Flange, also known as a flange collar or boss. A flange is a component that connects shafts together or is used for pipe-end connections; there are also flanges used at equipment inlets and outlets for connecting two devices, such as reducer flanges. Flange connection or flange joint refers to a detachable joint made up of the flange, gasket, and bolts, forming a combined sealing structure. Pipe flanges are flanges used for piping in pipe installations; on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure the two flanges together. Flanges are sealed with a gasket. Flanges are categorized into threaded (screwed) flanges,焊接 (welded) flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipes 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. Flange thickness and bolt types vary with pressure ratings. Pumps and valves, when connected to pipes, have locally shaped flanges to match, also known as flange joints. Any connection piece that uses bolts to connect two flat surfaces around the perimeter and is sealed is generally called a "flange," such as in ventilation pipe connections, these 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."