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, for connecting two devices. A flange connection or flange joint refers to a removable joint that consists of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are flanges used in piping installations, and on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes and bolts that secure them tightly 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 4 kg of pressure use welded flanges. Two flange discs are sealed with a gasket and then bolted together. Flange thickness varies with pressure, as do the bolts used. When pumps and valves are connected to pipelines, the local parts of these equipment items are also made in corresponding flange shapes, known as flange connections. Any connection component that uses bolts to connect two flat surfaces and is sealed is generally called a "flange," such as the connection of ventilation pipes. Such components can be referred to as "flange-type components." However, this type of connection is only a part of a device, such as 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."