EN ISO 5167-4:2003

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Principles of the method of measurement and computation
5 Classical Venturi tubes
   5.1 Field of application
   5.2 General shape
   5.3 Material and manufacture
   5.4 Pressure tappings
   5.5 Discharge coefficient, C
   5.6 Expansibility [expansion] factor, [epsilon]
   5.7 Uncertainty of the discharge coefficient, C
   5.8 Uncertainty of the expansibility [expansion]
        factor [epsilon]
   5.9 Pressure loss
6 Installation requirements
   6.1 General
   6.2 Minimum upstream and downstream straight lengths
        for installation between various fittings and the
        Venturi tube
   6.3 Flow conditioners
   6.4 Additional specific installation requirements
        for classical Venturi tubes
Annex A (informative) Table of expansibility [expansion]
         factor
Annex B (informative) Classical Venturi tubes used
         outside the scope of ISO 5167-4
Annex C (informative) Pressure loss in a classical
         Venturi tube
Bibliography

ISO 5167-4:2003 specifies the geometry and method of use (installation and operating conditions) of Venturi tubes when they are inserted in a conduit running full to determine the flowrate of the fluid flowing in the conduit. ISO 5167-4:2003 also provides background information for calculating the flow-rate and is applicable in conjunction with the requirements given in ISO 5167-1.ISO 5167-4:2003 is applicable only to Venturi tubes in which the flow remains subsonic throughout the measuring section and where the fluid can be considered as single-phase. In addition, each of these devices can only be used within specified limits of pipe size, roughness, diameter ratio and Reynolds number. ISO 5167-4:2003 is not applicable to the measurement of pulsating flow. It does not cover the use of Venturi tubes in pipes sized less than 50 mm or more than 1 200 mm, or for where the pipe Reynolds numbers are below 20 000.ISO 5167-4:2003 deals with the three types of classical Venturi tubes: cast, machined and rough welded sheet-iron.A Venturi tube is a device which consists of a convergent inlet connected to a cylindrical throat which is in turn connected to a conical expanding section called the "divergent". The differences between the values of the uncertainty of the discharge coefficient for the three types of classical Venturi tube show, on the one hand, the number of results available for each type of classical Venturi tube and, on the other hand, the more or less precise definition of the geometric profile. The values are based on data collected many years ago. Venturi nozzles (and other nozzles) are dealt with in ISO 5167-3.