7. Introduction of pneumatic control valve positioner
Valve positioners: after different periods of development, there are mechanical, intelligent, and other types in the early days. Valve positioners are the main accessories of the control valve, usually used together with the pneumatic control valve. It receives the output signal of the control system, and then uses its output signal to control the pneumatic control valve. When the control valve acts, The displacement of the valve stem is fed back to the valve positioner through the mechanical device. The valve position status can be transmitted to the industrial control system through electrical signals or additional valve position switches, or it can not be transmitted.

Specification and application of stainless steel pneumatic butterfly valve
Stainless steel pneumatic butterfly valve is the main component in modern industry. Stainless steel pneumatic butterfly valve is used as wire and cable maintenance tube and civil shower hose for wires, cables, automatic instrument signals, with specifications ranging from 3mm to 150mm. The small diameter stainless steel pneumatic butterfly valve (inner diameter: 3mm~25mm) is mainly used for the maintenance of the sensing line of the precision optical ruler and the industrial sensor line.
Pneumatic butterfly valve is mainly composed of flexible body (bellows), mesh body and various types of joints. The inner pipe of pneumatic butterfly valve is spiral or annular thin-walled stainless steel bellows, and its outer net sleeve is woven by stainless steel wire or steel strip according to certain parameters. The joints or flanges at both ends of the pneumatic butterfly valve are matched according to the joints or flanges of the user's pipeline. The bellows of the pneumatic butterfly valve is composed of extremely thin seamless or longitudinally welded stainless steel thin-walled tubes through high-precision plastic deformation processing. The flexibility and fatigue resistance of the hose are determined by the elastic characteristics of the bellows contour. The pneumatic butterfly valve is easy to absorb various movement deformation and cyclic loads, especially to meet the system's need for larger displacement compensation, and absorb the movement, heat shrinkage Vibration absorption plays an important role.