Flange, also known as a flanged disk or boss, is a component that connects shafts together, used for pipe end connections; it is also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a detachable connection made up of the flange, gasket, and bolt as a combined sealing structure. Pipe flanges refer to the flanges used for piping in pipe installations, while on equipment, they refer to the inlets and outlets of the equipment. Flanges have holes and bolts that securely connect the two flanges. They are sealed with a gasket. 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. Two flange disks are sealed with a gasket and then secured with bolts. The thickness of flanges varies with pressure, as do the bolts used. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes at their connection points, also known as flange joints. Any connection component used to join two flat surfaces around the perimeter with bolts and simultaneously seal them is generally called a "flange," such as in the case of ventilation pipe connections. Such 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's not appropriate to call the pump a "flange-type part." Smaller items like valves can be referred to as "flange-type parts."