It is mainly applicable to petroleum, chemical industry, metallurgy, electric power, construction, municipal, environmental protection. Features of Structure and Working Principle 1) Block-up And Excretion When the valve is in the closed state, the seat ring on the upstream and downstream sides cuts off the fluid and the accumulated matters in the middle cavity of the body can be excreted, The excreting device features the following functions: Can check if the seat ring leaks or gets damaged beforehand; Reduce pollution to the valve due to the medium replacement; The packing on the stem portion can be replaced when the valve is in the fully opened or closed state under the working pressure. 2) Automatic Pressure Discharge When an abnormal pressure rise occurs with the medium stayed in the middle cavity of the valve due to rising temperature, the seat ring will come off from the ball and automatically discharge pressure or the safety valve mounted on the body ensures the system safety. 3) Complete Seal The unique sealing mode of the ball valve makes the fluid completely cut off. 4) Fire-fighting Structure If the Teflon seat ring is made softened and burnt in case of a fire or an abnormal temperature rise, the valve can be contacted with the ball to act as an instantaneous seal, conforming with AP1607. 5) Electrostatic-proof Structure During valve operation, the friction between the ball and the PTFE seat ring will produce electrostatic charges and they will be accumulated onto the ball. To prevent electrostatic spark from being produced, an electrostatic-proof device is mounted on the valve, which can guide the charges out through the electric path formed by both ball and via the spring. 6) Emergent Rescue Of Sral When the sealing parts of both seat ring and stem get damaged and thus leaks are caused, an instantaneous sealing action can be made available by injecting sealing grease through the grease injecting valve. 7) Structure Of Seat Ring Two kinds: single-seal and dual-seal. In general, those of an automatic pressure discharge function are single-seal while the dual-seal means the additional safety pressure diacharge to the body.