Flange, also known as a flange disk or boss, is a component used for connecting shafts or for joining pipe ends; it can also be used at equipment inlets and outlets for connecting two devices, such as a reducer flange. A flange connection or flange joint refers to a detachable connection that consists of a flange, a gasket, and bolts, all interconnected as a set to form a sealing structure. Pipe flanges are those used in piping installations, while equipment flanges refer to the inlets and outlets on equipment. Flanges have holes, and bolts are used to tightly secure the two flanges. They are sealed with a gasket. Flanges are available in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those over four kilograms of pressure require焊接 flanges. Two flange disks are joined with a sealing gasket and then fastened with bolts. Flanges of different pressures have varying thicknesses and require different bolts. Pumps and valves, when connected to pipelines, have locally shaped flanges corresponding to these equipment components, also known 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 parts." 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 part." Smaller components like valves can be referred to as "flange-type parts."