Good sealing performance; Since the hard seal pneumatic ball valve is sealed by manual grinding, it cannot be used until the valve core and seal ring are completely matched. Therefore, its sealing performance is reliable. It has been widely used in petroleum, chemical industry, power generation, paper making, atomic energy, aviation, rocket and other sectors, as well as in people's daily life. 　　

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.