Flange, also known as a flanged disk or boss, 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 pieces of equipment. A flange connection or flange joint refers to a removable connection formed by the combination of a flange, a gasket, and bolts. Pipe flanges are specifically the flanges used for piping in a pipeline system, while on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes and bolts that secure them tightly 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 four kilograms of pressure require welding flanges. A sealing pad is placed between the two flange disks, and then bolts are used to tighten them. Flanges of different pressures have different thicknesses and require different bolts. Pumps and valves, when connected to pipes, have corresponding flange shapes for these equipment parts, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces around the perimeter and is sealed 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 part of a single piece of equipment, 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."