Optical Methane Detector

Optical Methane Detector mounted on a survey vehicle.

The Optical Methane Detector arose from pioneering work at the former Westinghouse Science and Technology Center and was developed for commercialization by our group while at Carnegie Mellon. As a new product for Heath Consultants, the OMD(TM) was named as the hottest new instrument of the year in 1998 by Gas Utility and Pipeline Industries. The Optical Methane Detector has been adopted by customers throughout the world becoming a preferred instrument for high speed, wide area vehicle leak surveys.

Technology Description

The Optical Methane Detector’s infrared light source is mounted on a crossbar at one side of a vehicle’s front bumper and then aimed at an optical detector mounted at the other end of the bumper. When methane molecules pass between the source and the detector, they absorb energy from the light beam, resulting in an attenuation of the beam that is proportional to the amount of gas present. This attenuation affects the detector’s reading and the driver is alerted to a leak. The concentration may then be observed, mapped and logged. The Optical Methane Detector is effective at detecting trace levels as low as 1 ppm of methane. Because only part of the infrared light beam is affected by partial obstruction of the light path (such as from deposits of dirt on the exterior or water) the unit can function in light rain and other non-ideal survey conditions.

Typical Characteristics

Display

Alarm
High clarity LCD with indication of concentration in actual value and trace graph Variable pitch audible with adjustable setpoint and volume

Construction

Weight
External Casing: Aluminum 7.7 kg (17 lb) for main crossbar

Operating Temp.

Power
-10°C to +50°C 12-16 VDC, 60 W @ 12 VDC

Sensitivity

Response
1 ppm / methane CH4 ta < 1 second

Ranges

Resolution
0 to 10 ppm
0 to 30 ppm
0 to 90 ppm		 1 ppm

Accuracy

Crossbar
± 10% of reading Variable

Advantages

3d Methane Molecule

Faster Survey Time

The Optical Methane Detector has been successfully tested at speeds of up to 60 mph(96.5 kph). Sensitivity can be maintained at higher speeds because of the inherent speed of the light and electronics.

Safer Operation

The Optical Methane Detector is safer for the survey technician because the vehicle can keep up with traffic and no hydrogen fuel gas is needed. Training and surveys may be completed faster with better reliability and lower cost.

Lower Maintenance

Typical FIDs are equipped with moving parts, plumbing, and sampling components, which can complicate installation and increase the need for maintenance. Our Optical Methane Detector is an entirely opto-electronic system, which means that installation can be made simple. The only routine maintenance required is occasional lens-cleaning with a tissue or soft paper towel.

Easier Calibration

Calibration involves only a quick and easy push-button check device located on the optical sensor. No expensive calibration gas or complex pump/pipework arrangements are required.

Reduced False Positives

Because the system is configured to react preferentially to methane, the occurrence of false positives is greatly reduced.

Global Positioning System (GPS)

As an added option, GPS has been utilized to accurately track the position and speed of the vehicle. The GPS data may be displayed on the screen in real-time and can also be included with the gas trace data.

User Friendly Operation

The equipment is user friendly, with push button commands, data display functions, and prompts displayed on the screen.

More Information

From Grid Magazine (GRI Digest) in 1998:

Gas Companies Finding Leaks Faster with the OMD

In Minneapolis, Chicago, Philadelphia, Brooklyn, San Francisco, Toronto, and other areas of North America, crews are speeding up the process of natural gas leak detection with the advanced technology built into the Optical Methane Detector[TM] (OMD), a product from the GTI program that entered the market in 1998.

With the (OMD) mounted on the front of utility vehicles, crews are accurately detecting methane leaks while traveling at normal traffic speeds. Field demonstrations–and, now, studies of real-life practice–show that mobile leak surveys using the OMD can be conducted up to four times faster than surveys using traditional methods (e.g., flame ionization detection, which limits speeds to 3 to 7 mph). The results are overall productivity improvements of 20 to 50 percent or more. Even at higher speeds, the OMD has shown the ability to respond to one-part-per-million (ppm) of methane or less.

References/Further Reading

  1. GRI-96/0447 – Development of the Optical Methane Detector and Related Applications for Improved Gas Leak Surveying – 1996
  2. Gas Utility and Pipeline Industries – 1998’s Hottest Products and Services – Dec. 1998 Cover Article
  3. Grid Magazine (GRI Digest) – Gas Companies Finding Leaks Faster with the OMD – Volume 22, No. 3, Fall 1999
  4. GRI-00/0126 – Benefits of Leak Surveying with OMD(TM) – 2000