Flange, also known as a flange disk or boss, is a component used for connecting shafts to each other, typically for pipe end connections; it is also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a removable connection consisting of a flange, gasket, and bolt, which together form a combined sealing structure. Pipe flanges are those used in piping installations, while equipment flanges refer to the inlets and outlets of equipment. Flanges have holes for bolts, which secure the two flanges together, and are sealed with a gasket. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are used in pairs; low-pressure piping can use threaded flanges, while pressures above four kilograms require焊接 flanges. Two flange disks are joined with a sealing pad and then tightened with bolts. Flange thickness and bolt types vary with pressure ratings. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes, also known as flange joints. Any connection piece that uses bolts to connect two flat surfaces and is sealed is generally called a "flange," such as in ventilation pipe connections. Such components can be referred to as "flange-type parts." 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 part." Smaller items like valves can be called "flange-type parts."