The goal is to improve the method by which the nation's natural gas pipelines are monitored for leaks. This project will flight test a high-sensitivity, broad-coverage, airborne, natural gas leak detection system developed by ITT Industries (formerly Eastman Kodak Company).
ITT Industries - Space Systems Division (formerly Eastman Kodak Company) – project management and research product development
Coherent Technologies, Inc. – leak detector design and construction
Rochester, NY 14653
Current transmission pipeline leak surveys rely heavily on inspection crews walking or driving slowly along the right of way while using flame ionization detectors to detect the presence of hydrocarbons. This technique is slow, expensive, and produces many false alarms. Recently developed, truck-mounted optical systems that detect methane appear to be an improvement, but are still quite limited (i.e. ground speed, sensor coverage area, ruggedness, and ability to navigate difficult terrain and ground cover). The ITT airborne system will accurately detect and locate small concentrations of natural gas associated with leaks from transmission pipelines with a very high degree of confidence. The system will operate in a wide variety of terrain and weather conditions, day or night, and provide a major breakthrough in speed, cost effectiveness, and safety of monitoring the nation's natural gas transmission systems.
ITT scientists tasked with determining the ideal manner in which to sense natural gas pipeline leaks from the air, investigated a number of approaches including: hyperspectral imaging (HSI), radar imaging, backscatter absorption gas imaging (BAGI), gas correlation spectroscopy (GCS), and active gas correlation spectroscopy (AGCS), before selecting differential absorption lidar (DIAL) as the most sensitive and effective technique for detecting and quantifying the methane and ethane in natural gas pipeline leaks.
The basic concept behind DIAL is that two pulses of laser light of slightly different wavelength are emitted, travel through the atmosphere, reflect off the ground, and are detected by the sensor. One pulse has a wavelength matching the spectral absorption feature of the gas of interest (on-line pulse) and the other has a wavelength that is not absorbed by the target gas (off-line pulse). The difference in the return energy of the on-line and off-line pulses can then be used to calculate the amount of the target gas between the sensor and the ground (measured in parts-per-million or ppm).
If the pulses from the airborne DIAL sensor are scanned back and forth across the path of the aircraft and rapidly pulsed, thousands of measurements can be acquired each second and an image of gas plumes can be constructed from the array of samples. A DIAL sensor designed to transmit and detect three wavelengths of light can be used to detect both methane and ethane simultaneously. Since DIAL is a technique in which the system provides its own illumination source, the ITT sensor can be used at all times of the day and will be largely unaffected by sun angle and cloud cover conditions.
In addition to the sensor/detection sub-system, the ITT system also incorporates an active pointing and scanning sub-system. The pointing sub-system allows the lasers to be accurately pointed at the pipeline right-of-way (ROW) by means of differential geo-positional system coordinates and an advanced inertial monitoring unit. The pointing system is independent of the pilot's control and allows the sensor to compensate for aircraft drift at altitude. Finally, the ITT system has a broad area scanner that provides for up to 250 feet of scan swath (field-of-view). Up to 6,000 individual laser samples will be taken per second across the entire scanning swath.
The system is designed to operate from a fixed-wing aircraft from an altitude of approximately 1,800 feet at airspeeds of 130 knots. As the sensor system is flown along the pipeline ROW, a real-time geo-referenced 2-D map of ethane and methane concentrations is created. The ITT sensor can be linked to an onboard real-time display system designed to display the size, shape, and concentration of detected gas plumes and to alert the flight crew to the presence of very large natural gas anomalies (leaks). Smaller gas anomalies can be identified and then more fully characterized during detailed processing on the ground at the conclusion of the flight.
The successful development and testing effort will lead to a commercial natural gas leak detector capable of airborne operation at altitudes of 250 – 1000 feet. ITT Industries will offer this leak detection system as a commercial service in the first quarter of 2005. This system will be the most complete airborne package for monitoring the natural gas pipeline system for gas leaks.
The project has been completed. All tasks have been carried out successfully. The final report is currently in preparation.
Final Report - October 2005: Flight Testing of an Advanced Airborne Natural Gas Leak Detection System [PDF-16123KB]
Status Assessment [PDF-268KB]
Results of the DOE leak detection demonstration [PDF-7327KB]