Issue regarding the hardening method of the sealing surface in 904L ball valves

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Dear sea industry professionals: In the production facilities for oxalic acid, due to the strong corrosive nature of oxalic acid, design institutes generally choose 904L material for the valve body, valve ball, and valve seat when designing ball valves. When selecting ball valves, the sealing surfaces of hard-sealed ball valves are hardened; this means that there should be a difference in hardness between the valve ball and the valve seat, and it is also necessary to ensure that the hardening method and materials are suitable for working under oxalic acid conditions. We invite all industry professionals and experts to share their opinions and views. Thank you! Note: 1. Due to the presence of oxalic acid crystals in the medium, the use of soft-sealed valve seats is not recommended according to the design. 2. Oxalic acid concentration: 25%-35%, temperature: 25°C~80°C.