp and fix the port vertical edges on the two pipes. Both ends of the semi-circular welding mold are provided with connecting plates and strengthening ribs, a fastening bolt is installed between the connecting plates of the two semi-circular welding molds, and a U-shaped clip is installed every 200 mm in the length direction of the semi-circular welding mold. The energizing heating time of the heating wire in step ⑤ is 25 - 35 minutes. The height of the outer reinforcement ring layer and the inner reinforcement ring layer is 10 mm, and the width is 20 mm.
[0005] The positive effects of the present invention are as follows: For a welding process of a large-diameter polyethylene pipe joint described in the present invention, through the prefabrication of the port vertical edge and the enhancement of the double joint end faces of the inner and outer reinforcement ring layers, a multi-layer molten composite structure is formed, effectively enhancing the axial tensile resistance and radial pressure-bearing capacity of the large-diameter pipe joint and solving the traditional hot-melt process. The uniform arrangement of the heating wires is combined with the clamping and fixing of the semi-circular welding die. Coupled with more than 30 minutes of airtight heating and pressurization, it fully ensures the plasticization and melting effect and strength of the joint.
[0006] The outer clamping card of the device, the U-shaped clips around the clamping card, and the weld inner support die wrap the joint inside and out, front and back, in an airtight die, realizing the high-temperature, high-pressure, and long-time welding and plasticization of the weld. The whole die structure is simple, very light in weight, and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 is a schematic diagram of the state after step ① of the present invention is completed; Figure 2 is a schematic diagram of the state after step ② of the present invention is completed; Figure 3 is a schematic diagram of the state after step ③ of the present invention is completed; Figure 4 is a schematic diagram of the state after step ④ of the present invention is completed; Figure 5 is a schematic diagram of the state after step ⑤ of the present invention is completed; Figure 6 is a schematic diagram of the state after step ⑥ of the present invention is completed; Figure 7 is a schematic diagram of the state after step ⑦ of the present invention is completed; Figure 8 is a schematic diagram of the arrangement of the heating wires on the pipe end face; Figure 9 is a schematic diagram of the structure of the semi-circular welding die; Figure 10 is Figure 5 a partial enlarged view of I in DETAILED DESCRIPTION OF THE INVENTION
[0008] A welding process of a large-diameter polyethylene pipe joint described in the present invention, as Figures 1-7 shown, includes the following steps: ① At one end of the pipe 1 to be welded, a linear high-molecular-weight polyethylene sheet is welded circumferentially at the outer peripheral position of the pipe joint to fabricate the port vertical edge 2 of the pipe joint; ②After the port vertical edge 2 in step ① is fabricated, use a saw blade to level the end face, and then use a welding torch to cover and seal the steel wire composite cut on the pipe end face to prevent the internal steel wires from being exposed, thus completing the processing of the joint of a single pipe. Subsequently, repeat steps ① and ② to fabricate the pipe joints of another pipe 1 to be welded. ③After the pipe joints of the two pipes 1 in step ② are fabricated, continuously bend a heating wire 3 into a W shape, use a nail gun to nail the heating wire 3 to the end face of one of the pipes 1, and closely align the joints of the two pipes 1. ④After the joints of the two pipes 1 are closely aligned in step ③, install a fixture at the position of the port vertical edge 2 to clamp and fix the port vertical edges 2 on the two pipes 1. ⑤After the fixture is installed in step ④, install a top support inner mold 5 inside the two pipes 1 corresponding to the joint position, and then energize and heat the heating wire 3 to achieve the melting and plasticization between the joints of the two pipes 1. ⑥After the two pipes 1 are connected in step ⑤, remove the fixture, cut off the energized wire of the heating wire 3, and use a polyethylene welding torch to weld an outer reinforcement ring layer 6 around the outer joint of the pipe joint. ⑦After the outer reinforcement ring layer 6 is welded in step ⑥, remove the internal top support inner mold 5, and use a polyethylene welding torch to weld an inner reinforcement ring layer 7 around the inner joint of the pipe joint, thus completing the joint welding of the large-diameter polyethylene pipe.
[0009] The fixture can be two semi-circular welding molds 4 that are sleeved up and down at the position of the port vertical edge 2. After the two semi-circular welding molds 4 are connected and tightened, tighten the U-shaped clips on the semi-circular welding molds 4 to clamp and fix the port vertical edges 2 on the two pipes 1.
