Laser Based Leak Detection with Vehicle Mounted Devices
Proceedings Publication Date
Andreas Stabla
Andreas Stabla
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Today, local gas distributors have very little choice for a modern way of gas leak detection in urban areas. Basically the technologies are still the same than more than 100 years ago. Gas sniffers are used, that analyse the presence of gas by heat effects based on semiconductor technology or by FID. While these technologies offer good results with the inspection on foot, they show a number of disadvantages, which limit their usage in car borne systems. These disadvantages are: detection is only possible in the direct driving path of the car. Leakages where the methane cloud escapes not directly in front of the car are not detectable. The driving speed is limited to arround 10 km/h which make the inspection vehicle a constant obstacle in flowing traffic and causes huge traffic jams in their path. The results are not very specific, even if the device is calibrated for methane, cross contaminations by cars or other emissions are constantly recorded. The measuring process is so slow, even at the mentioned speed, that the moment an alarm occurs, the inspection car already for a long time passed the location of the leakage, and the inspectors have to reverse till they find the spot.

Methane detection by infrared laser avoids most of these problems: Due to the elaborated laser positioning, the area in front of the driving path can be inspected as well as the adjacent area till the houses, bordering the street. The device is highly sensitive to methane, but only to methane. Even Butane or Propane does not show any effect.The reaction time of the system is extremely high: one pulse for measurement is < 1 msec, resulting in a prompt answer to an induced signal. Measuring frequency and setup allow carrying out the examinations at a speed up to 50 km/ h.The measuring principle is based on the absorption of laser energy in methane gas clouds, at a frequency of 1,65 µm. The device emits a laser signal pointing to the direction of the inspected area, and the scatter reflection is assessed. Of course the strength of the laser is limited to values, which do not pose any threat to people or animals. The working concept will be such, that one single person can drive the car, and at the same time operate the system. A light signal and an acoustic alarm inform the driver of a possible leakage. The leakage has then to be confirmed by traditional methods. Adaptations to client’s wishes and needs are possible. As well as (in limits) the adaptation to type of car preferred by the clients. The whole setup is available in Microvan cars; the prototype on display at the Hannover fair is a VW Multivan Type Bus. The future development is strictly based on practical aspects of everyday’s work. Pergam-Suisse AG develops the concept in close cooperation with one of the biggest Swiss gas suppliers, company “ERDGAS Zürich”.

The Gas Inspection Car will be available on the market in Q3 of 2006.

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