Flange pipe fittings are an important component for connecting pipes, usually composed of flanges, bolts, washers and seals. They are widely used in pipeline systems in petroleum, chemical industry, electric power, metallurgy, shipbuilding, construction and other industries. The main functions of flange pipe fittings are to connect pipes, prevent leaks, support pipes and adjust the direction of pipes. Depending on the working pressure and temperature, flange pipe fittings are usually made of different materials, such as carbon steel, stainless steel, alloy steel, etc. Common flange types include butt welding flange, blind flange, flange to flange, etc., and their standards include international standards and domestic standards, such as ASME, DIN, JIS, etc. The design and selection of flange fittings need to take into account the working conditions, media characteristics and safety requirements of the pipeline system.