Flange, also known as a flange disc or boss, is a component used for connecting shafts or for joining pipe ends. It is also used at equipment inlets and outlets, such as reducer flanges, to connect two devices. A flange connection or flange joint refers to a removable joint that consists of a flange, a gasket, and bolts, forming a combination seal structure. Pipe flanges are the flanges used for piping in pipeline installations, or in equipment, they refer to the equipment's inlet and outlet flanges. 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 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 different thicknesses and require different bolts. In the case of pumps and valves, when connected to pipelines, the local parts of these equipment are also made into 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 the connections in ventilation pipes, which can be referred to as "flange-type components." However, such a connection is only a part of a single device, like the connection between a flange and a pump, so it's not appropriate to call the pump a "flange-type component." Smaller items like valves can be called "flange-type components."