Project Reports, June 2005
Since the seventies an increasing use of Natural Gas as energy source and in Europe a vast network (gas-grid) has been realized. In this expanding gas grid more and more points of transfer of ownership are installed, leading ultimately to an increasing demand for reliable and stable reference values for high-pressure gas-flow measurements. The principle of Third Party Access, supported in the future by direct invoicing of energy-shipment, makes it of vital importance that Gas-transport organizations have at all times a clear knowledge about the contents of their transport-grid.
Hence, long term stability of reference values is gaining importance. Although small (insignificant) changes in (national) reference values are accepted by metrologists, the impact of variations on e.g. invoicing will probably never be understood nor accepted. The drive for one equivalent reference value in this working field of Natural Gas resulted in an extensive cooperation between three NMI’s holding test facilities for High Pressure Natural Gas in Europe.
Key-comparisons are used by National Metrology institutes to verify results of independent realizations of standards of measurement (directly traceable to SI-units) and differences in results to the KCRV are observed and regarded ’as is’. However the harmonization process is combining the information from the independant (national) to a new , more accurate value in a sound statistical way. In 1999 on agreement, the harmonization in the field of HP Gas volume was established with two partners NMi VSL and PTB and on 4th May 2004, BNM joined also. Main advantages: Dissemination of the same reference values, a better long term Stability, smaller uncertainties and the transfer of knowledge amongst the participants.
The purpose of this Euromet project is
to inform the flow community on a regular basis and to get feedback
to invite interested in this field to either actively join the project e.g. bringing their independantly realized reference values as information into the harmonization process or to implement the harmonized reference values into their traceability chain.