Preparation of calibration gas mixtures using dynamic methods: validation of mixing system using mass flow controllers

Jean-Luc Blanc, Air Liquide (FR)

The objective of the paper is to propose a protocol of validation for mixing  systems (MS) using thermal mass flow controllers.  This protocol is under discussion in the working group 5 of ISO 158 for the revised version of the IS 6145-1. Two approaches are proposed: one by calibration of each element (each mass flow controller in that case) and the other considering the MS as a global entity where the generated gas mixture is calibrating by comparison with reference gas mixtures. The study presented here will define the suitable protocol and the number of reference gas mixtures to use in order to validate the MS, having in mind the large range of flow combinations generated by the Mass Flow controllers. It takes into account the global range of mixtures that can be produced and it shows where are the critical points, with respect to their occurrences and their uncertainties. The goal of this investigation is to demonstrate that few reference gas mixtures are necessary to validate a MS. In addition to uncertainties coming from the generated flows, there are additional sources of gas mixture inaccuracy such as lack of homogeneity, adsorption / desorption issues or chemical reactions between gases. Some examples of these issues will be presented also. In conclusion, the study highlights the advantages of using reference gas mixtures to validate dynamic mixing systems and why the global approach is more interesting for the validation purpose.


Pen Profile

Jean-Luc Blanc is graduated from Centre National des Arts et Métiers, as Chemical Engineer with option in analytical science.
He joined AIR LIQUIDE more than 25 years ago and he had responsibilities in several departments: Sales Services development, IT and Production. During these activities he was involved in specialty gases.
Then, ten years ago, he joined the R&D center in Paris-Saclay to become project coordinator for R&D projects in the Analytical Sciences team.
He worked on different projects relative to cylinders and gas stability investigations, equipment development and analysis and had several patents. He is author or co-authors of more than 15 publications.


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