Latest Developments in Flow Measurement Using Differential-Pressure Meters
Michael Reader-Harris
Abstract:
After many years of discussion ISO 5167:2003 was published with several new features: it is divided into 4 parts; it has a new expansibility equation for orifice plates; the straight lengths required upstream of orifice plates and of Venturi tubes have been revised; a compliance test for flow conditioners is included, which leads to significant reductions in upstream straight length; an isenthalpic temperature correction between the downstream temperature measurement and the required upstream temperature is included; permissible steps in the upstream pipe diameter have been increased; and roughness limits have been revised. These changes are described and the reasons given. ISO/TR 9464 (the Code of Practice), ISO/TR 12767 (effects of departure from ISO 5167), and ISO/TR 15377 (nozzles and orifice plates beyond the scope of ISO 5167) all now require revision, to take account of both the changes to ISO 5167 and data collected recently. Some issues in these revisions are described. One area where work has been carried out in recent years is the performance of Venturi tubes in high-pressure gas. Some of the research work is briefly described.
Keywords:
Differential pressure meters, orifice plates, Venturi tubes, international standards
