Flange, also known as a flange boss or rim, is a component used to connect shafts to each other or to pipe ends. It is also used on equipment for connections between two devices, such as a reducer flange. A flange connection or flange joint refers to a removable connection that consists of a combination of flanges, gaskets, and bolts for a sealed assembly. Pipe flanges are those used for piping in equipment installations, while those used on equipment refer to the equipment's inlet and outlet flanges. Flanges have holes and bolts are used to tightly secure them. They are sealed with a gasket. Flanges come in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure require welded flanges. Two flange discs are joined with a sealing pad and then secured with bolts. The thickness of flanges varies with pressure, as do the bolts used. When pumps and valves are connected to pipelines, these equipment components are also made in corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces around the edges and is sealed simultaneously is generally called a "flange," such as the connection in ventilation pipes. These types of components can be referred to as "flange-type components." However, such connections are only 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 items like valves can be called "flange-type components."