Precautions for micro oxygen analyzer

1.The supporting pipeline of the analyzer should ensure the sealing, and the small leakage will cause the oxygen in the ambient air to diffuse in, thus making the measurement value higher.

Although the sample gas pressure is higher than the ambient pressure, the oxygen in the sample gas is a micro-level. According to Ferrari law, the partial pressure of oxygen is proportional to its volume content, the air contains about 21% of oxygen, and the difference between the partial pressure of the sample gas calculated by PPM is about 10,000 times, so the partial pressure of the trace oxygen in the sample gas is lower than the partial pressure of the air, when the leakage occurs, the oxygen in the air will diffuse rapidly from the leakage part.

In addition, the sampling pipeline should be as short as possible, the joint as few as possible, to ensure the good sealing of the joint and valve, after the pipeline connection, the air tightness check should be done.

The requirement of air tightness check: 0.25MPAm test pressure, 30 minutes, pressure drop is not more than 0.01MPA.

2.The material of the pipeline is basically copper or stainless steel pipeline, and the PTFE pipeline is secondary selected. The results show that the air tightness and the permeability of materials are too poor for the non-selection of latex tubes and white rubber tubes, and the measurement error of trace oxygen is too large under the standard measurement pressure. The outer diameter of the pipeline is usually 6 mm or 1/4IN, and also 3 mm or 1/8IN. In short, the stainless steel pipe is preferred, cleaning, degreasing, keeping the inner wall smooth and clean. For the analysis of trace level (<1PPMV) oxygen, the stainless steel pipe with inner wall polished should be chosen. The dead volume of the selected valve or joint shall be as small as possible.

3.In order to prevent the condensation of the water in the sample on the tube wall and cause the dissolution and absorption of the trace oxygen, the measures of heat insulation or heat insulation should be taken for the sampling pipeline according to the situation. When detecting trace oxygen in liquid nitrogen, special attention should be paid to heating measures, otherwise, because the oxygen boiling point is lower than the nitrogen boiling point by 13 degrees, the sample gas is not uniformly gasified, and the measured value is seriously low.

4.In principle, the measuring position of the micro-Oxygen Analyzer should be as close as possible to the measuring unit, so as to avoid too long pipeline and too many uncertain factors, and affect the reliability of the measuring data.

5.The sample gas can not contain oil components or solid particles, so as to avoid the blockage and pollution of permeable membrane

6.The sample gas should not contain sulfide, phosphide or acid gas components. These components can cause harm to fuel cells, especially alkaline fuel cells.