Copper nickel orifice flanges are flanges that are made from a copper nickel alloy. They are used in applications where high resistance to corrosion is required, particularly in seawater environments. Orifice flanges are used in pipelines for measuring the flow of liquids or gases, and they have a small hole, or orifice, drilled in the center. This orifice is used to measure the rate of flow of the fluid passing through the pipeline.