Flange, also known as a flange disk or boss, is a component that connects two shafts or is used to join pipe ends. It is also employed at equipment inlets and outlets, such as reducer flanges, for connecting two devices. A flange connection or flange joint refers to a removable connection made up of the flange, gasket, and bolts, forming a combination seal structure. Pipe flanges are those used in piping installations; on equipment, they refer to the inlets and outlets. Flanges have holes for bolts 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 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 bolted together. Flange thickness varies with pressure, and so does the type of bolt used. When pumps and valves are connected to pipes, the local components of these equipment are also shaped like flanges and are referred to as flange connections. Any connection piece that uses bolts to join two flat surfaces while sealing is generally called a "flange," such as the connections in ventilation piping. Such components can be called "flange-type parts." 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 part." Smaller items like valves can be referred to as "flange-type parts."