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 for connecting two devices, such as a reducer flange. A flange connection or flange joint refers to a removable joint consisting of a flange, a gasket, and bolts, which together form a sealing assembly. Pipe flanges are the flanges used in piping installations and, when used on equipment, refer to the equipment's inlet and outlet flanges. Flanges have holes for bolts, which secure the two flanges together, and are sealed with a gasket. Flanges are available in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those above 4 kg of pressure typically use焊接 flanges. Two flange discs are joined with a sealing pad and then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. In the case of pumps and valves, when connected to pipes, the local parts of these equipment items are also made in corresponding flange shapes, known as flange joints. Any connection that uses bolts to join and seal two flat surfaces is generally called a "flange," such as the connections in ventilation pipes, which can be referred to as "flange-type components." 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 component." Smaller items like valves can be referred to as "flange-type components."