Flange, also known as a flange disc or boss, 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 consisting of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are flanges used for piping in pipe installations, or for equipment inlets and outlets on equipment. 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 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. In the case of pumps and valves, when connected to pipes, these equipment components are also shaped to match the flange, also 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 the connection of ventilation pipes. Such components can be referred to as "flange-like parts." However, this type of connection is only a part of a single device, like the connection between a flange and a pump, so it's not appropriate to call the pump a "flange-like part." Smaller components like valves can be called "flange-like parts."