Flange, also known as a flange disc or rim, is a component used for connecting shafts or for joining pipe ends; it is also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a removable connection formed by the combination of a flange, a gasket, and bolts. Pipe flanges are those used in piping installations, and when used on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes for bolts, which secure the flanges together. They are sealed with a gasket. Flanges are available in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while pipelines above four kilograms of pressure use焊接 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. Equipment like pumps and valves, when connected to pipelines, have corresponding flange shapes at their local connections, also known as flange connections. Any connection piece that uses bolts to connect and seal two flat surfaces around the periphery is generally called a "flange," such as the connections on ventilation pipes. Such components can be referred to as "flange-type 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's not appropriate to call the pump a "flange-type part." Smaller components like valves can be called "flange-type parts."