Gas pressure regulating valve natural gas special valve classification and how to choose
September 20 00:27:36, 2025
Gas Valve Classification and Selection: A Comprehensive Guide
The development of gas valves in China has evolved significantly over the past few decades. Before the 1980s, only water valves were available for use. However, with the economic reforms and opening up, the gas industry experienced rapid growth, leading to a greater demand for specialized gas valves. Initially, these valves were designed to handle impurities found in coal-based gas, such as tar and aromatic compounds. These substances could cause valve stem sticking or seal failure due to the formation of "gas glue." The introduction of natural gas brought new challenges, as it is cleaner but contains more sand and higher pressure (up to 1.6 MPa). This necessitated the development of valves that could withstand harsh conditions while maintaining reliable performance.
Valves installed in underground pipelines must meet strict requirements. They need to have sufficient strength and stiffness to resist external forces without deforming, ensuring consistent sealing performance. Key design considerations include minimizing structural height to reduce burial depth, incorporating fully enclosed open/close indicators for operator visibility, and using full-path designs to allow easy passage of pipeline cleaners. Sealing performance must adhere to standards like CJ3055-95, which sets strict limits on internal leakage. Corrosion resistance is also essential, and materials should be selected based on the gas medium and pressure level. Maintenance-free designs are preferred to minimize disruption during repairs.
Material selection plays a critical role in valve performance. For low-pressure systems (0.2 MPa), gray cast iron valves are often used due to their cost-effectiveness and corrosion resistance. For medium-pressure systems (up to 0.8 MPa), ductile iron or cast steel valves are recommended, with ductile iron offering better mechanical properties and lower costs. High-pressure systems (1.6 MPa and above) typically require cast steel valves. In recent years, polyethylene (PE) valves have gained popularity for low-pressure applications due to their excellent sealing and direct burial capabilities.
Several types of gas valves are currently used in China, each with unique advantages and limitations. The RX series oil-sealed plug valve was developed to address issues with traditional gate valves, offering improved sealing and reduced stem sticking. The RZ series parallel gate valve, designed for larger diameters, features a self-cleaning mechanism and a lightweight structure. The RQZ series ductile iron gate valve enhances wear resistance and pressure handling. Butterfly valves, though lightweight and affordable, are generally unsuitable for gas pipelines due to poor sealing and flow resistance. Slab gate valves offer low flow resistance but may not be ideal for all applications. The TRZ series elastic sealing gate valve provides excellent sealing and is suitable for high-pressure systems. Ball valves, particularly fixed ball types, are widely used for their compact design and reliable performance.
Specialized gas valves, such as emergency shut-off valves and check valves, play crucial roles in safety and system integrity. Emergency shut-off valves are essential for preventing gas leaks from escalating into disasters. Check valves prevent backflow in compressors and storage facilities. Standards like CJ3005-1992 and CJ3055-1995 guide the design and testing of gas valves, ensuring quality and safety.
In conclusion, selecting the right gas valve depends on factors such as pressure level, gas type, and installation environment. Direct-buried valves are preferred for underground networks, while specific valve types are recommended for different pressure ranges and applications. As the gas industry continues to grow, especially with the expansion of natural gas infrastructure, the demand for innovative and reliable gas valves will only increase. With ongoing technological advancements, future developments in gas valve design are expected to further enhance efficiency, safety, and cost-effectiveness. (Source: Hebei Zhenxing Gas Pressure Regulator Co., Ltd.)