Technical report on the traceability chains for hydrogen flow metering with flow rates above 0.2 kg/min and three options for ensuring traceability from established primary standards for the 2030 European Industry and Hydrogen Community

This technical report presents the findings of an effort in the Met4H2 project to produce a traceability chain for hydrogen flow metering. Relevant flow metering points and requirements for fiscal metering points were found by surveying stakeholders involved in large-scale hydrogen applications. A route for traceability is suggested. It involves the operation of newly developed primary standards to calibrate Critical Flow Venturi Nozzles (CFVN). The primary standards that are suggested are of the pVTt type, for which a concept study and a cost estimate is provided. The CFVNs are then combined in an array to bootstrap to larger flow rate ranges, detailed in an experimental protocol. The array allows for calibration of master meters. Calibrations of CFVN with hydrogen gas were performed. Early results show that the discharge coefficient curve for hydrogen closely follows that of air, and both are within the uncertainty of the laboratory.