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, for connecting two pieces of equipment. 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, while equipment flanges refer to the inlets and outlets of equipment. Flanges have holes for bolts, which secure them together, and are sealed with gaskets. 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 require焊接 flanges. Two flange disks are joined with a sealing pad and then tightened with bolts. Flange thickness varies with pressure, and so do the bolts used. When pumps and valves are connected to pipes, the local parts of these equipment items are often made in the shape of a flange, also known as a flange connection. 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. 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."