Bilateral comparisons on COOMET Project 684/MD/16 “Pilot comparisons of national standards in the field of gas flow”

Abstract The article describes the procedure for performing international bilateral comparisons of the national measurement standards of the units of gas volume and volume flow in Ukraine and Moldova. The comparisons were carried out within COOMET Project 684/MD/16 “Pilot comparisons of national standards in the field of gas flow”. The list of reference standards that took part in comparisons is indicated. The range of gas volume flow, in which the comparisons were carried out, is from 0.5 m3/h to 50 m3/h. For the flow range from 0.5 m3/h to 1 m3/h, a drum-type meter was used, and for the range from 2 m3/h to 50 m3/h, comparisons were performed using a rotary gas meter. It is indicated that the national state primary and secondary standards of the gas volume and volume flow units took part in the comparisons from Ukraine, while from Moldova it was the national standard of the gas volume flow unit. A brief description of the national measurement standards and the principle of reproduction of the gas volume and volume flow units is presented. In particular, it was noted that the primary and secondary standards of Ukraine are built on the basis of bell-type prover, and the standard of Moldova combines a piston and bell-type prover. The method of calculating, calculation of expanded uncertainty and determining the degree of equivalence of the national standards of Ukraine and Moldova are demonstrated. The results of bilateral comparisons in the form of Table 1 are presented and shown in Fig. 4. The degree of equivalence of the national standards does not exceed 0.41, which indicates that the primary and secondary standards reproduce the gas volume and volume flow units with declared uncertainties, and transfer standards retain their metrological characteristics throughout the cycle of comparisons. General conclusions are drawn about the success of bilateral comparisons.