Flange, also known as a flange collar or boss, is a component used for connecting shafts to each other or for joining pipe ends; it's also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a removable joint consisting of a flange, a gasket, and bolts, which together form a sealing assembly. Pipe flanges are specifically used in piping systems for equipment inlets and outlets. Flanges have holes for bolts that secure them tightly together, and they are sealed with a gasket. Flanges are available in threaded (screwed) connections,焊接 (welded) connections, and clamp connections. Flanges are always used in pairs; low-pressure piping can use threaded flanges, while pressures above four kilograms require焊接 flanges. Two flange disks are joined with a sealing pad and then fastened with bolts. Flange thickness and bolt types vary depending on pressure ratings. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes, also known as flange joints. Any connection piece that uses bolts to connect two flat surfaces around the circumference and is sealed is generally called a "flange," such as in ventilation pipe connections. 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 items like valves can be called "flange-type parts."