Compared with ordinary types of valves, special valves have obvious characteristics such as extremely complex internal flow, special structure, special materials and special uses. As a special valve among many valve types, it is used in various special environments, can adapt to various complex working conditions, plays a special role, and undertakes particularly complex tasks.

Therefore, special valves are often referred to as the "throat" of industrial pipelines. Typical special valves include main feed water control valves, regulator spray valves, high-plus traps, Tesla valves, pilot-operated globe valves, multi-stage pressure reducing valves, sleeve control valves, heart valves, etc.

Safety valves for large-scale pressure equipment, steam traps for high-pressure steam heating systems, high-parameter pressure reducing valves for high-parameter cogeneration systems, cryogenic ball valves for liquefied natural gas transmission systems, heart valves for cardiovascular systems, and key nuclear power valves for pressurized water reactor nuclear power plants

There are two kinds of special valve classification: the first is to look at the characteristics and working conditions of pipeline fluids, special fluid media such as strong acid and alkali, high temperature and high pressure and other valves; The second is to look at the functional characteristics of the valve, whether it is a non-standard valve, such as a 45-degree angle valve on oil refining, such as an anti-asthma valve for a compressor, or a valve on a nuclear power plant, or a valve with special medium and special material, such as titanium pickaxe, etc.

The valves are divided into A1, A2 and B grades. Class B valve technical requirements Valve manufacturing license items (products): Valve grade: A1 represents the manufacturing scope of the product: the design temperature is greater than 425, the nominal pressure is greater than 10 megapascals, and the nominal diameter is greater than or equal to 300 mm. The nominal diameter is greater than or equal to 300 mm, and Class B represents the manufacturing range of the product. In detail, there are no B1 and B2 grades for general purpose valves and other special service valves.