Flange, also known as a flange disk or boss, is a component used for connecting shafts to each other or for pipe ends. It is also used at equipment inlets and outlets for connecting two devices, such as a reducer flange. A flange joint or connection refers to a removable joint that consists of a flange, a gasket, and bolts, forming a combination seal structure. Pipe flanges are specifically used for piping in pipe assemblies, or refer to the inlets and outlets of equipment. Flanges have holes, and bolts secure the two flanges together. They are sealed with a gasket. Flanges come in threaded (screwed) connections, welding flanges, and clamp flanges. Flanges are used in pairs; low-pressure piping can use threaded flanges, while pressures above 4 kg require welding flanges. Two flange disks are joined with a seal, then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. In the case of pumps and valves, when connected to pipes, the local components of these equipment are also made in the corresponding flange shape, also known as a flange connection. Any connection component that uses bolts to connect two flat surfaces around the periphery and is sealed is generally called a "flange," such as in the case of ventilation pipe connections. These types of components can be referred to as "flange-type parts." However, such connections are only a part of a single device, like the connection between a flange and a pump, so it wouldn't be appropriate to call the pump a "flange-type part." Smaller components like valves can be called "flange-type parts."