Flange, also known as a flange collar or boss. A flange is a component used for connecting shafts to each other or for joining pipe ends; it is also used at equipment inlets and outlets, such as reducer flanges. Flange connection or flange joint refers to a removable connection formed by the combination of flange, gasket, and bolt as a sealed assembly. Pipe flanges are flanges used for piping in pipe installations; when used on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure the two flanges together. They are sealed with a gasket. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those above 4 kg of pressure use焊接 flanges. A sealant pad is placed between the two flange disks, and then bolts are tightened. Flanges of different pressures have different thicknesses, and they 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 around the periphery and is sealed is generally called a "flange," such as the connection of ventilation pipes. Such parts can be called "flange-type parts." However, this type of connection is only a part of a device, such as 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."