Flange, also known as a flange disk or boss, is a component used for connecting shafts to shafts, typically for joining pipe ends; it's 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 specifically the flanges used for piping in pipe installations, or in equipment, they refer to the inlets and outlets of the equipment. Flanges have holes and bolts that secure them tightly together. They are sealed using a gasket. Flanges come in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above 4 kg of pressure use welded flanges. Two flange disks are sealed with a gasket and then fastened with bolts. Flanges of different pressures have varying thicknesses and require different bolts. Equipment like pumps and valves, when connected to pipes, have locally shaped flanges corresponding to the equipment, also known as flange connections. Any connection piece that uses bolts to join two flat surfaces around the perimeter and is sealed is generally called a "flange," such as the connection in ventilation pipes. These types of components can be referred to as "flange-type components." However, such connections are only part of a single piece of equipment, 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 called "flange-type components."