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, such as reducer flanges. A flange connection or flange joint refers to a removable connection formed by the combination of a flange, a gasket, and bolts. Pipe flanges are the flanges used in piping systems within equipment, referring to the inlets and outlets of the equipment. Flanges have holes and bolts that secure them tightly together, with gaskets used to seal the gaps between them. Flanges are available in threaded (screwed) connections, welded flanges, and clamping flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those above 4 kg of pressure require焊接 flanges. Two flange disks are joined with a sealing pad and then secured with bolts. Flanges of different pressure ratings have varying thicknesses and require different bolts. When pumps and valves are connected to pipelines, the local parts of these equipment items are also made in corresponding flange shapes, known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and is sealed is generally called a "flange," such as the connections in ventilation pipes. Such components can be referred to as "flange-type parts." However, this type of connection is only a part of a single 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."