|Handheld Sensor for Remote Detection of Natural Gas Leaks
The goal of this project is to enhance the technology of a lightweight handheld gas detector capable of distinguishing natural gas pipeline leaks from other hydrocarbon leaks or ambient methane sources, and quantifying the relative volume of the leak. The project will demonstrate the extended functionality and range of the prototype handheld remote methane leak detector (RMLD) and demonstrate its ability to function on a mobile platform.
Physical Sciences, Inc. previously developed an engineering prototype handheld sensor to permit remote detection of natural gas leaks from pipelines and service connections from distances up to 30 meters. The compact, relatively low-cost, self-contained, stand-off detection system was based on tunable diode laser absorption spectroscopy (TDLAS). The sensor is based on line-of-sight absorption of a low-power, eye-safe, telecommunications-grade diode laser operating at 1.65 microns. Unique absorption lines for methane can be used to measure the concentration of gas anywhere between the operator and topological targets such as buildings, grass, pavement, bushes, etc. In operation, the laser wavelength is rapidly swept across the isolated methane absorption line shape, and the well-known principles of Wavelength Modulation Spectroscopy are used to determine the presence of methane. The natural gas concentration along the laser and return path selectively absorbs the monochromatic light. The detected gas is measured as a concentration “x” path length product.
In the current project, the handheld leak detector will be adapted to operate on a moving vehicle (operator's truck or van). The mobile unit is not an imaging device, but rather employs a spinning turret that continually sweeps the laser beam across the survey area as the vehicle moves forward. Unlike currently utilized flame ionization (FI) and optical methane (OM) detectors, the vehicle bearing the mobile remote methane leak detector (RMLD) need not pass through the leak to detect it, but merely needs to pass by the leak. The mobile RMLD is intended to provide lateral coverage of 10 meters and one lateral scan for every meter of forward motion at forward speeds up to 10 meters per second, and to detect the same leaks as FI and OM technology.
Prototype handheld sensor
Physical Sciences, Inc. (PSI) – project management and product research and development
Heath Consultants, Inc. – commercialization/distribution
Andover, Massachusetts 01810
This sensor is an improved version of the handheld laser-based standoff natural gas leak detector previously developed by PSI, and known as the Remote Methane Leak Detector, or RMLD. The work demonstrated the extended functionality and range of the prototype remote gas leak detector. In contrast to current leak detection methods, the sensor does not need to be immersed within the gas plume and has the capability to detect leaks at distances of 35 - 50 feet. The increased range allows for rapid natural gas leak detection over an extended surface area.
The work completed in this project successfully demonstrated the feasibility and value of adapting the RMLD to a mobile platform for use in surveying transmission pipeline leaks. The mobile RMLD was also shown to possess the inherent sensitivity required to be useful for locating municipal gas distribution pipeline leaks. Additional effort is needed to package a system incorporating a rotating turret for permanent installation on a vehicle, and for understanding the optimum procedures for operating such a device in the presence of physical obstructions. Specific accomplishments include:
- Determined the requirements for sensitivity, range, survey speed, and price sensitivity of the potential user community.
- Completed design of a mobile unit.
- Fourier transform infra-red (FTIR) data showed that it is not practical to measure both methane and ethane using a single RMLD unit with a single laser. The accessible ethane spectral absorption features are too weak.
- Developed, installed, and successfully tested alarm algorithms. Improvements made in the RMLD algorithms include:
- Automatic adjustment of laser wavelength.
- Audio outputs representative of detected gas concentration.
- Settings of detection thresholds that improve standoff range.
- Restructuring of the signal processing algorithm to accommodate rapid changes in signal strength without generating false alarms.
- A prototype version of the Mobile RMLD with a spinning mirror was built and demonstrated on a moving cart. The signal-to-noise ratio of the prototype suggests a capability of detecting methane leaks smaller than 0.2 scfh, comparable to a pilot light flow rate. Actual leaks of 2 scfh were readily detected in outdoor tests.
- Completed system assembly and preliminary testing.
- A handheld RMLD operating from a vehicle traveling approximately 10 mph successfully located a host of blind leaks along a simulated pipeline at the DOE leak detection demonstrations at Rocky Mountain Oil Testing Center (RMOTC).
Low-cost Van-mounted Laser-based Sensor
Current Status and Remaining Tasks:
All tasks have been completed. The final report is listed below.
Project Start: September 30, 2002
Project End: December 31, 2004
DOE Contribution: $175,917
Performer Contribution: $43,986
NETL – Daniel Driscoll (firstname.lastname@example.org or 304-285-4717)
PSI – Mary DeLeo (email@example.com or 978-689-0003)
Final Report [PDF-3117KB]
Fossil Energy Techline: Vehicle-Mounted Natural Gas Leak Detector Passes Key "Road Test"
Kick-off Presentation [PDF-1581KB]