Flange, also known as a flanged disk or rim. A flange is a component used for connecting shafts together or for joining pipe ends; it can also be used at equipment inlets and outlets for connecting two pieces of equipment, such as a reducer flange. Flange connection or flange joint refers to a removable connection that consists of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are the flanges used for piping in pipe installations; when used on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure the two flanges together. Gaskets are used to seal between flanges. Flanges are available in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are always used in pairs; low-pressure piping can use threaded flanges, while those above four kilograms of pressure use welded flanges. Two flange disks are joined with a sealing gasket and then bolted together. The thickness of flanges varies with pressure, as do the bolts used. Pumps and valves, when connected to pipes, have corresponding flange shapes for these equipment components, also known as flange connections. Any connection that uses bolts to connect two flat surfaces and seal them is generally called a "flange," such as the connection of ventilation pipes. Such components can be referred to as "flange-like parts." However, such connections are only a part of a single piece of equipment, like the connection between a flange and a pump, so it is not appropriate to call the pump a "flange-like part." Smaller components like valves can be called "flange-like parts."