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1: For process handover, nitrogen purging is employed, and the oxygen pipeline is maintained in a slightly positive nitrogen pressure environment. II: The horizontal flanges of vertical pipelines are to be removed following these steps: 1. There are 8 bolts per flange; remove 4 of them first (remove them at intervals). 2. Use a steel brush and screwdriver to clean off the rust from the outer ring of the gasket, and blow it with nitrogen until no residual rust remains. 3. Install 4 new bolts and tighten them, then remove the other 4 old bolts. 4. Repeat step 2. 5. Verify through the process that nitrogen is at a slight positive pressure. 6. Before loosening the bolts, consult with the maintenance and workshop technicians to ensure that the flange surface is clean and free of scale. After the bolts are loosened, insert a 1 mm thick piece of stainless steel between the gasket and the lower flange in order to lift the gasket out. 7. Remove the flange from the valve, take the valve off, and degrease its interior before sealing it ； Clean the sealing surfaces of the upper and lower flanges by scraping from the inside out; the sealing surfaces can be soaked in CCL4 first to prevent dust formation, and attention should be paid to the wind direction in the environment. 8. The pipe section is removed and subjected to degreasing and sealing treatment. 9. Clean the sealing surface thoroughly, then install the new gasket and cross-pressure wires. The new gasket must be degreased in the factory and allowed to air-dry until it is odorless; it should then be wrapped in clean, oil-free plastic sheeting before being taken to the site. IV.3. Horizontal pipelines with vertical flanges shall be replaced following these procedures: 1. Remove the bolts at intervals, clean off any rust on the gaskets, and purge them with nitrogen. 2. Maintain a slight positive nitrogen pressure in accordance with the process requirements. 3. Remove the remaining bolts and pull out the gaskets. 4. Degrease the pipe ends on both sides and clean the flange sealing surfaces. 5. Reinstall the pad. V. Safety precautions: 1. Technical personnel from the repair and manufacturing department must be present during the construction process. 2. The personal protective equipment of construction workers, construction tools, and the work area must be free of oil to prevent secondary pollution; bolts used for pads must also be degreased. 3 The degreasing area should be well-ventilated, clean, and protected from rain and dust. 4. After degreasing, the parts should have any surface solvents removed until no residues or odors remain; they should then be wrapped in clean, oil-free plastic cloth and set aside for later use. 5. Cotton yarn should not be used for scrubbing degreased parts; instead, silk or glass fiber fabrics with fibers that do not easily fall off should be used. After degreasing, a thorough inspection should be carried out to ensure that there are no fiber residues on the surface of the parts. 6. The work on the disconnected flanges must be carried out continuously until completion, and the workers must not leave the site during this process. 7. During construction, pay attention to protecting the flange openings and prevent any foreign objects from entering ； If any foreign object falls in, contact us promptly to take action. 8. All tools used must be clean and oil-free, and the equipment used for cleaning the flange surfaces must be degreased. 9. All flanges should be tightened in two to three stages. Use a caliper to check that the gap between the flange surfaces is uniform, with the dimensional deviation at the symmetric points being less than 0.2 mm, to ensure no leakage after pressurization. 10. All jumper wires on the flanges shall be fully installed to ensure reliable contact.