Flange, also known as a flange disk or boss, is a component that connects shafts to each other, used for pipe end connections; it's also used on equipment inlets and outlets for connecting two devices, such as reducer flanges. A flange joint refers to a detachable connection formed by the combination of a flange, a gasket, and bolts as a sealed assembly. Pipe flanges are flanges used in piping installations; when used on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes and bolts that secure them tightly together. Gaskets are used to seal between flanges. Flanges come in threaded (screwed) connections, welding flanges, and clamping flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above 4 kg of pressure use welding flanges. A sealant is placed between two flange disks, then secured with bolts. Flange thickness varies with pressure, and so do the bolts used. Equipment like pumps and valves, when connected to pipes, have parts shaped like corresponding flanges, also known as flange connections. Any connection component that uses bolts to connect two flat surfaces and seal them is generally called a "flange," such as ventilation pipe connections, which can be referred to as "flange-type components." 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 component." Smaller equipment like valves can be called "flange-type components."