Flanges, also known as flange hubs or raised rings, are components that connect shafts to each other, used for joining pipe ends; they are also used on equipment进出口, such as reducer flanges, for connecting two devices. Flange connections or flange joints refer to removable joints made up of flanges, gaskets, and bolts, functioning as a combined sealing structure. Pipe flanges are those 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 gaps between them. 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 of pressure require welded flanges. Two flange disks are joined with a sealing pad and then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. When pumps and valves are connected to pipelines, the respective parts of these equipment components are also shaped as flanges, known as flange connections. Any connection piece that uses bolts to join two flat surfaces around the perimeter and is sealed is generally called a "flange," such as in ventilation pipe connections. Such components can be referred to as "flange-type parts." However, such connections are only a part of a 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 called "flange-type parts."