Flange, also known as a flange disc or raised rim. A flange is a component used for connecting shafts to each other, serving as a connection point for pipe ends; it's also used on equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a removable joint made up of a flange, a gasket, and bolts, acting as a combined sealing structure. Pipe flanges are the flanges used in piping systems within equipment, referring to the inlets and outlets of the equipment. Flanges have holes, and bolts secure them tightly 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 4 kg pressure require 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. In the case of pumps and valves, when connected to pipes, these equipment components are also shaped like corresponding flanges, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and is sealed simultaneously is generally called a "flange," such as the connection of ventilation pipes. 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 components like valves can be called "flange-type parts."