Flange, also known as a flange disk or boss, is a component used for connecting shafts or for joining pipe ends. It is also used at equipment inlets and outlets for connecting two devices, such as reducer flanges. A flange connection or flange joint refers to a removable joint consisting of a flange, a gasket, and bolts, all connected to form a combined sealing structure. Pipe flanges are the flanges used in piping installations, while on equipment, they refer to the inlets and outlets of the equipment. Flanges have holes for bolts, which secure the two flanges together. They are sealed with a gasket. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamping flanges. Flanges are used in pairs; low-pressure piping can use threaded flanges, while those above four kilograms of pressure require welding flanges. Two flange disks are joined with a sealing pad and then fastened with bolts. Flange thickness varies with pressure, and so do the bolts used. In pumps and valves, the parts that connect to pipes are also made into corresponding flange shapes, 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 connection of ventilation pipes. These 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."