Flanges, also known as raised face plates or flanged discs, are components used for connecting shafts to each other, typically for joining pipe ends; they are also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a removable connection made up of a flange, a gasket, and bolts, all interconnected to form a combined sealing structure. Pipe flanges are the flanges used in piping installations, while equipment flanges refer to the inlets and outlets of the equipment. Flanges have holes, and bolts are used to tightly secure the two flanges together. They are sealed with a gasket. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure require welding 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 items are also made into corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and is sealed simultaneously is generally called a "flange," such as the connection of ventilation pipes. Such components can be referred to as "flange-type parts." However, this type of connection is only a part of a single device, such as the connection between a flange and a pump, so it's not appropriate to call the pump a "flange-type part." Smaller items like valves can be called "flange-type parts."