After welding the fire protection pipes, they are galvanized; how can the flange surfaces be protected from damage?
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For fire protection pipes larger than 2 inches in diameter, it is required to first weld them into sections equipped with flanges, and then subject those sections to hot-dip galvanizing. The flanges used are those with protrusions and water ripple patterns. How can the sealing surfaces of the flanges be protected from being damaged by the galvanizing process?
Before hot-dip galvanizing, the sealing surfaces of the flanges can be covered with a high-temperature resistant protective film or temporary sealant. Ensure that the selected material can prevent zinc melt from seeping in and can withstand the high temperatures during the hot-dip galvanizing process. After galvanizing is complete, remove the protective material thoroughly. .
【Ten Years of Rapid Development in Chemical Engineering Equipment】1982–2024: The complete set of equipment for Shudao Equipment’s first overseas LNG integrated fueling station project https://bbs.hcbbs.com/thread-5671905-1-1.html (Source: Haichuan Chemical Industry Forum)
On the flange sealing surfaces of the entire pipeline, the polyurethane coating is applied repeatedly, left to dry, followed by overall pickling, immersion in a pre-treatment solvent, and treatment in a liquid zinc bath. See the invention patent “A method for isolating the sealing surface of pipeline hot-dip galvanized flanges”. https://wenku.baidu.com/view/e71f97c07175a417866fb84ae45c3b3566ecdd47?fr=xueshu&_wkts_=1760600582507 It has also been suggested to apply high-temperature greases such as Molykote to the flange sealing surfaces; it’s not clear whether this approach is feasible.