Flange, also known as a flange dish or boss, is a component used for connecting shafts to each other or for joining pipe ends. It is also used on equipment inlets and outlets, such as reducer flanges, for connecting two devices. A flange connection or flange joint refers to a removable connection consisting of a flange, a gasket, and bolts, all interconnected to form a sealing assembly. Pipe flanges are the flanges used for piping in pipeline installations, and on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes for bolts, which secure the 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 4 kg pressure use welded flanges. Two flange disks are joined with a sealing pad and then bolted together. Flanges of different pressures have different thicknesses and require different bolts. When pumps and valves are connected to pipelines, the local parts of these equipment items are also made into corresponding flange shapes, also 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 the connection of ventilation pipes. Such parts can be referred to as "flange-type parts." However, this type of connection is only a local 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."