[0010] In step ①, one end of the pipe 1 can be sleeved on a rotating mold and clamped and fixed. The pipe 1 is driven to rotate by the rotating mold. At the joint end of the pipe 1, a linear high molecular weight polyethylene sheet can be extruded through an extruder. During the rotation of the pipe 1, it is heated and pressed and welded to the outer circle of the pipe port through a welding device, so that the sheet and the pipe body form a continuous and uniform molten bonding layer. For a pipe 1 with a smaller diameter, one circle of sheet can be welded; for a pipe 1 with a larger diameter and higher pressure, two to three circles can be welded. After each layer of welding is completed, use an infrared thermometer to detect the temperature of the fusion line, and wait until it drops below 80 °C for subsequent operations. The width of the linear high molecular weight polyethylene sheet used in step ① can be 80 mm, and the thickness can be 10 mm.
[0011] In step ②, level the end face of the welded port to ensure that the flatness tolerance is within the set range. After cleaning the chips, the welding torch seals and welds the steel wire composite cut. The sealing layer needs to cover the cut edge and extend 10 mm to the pipe body to form a smoothly transitioning closed surface.
[0012] In step ③, the heating wire 3 is evenly arranged on the end faces of the pipe 1 and the port vertical edge 2. The diameter of the heating wire 3 can be 0.8 - 1 mm, the center distance between adjacent bent heating wires is 10 mm, and there is a 5 - mm clearance between the heating wire 3 and the inner peripheral surface of the pipe 1 and the outer peripheral surface of the port vertical edge 2. The heating wire 3 covers the pipe 1 and the port vertical edge 2 added on the outer periphery, realizing the simultaneous welding of the pipe 1 and the port vertical edge 2 to ensure sufficient heating and melting of the pipe end face without affecting the initial structure and connection performance of the pipe. When two pipes are butted, a laser alignment instrument can be used to adjust the axial deviation ≤ 0.5 mm, and the end face misalignment is controlled within 0.2 mm.
[0013] In step ④, two semi - circular welding molds 4 are sleeved at the port vertical edge 2. First, the lower mold is installed, and then the upper mold is closed. A set torque is applied for pre - tightening through the fastening bolt 10, and the U - shaped clips are tightened every 200 mm along the length direction of the mold. One end of the U - shaped clip is a fixed end, and the other end is a movable end. The movable end can be a screw rod, which is threadedly fastened to the U - shaped clip, and a hexagonal block is installed on the screw rod to facilitate the rotation and clamping of the movable end by tools such as a wrench.
[0014] The main structure of the semi - circular welding mold 4 is a semi - circular arc - shaped stainless - steel plate. Connecting plates 8 and reinforcing ribs 9 are arranged at both ends of the semi - circular welding mold 4. A fastening bolt 10 is installed between the connecting plates 8 of the two semi - circular welding molds 4, and a U - shaped clip is installed every 200 mm in the length direction of the semi - circular welding mold. Through the fastening bolt 10, the upper and lower groups of semi - circular welding molds 4 can be connected and tightened at the pipe joint position, and through the U - shaped clip, the port vertical edge 2 of the pipe joint can be clamped and fixed.
[0015] In step ⑤, a top - support inner mold 5 made of stainless - steel plate is installed at the joint part inside the pipe, which abuts against the weld. In this way, the joint with the heating wire is tightly pressed and sealed on four sides by the top - support inner mold 5 and the two semi - circular welding molds 4. After being energized for about 25 - 35 minutes, the joint has sufficient time to melt and plasticize in the high - temperature and high - pressure mold, ensuring the welding strength of the joint and the reliability of the welding process. A hydraulic device can be used to push the top - support inner mold 5 into the pipe interior to make it evenly contact with the inner wall of the pipe. A programmable power supply can be used to energize the heating wire for staged temperature rise: keep at 220 °C for the first 10 minutes, rise to 240 °C in the middle 15 minutes, and keep constant temperature for the last 10 minutes. After heating is completed, keep the pressure and cool for 30 minutes, and continuously monitor the temperature field distribution of the mold during this period.
[0016] In steps ⑥ and ⑦, first remove the semi-circular welding die 4 on the outer side of the pipeline, then weld the outer reinforcement ring layer 6 at the outer joint, and subsequently remove the top support inner die 5 inside the pipeline, and weld the inner reinforcement ring layer 7 at the inner joint position of the pipeline to form a reinforcement structure symmetrical to the outer joint. During the welding process, the weaving welding process can be adopted to make the outer reinforcement ring layer 6 and the inner reinforcement ring layer 7 form a trapezoidal cross-section weld bead with a height of 10 mm and a width of 20 mm. After welding, ultrasonic testing is carried out to ensure that there are no defects such as pores and cracks. Finally, a hydrostatic test is carried out, and the test pressure is 1.5 times the working pressure. It is qualified if there is no leakage after maintaining the pressure for 2 hours.
