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 the inlets and outlets of equipment, 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 the flanges used for piping in pipe installations, or the inlets and outlets of equipment. Flanges have holes, and bolts are used to tightly secure the two flanges. 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 of pressure use焊接 flanges. Two flange disks are joined with a sealing pad and then bolted together. Flanges of different pressures have different thicknesses and require different bolts. In pumps and valves, when connected to pipelines, these equipment components are also made in the corresponding flange shape and are referred to 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 connection of ventilation pipes. Such components can be called "flange-type parts." However, this type of connection is 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 part." Smaller components like valves can be referred to as "flange-type parts."