Flange, also known as a flange boss or rim. A flange is a component used for connecting pipes to each other, serving as a connection between pipe ends; there are also flanges used at equipment inlets and outlets for connecting two pieces of equipment, such as reducer flanges. Flange connection or flange joint refers to a detachable connection that consists of a flange, a gasket, and bolts, all interconnected to form a combined sealing structure. Pipe flanges refer to flanges used for piping in pipeline installations, or specifically to the inlet and outlet flanges on equipment. Flanges have holes and bolts are used to tightly secure the two flanges together. A gasket is used to seal between the flanges. Flanges are available in threaded connection (threaded flanges), welding flanges, and clamping flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while pipelines with a pressure of 4 kg or more should use welding flanges.