NF EN ISO 6145-6
Gas analysis - Preparation of calibration gas mixtures using dynamic methods - Part 6 : critical flow orifices
ISO 6145-6:2017 specifies a method for the dynamic preparation of calibration gas mixtures containing at least two gases (usually one of them is a complementary gas) from pure gases or gas pre-mixtures using critical flow orifices systems. The method applies principally to the preparation of mixtures of non-reactive gases that do not react with any of the materials forming the gas circuit inside the critical flow orifices system or auxiliary equipment. It has the merit of allowing multi-component mixtures to be prepared as readily as binary mixtures if an appropriate number of critical flow orifices are used. By selecting appropriate combinations of critical flow orifices, a dilution ratio of 1 × 104 is achievable. Although it is more particularly applicable to the preparation of gas mixtures at atmospheric pressure, the method also offers the possibility of preparing calibration gas mixtures at pressures greater than atmospheric. The upstream pressure will need to be at least two times higher than downstream pressure. The range of flow rates covered by this document extends from 1 ml/min to 10 l/min.
ISO 6145-6:2017 specifies a method for the dynamic preparation of calibration gas mixtures containing at least two gases (usually one of them is a complementary gas) from pure gases or gas pre-mixtures using critical flow orifices systems.
The method applies principally to the preparation of mixtures of non-reactive gases that do not react with any of the materials forming the gas circuit inside the critical flow orifices system or auxiliary equipment. It has the merit of allowing multi-component mixtures to be prepared as readily as binary mixtures if an appropriate number of critical flow orifices are used.
By selecting appropriate combinations of critical flow orifices, a dilution ratio of 1 × 104 is achievable.
Although it is more particularly applicable to the preparation of gas mixtures at atmospheric pressure, the method also offers the possibility of preparing calibration gas mixtures at pressures greater than atmospheric. The upstream pressure will need to be at least two times higher than downstream pressure.
The range of flow rates covered by this document extends from 1 ml/min to 10 l/min.
Le présent document spécifie une méthode de préparation en continu de mélanges de gaz pour étalonnage, contenant au moins deux constituants, à partir de gaz purs ou d'autres mélanges de gaz à l'aide de systèmes à orifices critiques. Cette méthode, particulièrement applicable à la préparation de mélanges de gaz à pression atmosphérique, offre également la possibilité de préparer des mélanges de gaz pour étalonnage à des pressions supérieures à la pression atmosphérique. Ce document fait partie d'une série de normes présentant différentes méthodes volumétriques dynamiques, utilisées pour préparer des mélanges de gaz pour étalonnage.
- Avant-propos
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1
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2 Références normatives
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3 Termes et définitions
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4 Symboles
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5 Principe
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6 Calcul du débit massique et du débit volumique
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7 Calcul de la fraction molaire et de la fraction volumique et évaluation de l'incertitude associée
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8 Application à la préparation des mélanges de gaz
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9 Étalonnage et vérification
- Annexe A (informative) Exemple de calcul du coefficient isentropique, de la viscosité et du coefficient critique
- Annexe B (informative) Calcul du débit massique et du débit volumique dans des conditions réelles
- Annexe Annexe C (informative) Exemple de calcul de débit pour des orifices critiques à col toroïdal dans des conditions idéales et réelles
- Annexe D (informative) Calcul du débit massique en réalisant l'étalonnage du débit avec de l'azote pur: exemples
- Bibliographie
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