Due to the ball valve is usually rubber, nylon and PTFE as the seat ring material, so its temperature is limited by the seat ring material. The cut-off effect of the ball valve is achieved by pressing the metal ball against the plastic seat under the action of the medium (floating ball valve). Seat ring in a certain amount of contact pressure, elastic deformation occurs in some areas. This deformation can compensate for the ball manufacturing accuracy and surface roughness, to ensure the sealing performance of the ball valve. And because the ball valve seat ring is usually made of plastic, so in the choice of ball valve structure and performance, to consider the ball valve fire and fire, especially in petroleum, chemical, metallurgical and other departments, flammable and explosive media The use of equipment and piping system ball valve, but should pay attention to fire and fire. Normally, the sealing performance is strictly controlled at two positions, the mud, wear and contraction channels, rapid opening and closing movements (1/4 turn on and off), high pressure cutoff (large pressure drop), low noise, cavitation and gasification, A small amount of leakage to the atmosphere, the operating torque is small, the fluid resistance of small pipe systems, the recommended use of the ball valve. Ball valve is also suitable for light structure, low pressure cutoff (small pressure difference), corrosive medium piping system. Ball valves are also available in cryogenic (cryogenic) systems and piping systems. Oxygen pipeline system in the metallurgical industry, to be used to the strict degreasing ball valve. In the oil pipeline and gas pipeline in the main line to be buried in the ground, you need to use full-bore welded ball valve. When required to have regulatory performance, the need to use a special structure with a V-shaped opening ball valve. In petroleum, petrochemical, chemical, electric power, urban construction, the working temperature above 200 ℃ piping system can choose metal to metal sealed ball valve.