Flange connections involve securing two pipes, fittings, or equipment to separate flange plates, inserting a flange gasket between them, and then bolting them together to complete the connection. Some fittings and equipment come with built-in flange plates and are also considered flange connections. Flange connections are a crucial method in pipeline construction. They are convenient to use and can withstand high pressure. In industrial pipelines and residential settings, where pipe diameters are small and pressure is low, flange connections are not visible. However, in boiler rooms or production sites, flange connections are ubiquitous on pipes and equipment.

According to the connection method, flange types can be categorized as: flat welding flanges, socket welding flanges, blind flanges, threaded flanges, flange covers, loose fit socket welding flanges, flat socket welding flanges, ring groove flanges, large diameter flat flanges, large diameter long-neck flanges, blind flanges with a "V" shape, socket welding ring loose fit flanges, and others.