Flange, also known as a flange boss or rim, is a component used for connecting shafts to shafts, typically for pipe end connections; it is also used on equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a detachable connection formed by the combination of flange, gasket, and bolt for a sealing structure. Pipe flanges are the flanges used in piping installations for equipment, referring to the inlets and outlets of the equipment. Flanges have holes, and bolts secure them tightly together. They are sealed with a gasket. Flanges are available 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 those over 4 kg 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, also known as flange joints. Any connection piece that uses bolts to connect and seal two flat surfaces 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 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 components like valves can be referred to as "flange-type parts."