Flange, also known as a flange disk or boss, is a component used for connecting shafts to each other or for joining 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 detachable connection that consists of a combination of flanges, gaskets, and bolts for a sealed structure. Pipe flanges are those used for piping in pipeline installations, while equipment flanges refer to the inlets and outlets of the equipment. Flanges have holes, and bolts are used to tightly secure the two flanges together. Gaskets are used to seal between the flanges. Flanges are available in threaded (screwed) connections, welding connections, and clamp connections. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure use welding flanges. Two flange disks are fitted with a sealing pad and then secured with bolts. Flange thickness and the bolts used vary with pressure ratings. Pumps and valves, when connected to pipes, have locally shaped flanges that are also referred to as flange connections. Any connection piece that uses bolts to connect two flat surfaces and seal them is generally called a "flange," such as in ventilation pipe connections. These types of 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 referred to as "flange-type parts."