Air tightness monitoring by IR thermography

The standard air tightness test of containers is based on measurement of global parameters as the outlet of a specific gas, detected by specialised mass spectrometers. The identification and location of air leakages is extremely important especially for the container manufacturer. At the same time, the measure of the mass flux is of importance. IR Thermography has been successfully applied for leakage detection on buildings, but unfortunately, the noise due to environment limits its applicability, particularly in case of a small flux. A new thermal procedure has been developed for the leakage detection. The technique is based on the stimulation of the envelope with a low oscillating heat flux and lock-in analysis. An airflow is injected, with a harmonically varying flowrate and a slightly higher temperature than the ambient. Then, the thermograms sequence is analyzed in the frequency domain. A review of quantitative techniques for the convective heat exchange measurement is reported. The procedure has been utilized for special containers used for both transport and exhibition of pictures inside museums. Tests performed before and after gaskets improvements show the capability of the technique to estimate qualitatively the airflow.