Flange, also known as a flange disk or boss, is a component used for connecting shafts to each other, typically for pipe end connections; it's also used on 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, gasket, and bolt, serving as a seal assembly. Pipe flanges are the flanges used for piping in pipe installations; on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes for bolts, which secure the two flanges together, and 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 pressure use welded flanges. A sealant pad is placed between the two flange disks, then secured with bolts. Flange thickness and bolt types vary with pressure ratings. Equipment like pumps and valves, when connected to pipes, have locally shaped flanges, also known as flange connections. Any connection piece that uses bolts to join two flat surfaces around the perimeter and seal them is generally called a "flange," such as in ventilation pipe connections. 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 equipment like valves can be called "flange-type parts."