Flange, also known as a flange collar or rim. A flange 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. Flange connection or flange joint refers to a removable joint consisting of a flange, a gasket, and bolts, which together form a combined sealing structure. Pipe flanges are flanges used in piping systems, and 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 come in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure use welded flanges. Two flange disks are joined with a sealing pad and then bolted together. Flange thickness varies with pressure, as do the bolts used. In pumps and valves, the local parts that connect to pipes are also made into corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces around the periphery and is sealed is generally called a "flange," such as the connection of ventilation pipes, which can be referred to as "flange-like parts." However, such connections are only a part of a single device, like the connection between a flange and a pump, so it's not appropriate to call the pump "flange-like parts." Smaller components like valves can be referred to as "flange-like parts."