Flange, also known as a flange disc or rim, is a component used for connecting shafts or for joining pipe ends. It is also used at equipment inlets and outlets, such as reducer flanges, for connecting two devices. A flange joint or flange connection refers to a removable joint that consists of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are flanges used in piping systems, while those on equipment refer to the equipment's inlet and outlet flanges. Flanges have holes for bolts, which secure the two flanges together. They are sealed with a gasket. Flanges come in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure use welded flanges. Two flange discs are joined with a sealing pad and then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. When pumps and valves are connected to pipelines, the respective parts of these equipment are also made in flange shape, known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and 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, this type of connection is only a 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 part." Smaller items like valves can be called "flange-type parts."