2. The sealed floating ball pneumatic ball valve of the floating pneumatic ball valve has simple structure and good sealing performance, but the load of the working medium borne by the ball is all transferred to the outlet seal ring, so whether the seal ring material can withstand the working load of the ball medium is the key. Generally speaking, sealing rings are made of elastic materials such as polytetrafluoroethylene, and metal and non-metallic materials form a sealing pair, which is usually called soft seal.

Principle of electromagnetic flowmeter 2. Characteristics of electromagnetic flowmeter Electromagnetic flowmeter is not affected by temperature, pressure, viscosity and other external factors, and there is no pressure loss caused by shrinkage or bulge inside the measuring pipe. In addition, the initial signal detected by the flow element is a voltage that changes in an accurate linear manner with the average flow rate of the fluid, and it is independent of other properties of the fluid, It has great advantages. According to the characteristics of sewage, such as large flow change, impurities, low corrosivity, and certain conductivity, electromagnetic flowmeter is a good choice for measuring sewage flow. It has compact structure and small volume. It is easy to install, operate and maintain. The measuring system adopts intelligent design, and the overall sealing is strengthened, so it can work normally in a harsh environment. However, due to technical reasons, it is difficult to enlarge the diameter of vortex flowmeter and its quality. Pipeline ultrasonic flowmeter lacks competitive advantage in price compared with electromagnetic flowmeter. Therefore, in the water and sewage industry, electromagnetic flowmeter, especially large diameter electromagnetic flowmeter, has great advantages and has been widely used.