Have you ever used high-temperature resistant, oxygen-resistant soft seals?
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The medium is pure oxygen, at a temperature of around 350 degrees Celsius. For sealing the gap between the two tubes, it’s also important to consider how to install and remove the tubes. Using metal seals can easily damage the inner wall of the outer tube, while with graphite-based seals, the wall of the tube may stick to the graphite. It would be best to use inorganic seal rings that are flexible and capable of withstanding high temperatures. I wonder if anyone has used such seals before?
The gasket to be used for oxygen pipelines is selected based on the operating pressure of the oxygen. It is specified in 8.4.2 of GB 16912-1997 Safety Technical Regulations for Oxygen and Related Gases. 8.4.2 Flanges on oxygen pipelines shall be selected in accordance with **relevant current standards ； The gaskets for pipe flanges should be selected according to Table 12. Table 12 Gaskets for oxygen pipeline flanges. Working pressure in MPa: Gaskets for pressures ≤ 0.6 – rubber-asbestos sheets; for pressures >0.6–≤ 3.0 – wound gaskets, polytetrafluoroethylene gaskets; for pressures >3.0–≤ 10 – corrugated metal-asbestos gaskets, wound gaskets, polytetrafluoroethylene gaskets, annealed and softened aluminum sheets, copper sheets; for pressures >10 – annealed and softened copper sheets. This is also specified in Article 9.0.4 of the “GB50030—91 Code for Design of Oxygen Stations”. Article 9.0.4 Flanges on oxygen pipelines shall be selected in accordance with **the relevant current JB standards ； The gaskets for pipe flanges should be selected in accordance with Table 9.0.4. Gaskets for oxygen pipeline flanges: Table 9.0.4 – Operating pressure (MPa). For pressures ≤0.6, rubber-asbestos sheets are used; for pressures between 0.6 and 3, wound gaskets or wave-shaped metal-encased asbestos gaskets are employed. For pressures >10, annealed and softened aluminum sheets or annealed and softened copper sheets are used. Considering the temperature of the oxygen, annealed and softened copper sheets seem to be the only viable option. However, if you do not want to use metallic seals due to certain concerns outlined in the equipment specifications, you might consider trying high-temperature resistant single-component silicone sealants used in automotive applications, such as Loctite 569. Please feel free to offer your suggestions