Flange, also known as a flange disc or rim, is a component used for connecting shafts or for joining 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 connection consisting of a flange, a gasket, and bolts, which together form a sealing assembly. Pipe flanges are those used in piping systems, while equipment flanges refer to the inlets and outlets of a device. Flanges have holes for bolts, which secure them together, and are sealed with a gasket. Flanges come in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are always used in pairs; low-pressure piping can use threaded flanges, while those above four kilograms of pressure use welded flanges. Two flange discs are joined with a sealing pad and then tightened with bolts. Flanges of different pressure ratings have varying thicknesses and require different bolts. When pumps and valves are connected to pipes, the local parts of these equipment components are also made in the shape of corresponding flanges, also known as flange joints. Any connection component that uses bolts to connect two flat surfaces and is sealed simultaneously is generally called a "flange," such as the connection of ventilation pipes. These types of components can be referred to as "flange-type components." However, such connections are only a part of a device, so it's not appropriate to call a pump a "flange-type component." Smaller components like valves can be referred to as "flange-type components."