The variable eccentric sealing structure of pneumatic butterfly valve with variable eccentric sealing is different from the above two. It has a unique feature that the valve rod shaft with butterfly plate is a three section shaft type, that is, the two shaft sections are concentric, and the center line of the central section shaft will deviate from the axis at both ends, so the butterfly plate will be installed on this intermediate shaft section. If the eccentric structure is in the fully open state, it can become a double eccentric structure. If the butterfly plate is turned to the closed state, it will appear as a single eccentric structure. In this way, the pneumatic butterfly valve which can switch the sealing structure can also reduce the extrusion pressure and ensure the sealing performance. 　　

3. When using the electric control valve in daily life, it is necessary to record the working condition of the electric control valve in a timely manner, because in many cases, some detailed changes are signs of detailed damage to the electric control valve. If ignored, it may lead to greater failure of the electric control valve.