GB/T 38527-2020Technologic rules for calibration gas mixtures (English PDF)

4.1 Equipment requirements

4.1.1 Preparation equipment

The equipment for preparing bottled calibration gas mixtures shall meet the The final pressure of the bottled calibration gas mixture at 20 °C shall not be higher than the nominal working pressure of the target gas cylinder.

When preparing the calibration gas mixture, the flow shall be limited, static electricity shall be prevented, and tail gas treatment measures shall be taken.

6.1.1.2 Reaction and adsorption with system materials

Before preparing the gas mixture, the chemical reaction or adsorption that may occur between the gas mixture components and the pipelines, valves, as well as packaging containers for calibration gas mixtures shall be considered. Particular consideration shall be given to the reaction of corrosive gases with metals and with the seals used.

Materials that are non-reactive with all components of the gas mixture shall be used to prevent reactions from occurring. If it is not feasible, measures shall be taken to minimize the corrosion of materials in contact with the gas, so as to avoid significant changes and any danger in the composition of the gas mixture during storage and use.

According to the characteristics of the gas mixture, the appropriate gas cylinder and cylinder valve shall be selected according to the provisions of GB/T 7144 and TSG 23.

6.1.2 Preparation method

6.1.2.1 Selection of preparation methods

The preparation method shall be selected according to the characteristics of the calibration gas mixture components, preparation purpose, and on-site preparation conditions, such as the gravimetric method, static volumetric method, and dynamic volumetric method.

6.1.2.2 Selection of preparation procedures

When selecting a preparation procedure, the following factors shall be considered:

-- The target composition and uncertainty requirements of the calibration gas mixture;

-- Requirements for preparation deviations;

-- The target applicable temperature and pressure of the calibrated gas mixture;

-- The use occasion of the calibration gas mixture;

-- The reliability, safety, and ease of operation of the preparation procedure;

-- The degree of difficulty to achieve traceability;

-- Requirements for the environment and equipment of the preparation procedure;

-- Whether the raw materials are easy to obtain, and whether the composition and quality can meet the requirements.

6.2 Implementation

6.2.1 Raw material purity analysis

When preparing the calibration gas mixture, the raw materials shall be analyzed for purity in advance. The purity of raw gas can be analyzed according to GB/T 38521. The content of significant impurities in raw materials can be reduced by selecting pure gas or pure liquid with higher purity. The significant impurities that affect the uncertainty of any component concentration of the calibration gas mixture by more than 10% shall be accurately quantitatively analyzed, and the measurement results shall have metrological traceability.

6.2.2 Preparation method implementation

When the gravimetric method is selected for preparation, it shall be implemented in accordance with the provisions of GB/T 5274.1. When the static volumetric method is selected for preparation, it shall be carried out in accordance with the provisions of GB/T 10248. When the dynamic volumetric method is selected for preparation, it shall be implemented in accordance with the provisions of GB/T 5275.2, GB/T 5275.4, GB/T 5275.5, GB/T 5275.6, GB/T 5275.7, GB/T 5275.8, GB/T 5275.9, GB/T5275.10 and GB/T5275.11.

6.2.3 Filling of gas cylinders for calibration gas mixtures

When the gas cylinder is used for the calibration gas mixture, the filling shall be carried out in accordance with the provisions of GB/T 34526.

6.3.1 Evaluation of homogeneity

The homogeneity of the calibration gas mixture shall be evaluated, and it shall be ensured to be homogeneous before analysis and use.

6.3.2 Evaluation of the stability

Stability evaluation shall be carried out on the calibration gas mixture packaged in containers to determine the shelf life of the calibration gas mixture. The calibration gas mixture prepared by the dynamic method shall also be subjected to stability studies to determine the stability of its dynamic generation system. […]

6.4 Verification of calibration gas mixture composition