Supplementary comparison SIM.M.FF-S9.2016 for water flow measurement
Authors: Frahm E , Arias R , Maldonado M , Vargas J , Mendoza J J , Arredondo A , Silvosa M A 
Published: January 2024

Main text
The objective of the Supplementary Comparison (SC) SIM.M.FF-S9 for water flow measurement was to support and prove the Calibration and Measurement Capabilities (CMC) of the participating NMIs of Chile (CISA), Peru (INACAL), Bolivia (IBMETRO) and Argentina (INTI). As pilot laboratories, the national metrology institutes of Germany (PTB) and CENAM (Mexico) supported the comparison with reference values. The comparison was organized as a single round robin, started in January 2016 at PTB and finished in August 2019, also at PTB. A combined setup of a turbine meter and Coriolis meter was used as a transfer standard. The nominal calibration conditions of the SC were defined in the flow range between 10 m3/h and 130 m3/h, 20 °C fluid temperature and 0.3 MPa line pressure. In order to estimate the uncertainties u
TS, both transfer meters were subjected to extensive characterization measurements at pilot laboratory PTB. The following parameters were researched in detail: fluid temperature, line pressure, reproducibility, flow stability and meter sensitivity to different inflow conditions. The E
N values for the turbine meter were calculated based on PTB data, only. The E
N values for the Coriolis meter are partly linked to Key Comparison CCM.FF-K1.2015 and were calculated using a common reference value of PTB and CENAM data. The uncertainty of turbine meter u
TS was clearly dominated by the sensitivity to disturbed inflow conditions which leads to large values of u
TS with > 0.20 %. Beside one calibration, all labs passed the E
N criteria of ≤ 1.20. But, due to large values of u
TS, the calibrations for all labs were evaluated as inconclusive. The evaluation criteria u
comp/u
base exceeded the critical value of 2.00 for all calibrations. Finally, the turbine meter was not suitable for a confirmation of the submitted CMC values. The calibration results of the Coriolis meter were characterized by a strong dependency on zero setting. The observed effect was adjusted for the data of both reference laboratories by introducing a new method for autozero correction. Maximum uncertainty values for Coriolis u
TS were estimated with 0.069 % at low flowrates and 0.033 % at high flowrates. Besides two calibrations, all laboratories complied with the E
N criteria of ≤ 1.20. In contrast to turbine meter, the evaluation criteria u
comp/u
base exceeded the critical value of 2.00 at one calibration, only. In consequence, the calibrations by using the Coriolis meter were suitable for a confirmation of the submitted CMC values. In summary, the comparison was successfully finished for a confirmation of the submitted CMC values, related to mass calibrations. For volume related CMCs this comparison was not suitable.
The comparison was partially financially supported by the German Federal Ministry for Economic Cooperation and Development (BMZ) - PNs: 2012.2296.7-95259, 2015.2037.8-95306 and 2017.2073.9-95328.
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.
The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).