Flange, also known as a flange 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 devices. A flange connection or flange joint refers to a detachable connection formed by the combination of flanges, gaskets, 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. They are sealed with gaskets. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are always used in pairs; low-pressure piping can use threaded flanges, while pressures above four kilograms require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, the parts that connect to pipes are also shaped like flanges, known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and is sealed is generally called a "flange," such as in ventilation pipe connections. Such components can be referred to as "flange-type parts." However, such connections are only 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 called "flange-type parts."