Flange, also known as a flange disc or boss, 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. A flange connection or flange joint refers to a removable connection formed by the combination of flanges, gaskets, and bolts. Pipe flanges are those used in piping systems for equipment, referring to the inlets and outlets of the equipment. Flanges have holes, and bolts are used to tightly secure the two flanges. Gaskets are used to seal between the flanges. Flanges are available in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure use焊接 flanges. Two flange disks are joined with a sealing pad and then fastened with bolts. Flanges of different pressures have varying thicknesses and require different bolts. When pumps and valves are connected to pipelines, the local parts of these equipment items are also made into corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and seal them is generally called a "flange," such as the connections in ventilation pipes, which can be referred to as "flange-type components." However, such connections are only 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."