Flange, also known as a flange disc or rim, is a component used for connecting shafts to each other, typically for pipe end connections; it is also used on equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a removable connection formed by the combination of flanges, gaskets, and bolts. Pipe flanges are flanges used in piping installations, while equipment flanges refer to the inlets and outlets of equipment. Flanges have holes and bolts that secure them tightly together, with gaskets used to seal the flange gaps. Flanges come in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines 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. The thickness of flanges varies with pressure, as do the bolts used. In the case of pumps and valves, when connected to pipes, these equipment components are also shaped like corresponding flanges and are called flange connections. Any connection component that uses bolts to connect two flat surfaces and seal them is generally referred to as a "flange," such as the connection of ventilation pipes. These types of components can be called "flange-type 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 a "flange-type part." Smaller components like valves can be referred to as "flange-type parts."