What is the required upstream and downstream straight length run that is suitable for an orifice plate flow measurement
5D-10D minimum for straight horizontal pipe length will be increased depends upon the number of bends in the pipe. 10D to 15 D at the Inlet and 5D to 7D at the outlet
The upstream/downstream straight run requirements can be quite significant for flow obstructions without the use of flow straightening conditioners - in one case as high as 75 upstream diameters.
Both ISO 5167-2 (Orifice Plates) 2012 and ASME-MFC-3M (2004) standards have similar, if not identical charts with experimentally determined requirements, but there’s an entire page of listing additional considerations.Straight run upstream-downstream for Orifice plate requirements, ISO 5167-2, 2003.pdf (96.4 KB)