Flange, also known as a flange boss or rim, is a component used for connecting shafts to each other, typically for pipe end connections; it is also used on equipment for connecting two devices, such as a reducer flange. 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 those used in piping systems, while equipment flanges refer to the inlets and outlets of equipment. Flanges have holes and bolts that secure them tightly together, with a gasket used for sealing between them. Flanges are available 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 those above 4 kg of pressure typically use焊接 flanges. Two flange discs are joined with a sealing gasket and then bolted together. Flange thickness varies with pressure, as do the bolts used. In pumps and valves, the parts that connect to pipes are also made in flange shape, known as flange connections. Any connection that uses bolts to join two flat surfaces and seal them is generally called a "flange," such as in ventilation pipe connections. Such parts can be referred to as "flange-type components." However, this type of connection is 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."