Flange, also known as a flange disk or boss, is a component used for connecting shafts or for joining pipe ends. It is also 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 made up of the flange, gasket, and bolts working together as a combined sealing structure. Pipe flanges are specifically used for piping in pipeline installations and refer to the flanges at the equipment inlets and outlets. 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 pipelines can use threaded flanges, while those above 4 kg pressure require welding flanges. Two flange disks are joined with a sealing pad and then bolted together. Flange thickness and bolt types vary with pressure ratings. Equipment like pumps and valves, when connected to pipes, have 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 in ventilation pipe connections. These types of components can be referred to as "flange-like 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-like part." Smaller components like valves can be called "flange-like parts."