Pneumatic regulating butterfly valve is a valve (valve plate) rotating around a fixed axis perpendicular to the channel. It consists of a piston type double action or single action (spring return type) pneumatic actuator and a butterfly valve. It is a rotary high-performance regulating or shut-off valve, equipped with electric, pneumatic valve positioner or solenoid valve, air filter pressure reducer, limit switch (valve position indicator), It can realize the proportional regulation and two position cut-off control of the fluid medium in the process pipeline, so as to achieve the automatic control of the flow, pressure, temperature, liquid level and other parameters of the fluid medium.

4. How is China's measurement laws and regulations system constituted? China's metrological supervision system consists of three parts: 1) the metrological methods of the People's Republic of China; 2) the metrological administrative regulations formulated or approved by the State Council and the local metrological regulations formulated by the people's congresses of provinces, cities and autonomous regions. Standing Committee: 3) The metrological management measures and technical specifications formulated by the metrological management department of the State Council, the departmental metrological management measures formulated by the relevant departments of the State Council, and the local metrological management measures formulated by the governmental metrological management department. Above the county level.