Flange, also known as a flange disc or rim, is a component used for connecting shafts or for joining pipe ends. It is also used on equipment for connecting two devices, such as a reducer flange. A flange connection or flange joint refers to a removable connection made up of the flange, gasket, and bolts, forming a combination seal structure. Pipe flanges are the flanges used in piping installations; on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts 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 use焊接 flanges. Two flange discs are joined with a sealing pad and then tightened with bolts. Flanges of different pressures have different thicknesses and require different bolts. In the connection of equipment like pumps and valves to pipelines, the local parts of these equipment are also made into corresponding flange shapes, known as flange connections. Any connection piece that uses bolts to connect two flat surfaces around the circumference and is sealed is generally called a "flange," such as the connection of ventilation pipes. These types of components can be referred to as "flange-type components." However, such connections are 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 component." Smaller items like valves can be called "flange-type components."