BS ISO 3966:2020

What is ISO 3966 about?  

ISO 3966 specifies a method for the determination in a closed conduit of the volume rate of flow of a regular flow 

• Of a fluid of substantially constant density or corresponding to a Mach number not exceeding 0,25, 
• With substantially uniform stagnation temperature across the measuring cross-section, 
• Running full in the conduit 
• Under steady flow conditions. 

In particular, it deals with the technology and maintenance of Pitot static tubes, with the calculation of local velocities from measured differential pressures and with the computation of the flow rate by velocity integration. 

Who is ISO 3966 for?  

ISO 3966 on measurement of fluid flow in closed conduits is beneficial for 

• Fluid engineer 
• Fluid testing laboratory 

Why should you use ISO 3966?  

The velocity-area method is the most common method of estimating fluid flow. 

ISO 3966 provide guidance on the design of pitot tubes, requirements for use of pitot tubes,  

positioning of the pitot tube, velocity computation, determination of the discharge velocity by graphical integration of the velocity area, numerical integration of the velocity area, arithmetic methods  

As a user of ISO 3966, you can efficiently determine the flow rate of fluid under steady flow conditions or of a fluid of substantially constant density, using the velocity area method. ISO 3966 helps the user to acquire knowledge on the velocity-area method, Pitot static tubes. Overall ISO 3966 assist the user in dealing with the technology and maintenance of pitot-static tubes 

What’s changed since the last update?  

BS ISO 3966:2020 supersedes BS ISO 3966:2008, which is withdrawn 

The main changes compared to the previous edition are as follows: 

• All the mathematical formulae have been numbered 
• The essential Formula 4 has been corrected from Δρ/p to Δp/p 
• The related Table 2 on Examples of values is corrected likewise 
• The last sentence in Formulae for velocity computation (8.2) “for selected values of g and the Δρ/p…..” Was corrected accordingly; 
• In Rectangular cross-sections (11.2.2) in the 2nd paragraph ef is corrected by e or f. 
• Figure A.5 was changed editorially, the millimetre grid has been removed.