Flange, also known as a flange disc or raised boss. A flange is a component that connects two shafts and is used for pipe end connections; there are also flanges used on equipment inlets and outlets for connecting two devices, such as reducer flanges. Flange connection or flange joint refers to the detachable connection formed by the combination of flange, gasket, and bolt. Pipe flange refers to the flange used for piping in a pipeline installation; when used on equipment, it refers to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure the two flanges together. The space between flanges is sealed with a gasket. Flanges are available in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those over 4 kg pressure require welded flanges. Two flange discs are joined with a sealing pad and then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. Pumps and valves, when connected to pipelines, the local parts of these equipment items are also made into corresponding flange shapes and are called flange connections. Any connection piece that uses bolts to connect two flat perimeters and is sealed is generally called a "flange," such as the connection of ventilation pipes. Such components can be referred to as "flange-type parts." However, such connections are only part of a single device, like the connection between a flange and a pump, so it is not appropriate to call the pump a "flange-type part." Smaller components like valves can be called "flange-type parts."