Comparison of major domestic safety valve manufacturers and selection of connection dimensions

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Comparison of major domestic safety valve manufacturers and selection of connection dimensions: There are many manufacturers in China that produce safety valves, and their connection dimensions are often not standardized. It is mainly divided into the following categories: (1) General categories based on JB/T2203－1999 \"Structural Length of Spring-Operated Safety Valves\". At present, most domestic safety valve manufacturers design and produce in accordance with this standard. Such as Zhejiang Luofu Boiler Accessories Factory, Hangzhou Valve Factory, Jiangsu Wujiang Valve Tools Factory, Shanghai Valve Factory, Kaifeng High-Pressure Valve Factory, Hai’an Valve Factory, and others. However, this standard is not perfect either; its specifications are incomplete. The maximum nominal diameter for slightly opening safety valves is DN100, while that for fully opening safety valves is DN200. The sizes DN65 and DN125 are missing in between. Based on the specifications of the safety valves produced by our factory and the information available to us, the maximum nominal diameter for slightly opening safety valves is currently DN250, while that for fully opening safety valves is DN400. After my own verification, the connection dimensions provided by different manufacturers are not uniform; for example, for DN150 full-open safety valves, those produced by Zhejiang Luofu Boiler Accessories Factory, Shanghai Valve Factory, and Jiangsu Wujiang Valve Tools Factory all differ from each other. To establish a unified standard that allows components of the same specification to be interchanged during selection and installation, it is recommended that Hefei General Machinery Research Institute revise JB/T 2203–1999 \"Structural Length of Spring-Operated Safety Valves\". It is recommended that design institutes and users select products in accordance with the standards, while valve manufacturers should design and produce them in line with these standards. (2) The American standard system, based primarily on API526 \"Flanged Steel Safety Relief Valve\". The connection dimensions of safety valves used in domestically imported chemical equipment generally follow this standard, as shown in Figure 5. The nominal diameter of this standard ranges from DN25 to DN200 (1” to 8”), the nominal pressure is 2 to 42 MPa, and the throat diameter ranges from D-T (9.5 to 146 mm). This standard is relatively scientific and standardized, taking into account factors such as pressure, materials, temperature, and throat diameter as a whole. The specifications are determined based on the throat diameter; several specifications can exist for the same throat diameter, and conversely, several throat diameters may be available for the same specification. For throat diameters of DN100~DN150 (4”~6”), there are four options: L, M, N, and P. With the ongoing advancement of international trade and the localization of imported equipment, this standard will be widely adopted in China. At present, this standard has not been converted into a national standard. (3) A series of pilot-operated pressure relief valves based on the internationally influential Anderson Greenwood & Co. company. In China, it is generally referred to as a pilot-operated safety valve. As shown in Figure 6, a pilot-operated safety valve consists of a main valve and a pilot valve, with the pilot valve controlling the opening and closing of the main valve. This type of valve has a large flow rate ； Unaffected by back pressure ； Leak-free operation can be carried out at a pressure very close to the operating pressure ； Advantages such as a low opening and closing pressure difference. It is generally applicable to natural gas pipelines and similar systems. Currently, there are no domestic standards for pilot-operated safety valves or connection dimensions. Moreover, this type of valve has just been developed and has not yet been widely adopted. Based on our factory’s experience and the information we have, most domestic manufacturers design and produce products according to that company’s specifications, such as Zhejiang Luofu Boiler Accessories Factory and the 11th Aerospace Research Institute. It is recommended that the Hefei General Machinery Research Institute draft and issue standards for pilot-operated safety valves as soon as possible. (4) The safety valves designed and developed by the 11th Research Institute of China National Aerospace Industry Corporation form their own system. The HT series of safety valves developed by the 11th Aerospace Research Institute comes in a variety of types, including the HTO standard safety valve (as shown in Figure 1), the HTB balanced diaphragm safety valve, the HTR drain valve, the HTN special safety valve, and the HTGS high-performance steam safety valve. HTXY liquid pressure relief valves, HTXD pilot-operated safety valves, etc., all exhibit excellent performance. However, except that the pilot-operated safety valves of the HTXD series have the same connection dimensions as those of Anderson Greenwood Company, the rest do not conform to either American or Chinese standards. Please be sure to keep this in mind when making your choice. (5) The Type A and TA closed, fully open spring-loaded safety valves designed and developed by Lanzhou Refinery form their own system. This series has diameters ranging from DN25 to DN150 (1” to 6’), a nominal pressure of 1.6 to 4.0 MPa, and a throat diameter of D–R (9.5–115 mm). The connection dimensions of this system differ from both American and Chinese standards, and it is designed specifically for Lanzhou Refinery. (6) The impulse-type safety valve series designed for use with boilers, power plant equipment, and temperature and pressure reduction devices (as shown in Figure 8). Special safety valves designed for use with facilities such as Harbin Boiler Factory, Dongfang Boiler Factory, Wuhan Boiler Factory, and Qingdao Power Plant Auxiliary Equipment Factory. The structure and connection dimensions of such series of valves generally vary among different manufacturers, although some similarities may exist. When selecting, be sure to pay attention to the valve throat diameter and connection dimensions