Operating Procedures for Butt Welding of PE Pipeline Systems

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Operating procedures for butt welding of PE pipe systems – General provisions: 1 Before connecting polyethylene gas pipes, the pipes, fittings, and associated equipment must be checked in accordance with the design requirements, and a visual inspection must be carried out at the construction site; they may only be used if they meet these requirements. 　　2 The connection of polyethylene gas pipelines shall be achieved through electrofusion joining (electrofusion socket spigot joining, electrofusion saddle joining) or heat fusion joining (heat fusion socket spigot joining, heat fusion butt joining, heat fusion saddle joining); threaded joining and bonding shall not be used. When connecting polyethylene pipes to metal pipes, steel-plastic transition fittings must be used. 　　3 Different connection types for polyethylene gas pipelines should use corresponding specialized connection tools. Do not use an open flame for heating during connection. 　　4 For the connection of polyethylene gas pipelines, it is advisable to use pipes and fittings of the same grade and material. For the connection between pipes of different grades and materials with similar performance, or between pipes and fittings, testing must be conducted; such connections may only be carried out once it is confirmed that the quality of the connection can be guaranteed. 　　5 Before starting work on connecting polyethylene gas pipelines, operators must receive specialized training; they may only begin working after passing examinations and technical assessments. 　 6 When performing connection operations in cold climates (below -5°C) and strong wind conditions, protective measures should be taken or the connection process adjusted. 　　7 When there is a significant temperature difference between the storage area for polyethylene gas pipes and fittings and the construction site, the pipes and fittings should be placed at the construction site for a certain period of time before connection, so that their temperature approaches that of the construction site. 　　8 When connecting polyethylene gas pipelines, the pipe ends must be clean. At the end of each shift, the pipe outlet should be temporarily sealed. 　　9 After the connection of polyethylene gas pipelines is completed, an inspection of the visual quality of the joints should be carried out. Those that fail must be reworked, and after rework, the visual quality of the joints must be inspected again. Hot melt welding: 1. Before and after hot melt welding, any dirt on the heating surface of the welding tool should be wiped clean with a clean cotton cloth. 　　2 The heating time and temperature for heat fusion welding shall comply with the specifications set by the manufacturer of the heat fusion welding tool, as well as those of the manufacturers of the pipes and fittings. 　 3 The holding time and cooling time for heat fusion bonding shall comply with the specifications set by the manufacturers of the heat fusion bonding tools as well as those of the pipes and fittings. During the holding and cooling periods, the connected components must not be moved, nor any external force applied to them. 　　4. Hot melt butt joints shall comply with the following requirements: (1) Before performing the butt joint, each pipe segment shall extend a certain free length outside the fixture, and the corresponding connectors shall be aligned so that they are on the same axis; the misalignment shall not exceed 10% of the wall thickness. 　　(2) The dirt on the connection surfaces of the pipes or fittings should be wiped clean with a clean cotton cloth. The connection surfaces should be milled to be perpendicular to the axis and to fit precisely with the corresponding sections to be connected. 　　(3) The end faces to be connected should be heated using a butt jointing tool. 　　(4) After heating is complete, the connectors should be quickly removed from the heating tool used for joining them, and a uniform external force should be applied to ensure full contact between them, thereby forming a uniform flange. Relevant procedures: 1. Check whether the temperature of the heating plate is within the range required by the process (210±10 degrees). 2. Clean the heating plate with a clean cotton cloth. 3. The welding pressure for the budgeting system of welding equipment driven by a hydraulic system. 4. Clamp the pipe (components) together on the welder simultaneously, and keep the ends aligned. 5. Mill the two end surfaces to be welded using a milling tool, and start welding immediately after milling is completed. 6. Place the heating plate in position so that the two end surfaces of the pipe (component) are in close contact with the heating plate, and apply a certain amount of pressure. The timing for the first phase begins at the same time. 7. When the height of the molten ring reaches the standard height, reduce the applied pressure to only that required for traction, and simultaneously start timing for the second phase. 8. When the time meets the specified requirements, turn the feed handle to release the pipes (components) at both ends and remove the heating plate. 9. Smoothly close the tubing (components); timing for the fourth stage begins when the pressure reaches the specified value. 10. After the completion of the fourth stage, if necessary, the pressure can be reduced and timing for the fifth stage (cooling stage) can be started again. 11. Allow the molten zone to cool fully; external forces must be avoided, and no forced cooling methods shall be used. After cooling is complete, remove the fixture. Hot melting parameters: 1. Temperature range of the heating plate: (210±10 degrees). 2. Hot melting time: Nominal wall thickness × 10 seconds. 3. Cooling time: Nominal wall thickness / 2 + 10 minutes. Joint parameters: The flanging width (for dn75–125) is between 8–15 mm. Mechanical properties: The joint strength must be higher than that of the pipe itself; the elongation at break should be ≥350%, and the crack should not occur at the joint. The hydraulic test meets the requirements for the pipes.