Flange, also known as a flange disc or boss, is a component that connects shafts together, used for pipe end connections; it is also used on equipment inlets and outlets for connecting two devices, such as a reducer flange. Flange connection or flange joint refers to a removable connection formed by the combination of flange, gasket, and bolt. Pipe flanges are flanges used for piping in pipe installations, and on equipment, they refer to the equipment's inlets and outlets. Flanges have holes, and bolts secure the two flanges together. They are sealed with a gasket. Flanges come 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 four kilograms of pressure use welded flanges. Two flange discs are joined with a sealing pad and then fastened with bolts. Flanges of different pressures have different thicknesses and require different bolts. Pumps and valves, when connected to pipes, have locally shaped flanges that correspond to these equipment components, also known as flange connections. Any connection component that uses bolts to connect two flat surfaces around the perimeter and seal them is generally called a "flange," such as the connection of ventilation pipes. These components 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 called "flange-type components."