ISO 5167-4:2022

Overview

ISO 5167-4:2022 specifies the geometry, installation and operating requirements for Venturi tubes used to measure fluid flow in circular conduits running full. Part 4 of the ISO 5167 series applies to classical Venturi tubes (as‑cast, machined, and fabricated) for single‑phase, subsonic flows. The standard gives the background and formulae needed to compute flow rate from differential pressure, and it is intended to be used together with ISO 5167‑1. ISO 5167‑4:2022 is the second edition and includes updated guidance on pressure tappings and calibration.

Key topics and requirements

• Field of application
  • Applicable only where flow remains subsonic and the fluid is single‑phase.
  • Uncalibrated use is limited by pipe size, roughness, diameter ratio and Reynolds number; alternatively, devices can be used across their calibrated range.
  • Not applicable for pulsating flow or uncalibrated pipes < 50 mm or > 1 200 mm, or where pipe Reynolds numbers are below 2 × 10^5.
• Device geometry
  • Defines the components of a classical Venturi tube: entrance cylinder, convergent section, cylindrical throat, and divergent (diffuser) section.
  • Covers three construction types: as‑cast, machined, and fabricated (rough‑welded).
• Measurement elements
  • Pressure tappings: locations and permitted configurations (single tappings permitted in this edition).
  • Discharge coefficient (C) and expansibility (expansion) factor (ε): guidance, limits of use and uncertainty estimates.
  • Pressure loss: definition and relative loss characteristics.
• Installation & operation
  • Minimum upstream/downstream straight lengths, flow conditioner recommendations, circularity/alignment and pipe roughness requirements.
• Calibration & uncertainty
  • Procedures for flow calibration in test facilities, test program design, calibration reporting and uncertainty analysis.

Practical applications and users

ISO 5167-4:2022 is used by:

• Instrumentation and measurement engineers selecting or specifying Venturi flow meters for liquid or gas pipelines
• Manufacturers designing classical Venturi tubes to comply with international metrology practice
• Calibration laboratories and test facilities performing flow calibration and uncertainty analysis
• Pipeline operators, HVAC and process engineers requiring standardized differential‑pressure flow measurement procedures

Benefits include repeatable, low‑loss flow measurement, clear guidance on installation and achievable measurement uncertainty, and interoperability when purchasing or certifying Venturi meters.

Related standards

• ISO 5167-1: General principles and computation methods for pressure‑differential flowmeters (use in conjunction with 5167‑4)
• ISO 5167-3: Nozzles (covers Venturi nozzles and other nozzle types)
• ISO 4006: Vocabulary and symbols for flow measurement

Keywords: ISO 5167-4:2022, Venturi tubes, differential pressure flow measurement, discharge coefficient, expansibility factor, flow calibration, pipe flow standards.