The foundation of Leak Detection and Repair (LDAR) programs in many regions globally is Method 21, which was promulgated by the U.S. EPA to screen equipment components for potential fugitive emissions. Method 21 uses screening values and empirical relationships developed from field test data to estimate (not measure) the mass rate of fugitive emissions using concentration data measured near the potentially leaking component. Because Method 21 is very labor intensive, compliance with LDAR requirements can be very costly. Optical gas imaging (OGI) technology offers significant productivity improvements that could reduce considerably costs for LDAR compliance. Despite the potential for these cost savings, OGI technology has not been adopted by regulatory agencies for LDAR as a replacement for Method 21 because it has not been considered to be sufficiently quantitative.
With support from ExxonMobil Corporation, Providence Photonics, LLC has been developing a quantitative OGI technology, or QOGI, that could become a truly viable alternative to Method 21. The QOGI technology can be deployed using existing gas detection Infrared (IR) cameras combined with a companion tablet for real-time processing of measured IR data. The only parameters that the user may need to input are the ambient temperature and the estimated distance to the component being tested. This QOGI technology has been demonstrated using controlled lab and field experiments to determine the volumetric and mass rates of simulated leaks. Testing to date has shown measurement sensitivity that is an order of magnitude better than existing IR camera technology that has been promulgated by the U.S. EPA as an Alternative Work Practice for LDAR compliance (but not a full replacement for Method 21). A patent covering the QOGI technology was granted in January 2016.
This paper will discuss the precision, accuracy, and detection limits of this new technology, as determined from the significant number of controlled and field experiments that have been run. This new technology, once deployed for LDAR, will significantly reduce the cost of compliance and could potentially provide an approach for reporting fugitive emissions on a measurement vs. estimation basis.