Flange, also known as a flange disk or boss, is a component used for connecting shafts or for joining pipe ends. It can also be used at equipment inlets and outlets for connecting two devices, such as a reducer flange. A flange connection or flange joint refers to a removable joint made up of a flange, a gasket, and bolts, which together form a sealing assembly. Pipe flanges are the flanges used for piping in pipe installations, and on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes and bolts are used to tightly secure them together. They are sealed with a gasket. Flanges are available 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 4 kg of pressure require welding 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. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes, also known as flange connections. Any connection piece 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 parts." However, this type of connection is 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."