Since the ball valve usually uses rubber, nylon and polytetrafluoroethylene as the material of the seat seal, its operating temperature is limited by the material of the seat seal. The cut-off function of the ball valve is accomplished by pressing the metal ball against the plastic valve seat under the action of the medium (floating ball valve). Under the action of a certain contact pressure, the valve seat sealing ring undergoes elastic-plastic deformation in local areas. This deformation can compensate for the manufacturing accuracy and surface roughness of the sphere and ensure the sealing performance of the ball valve.
And because the valve seat sealing ring of the ball valve is usually made of plastic, when choosing the structure and performance of the ball valve, the fire resistance and fire resistance of the ball valve should be considered, especially in the petroleum, chemical, metallurgical and other departments, in flammable and explosive media. If ball valves are used in the equipment and pipeline systems, more attention should be paid to fire resistance and fire protection.
Usually, in two-position adjustment, strict sealing performance, mud, wear, shrinking channel, quick opening and closing (1/4 turn opening and closing), high pressure cut-off (large pressure difference), low noise, cavitation and gasification, Ball valves are recommended for pipeline systems with small amount of leakage to the atmosphere, small operating torque and small fluid resistance.
Ball valves are also suitable for pipeline systems with light structure, low pressure cut-off (small pressure difference) and corrosive media. Ball valves can also be used in cryogenic (cryogenic) installations and piping systems. In the oxygen pipeline system in the metallurgical industry, ball valves that have undergone strict degreasing treatment are required. When the main lines in oil pipelines and gas pipelines need to be buried underground, full-bore welded ball valves are required. When the adjustment performance is required, a ball valve with a special structure with a V-shaped opening should be selected. In petroleum, petrochemical, chemical, electric power, and urban construction, metal-to-metal sealing ball valves can be selected for pipeline systems with a working temperature above 200 degrees.
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