The leak rate detection methods of the glove box include the oxygen method and the pressure method.
The oxygen method can accurately measure the leakage rate of the glove box, and changes in the temperature and pressure of the environment during the detection time have little effect on the detection results. The oxygen method is simple, accurate and reliable. The main testing equipment is an oxygen analyzer. Many glove boxes have been equipped with oxygen analyzers, so that no other equipment is needed to detect the leakage rate. The user of the glove box can detect the leakage rate of the chamber according to the following steps.
oxygen probe is installed on a debugged glove box. The volume of the
single-station glove box is about 750 liters.
Adjust the upper and lower limits of the tank pressure to +10 and -10 mbar respectively.
Turn off the gas circulation system, wait ten minutes, and adjust the pressure of the glove box to -8 mbar.
Record the oxygen content O2i (such as 3PPM), chamber pressure, and room temperature.
After a certain period of time t (such as 1 hour), record the oxygen content 63PPM), chamber pressure, and chamber temperature.
The oxygen content has risen by 60 PPM.
In order to eliminate the influence of the deviation of the oxygen analyzer on the test results, a known amount of air is injected into the glove box, and the volume of air leaking into the glove box can be calculated by the ratio of the readings of the oxygen analyzer.
Turn on the circulation system, reduce the oxygen content to about 3PPM, and adjust the tank pressure to about +6 mbar. Stop the circulation, wait for 5 minutes and adjust the chamber pressure to 0 to completely hang down the gloves, inject 300ml of air, reach into a hand and stir the gas in the tank to balance the gas concentration as soon as possible, and the oxygen rises by 90PPM.
The amount of leaked air=300ml*60PPM/90PPM=200ml (The error of the oxygen analyzer is excluded by the ratio method)
Leakage rate of the glove box = 200 ml/1000/750 liters * 100%/1 hour = 0.027% (vol/h)
Another relatively simple method is to stop the cycle and directly observe the changes in the oxygen analyzer data to calculate the leakage rate. Stop the circle, record the value of oxygen content in different time periods, take a point on the coordinate axis and draw a straight line to get the slope value, and then convert it into the leakage rate value.