Flange, also known as a flange disc or boss, 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, to connect two devices. A flange joint or flange connection refers to a removable connection consisting of a flange, a gasket, and bolts, all interconnected as a sealed assembly. Pipe flanges are flanges used for piping in pipe assemblies, and on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes and bolts that 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 piping can use threaded flanges, while those above 4 kg pressure use welded flanges. Two flange discs are joined with a sealing pad and then bolted together. Flanges of different pressures have different thicknesses and require different bolts. In the case of pumps and valves, when connected to pipes, the local parts of these equipment pieces are also made in corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and seal them is generally called a "flange," such as the connection of ventilation pipes. Such parts can be referred to as "flange-type components." 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 a "flange-type component." Smaller items like valves can be called "flange-type components."