Flange, also known as a flanged boss 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 pieces of equipment. 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 systems, or the inlets and outlets of equipment. Flanges have holes, and bolts secure them tightly. Gaskets are used to seal between flanges. 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 over 4 kg of pressure use焊接 flanges. A sealant is placed between the two flange disks, and then bolts are tightened. Flanges of different pressures have different thicknesses and require different bolts. When pumps and valves are connected to pipelines, the local parts of these equipment items 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, this type of connection is only a part of a device, such as 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."