Precautions for standard gas in sampling

Precautions for standard gas in sampling:

The particularity of the standard gas has special requirements for sampling. Many users have large data deviations due to non-standard sampling. Here I provide several aspects that should be paid attention to in sample sampling:

1. The choice of sampling pipeline. Because the hose is very convenient to use, many traditional sampling pipelines use this type. However, as we all know, the hose has strong adsorption to most organic gases and sulfur-containing gases, and its permeability The performance is also very strong, so it is not advisable to use various types of hoses for sampling, which will cause great deviations in the analysis data. It is recommended to use copper tubes, stainless steel tubes, and PTFE tubes according to different gas properties, and stainless steel tubes coated with quartz for sulfur-containing standard gas and sample gas.

2. The replacement of sample gas. Since the standard gas must pass through the pressure reducer and pipeline before sampling, the pressure reducer and pipeline must be fully replaced for accurate sampling. This replacement is not simply purging. Because the dead volume of the pressure reducer is very large, the cylinder valve is opened and closed repeatedly for more than 3 times, each time the gas in the pressure reducer is exhausted, and then the system is purged to correctly sample.

3. The airtightness of the sampling pipeline and the leakage of the sampling pipeline have a great influence on the accuracy of the sample data, and it has a greater influence on the low concentration of oxygen. Therefore, the air tightness of the sampling pipeline must be strictly checked.

4. It is not advisable to try to take the standard gas from the standard gas cylinder into a sampling bag or other container, and then sample and analyze it from the container, which causes secondary pollution. The data of the sample gas cannot be displayed truly.