An evaluation of an optical gas imaging system for the quantification of fugitive hydrocarbon emissions

Report no. 2/17: This report provides the results of a preliminary study undertaken to test the performance of a quantitative optical gas imaging (QOGI) system. This has been developed to measure the mass emission rate of hydrocarbon leaks from industrial process equipment.

Testing was performed using controlled releases in the range 1.7 g/h to 1000 g/h. For comparison purposes a conventional sniffing technique was also used for leak detection with emission estimates determined using the correlation equations from US EPA Method 21.

Sixty one leak tests were performed. The QOGI system detected all of these leaks but it was found that quantification required a differential temperature of > 5°C between the released gas and the background.
Where leak rate quantification was achieved with the QOGI system the differences between the values determined and the known release rates were within a range of -23% to 69%, with an average difference of 6%. By comparison, where the US EPA Method 21 correlations were used to estimate leak rates these differed from the known release rates within a range of -92% to 667%, with an average difference of 31%.