EuroLoop: Metrological concepts for efficient calibrations and primary realization of accurate reference values in flow

摘要

In a previous introductory paper, the ranges, possibilities and operation practice of the new calibration facilities for Natural Gas and several Oil products in Europe, are depicted. The stringent claim on CMC or 'Calibration and Measurement Capability' is the driving force for criteria set for process stability, day-to-day reproducibility, long-term behavior of working standards and finally accuracy of the international linked reference value at the position of the device under test. The superb CMC claims imply highest demands in innovative designing. This paper focuses on a 'metrological engineering' concept in which via an iterative process a balance is found between: optimal piping configuration, smallest uncertainties, sustainable traceability maintenance at one side and effective operation, lowest operational and capital expenses on the other. The International traceability of the Hydro Carbon calibration facility (HyCal) will be realized by unique piston provers covering a range up to 5000 m~3/h. Theoretic and empirical correction methods will be avoided and most 'sensitive' parameters will be determined on the spot to increase credibility of estimated uncertainty sources. For instance, e.g. seal leakage, line-pack effects, diameter change will be measured and processed. International acceptability of these rather small uncertainties will increase when uncertainty estimations are supported by 'on scale demonstration of auxiliary instrument performance' therefore a significant set of tests is scheduled in the near future. The design of the intelligent piston will be shown as well as simulations of the piston behavior related to pump performance, inertia's, control characteristics of valves etc. The primary realization will be intrinsic in the piston prover itself and changes of the reference volumes due to pressure, temperature and oil movement will be measured on line. Traceability of the HP Gas Calibration laboratory will be based upon a Gas Oil Piston Prover and the Dutch-German-French Harmonized Reference Value. The prover was built in 2001 together with a multiplier and carrier of reference values, embodying the new traceability chain. The paper also focuses on the methods and steps to validate and certify such large Natural Gas calibration loop, In due coarse, the public will be informed regularly through series publications.