Fireproof and anti-static ball valves are predominantly utilized in gas pipelines containing flammable and explosive media like natural gas, liquefied petroleum gas, and their mixtures. Conversely, standard ball valves are employed in non-flammable and non-explosive pipelines such as water and air. The primary distinction between them lies in their internal structure, discernible only through markings on their appearance; anti-static ball valves are labeled as AS, while fireproof ball valves are denoted by FD.
Fire prevention encompasses three aspects: protection at the ball core and valve seat, prevention at the flange within the valve body, and safeguarding the valve stem.
In the event of a fire, the soft-sealed ball valve is engineered to sustain a certain sealing performance even after the valve seat is subjected to high temperatures, minimizing internal leakage occurrences. While hard-sealed ball valves can prevent the burning of soft-sealed ball valve seats during fires, they may struggle to match the sealing performance of soft-sealed ball valves under normal operation, potentially leading to minor internal leakage, particularly in gas pipelines, thus rendering soft-sealed ball valves more widely adopted.
In a fireproof ball valve, the soft-sealed seat is embedded in the valve body's groove, ensuring continued sealing during normal operation. Upon burning out, the ball core is pushed by medium pressure to maintain a hard-sealing state near the metal sealing surface of the inner ring, reducing internal leakage. Conversely, in a standard ball valve, the valve seat is directly installed between the valve body and the ball core, and after burning out, it cannot effectively form a metal hard seal.
Furthermore, the flange in a ball valve is fireproof, usually featuring a two-piece or three-piece split structure assembled by bolts with O-ring seals and graphite metal wound gaskets between sections to maintain sealing. Additionally, fire protection at the valve stem is crucial, achieved by the sealing packing of the valve stem, typically employing high-temperature-resistant fillers like flexible graphite fillers or graphite metal wire combinations.
Lastly, to ensure anti-static functionality, small holes are drilled in two positions on the valve stem—one in contact with the valve body and the other with the ball core. Springs and small metal balls installed in these holes maintain contact with the valve body, stem, and ball core, creating a conductive circuit compliant with national standards.
In conclusion, the incorporation of fireproof and anti-static features in ball valves is paramount for ensuring safety and reliability in critical applications such as gas pipelines. By understanding the unique design and functionalities of these valves, industries can make informed decisions to mitigate risks associated with flammable and explosive media. Moreover, adherence to national standards and continuous advancements in valve technology will further enhance the performance and resilience of these essential components in industrial settings, promoting safer operations and environmental protection.