Flange, also known as a flange disk or boss, 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, for connecting two pieces of equipment. A flange connection or flange joint refers to a detachable connection made up of a flange, a gasket, and bolts, forming a combination seal structure. Pipe flanges are the flanges used in piping installations, or the inlet and outlet flanges on equipment. Flanges have holes, and bolts are used to tightly secure the two flanges. They are sealed with a gasket. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure require welding flanges. Two flange disks are sealed with a gasket and then bolted together. Flange thickness and the type of bolts vary with pressure ratings. Pumps and valves, when connected to pipes, have corresponding flange shapes for local connections, also known as flange joints. Any connection piece that uses bolts to connect two flat surfaces and seal them is generally called a "flange," such as in the case of ventilation pipe connections. These components can be referred to as "flange-type parts." However, such connections are only 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 referred to as "flange-type parts."