Flange, also known as a flange dish or boss. A flange is a component used to connect pipes to each other, serving as a connection between pipe ends; there are also flanges used on equipment inlets and outlets for connecting two devices, such as reducer flanges. Flange connection or flange joint refers to a detachable connection that consists of a combination seal structure formed by the flange, gasket, and bolts. Pipe flanges refer to the flanges used for piping in pipe installations; on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure the two flanges together. Gaskets are used to seal between the flanges. Flanges are available in threaded (screwed) connections,焊接 (welded) flanges, and clamping flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while pipelines with pressures above 4 kg require焊接 flanges.