In this episode, Mike and Bob discuss a new tool for laser methane detection, which has been in the hazmat industry for a long time.
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Complete Show Notes
3:45 What are Laser Methane Detectors?
- Like so many of our meters, laser methane detectors have their roots in industry
- Originally a piece of large, non-portable equipment consisting of a laser source and a detector
- Laser source and detector were placed in such a way that if a container (pipeline, cylinder, rail car, etc.) started to leak, the rising gas would go between the source and the detector and trigger an alarm
- As with most technology, this basic technology became smaller and smaller until we reached today’s topic – the portable laser methane detector
7:25 How Do Laser Methane Detectors Work?
- Each unit is equipped with 2-3 lasers
- Visible light laser
- Difference between 2 and 3 laser units depends on whether it has a visible light laser
- This type of laser acts as a visual cue to see the end point and is also a distance calculator
- Some detectors also use a screen similar to that of a thermal imaging camera – look through the screen and place a dot on the end target
- IR laser
- Methane has a very specific frequency and absorbs IR radiation, so one of these lasers will be set to frequency (most popular is around 3.3um)
- Reference laser
- Isn’t picked up by methane, so it passes through it unchanged
- Note that some units split one laser and use it as a reference, but the idea is the same – one for spotting/distance taking, one for reference, and one to hit/be absorbed by methane
- Keep in mind that the laser must always have something to bounce off of – if it doesn’t have anything to reflect off of, it can’t get the IR light back to the sensor
11:35 Example Scenario
- We shoot the laser across the room – it encounters a cloud of methane and adsorbs some of the light photons
- The rest of the laser moves through the cloud, hits a surface, and scatters
- Some of the light makes its way back to the meter, and the differences between the two are analyzed
- Detector gives us a reading of 500 ppm m.
- Keep in mind that these aren’t point source detectors – they’re only seeing the total distance the laser travels and the amount of light absorbed by the methane during travel
- We’re not measuring ppm in a specific spot like we would with a point source detector – instead, our reading represents the concentration through all the points in space the laser traveled (both high and low methane areas)
- This means that instead of just saying “ppm,” we have to clarify that it’s an averaged ppm based on distance traveled
19:10 Operational Uses of Laser Methane Detectors
- We are NOT using these meters to determine whether we’re in a flammable range
- We use laser methane detectors in three different ways:
- To determine if there’s methane present in a quick and safe way
- To determine if our actions produced a difference
- To triangulate where a gas leak is coming from (especially useful for underground leaks or leaks along pipelines)
- As you can see, there are many uses for these meters, but we’re never using them to determine if we’re in an LEL
26:25 Pros and Cons of Laser Methane Detectors
- Can cover large open areas, reducing the time spent on searching for leaks, as well as manpower
- Measurements can be made remotely, keeping team members out of harm’s way
- Calibration is minimal, and drift is non-existent
- Units respond almost instantaneously
- No cross-sensitivity – methane lasers only pick up methane
- Only picks up methane
- Corners really screw with readings, so make sure you’re not shining off of a corner
- Can’t use in open fields since there’s no spot for the laser to reflect back to you
- Unless there’s some kind of ceiling, you won’t get a reading outside above ground
- Can’t be used for gauging flammability
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- THMG014 – Metering Overview and Basic Sensors
- THMG015 – Advanced Metering
- THMG016 – Metering Techniques and Reading the Numbers