Flanges, also known as flange hubs or raised rings, are components that connect shafts to each other, typically used for joining pipe ends. They are also employed at the inlets and outlets of equipment, such as reducer flanges, for connecting two devices. A flange connection or flange joint refers to a removable connection formed by the combination of a flange, a gasket, and bolts. Pipe flanges are those used in piping installations, while equipment flanges refer to the inlets and outlets of equipment. Flanges have holes and bolts that secure them tightly together, with gaskets used for sealing between flanges. Flanges come in threaded (screwed) connections, welded flanges, and clamp flanges. They are used in pairs, with threaded flanges suitable for low-pressure piping and welded flanges for pressures above four kilograms. Two flange discs are joined with a sealing pad and then fastened with bolts. Flange thickness varies with pressure, as do the bolts used. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes at the local connection points, also known as 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 in ventilation pipe connections. Such components can be referred to as "flange-type parts." However, this type of connection is only a local 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 part." Smaller devices like valves can be called "flange-type parts."