Flange, also known as a flange disc or boss, is a component used for inter-axial connections, typically for joining pipe ends; it is also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a detachable connection formed by the combination of a flange, a gasket, and bolts. Pipe flanges are flanges used in piping systems, while equipment flanges refer to the inlets and outlets of equipment. 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 clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure require焊接 flanges. Two flange discs are joined with a sealing pad and then fastened with bolts. Flange thickness and bolt types vary depending on the pressure. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes, also known as flange joints. Any connection component that uses bolts to connect two flat surfaces and seal them is generally called a "flange," such as in ventilation pipe connections. Such components can be referred to as "flange-like 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-like part." Smaller components like valves can be called "flange-like parts."