However, it is found that the elastoplastic deformation ability and stability of PTFE under temperature change are still not very ideal, and there is a large cold flow trend; At the same time, since the operating pressure of pneumatic ball valve varies widely, the lip seal seat made of polytetrafluoroethylene as the sealing material is still prone to leakage under low pressure conditions or in long-term use. The way to solve this problem is to use a combined seal seat composed of an elastic expansion ring and a PTFE lip seal seat. It can rely on the good elastic-plastic deformation ability of the metal elastic expansion ring, enhance its overall elastic-plastic deformation ability and compensation ability, and improve the sealing ability of the pneumatic ball valve.

The butterfly valve has a small flow resistance when it is fully opened. When it is opened between about 15 ° and 70 °, it can also perform sensitive flow control. Therefore, in the field of large diameter regulation, butterfly valves are widely used and will gradually become the dominant valve type