Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full - Part 3: Nozzles and Venturi nozzles (ISO 5167-3:2022)

This document establishes technical specifications for determining the flow rate of liquids, gases, and vapours by measuring the pressure difference across a restriction element installed in a fully filled circular conduit. Specifically, it addresses flow measurement techniques utilizing nozzles and Venturi nozzles. The scope defines the geometrical requirements, installation conditions, and operational limits necessary to ensure accurate measurement results. It outlines the procedures for calculating the mass or volumetric flow rate based on differential pressure data, taking into account the properties of the fluid and the specific dimensions of the restriction element. The standard provides the mathematical framework and correction factors applicable to these devices under steady-state flow conditions. It serves as a reference for the design, calibration, and installation of flow measurement systems in industrial applications. The content aligns with internationally recognized practices for differential pressure flow measurement, ensuring consistency and reliability across different environments. The document details the permissible uncertainties and the necessary documentation for verifying compliance with the specified measurement criteria.