Alcance
This Technical Report provides guidance on estimating the flowrate when using pressure differential devicesconstructed or operated outside the scope of ISO 5167.Additional tolerances or corrections cannot necessarily compensate for the effects of deviating from ISO 5167(all parts). The information is given, in the first place, to indicate the degree of care necessary in themanufacture, installation and maintenance of pressure differential devices by describing some of the effects ofnon-conformity to the requirements; and in the second place, to permit those users who cannot comply fullywith the requirements to assess, however roughly, the magnitude and direction of the resulting error inflowrate.Each variation dealt with is treated as though it were the only one present. Where more than one is known toexist, there may be unpredictable interactions and care has to be taken when combining the assessment ofthese errors. If there is a significant number of errors, means of eliminating some of them have to beconsidered. The variations included in this Technical Report are by no means complete and relate largely toexamples with orifice plates. An example with Venturi tubes has been placed at the end of its section. Thereare, no doubt, many similar examples of installations not conforming to ISO 5167 (all parts) for which nocomparable data have been published. Such additional information from users, manufacturers and any othersmay be taken into account in future revisions of this Technical Report.