Flange, also known as a flange disk or boss, is a component used for inter-axial connections, specifically for connecting pipe ends; it is also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a detachable connection consisting of a flange, a gasket, and bolts, which together form a sealed assembly. Pipe flanges are the flanges used in piping systems within equipment, or they refer to the inlets and outlets of the equipment. Flanges have holes for bolts that secure them tightly together, with a gasket used between them for sealing. Flanges come in threaded (screwed) connections, welding connections, and clamp connections. Flanges are typically used in pairs; low-pressure pipelines can use threaded flanges, while those over four kilograms of pressure use welding flanges. Two flange disks are joined with a sealing gasket and then fastened with bolts. Flange thickness varies with pressure, as do the bolts used. Equipment like pumps and valves, when connected to pipes, have parts shaped like flanges, also known as flange connections. Any connection piece that uses bolts to connect and seal two flat surfaces 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 a pump connected to a flange, so it's not advisable to call the pump a "flange-type part." Smaller items like valves can be referred to as "flange-type parts."