Flange, also known as a flange disk or rim, is a component used for connecting shafts or for joining pipe ends. It is also used at equipment inlets and outlets, such as reducer flanges, for connecting two pieces of equipment. A flange connection or flange joint refers to a removable joint that consists of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are flanges used for piping in pipe installations, or they refer to the inlet and outlet flanges of equipment. Flanges have holes and bolts are used to tightly secure them. They are sealed with a gasket. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while pipelines with pressures over four kilograms require焊接 flanges. Two flange disks are fitted with a sealing pad and then secured with bolts. Flange thickness varies with pressure, as do the bolts used. In the case of pumps and valves, when connected to pipelines, these equipment components are also shaped like flanges and are referred to as flange connections. Any connection piece that uses bolts to connect two flat surfaces and is sealed is generally called a "flange," such as the connection of ventilation pipes. Such components can be referred to as "flange-type components." However, such connections are only a part of a device, like the connection between a flange and a pump, so it's not appropriate to call the pump a "flange-type component." Smaller items like valves can be called "flange-type components."