Flange, also known as a flanged disk or boss, is a component used for connecting shafts or for joining pipe ends. It can also be used at equipment inlets and outlets for connecting two devices, such as a reducer flange. 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 pipe installations, and on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure them tightly 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 piping 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 fastened with bolts. Flange thickness and bolt types vary with pressure ratings. In equipment like pumps and valves, the parts that connect to pipes are also shaped like flanges, 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 ventilation pipe connections. These types of components can be referred to as "flange-type parts." 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 part." Smaller components like valves can be called "flange-type parts."