What are the precautions for using fluorine lined gate valves?

With the maturity of fluorine lining technology, there are more and more varieties of fluorine lining gate valves, including fluorine lining diaphragm valves, fluorine lining butterfly valves, fluorine lining ball valves, fluorine lining check valves, fluorine lining stop valves, fluorine lining filters, etc. The great advantage of fluorine lined gate valves is that they can control highly corrosive media. The rated pressure is 0.6-1.6Mpa, suitable for working conditions with temperatures below 150 ℃. There are various lining materials for fluorine lined valves, and different materials are suitable for different media and temperatures. Users should choose the correct type based on actual working conditions.



Fluorine lined gate valves are widely used in equipment exposed to strong corrosive media such as acid and alkali in industries such as petroleum, chemical, pharmaceutical, metallurgy, and power. However, based on the on-site application experience of many users over the years, when selecting fluorine lined gate valves, the following precautions should be proposed for the use conditions such as medium temperature, pressure, and differential pressure:



1. Medium requirements for fluorine lined gate valves: There should be no hard particles, crystals, impurities, etc. to prevent the valve from wearing the fluorine lining layer or PTFE corrugated pipe of the valve core and valve seat during opening and closing operations. For media containing hard particles, crystals, and impurities, when choosing fluorine lined gate valves, Hastelloy alloy can be used for the valve core and seat.



2. The medium temperature used for fluorine lined gate valves: The common fluorine lined gate valves use F46 (FEP), and the medium temperature used should not exceed 150 ℃ (the medium temperature can reach 150 ℃ for a short time, and be controlled within 120 ℃ for a long time). Otherwise, the F46 lining of each component of the valve is prone to softening and deformation, resulting in the valve being unable to fully close and a large amount of leakage. If the medium temperature used is below 180 ℃ for a short period of time and below 150 ℃ for a long period of time, another fluoroplastic PFA can be chosen.



3. When using fluorine lined gate valves, the pressure and differential pressure conditions should be controlled within the allowable range, especially for fluorine lined regulating valves and fluorine lined globe valves sealed with corrugated pipes. Due to the fact that the corrugated pipe is made of PTFE material, the pressure and pressure difference are relatively large, which can easily lead to the rupture of the corrugated pipe. If the pressure and pressure difference are large, the fluorine lined regulating valve sealed by the corrugated pipe can be replaced with a PTFE packing seal.



4. When using fluorine lined valves, there should be no negative pressure. Fluorine lined valves should avoid generating negative pressure in the pipeline in use. If there is negative pressure, it is easy to cause the fluorine lining layer in the valve chamber to be sucked out (bulged out) and peeled off, resulting in valve opening and closing failure.



5. The diameter and opening of the fluorine lined valve should be calculated based on the required flow rate (Cv value) and other technical parameters. If the valve diameter is too large, it will inevitably cause the valve to operate at a small opening for a long time. With the pressure of the medium, it is easy for the valve core and valve stem to vibrate under the impact of the medium. The valve core rod is prone to fracture under long-term impact of the medium. When selecting various fluorine lined gate valves, it is necessary to understand and master the technical conditions of use as much as possible, in order to better select and use fluorine lined gate valves, thereby improving the service life of the valves.