Orifice flange is a flow measurement device installed in the pipeline system, which consists of a standard flange, an orifice plate and a sealing gasket. The orifice plate is a special plate with holes. The holes of different shapes are used to make the fluid flow in different forms on the orifice plate. Orifice flanges are classified according to different standards, among which the most commonly used are ISO standards and ASME B16.36 standards.