Flange, also known as a flange collar or boss. A flange is a component used to connect shafts to each other or to pipe ends; it is also used at equipment inlets and outlets for connecting two devices, such as a reducer flange. A flange connection or flange joint refers to a removable joint consisting of a flange, a gasket, and bolts, which together form a combined sealing structure. Pipe flanges are flanges used in piping installations, while those used on equipment refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure them tightly together. Seals are used between flanges. Flanges come 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 disks are sealed with a gasket and then bolted together. Flanges of different pressures have different thicknesses, and they use different bolts. In the connection of equipment like pumps and valves to pipes, these components are also shaped like corresponding flanges and are called flange connections. Any connection piece that uses bolts to connect two flat surfaces around the perimeter 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."