Flange, also known as a flanged boss or rim, is a component used for connecting shafts or for pipe-end connections; it is also used on equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a detachable connection made up of a flange, a gasket, and bolts as a combined sealing structure. Pipe flanges are the flanges used in pipe installations; on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes for bolts to secure them tightly. They are sealed using gaskets between them. Flanges are categorized into threaded (screwed) flanges, welded flanges, and clamped flanges. Flanges are used in pairs; low-pressure piping can use threaded flanges, while those above four kilograms of pressure use welded flanges. Two flange discs are sealed with a gasket and then secured with bolts. The thickness of flanges varies with pressure, and so does the type of bolts used. When pumps and valves are connected to pipes, these equipment components are also made in corresponding flange shapes, known as flange connections. Any connection component that uses bolts to connect two flat surfaces around the edges and is sealed is generally called a "flange," such as in ventilation pipe connections, these components can be referred to as "flange-type parts." However, such a connection is only a part of a single piece of equipment, like a flange connected to 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."