Flange, also known as a flange boss or rim, is a component used for connecting shafts to shafts, typically for joining pipe ends. It is also used at equipment inlets and outlets, such as reducer flanges, for connecting two devices. A flange connection or flange joint refers to a removable connection that consists of a combination of flanges, gaskets, and bolts for a seal. Pipe flanges are flanges used in piping installations; on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes for bolts, which secure them together, and are sealed with gaskets. Flanges are available in threaded (screwed) connections, welding connections, and clamp connections. Flanges are used in pairs; low-pressure piping can use threaded flanges, while those over four kilograms of pressure require welding flanges. Two flange discs are joined with a sealing pad and then bolted together. Flange thickness and bolt types vary with pressure ratings. Equipment like pumps and valves, when connected to piping, have corresponding flange shapes, also known as flange joints. 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, such connections are 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 part." Smaller items like valves can be called "flange-type parts."