Pneumatic ball valve was introduced in the 1950s. With the rapid development of science and technology, the continuous improvement of production process and product structure, it has rapidly developed into a major valve category in just 40 years. In western industrial developed countries, the use of pneumatic ball valves is increasing year by year. Pneumatic ball valve is most suitable for use as switch and shut-off valve, V-type pneumatic ball valve. In addition to the pipeline parameters, special attention should be paid to the environmental conditions for the use of electric valves. Since the electric device in the electric valve is an electromechanical device, its use status is greatly affected by its use environment. 　　

Electromagnetic flowmeter consists of flow sensor and transmitter. The upper and lower parts of the sensor measuring tube are equipped with excitation coils. After the excitation current is applied, a magnetic field is generated and passes through the measuring tube. A pair of electrodes are installed on the inner wall of the measuring tube to contact the liquid, leading out the induced potential and sending it to the transmitter. The excitation current is provided by the transmitter. According to the assembly mode of converter and sensor, there are two types: separated type and integrated type. In the sewage treatment process, the large diameter flowmeter is mostly split type, one part is installed underground, and the other part is installed on the ground. The small caliber is mostly integrated.