标准编号：ISO 6145-2:2014
中文名称：气体分析 运用动力测定体积方法制备校准气体混合物 第2部分：测定体积的泵
英文名称：Gas analysis — Preparation of calibration gas mixtures using dynamic methods — Part 2: Piston pumps
发布日期：2014-08
标准范围
ISO 6145 comprises a series of International Standards dealing with various dynamic methods used forthe preparation of calibration gas mixtures. This part of ISO 6145 describes a method and preparationsystem using piston pumps. The mixture composition and its associated uncertainty are based oncalibration of the piston pumps by dimensional measurements.The calibration gas mixtures prepared using this method consist of two or more components, preparedfrom pure gases or other gas mixtures using gas-mixing pumps. Such gas-mixing pumps contain atleast two piston pumps, each driven with a defined ratio of strokes, and appropriate accessories for gasfeeding and mixture homogenization.This part of ISO 6145 is applicable only to mixtures of gaseous or totally vaporized components includingcorrosive gases, as long as these components neither react with each other nor with the wetted surfacesof the mixing pump. The use of gas mixtures as parent gases is covered as well. Multi-component gasmixtures and multi-step dilution procedures are included in this International Standard as they areconsidered to be special cases of the preparation of two-component mixtures.This part of ISO 6145 describes a method of preparing calibration gas mixtures whose compositionis expressed in volume fractions. The necessary equations and associated uncertainty evaluation toexpress the gas composition in amount–of–substance fractions are given in Annex A.With this method, provided that sufficient quality assurance and control measures are taken, calibrationgas mixtures can be prepared with a relative expanded uncertainty of 0,5 % (coverage factor k = 2) inthe volume fraction. Numerical examples showing that under specified conditions smaller uncertaintiesare attainable are given in Annexes B through D.Using this method, dilution ratios of 1:10 000 can be achieved in discrete increments. Lower fractions(down to 1 × 10?8) can be achieved by multi-stage dilution or by the use of gas mixtures as input gases.Final mixture flow rates of 5 l/h to 500 l/h can be realized depending on the equipment used.
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