How to choose materials for liquid chlorine, cyanogen chloride, and highly toxic chlorinated substances
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I urge all experts to share their insights: I’m not sure which material to choose among the several available options; please help me make a decision. 1. Liquid chlorine: to be transported at 25°C (under an operating pressure of 1.5 MPa), with the pipes insulated. Liquid chlorine is commonly transported at low temperatures; 16MnD steel is used for the pipelines. According to corrosion manuals, carbon steel can be used only at 25°C and not at 50°C, so it’s unclear what material would be suitable in this case. 2. Process gas: low pressure, high temperature (380°C); mainly cyanuric chloride gas, with an additional amount of Cl2 at 10 kg/h ； CO2: 3.5kg/h ； CNCl: small amount ； H2O ＜1kg/h ； This medium is characterized by high temperatures, extreme toxicity, and chlorine corrosion; it’s not clear whether M400 or IN600 should be used, or if some other more suitable material would be better. 3. Exhaust gas: low pressure, temperature of 250°C; the main component is air, with small amounts of Cl2 present as well ； CNCl: small amount ； A small amount of H2O ； This medium is highly toxic and corrosive due to chlorine; it’s not clear whether 304L or some other more suitable material should be used. 4. Cyanogen chloride gas: At low pressure and a temperature of 250°C, it might be possible to use 316L, given its similar properties to hydrogen chloride. 5. For waste gases and liquids with moderate temperatures (below 140°C) whose main components are Cl2, CNCl, HCN, HCl, NH4Cl, HCl, and H2O, the composition is complex, involving both corrosive effects and high toxicity. It is considered appropriate to increase the pressure rating to PN25 and use PTFE-lined pipes; in this case, soft gaskets would be required. According to GB50316, soft gaskets must be used for highly toxic media, and flanges with male and female threads are required. However, it turns out that flanges with such threading cannot be manufactured for lining purposes, so it’s not clear what to do.
Fourth question: The lined flange comes with a flange edge, which is equivalent to an RF flange. As long as the pressure rating is sufficient, there will be no problem. PN25 is too demanding; 1.5 MPa is sufficient
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1. Liquid chlorine (high purity), at 25 degrees Celsius: The valve body should be made of WCB; the diaphragm can be made of either 304 or 316. Pads made of PTFE offer a high level of safety.
2. Process gas (380 degrees Celsius): The valve body should be made of WC6; the diaphragm can be made of 316L or HC276 – the choice depends on the corrosivity under actual operating conditions. Pads made of graphite or 304 metal-wound gaskets provide a high level of safety.
3. Waste gas (250 degrees Celsius): The valve body should be made of WCB; the diaphragm can be made of 316L or HC276 – the choice depends on the corrosivity under actual operating conditions. Pads made of graphite or 304 metal-wound gaskets provide a high level of safety.
4. Cyanogen chloride gas (250 degrees Celsius): The valve body should be made of WCB; the diaphragm can be made of 316L or HC276 – the choice depends on the corrosivity under actual operating conditions. Pads made of graphite or 304 metal-wound gaskets provide a high level of safety.
5. For temperatures below 140 degrees Celsius, PTFE pads can be used due to their excellent corrosion resistance. (For media in items 2, 3, and 4, which are not highly corrosive in gaseous form, it is necessary to consider whether moisture may be generated after shutdown or cooling, thereby increasing corrosion in the pipes; specific measures such as pipe flushing should be implemented.) ——————The above information relates to valve material selection and is not applicable to other components. For further technical consultations, please call 0577-67978896. Newton Fluid Technology Co., Ltd., China – a company with over a decade of experience in manufacturing diaphragm valves
2. Process gas (380 degrees Celsius): The valve body should be made of WC6; the diaphragm can be made of 316L or HC276 – the choice depends on the corrosivity under actual operating conditions. Pads made of graphite or 304 metal-wound gaskets provide a high level of safety.
3. Waste gas (250 degrees Celsius): The valve body should be made of WCB; the diaphragm can be made of 316L or HC276 – the choice depends on the corrosivity under actual operating conditions. Pads made of graphite or 304 metal-wound gaskets provide a high level of safety.
4. Cyanogen chloride gas (250 degrees Celsius): The valve body should be made of WCB; the diaphragm can be made of 316L or HC276 – the choice depends on the corrosivity under actual operating conditions. Pads made of graphite or 304 metal-wound gaskets provide a high level of safety.
5. For temperatures below 140 degrees Celsius, PTFE pads can be used due to their excellent corrosion resistance. (For media in items 2, 3, and 4, which are not highly corrosive in gaseous form, it is necessary to consider whether moisture may be generated after shutdown or cooling, thereby increasing corrosion in the pipes; specific measures such as pipe flushing should be implemented.) ——————The above information relates to valve material selection and is not applicable to other components. For further technical consultations, please call 0577-67978896. Newton Fluid Technology Co., Ltd., China – a company with over a decade of experience in manufacturing diaphragm valves