ISO 3966:2008,Measurement of fluid flow in closed conduits — Velocity area method using Pitot static tubes.ISO 3966:2008 pdf free download.
ISO 3966:2008 specifies a method for the determination in a closed conduit of the volume rate of flow of a regular flow: a) of a fluid of substantially constant density or corresponding to a Mach number not exceeding 0,25; b) with substantially uniform stagnation temperature across the measuring cross-section; c) running full in the conduit; d) under steady flow conditions.
In particular, ISO 3966:2008 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.
2 Normative references
ISO 2186, Fluid fiow in closed conduits-Connections for pressure signal transmissions between primary and secondary elements;
ISO 7194, Measurement of fluid flow in closed conduits-Velocity-area methods of flow measurement in
swirling or asymmetric flow conditions in circular ducts by means of current-meters or Pitot static tubes.
Errors in the techniques described in a) to ) contribute to the error in the flow-rate measurement other sources of error (such as the shape of the velocity distribution and the number of measuring points) are discussed in Clause 13.
The method of measurement and the requirements defined in this International Standard aim at reaching, at the 95 confidence level, an uncertainty in flow rate not greater than +2 %.To attain this result, it may be necessary, according to measurement conditions, to take into account the corrections given in Clause 12.If any of the requirements of this International Standard are not fulfilled, this method may still be applied in special cases but the uncertainty on flow rate will be larger.
ISO 3966:2008 presents three types of methods for determining the discharge velocity.