Flange, also known as a flange disk or raised rim. A flange is a component used for connecting shafts or for joining pipe ends; it is also used on equipment inlets and outlets, such as reducer flanges. Flange connection or flange joint refers to a removable connection formed by the combination of flange, gasket, and bolt as a sealing structure. Pipe flanges are flanges used for piping in pipe systems; when used on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure the two flanges together. They are sealed with a gasket. Flanges are categorized into threaded (screwed) flanges, welded flanges, and clamp flanges. Flanges are used in pairs; low-pressure piping can use threaded flanges, while pressures above four kilograms require welded flanges. Two flange disks are joined with a sealing pad and then tightened with bolts. Flange thickness and bolt types vary with pressure ratings. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to join two flat surfaces and seal them is generally called a "flange," such as in the connection of ventilation pipes. These types of components can be referred to as "flange-like 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-like part." Smaller items like valves can be referred to as "flange-like parts."