How to determine whether the nitrogen purity of the liquid nitrogen generator meets the standard?
Date: 2025-10-30Read: 0
To determine whether the nitrogen purity of the liquid nitrogen generator meets the standard, the core is to conduct triple verification through "instrument self inspection+third-party testing+liquid quality system feedback" to ensure that the purity is ≥ 99.999% (meeting the requirements of liquid chromatography-mass spectrometry).
- Check the readings of the built-in purity detector in the device. Most high-end models are equipped with online oxygen content sensors, which can display impurity oxygen content in real time (≤ 5ppm is required to meet the standard, corresponding to nitrogen purity ≥ 99.999%).
- Observing the operation status of the equipment, if the generator frequently alarms, the gas production pressure fluctuates greatly, or the regeneration cycle is abnormally shortened, it may be due to a decrease in the adsorption efficiency of the molecular sieve, resulting in the purity not meeting the standard.
- Check the equipment parameter settings and confirm that the output pressure and flow rate meet the requirements of the liquid quality system. Unstable pressure/flow rate may indirectly affect the accuracy of purity testing.
- Entrust qualified testing institutions to use gas chromatographs (GC-TCD) or specialized nitrogen purity analyzers for offline testing, directly measuring impurities such as oxygen, carbon dioxide, and moisture in nitrogen.
- During testing, it is necessary to directly sample at the outlet of the generator to avoid pipeline contamination affecting the results. The testing report should clearly indicate the content of each impurity to ensure that they are all below the allowable threshold for liquid chromatography-mass spectrometry (such as moisture ≤ 10ppm).
- It is recommended to conduct testing every 6-12 months. If the equipment is frequently used or the environment is dusty or humid, the testing cycle can be shortened.
- Observe the atomization effect of the liquid quality system and the stability of the ion source. If the spray is uneven and the ion source is easy to be polluted, it may be that the nitrogen contains oil and water, resulting in insufficient purity.
- Check the quality of the detection data. If the chromatographic peak shape is tailing, the response value fluctuates greatly, the signal-to-noise ratio decreases, or the qualitative and quantitative results have poor repeatability, it may be due to the nitrogen purity not meeting the standard, which interferes with the ionization process.
- Comparing the liquid quality operation status before and after replacing the molecular sieve/filter element, if the system stability is significantly improved after replacement, it indicates that the purity may not have met the standard due to consumable aging.
- Check the status of the post filter elements (such as activated carbon filter elements and water removal filter elements) of the generator. If the filter elements change color or become clogged, it may cause impurities to remain and affect the purity of nitrogen gas.
- Check whether the gas pipeline is leaking or contaminated. Aging of the pipeline and loose joints can introduce air impurities. It is necessary to apply soapy water to the joints and observe whether bubbles are generated.
- If the generator has been used for more than 2-3 years and the molecular sieve has not been replaced, the purity may decrease due to saturation of the adsorbent. The purity can be verified by replacing the molecular sieve.