What material should be used for valves in formaldehyde pipelines?

304 will suffice; formalin solution causes little corrosion. The main problems are abrasion and crystallization caused by the slurry, so valves with a large sealing area and no dead corners should be chosen. Currently, three types of valves are in use in China: 1. Soft-sealed ball valves: Their performance is poor; the PTFE seat provides a linear seal, is not resistant to erosion, and prone to internal leakage ； The valve body has dead corners where the medium can accumulate and crystallize, resulting in an increase in torque. 2. Metal-sealed ball valves: These address the issue of seat vulnerability to erosion; however, the valve body still has dead corners, which lead to an increase in torque over time. Additionally, the cost is high; the overall cost is 3-4 times that of soft-sealed ball valves ； 3. Bushing plug valve: The valve seat features a 360-degree PTFE surface seal, providing a large sealing area and resistance to erosion ； The valve body has no dead corners or cavities, so there is no accumulation of fluid; the bushing is self-lubricating, allowing the valve to open and close smoothly even after long periods of inactivity. The cost is only about 10–20% higher than that of soft-sealed ball valves.

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