How to select and use fluorine-lined valves
Release date:
2022-07-12
In the chemical industry, many materials are corrosive. In these special cases, the selection of equipment, pipelines, and valves is crucial to ensure the stable operation of the facility. Most corrosive media have strong corrosive effects on metals; common metal valves such as carbon steel and stainless steel valves are quickly corroded. Additionally, fluorine-lined valves are expensive and have long processing cycles. So, let's learn together how to select and use fluorine-lined valves!
In the chemical industry, many materials are corrosive. In these special cases, the selection of equipment, pipelines, and valves is crucial to ensure the stable operation of the facility. Most corrosive media have strong corrosive effects on metals. Common metal valves such as carbon steel and stainless steel valves are quickly corroded; moreover, Fluorine-lined valves are expensive and have long processing cycles. So, let's learn together how to select and use fluorine-lined valves!
With the application of new chemical materials and improvements in furnace lining technology, fluorine-lined valves are safe, reliable, and cost-effective, favored by manufacturers and users. They are increasingly used in highly corrosive technical media in industries such as petroleum, chemical, and pharmaceuticals. However, fluorine-lined valves cannot adapt to all corrosive conditions. Like other valves, how to choose Fluorine-lined valves is a professional task.
Fluorine-lined valves The temperature should be about 30% below the upper limit.
Fluorine-lined valves Operating temperature: Common valve lining materials currently used include synthetic rubber (-10 to 120°C), polytetrafluoroethylene (PTFE) (-200 to 180°C), soluble polytetrafluoroethylene (PFA), and fluorinated ethylene propylene (F46) (-85 to 150°C). These are the publicly available temperature tolerances for various detectable materials, but the actual operating temperature of the medium varies depending on the material and pressure. Long-term operating temperature usually needs to be about 30% below the upper limit. Otherwise, the valve lining components are prone to deformation, causing increased leakage and valve malfunction such as failure to open or close properly.
Fluorine-lined valves are not suitable for high pressure and high pressure difference conditions.
Fluorine-lined valves use fluoroplastic linings and are generally not suitable for high vacuum conditions. When used in high vacuum, corresponding measures (such as grooving the inner cavity of the metal valve body or drilling holes in the valve plate) must be taken. The fluoroplastic lining inside the valve cavity may be pulled out and wrapped, causing the lining to separate from the metal layer, resulting in valve malfunction.
Similarly, fluorine-lined valves are not suitable for high pressure and high pressure difference conditions. Especially for bellows packing regulators (since bellows are mostly made of PTFE, they are prone to rupture under excessive pressure or pressure difference). For safety, manufacturers specify a nominal pressure of PN2.5MPa. However, due to special circumstances, solutions sometimes need to be found. The medium must not contain hard particles, crystals, impurities, etc.
Requirements for the medium of fluorine-lined valves:
The medium used in fluorine-lined valves must be free of hard particles, crystals, impurities, etc. The valve lining and bellows must not be worn during valve operation. If the medium contains hard particles, crystals, or impurities, corrosion-resistant precious metal materials such as Hastelloy, nickel-based alloys, or alloy steel hard-sealed valves can be selected according to the characteristics of the process medium. The valve size of fluorine-lined valves needs to be between 30% and 85%.
Fluorine-lined valves usually have a fluorine-lined bellows sealing structure, which has the advantages of good corrosion resistance and no leakage. When selecting, calculate the valve size based on process parameters. The normal opening should be within the range of 30% to 85%. If the valve size is too large, it will operate for a long time at a small opening, leading to a decline in valve regulation performance. Especially at small openings, not only does flushing become intense, but the medium's impact on the valve body and valve stem causes vibration, valve stem fracture, and bellows deformation.
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