Domestic safety valve manufacturers compare the main dimensions and the choice of connection

Safety valves manufactured domestically often have inconsistent connection sizes, and the standards vary across different manufacturers. These valves are mainly categorized into several types: (1) The first category is based on the Chinese standard JB/T 2203-1999, "Spring-Loaded Safety Valve Structural Length." Most domestic manufacturers follow this standard for design and production. Examples include Zhejiang Luofu Boiler Accessories Plant, Hangzhou Valve Factory, Wujiang Valve Factory in Jiangsu, Shanghai Valve Factory, Kaifeng High-Pressure Valve Factory, and MSC Valve Factory. However, this standard has some limitations—such as incomplete specifications. For example, it lacks dimensions for DN65 and DN125, while the maximum nominal diameter for micro-opening safety valves is DN200, and for full-opening valves, it's DN200 as well. According to our factory’s experience, the actual sizes can go up to DN250 for micro-opening valves and even DN400 for full-opening ones. Moreover, there are discrepancies in connection sizes among manufacturers. For instance, the DN150 micro-opening safety valve from different factories may have different dimensions. To improve interchangeability and standardization, it is recommended that the Hefei General Machinery Research Institute revise JB/T 2203-1999. Design institutes and users should refer to the standard when selecting safety valves, and manufacturers should produce according to it. (2) Another common system is the American API 526 standard, which applies to flanged steel safety relief valves. Many imported chemical equipment and related safety valves use this standard. It covers nominal diameters from DN25 to DN200 (1" to 8") and pressures ranging from 2 MPa to 42 MPa. The throat diameter varies from 9.5 mm to 146 mm. This standard is more scientific and comprehensive in terms of pressure, materials, temperature, and throat diameter. Different specifications can have multiple throat diameters, and vice versa. For example, a DN100–DN150 (4"–6") valve can have four throat diameter options: L, M, N, and P. As international trade expands and imported equipment becomes more localized, this standard is expected to gain wider acceptance. However, it is not yet an official national standard in China. (3) Pilot-operated safety valves, often designed by companies like Anderson Greenwood & Co., represent another type. These valves consist of a main valve and a pilot valve, offering advantages such as minimal leakage, close-to-set pressure operation, and controlled opening/closing differential. They are commonly used in natural gas pipelines. Currently, there is no official standard or uniform connection size for these valves, as they are still in early development stages and not widely adopted. Most domestic manufacturers rely on the company’s technical data for design and production. Examples include Luoyang Boiler Accessories Factory and the 11th Institute of Aerospace Industry. It is recommended that the Hefei General Machinery Research Institute develop a specific standard for pilot-operated safety valves soon. (4) The 11th Institute of China Aerospace Industry Corporation has developed its own series of safety valves, including the HT series. These include the HTO general safety valve, HTB balanced bellows safety valve, HTR discharge valve, HTN special safety valve, HTGS high-performance steam safety valve, HTXY liquid pressure relief valve, and HTXD pilot safety valve. While most of these valves differ in connection dimensions from both the American standard and GB standards, the HTXD series shares the same size as Anderson Greenwood valves. Users should be cautious when selecting these valves. (5) Lanzhou Refinery has developed the A-type and TA-type fully open spring-loaded safety valves, forming a distinct system. These valves cover nominal diameters from DN25 to DN150 (1" to 6") and nominal pressures from 1.6 MPa to 4.0 MPa. Their connection sizes differ from both the American standard and GB, so users must pay attention to the differences in throat diameter and connection dimensions. (6) Impulse safety valves are commonly used in boiler and power plant equipment. Manufacturers like Harbin Boiler Factory, Dongfang Boiler Factory, Wuhan Boiler Factory, and Qingdao Power Station Auxiliary Plant produce these valves. The structure and connection dimensions vary among manufacturers, and users should carefully check the throat diameter and connection size differences before installation. In summary, the lack of standardized connection sizes and specifications among domestic safety valve manufacturers presents challenges for users. It is crucial to select valves based on accurate technical data and to consider the need for updated standards to ensure compatibility and safety.

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