Domestic safety valve manufacturers compare the main dimensions and the choice of connection
In China, domestic manufacturers of safety valves often have inconsistent connection sizes. These valves are mainly categorized into the following types:
(1) The first category is based on the Chinese standard JB/T 2203-1999 titled "Spring-loaded Safety Valve Structural Length." Most safety valve manufacturers currently design and produce their products according to this standard. 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. It lacks specifications for certain nominal diameters, such as DN65 and DN125, while the maximum for micro-opening safety valves is DN100 and all-relief valves go up to DN200. According to our factory's production experience and available data, micro-opening safety valves can now reach up to DN250, and all-relief valves can be as large as DN400. Additionally, there are discrepancies in connection dimensions among different manufacturers. For example, the DN150 micro-opening safety valves from Shanghai Boiler Accessories Plant, Shanghai Valve Factory, and Wujiang Valve Factory differ in size. To ensure interchangeability and ease of installation, it is recommended that the Hefei General Machinery Research Institute revise the JB/T 2203-1999 standard. Design institutes and users should follow this standard when selecting safety valves, and manufacturers should design and produce according to it.
(2) The second category follows the American API 526 standard, "Flanged Steel Safety Relief Valve." Many imported chemical equipment and other safety valves in China use this standard for connection dimensions, as shown in Figure 5. This standard covers nominal diameters from DN25 to DN200 (1" to 8"), with pressure ratings from 2 MPa to 42 MPa and throat diameters ranging from 9.5 mm to 146 mm. It is more scientific and standardized in terms of pressure, materials, temperature, and throat diameter. Specifications are determined by throat diameter, meaning that the same throat diameter can have multiple specifications, and vice versa. For instance, 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 has not yet been adopted as a national standard in China.
(3) The third category includes pilot-operated pressure relief valves developed by Anderson Greenwood & Co., a globally renowned company. These valves, often referred to as pilot safety valves, consist of a main valve and a pilot valve. The pilot valve controls the opening and closing of the main valve, offering advantages such as minimal displacement, resistance to back pressure, and near-leak-free operation close to the set pressure. They are commonly used in natural gas pipelines. Currently, there is no established standard or uniform connection dimensions for these valves. Since they are relatively new, they have not been widely adopted. Based on our factory’s experience and available information, most domestic manufacturers design and produce these valves based on the company’s technical data. Examples include Luoyang Boiler Accessories Plant and the 11th Institute of Aerospace Industry. It is recommended that the Hefei General Machinery Research Institute draft and issue a standard for pilot-operated safety valves as soon as possible.
(4) The fourth category consists of safety valves designed and developed by the 11th Institute of China Aerospace Industry Corporation. These valves have formed their own system, including the HT series, which includes the HTO general safety valve, HTB balanced bellows safety valve, HTR discharge valve, HTN special safety valve, and HTGS high-performance steam safety valve, among others. While these valves perform well, except for the HTXD pilot series, which matches the size of Anderson Greenwood’s valves, the rest do not conform to either the American Standard or GB standards. Users should pay attention to this difference when selecting these valves.
(5) The fifth category includes A-type and TA-type fully open spring-loaded safety valves developed by Lanzhou Refinery. These valves cover nominal diameters from DN25 to DN150 (1" to 6") and pressure ratings from 1.6 MPa to 4.0 MPa, with throat diameters ranging from D to R (9.5 mm to 115 mm). Their connection dimensions differ from both the American Standard and GB standards.
(6) Lastly, there are impulse safety valve series used in boiler and power plant equipment, such as those produced by Harbin Boiler Factory, Dongfang Boiler Factory, Wuhan Boiler Factory, and Qingdao Power Station Auxiliary Plant. The structure and connection dimensions of these valves vary among manufacturers, though some may share similarities. Users must carefully check the differences in throat diameter and connection dimensions when selecting these valves.
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