Overview
EN ISO 5167-1:2022 (ISO 5167-1:2022) establishes the general principles and requirements for measuring fluid flow in circular cross-section conduits running full using differential pressure (DP) devices. It defines terms, symbols and the measurement/computation methodology for primary devices such as orifice plates, nozzles, Venturi tubes, cone meters and wedge meters. The standard applies to single‑phase, subsonic, non‑pulsating flows and sets out rules for measurement, installation and the determination of measurement uncertainty.
Key topics and requirements
- Scope and definitions: standard symbols, subscripts and terminology used across the ISO 5167 series.
- Measurement principle: calculation of volumetric (and mass) flow from measured differential pressure across a primary device.
- Primary device selection and sizing: guidance on diameter ratios and selection of standard primary devices compatible with circular conduits.
- Installation requirements: provisions for minimum upstream/downstream straight lengths, flow profile and swirl control, and use of flow conditioners where needed.
- Instrumentation and piping: requirements for impulse lines, transmitters, valve manifolds and flow computers that form the DP metering system.
- Performance and operational considerations: turndown, meter calibration, diagnostics, permanent pressure loss and practical metering design.
- Uncertainty and verification: methods to determine and report overall measurement uncertainty, component uncertainties and practical computation approaches.
- Informative annexes: examples and guidance on iterative computations, pipe roughness, flow conditioners, transmitter turndown, uncertainty examples and permanent pressure loss.
Applications and who uses it
EN ISO 5167-1:2022 is essential for professionals who design, operate or verify flow measurement systems in industries such as:
- oil & gas, petrochemical and chemical processing
- water and wastewater utilities
- HVAC and building services engineering
- power generation and steam systems
- flow instrumentation manufacturers, calibration and metrology laboratories
- pipeline and process engineers responsible for custody transfer, process control or energy accounting
It is used to ensure traceable, repeatable DP flow measurements, to support procurement/specification of meters and transmitters, to design meter runs and to calculate measurement uncertainty for compliance and custody transfer.
Related standards
- ISO 5167 (all parts) - Part 1 provides the general principles; other parts detail specific primary devices and application guidance.
- EN adoption: EN ISO 5167-1:2022 is the CEN-endorsed version for Europe.
EN ISO 5167-1:2022 is a foundational standard for accurate, reproducible DP flow metering and is commonly cited in instrument specifications, procurement documents and metering best practices.
