ISO 9464-2008 pdf download.Guidelines for the use of ISO 51 67:2003.
5.1.7.2.1 No comments on this subclause.
5.1 .7.2.2 When designing a metering pipe installation, It is recommended that the required minimum straight lengths are determined by the maximum diameter ratio that is expected in the life of the installation.
For diameter ratios not actually shown in ISO 5167-2:2003, Table 3. ISO 5167-3:2003, Table 3 or ISO 5167-4:2003, Table 1 but which are inside the limits of the standard, it is reasonable practice to interpolate linearly between the values obtained at the nearest two diameter ratios.
If an orifice meter is designed to measure the flowrate in either direction, the minimum straight lengths of pipe on both sides of the orifice plate should conform to the minimum requirements for upstream and downstream straight lengths as specified in ISO 5167-2:2003, 6.2 and Table 3.
5.1.7.3 General requirement for flow conditions at the primary device
No comments on this subclause.
5.1.7.4 Flow conditioners
It should be noted that although swirl is generally not detectable in visual inspection of the pipe, swirl and asymmetry are sometimes visible in the coating, if present, on an orifice plate. A typical herring bone or chevron pattern that may be seen on a plate that has been in service for some time may indicate that the flow at the orifice plate may be swirling or asymmetrical. Swirl has a greater effect on measurement than any other fluid dynamic mechanism and, although straight lengths of pipe will eliminate swirl, decay may occur very slowly and the swirl may persist over considerable distances. The use of straight lengths of pipe to eliminate swirl is questionable, especially in large pipe sizes, as the decay of induced swirl from common pipe components may not be sufficient to ensure fully developed profiles within the minimum lengths required in the tables.
Flow conditioners are strongly recommended for use downstream of a metering system header and in the following circumstances:
a) where the upstream fittings or arrangement of fittings are not defined in the tables;
b) where a primary device of high ft ratio is to be used for a given fitting, a flow conditioner which has passed the compliance test may reduce the upstream length necessary to achieve a good velocity profile, or may improve the velocity profile for a given straight length.
Many new flow conditioners have been developed since the previous edition of ISO 5167 published in 1991, and ISO 5167-1:2003 describes compliance testing for flow conditioners.
Various flow conditioners and straighteners are described in ISO 51 67-1 :2003, Annex C and ISO 5167-2:2003, Annex B, respectively. Not all of the conditioners described have been subjected to or have necessarily passed the compliance testing procedure.
5.1.8 Uncertainty on the measurement of flowrate
In 1995, ISO in cooperation with BIPM, IEC, IFCC, IUPAC, IUAP and OIML published the Guide to the expression of uncertainty in measurement (GUM). The content of this document and ISO 5168 should be taken into account when performing uncertainty analyses.ISO 9464 pdf download.