Abstract
We have developed an imaging system for the detection and visualization of methane gas leaks. The system is based on a distributed feedback InGaAs laser diode emitting at 1.65 μm, the beam from which is directed at neighbouring objects. The backscattered light is collected by a Fresnel lens and the gas concentration is deduced from the reduction in collected intensity as measured using a second derivative wavelength modulation technique. The incident laser and the collected beam are both scanned over an area to form an image of the gas emission. To ease the task of locating the source of the emission, we combine the resulting low-resolution image of the gas emission with a high-resolution colour image of the scene. Our results show that the system can image a gas cloud of 1 mm effective thickness at a range of several metres, sufficient to detect a gas leak of 1 litre min−1 in light to moderate winds.
Highlights
Low cost portable systems for detecting and locating methane gas have wide use amongst the gas utility companies for routine inspection of leaks from pipelines and storage facilities, and for leak-report response applications
The conventional approach to low-level leak detection is based upon flame ionisation detectors (FIDs) [1] but such technology measures concentration at only a single point
When trying to locate the source of a leak, the spatial distribution of the gas cloud is more informative than the precise measurement of concentration at a single point
Summary
Low cost portable systems for detecting and locating methane gas have wide use amongst the gas utility companies for routine inspection of leaks from pipelines and storage facilities, and for leak-report response applications. The conventional approach to low-level (ppm) leak detection is based upon flame ionisation detectors (FIDs) [1] but such technology measures concentration at only a single point. Differential Absorption LIDAR (DIAL) instruments, which actively monitor gas using pulsed laser light, have been reported [2] Such systems can detect gas over the line-of-sight of the light beam using the light backscattered from the gas to give concentration (from the signal size) and range (from the delay time). Other examples of active imaging include backscatter absorption [3][4], and differential backscatter absorption [5] These systems can detect gas distributions by illuminating a scene using IR laser radiation and imaging the dark region arising from the attenuation of the backscattered light. It has been shown previously that a measurement of 1mm gas is sufficient to detect a leak of 1 litre/minute in light to moderate winds [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
