Selection of float material for magnetic flap level gauge under different application conditions

　　The magnetic flap level gauge works on the principle of connected vessels and magnetic coupling. The magnetic flap level gauge forms a connected vessel structure with the measured container through its main float. Since the main float, as the core component of the magnetic flap level gauge, is in direct contact with the measured liquid, if the material of the main float is not properly selected, it will either increase the cost of the instrument or the cylinder will be easily corroded, causing leakage, thus causing failures and even production accidents. It can be seen that the choice of the material of the float of the magnetic flap level gauge will directly affect the reliability and economy of the instrument.

　　Due to the complex and changeable working conditions of industrial production sites, there are many types of media, such as highly corrosive, highly permeable, and highly viscous media, and the requirements for the material specifications of the main float are also different. This requires us to select the material specifications of the float according to the actual application conditions and the characteristics of the measured medium. So, how should the material of the magnetic flap level gauge float be selected under different application conditions?

　　1. The main float is made of 304 stainless steel. 304 stainless steel is a chromium-nickel stainless steel material with strong versatility. Its density is about 7.93g/cm3. It has good welding performance and general corrosion resistance. It is cheap and widely used in the instrument industry. Especially in a dry and clean atmospheric environment, 304 stainless steel is often used to measure the liquid level of circulating water, industrial discharge water, industrial waste water, tap water, grease, and some weak acids and alkalis in the industrial production process.

　　2. The main buoy is made of 316L stainless steel. If the liquid medium mentioned above is high temperature or has a certain degree of corrosiveness, 304 stainless steel is generally not used, but 316L stainless steel is used instead. This is because 316L stainless steel is a type of molybdenum-containing stainless steel with a density of 0.78 g/cm3. Since the steel contains molybdenum and has a low carbon content, it is more resistant to the precipitation of carbides at high temperatures, which improves the corrosion resistance and is more corrosion-resistant than 304 stainless steel in high temperature environments. Furthermore, since 316L contains the Mo element, it has good resistance to pitting corrosion and is more resistant to chloride erosion. Generally, 316L stainless steel is also used for the main buoy in marine environments and corrosive industrial atmospheres. In addition, 316L stainless steel also has good welding performance, can be welded using standard stainless steel welding methods, and does not require annealing treatment.

　　3. The main float is made of PP material. In the chemical production industry, there are often some low-concentration organic or inorganic acids, alkalis, salt liquids and industrial wastewater. These liquids are corrosive to a certain extent. For example, under normal temperature and low pressure conditions, PP plastic magnetic flap level gauges are generally used, which are more economical and applicable. PP polypropylene plastic is a semi-crystalline thermoplastic plastic with a melting point of 164-170°C and a density of 0.90-0.91g/cm3. It can withstand the corrosion of most low-concentration organic and inorganic acids, alkalis and salts. However, its corrosion resistance is not as good as that of polytetrafluoroethylene material, it is sensitive to ultraviolet rays, and its weather resistance is slightly worse. Therefore, PP plastic is generally not used for highly corrosive media and when there are high requirements for weather resistance. PP plastic magnetic flap level gauges are generally used in indoor working conditions with a temperature of T≤60°C and a pressure of P≤0.4MPa.

　　4. The main float is lined with F4 or F46. When encountering some highly corrosive liquid media, such as strong acid and alkali solutions, and various organic solvents, etc., to measure the liquid level of these media, it is necessary to use a lined anti-corrosion magnetic flap level gauge. It achieves the required corrosion resistance by lining the inner wall of the measuring tube. Jiwei Automation can provide the market with lined polytetrafluoroethylene type and lined polytetrafluoroethylene propylene type. For most strong acids and alkalis such as sodium hydroxide, concentrated sulfuric acid, hydrochloric acid, tetrachloroethylene, etc., use lined F4 (polytetrafluoroethylene) anti-corrosion magnetic flap level gauge; for highly permeable media such as liquid chlorine, it is generally necessary to use lined F46 (polytetrafluoroethylene propylene) anti-corrosion magnetic flap level gauge. Polytetrafluoroethylene material is one of the most corrosion-resistant materials in the world today, commonly known as the "plastic king", with high chemical stability and excellent chemical corrosion resistance. The long-term use temperature is -200~+250℃, and it is widely used in lining anti-corrosion materials. Usually, stainless steel lined magnetic flap level gauges have high structural strength and corrosion resistance, and can generally be used under working conditions of temperature T≤120℃ and P≤1.6MPa.

　　5. Vacuum jacket, electric heating or steam jacket is used on the outside of the float. For the measurement of the liquid level of some low-temperature liquid media, such as liquids below -5℃, frost is easy to form on the outer surface of the float or indicator, covering the indicator flag and even causing the indicator to fail to work. For such working conditions, a vacuum jacket structure is generally used for isolation to prevent frost. If the measured liquid is viscous and easy to freeze in winter, electric heating or steam jacket can be used for insulation to ensure the fluidity of the liquid and enable the magnetic float to work normally.

　　Therefore, when selecting a magnetic flap level gauge, the corresponding material and model should be selected according to different working conditions and medium characteristics, so that it is both economical and practical, reliable and durable.