Flange, also known as a flange disc or rim, is a component that connects shafts to each other, used for joining pipe ends; 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 removable joint that consists of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are flanges used in piping installations; when used on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts are used to tightly secure the two flanges. A gasket is used to seal between the flanges. Flanges are available in threaded (screwed) connections, welding flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those above 4 kg of pressure use welding flanges. A sealing pad is placed between the two flange discs, and then bolts are tightened. Flanges of different pressures have different thicknesses, and they also use different bolts. In the connection of pumps and valves with pipelines, the local parts of these equipment are also made into corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and is sealed is generally called a "flange," such as the connection of ventilation pipes, which can be referred to as "flange-like parts." However, such a connection is only a part of a device, such as the connection between a flange and a pump, where it is not appropriate to call the pump a "flange-like part." Smaller items like valves can be called "flange-like parts."
