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 devices. A flange joint or flange connection refers to a removable joint consisting of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are flanges used in piping systems within equipment, specifically referring to the inlets and outlets of the equipment. Flanges have holes for bolts, which secure the two flanges together, and 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 over four kilograms of pressure use焊接 flanges. Two flange discs are joined with a sealing pad and then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. When pumps and valves are connected to pipes, the local parts of these equipment items are also made in the corresponding flange shape, also known as a flange connection. Any connection piece that uses bolts to join two flat surfaces around the perimeter and is sealed is generally called a "flange," such as the connection of ventilation pipes. Such components can be referred to as "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 items like valves can be called "flange-type parts."