Flange, also known as a flange disc or boss, is a component used for connecting shafts or for joining pipe ends. It can also be used at the inlets and outlets of equipment, such as a reducer flange. A flange connection or flange joint refers to a detachable connection that consists of a flange, a gasket, and bolts, all interconnected to form a sealing assembly. Pipe flanges are flanges used in piping installations, while flanges on equipment refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure them together. They are sealed with a gasket. Flanges are available in threaded (screwed) connections,焊接 (welded) flanges, and clamping flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those above 4 kg pressure require welding flanges. Two flange discs are joined with a sealing pad in between, then tightened with bolts. Flanges of different pressures have varying thicknesses and require different bolts. Pumps and valves, when connected to pipelines, have locally shaped flanges corresponding to the equipment, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces while sealing is generally called a "flange," such as the connection of ventilation pipes. These types of components can be referred to as "flange-type parts." However, such a 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-type part." Smaller items like valves can be referred to as "flange-type parts."