[0017] The above welding process solves the long-standing problem that large-diameter and extra-large-diameter pipelines cannot be welded. It paves the way for the popularization and use of large-diameter and extra-large-diameter pipelines. This process breaks through the diameter limitation of traditional hot-melt welding and is especially suitable for long-distance large-diameter polyethylene pipeline projects such as municipal sewage discharge and industrial transportation, providing reliable technical guarantee for pipeline connection.
[0018] The technical solution of the present invention is not limited within the scope of the embodiments described in the present invention. The technical content not described in detail in the present invention is all well-known technologies.
Claims
1. A large-diameter polyethylene pipe joint welding process, characterized in that: The method comprises the following steps: ① at one end of a pipe (1) to be welded, a linear high molecular weight polyethylene sheet is circumferentially welded to the outer circumference of a pipe joint to produce a vertical edge (2) of the pipe joint; ② After the end vertical edge (2) of step ① is completed, the end face is leveled using a saw blade, and then the composite steel wire cut of the pipe end face is sealed and covered using a welding gun to prevent the internal steel wire from being exposed, completing the processing of a single pipe joint, and then repeating steps ① and ② to make another pipe joint for the pipe to be welded (1); ③ After the pipe joints of the two pipes (1) in step ② are completed, a heating wire (3) is continuously bent into a W shape, and the heating wire (3) is nailed to the end surface of one of the pipes (1) using a nail gun, and the joints of the two pipes (1) are closely aligned; ④ After the joints of the two pipes (1) are aligned closely in step ③, a clamp is installed at the position of the port vertical edge (2) to clamp and fix the port vertical edge (2) on the two pipes (1); ⑤ After the fixture is installed in step ④, a top support inner mold (5) is installed inside the two pipes (1) corresponding to the joint position, and then the heating wire (3) is powered on for heating to achieve melting and plasticization between the joints of the two pipes (1); ⑥ After the two pipes (1) are connected in step ⑤, remove the clamp, cut off the live wire of the heating wire (3), and use a polyethylene welding gun to weld a circle of outer reinforcement ring layer (6) at the outer seam position of the pipe joint; ⑦ After the repair welding of the outer reinforcement ring layer (6) in step ⑥ is completed, the internal top support inner mold (5) is removed, and a polyethylene welding gun is used to repair weld a circle of the inner reinforcement ring layer (7) at the inner seam position of the pipe joint, thereby completing the joint welding of the large-diameter polyethylene pipe.
2. A large-diameter polyethylene pipe joint welding process according to claim 1, characterized in that: The linear high molecular weight polyethylene sheet used in step ① has a width of 80 mm and a thickness of 10 mm.
3. A large-diameter polyethylene pipe joint welding process according to claim 1, characterized in that: In step ①, the linear high molecular weight polyethylene sheet is circumferentially welded two to three times at the pipe joint position.
4. A large-diameter polyethylene pipe joint welding process according to claim 1, characterized in that: The heating wires (3) are evenly arranged on the end surface of the pipe (1), the diameter of the heating wires (3) is 0.8-1 mm, the center spacing of adjacent bent heating wires is 10 mm, and a gap of 5 mm is left between the heating wires (3) and the inner circumference of the pipe (1) and the outer circumference of the port vertical edge (2).
5. A large-diameter polyethylene pipe joint welding process according to claim 1, characterized in that: The clamp comprises two semicircular welding dies (4) which are mounted on top of each other at the position of the port vertical edge (2). After the two semicircular welding dies (4) are connected and tightened, the U-shaped clamps on the semicircular welding dies (4) are screwed to clamp and fix the port vertical edges (2) on the two pipes (1). Both ends of the semicircular welding dies (4) are provided with connecting plates (8) and reinforcing ribs (9). A fastening bolt (10) is installed between the connecting plates (8) of the two semicircular welding dies (4). A U-shaped clamp is installed every 200 mm in the length direction of the semicircular welding dies.
6. A large-diameter polyethylene pipe joint welding process according to claim 1, characterized in that: In step ⑤, the heating wire (3) is powered on for 25-35 minutes.
7. A large-diameter polyethylene pipe joint welding process according to claim 1, characterized in that: The outer reinforcement ring layer (6) and the inner reinforcement ring layer (7) have a height of 10 mm and a width of 20 mm.