Orifice Flow Meter Discharge Coefficient Values Using ISO 5167

The orifice flow meter is widely used for pipe flow measurement. The value of the orifice discharge coefficient for a particular orifice flow meter is needed to calculate the pipe flow rate from the measured pressure difference across an orifice in the flow path. Prior to 1991 changing the orifice opening size caused problems for determining the orifice discharge coefficient. In 1991 ISO 5167 came out with three standard pressure tap configurations and an equation for calculating the orifice discharge coefficient, independent of the orifice size. This allows for a wider range of flow rate measurement, by allowing different size orifices in a given orifice flow meter, while still allowing determination of the orifice discharge coefficient