Flange, also known as a flange disc or boss, is a component used for connecting shafts to each other, typically for pipe end connections; it is also used on equipment进出口 for connecting two devices, such as reducer flanges. A flange connection or flange joint refers to a removable joint made up of a flange, gasket, and bolts, forming a combination seal structure. Pipe flanges are the flanges used for piping in pipeline installations; on equipment, they refer to the equipment's进出口 flanges. Flanges have holes, and bolts secure them tightly together. Gaskets are used to seal between flanges. Flanges come in threaded (screwed) connections,焊接 connections, and clamp connections. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above 4 kg pressure use焊接 connections. Two flange discs are joined with a sealing gasket and then bolted together. Flange thickness varies with pressure, as do the bolts used. When pumps and valves are connected to pipelines, the local parts of these equipment items are also made in corresponding flange shapes, also known as flange joints. Any connection piece that uses bolts to connect two flat surfaces and is sealed simultaneously is generally called a "flange," such as the connection in ventilation pipes. These types of parts 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 items like valves can be called "flange-type parts."