Methane Detection from Vehicle Mounted LMD(VMLMD)

LMD is a very useful tool in finding gas leaks at houses and other facilities where conventional gas detector cannot be reached easily such as pipes near ceilings. But the applications are not only limited in those places; LMD can drastically improve efficiencies of regular inspections in large scale gas facilities such as city gas production terminals and gas transmission pipelines. In those applications, we are getting inquiries from potential customers, especially from foreign gas related companies about mounting LMD on vehicles. The following is what we suggest in installing a LMD on a vehicle using a commercial camcorder mount with an attachment between the LMD and the mount.

 

 

Installation of an LMD on a vehicle

Installation of an LMD on a vehicle. A vacuum camcorder tripod is utilized.

The idea to mount an LMD on a vehicle does not require high levels of optical or electrical knowledge, but attachment of an LMD to vehicles with varieties of different designs is still a challenge. Special adapters solely for a specific vehicle will cost excessively and, of course, cannot be used for other types of vehicles. As a solution to the problem, a vacuum type tripod mount can be used to attach an LMD on the inner surface of a front shield. Detailed description of the attachment is given in Mounting LMD on Vehicles . The LMD is attached in the inner surface of the windshield, and the left side window (the same side with the LMD) should be opened during operations. There is no exterior modification of the vehicles. Data from the LMD can be accumulated in a computer. The description of software to support the data acquisition is given here.

 

Effect of incident angles and surface texture

When LMD is used from a vehicle, the incident angle to the ground will become shallow. The figure below shows the effect of the incident angle for different surface materials. It can be seen from the plot that the signal intensity decreases as reducing the incident angles. Note that the signal intensity is still large enough for LMD to work properly even at 20 degrees.

Intensities of received signals as a function of incident angles for different surface materials.

 

Experiment of Methane detection from VMLMD

 

The data above was taken at experimental conditions as follows:

Gas leak rate:2.5 littler/min

Gas ejection depth: 0.2m from the ground surface

Vehicle speed: 30km/h

 

The experiment was repeated ten times, and the leak was detected in all the trials as obvious signal peaks shown in the plot. The noise level at 30km/h is as high as 50 ppm m; this is much smaller than the signal from the leak. It is important to note, however, that small gas plume may not be detected regardless of its gas concentration because the sampling speed of the LMD is 0.5 sec.

 

The content in this page was prepared based on experiments performed by Shikoku Research Institute. We are grateful for their contribution.

If you have further questions, please send an email to us.

 

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