When pipelines transport toxic, flammable, explosive and highly hazardous media, ball valves are often required to have a fire-resistant structure in order to improve the safety of the valve. When operating normally in the above-mentioned media, the sealing pair of the valve often adopts a soft sealing structure (generally, the working temperature of the medium is normal temperature). Once a fire breaks out outside, the plastic, rubber and other soft polymer materials inside the valve are burned. At this time, the metal sealing surface of the valve seat will come into contact with the ball under the action of the medium pressure, achieving temporary sealing performance.
