Flange, also known as a flanged disk or boss, is a component used to connect shafts or for pipe end connections; it is also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a removable connection formed by the combination of a flange, a gasket, and bolts. Pipe flanges are the flanges used for piping in a pipeline system, or for equipment inlets and outlets. Flanges have holes and bolts that secure them tightly together. They are sealed using 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 pressure use焊接 flanges. Two flange disks are joined with a sealing pad and then secured with bolts. 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 seal them is generally called a "flange," such as in the connection of ventilation pipes. Such components can be referred to as "flange-type parts." However, such connections are only 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."