1.PVDF material properties
Poly(vinylidene fluoride), the abbreviation PVDF, mainly refers to a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and another small amount of fluorine-containing vinyl monomer.
PVDF applications are mainly used in the three major fields of petrochemical, electrical and electronic and fluorocarbon coatings. It has the following advantages:
1. It combines the characteristics of fluororesin and general-purpose resin.
2. It has good chemical resistance, high-temperature resistance, oxidation resistance, weather resistance, radiation resistance, electrical insulation, so that the equipment can meet TOCS and flame retardant requirements, and is widely used in the semiconductor industry. Storage and transportation of pure chemicals.
3. It also has special properties such as piezoelectricity, dielectric properties, and thermoelectric properties.
4. Good processability and resistance to fatigue and creep are one of the best materials for pumps, valves, pipes, piping fittings, storage tanks and heat exchangers for the whole or lining of fluid processing systems in petrochemical plants.
2.PVDF diaphragm valve actual use case
One of our customers purchased two PVDF diaphragm valves in 2013, which were used in a chlorine-containing brine and dechlorinated brine system.
Its working temperature is about 80 ° C, and the working pressure is 0.4 Mpa. Among them, the chlorine salt water is acidic and contains free chlorine, which is highly corrosive. The chlorine salt water is alkaline and the sodium chloride content is about 200 g/l. After one year of use, the valve diaphragm is intact, there is no leakage, and the use is good.
In view of the good use of the diaphragm valve in the light brine system, we continued to purchase a number of diaphragm valves for use in subsequent project projects.
It was reused in the chlorate decomposition tank unit and the secondary brine refining system, respectively.
Among them, the temperature of the light salt water in the chlorate decomposition device is above 90 ° C, and because of the strong acidity, containing free chlorine, the corrosion is strong, and the material requirements are relatively high.
The refined brine of the secondary brine refining system is alkaline, the temperature is about 60 ° C, the NaCl content is about 300-310 g / l, and the corrosion is relatively weak.
At present, the purchased by the PVDF diaphragm valve is kept intact, and there is no leakage of the valve or failure to switch due to corrosion. The use condition is good and does not affect production.