Flange, also known as a flange disc or rim, 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 devices. 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 flanges used for piping in pipe systems, or for equipment inlets and outlets on equipment. Flanges have holes and bolts are used to tightly connect them. 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 4 kg pressure use焊接 flanges. Two flange discs are joined with a sealing pad and then bolted together. Flanges of different pressures have different thicknesses and require different bolts. When pumps and valves are connected to pipes, the local parts of these equipment are also made into corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces around the periphery and is sealed is generally called a "flange," such as the connection of ventilation pipes. Such 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 components like valves can be called "flange-type components."