Flange, also known as a flange dish or boss, is a component used for connecting shafts to each other, typically for pipe end connections; it is also used on equipment for connections between two devices, such as a reducer flange. A flange connection or flange joint refers to a removable connection that consists of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are the flanges used for piping in pipe installations, or on equipment, referring to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure them tightly 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 4 kg of pressure use焊接 flanges. Two flange disks are joined with a sealing gasket and then bolted together. Flanges of different pressures have different thicknesses and require different bolts. Pumps and valves, when connected to pipes, have locally shaped flanges, 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 referred to as "flange-type parts."