How to choose the material for chlorine pipelines
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The pipes used for chlorine transfer in the production of benzyl chloride are steel-lined PTFE pipes. Experts, considering that chlorine is a highly toxic substance, required that the pipes be equipped with flanges of at least 20 kilograms capacity and a concave-convex design. However, it is essential that no metal ions enter the reaction system during the production of benzyl chloride; the existing standards for steel-lined PTFE pipes do not provide for flanges with a concave-convex design. The chlorine buffer tanks connected to these PTFE-lined pipes are fitted with safety valves and rupture discs set at a pressure of 0.3 MPa, while the PTFE-lined pipes themselves use flat-welded flanges rated at 2.5 MPa. These arrangements fully meet the requirements of the production process. Nevertheless, based on GB50316-2000, experts demanded that adjustments be made.
Just entrust experts with the funds allocated for the rectification efforts to purchase qualified equipment and components, right?
Chlorine is a highly toxic and highly corrosive substance; safety and process requirements must be taken into account when selecting pipe materials. Steel-lined PTFE pipes are very suitable for transporting chlorine, but according to the GB50316-2000 standard, experts recommend the use of flanges with a neck and a raised/recessed design of at least 20 kilograms to ensure higher safety levels; this may not be in line with the existing standard for butt-welded flanges at 2.5 MPa. Since metal ion contamination is not allowed in the production of benzyl chloride, it is possible to consider researching and developing suitable non-metallic flanges with necks and ridges, or to make technical improvements to meet the GB50316-2000 standards without affecting the production process. The installation of safety valves and rupture discs is a safety measure to ensure timely pressure release in case of overpressure. Overall, it is necessary to balance safety and process requirements to ensure that the pipeline system is both safe and capable of meeting production needs. It may be necessary to further communicate and negotiate with experts to reach a mutually agreed solution. .
The standards for steel-lined PTFE pipes do not specify flanges with necks; instead, flat-welded and slip-on flanges are used for PTFE pipes to facilitate their installation.
……It is indeed very difficult to solve; there is no better alternative… Our chlorine transmission pipes are also made of fluorinated steel tubes. Experts who inspected them raised this issue, explaining that the reaction is sensitive to metal ion contamination. Such pipes do not have flanges with uneven surfaces… After all, the operating pressure is low, usually around 1 kilogram, so this matter wasn’t addressed in the end. :)
Friends who are involved in design work and the use of chlorine are welcome to join the discussion
Talk to the expert and try to avoid having him mention it.
As the designer, I have checked it – the requirements regarding flanges fall under the mandatory provision 13.1.3.6 and must be met: 1. Flat welding (plate-type) flanges are prohibited; other types of flanges should be used instead； 2. Except when using weld lip gaskets, when other types of gaskets are used, the nominal pressure of the flange must be no less than 2.0 Mpa ； 3. When using soft gaskets, the sealing surfaces can only be male-female surfaces or tenon-socket surfaces ； 4. When hard gaskets are used, the sealing surface can be a raised surface or a ring-type joint surface ； If your equipment is properly designed, then you can hold them accountable and make them pay to make the necessary repairs; if not, then discuss with experts how to carry out the repairs.
Butt-welded raised-face flanges can be used; grooved or tenon-faced flanges cannot be lined