Flange, also known as a flange disc or boss, is a component that connects shafts together, used for pipe-end connections; there are also flanges used at equipment inlets and outlets for connecting two pieces of equipment, such as a reducer flange. Flange connection or flange joint refers to a removable joint consisting of a flange, gasket, and bolt, which together form a sealing assembly. Pipe flanges are flanges used for piping in pipe installations; on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure the two flanges together. Flanges are sealed with a gasket. Flanges are divided into threaded connection (threaded) flanges, welding flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipes can use threaded flanges, while those above four kilograms of pressure use welding flanges. A sealant pad is placed between two flange discs, and then bolts are used to tighten them. Flanges of different pressures have different thicknesses, and they use different bolts. In the case of pumps and valves, when connected to pipes, these equipment components are also shaped into corresponding flange patterns and are called flange connections. Any connection piece that uses bolts to connect two flat surfaces around the periphery and is sealed is generally called a "flange," such as the connection of ventilation pipes, which can be referred to as "flange-type components." However, such a connection is 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 component." Smaller components like valves can be called "flange-type components."