Author Topic: Propane & Natural Gas Leak Detection  (Read 1249 times)

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Offline adammunich

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Propane & Natural Gas Leak Detection
« on: May 20, 2020, 01:23:13 am »
I did some experiments today with trying to detect propane using a 3.33um filter. This filter is selective for methane, which should be inside "natural gas" in detectable amounts. I've published my results so far on this page here: https://civilpedia.org/p/?pid=355&h=Seeing+Propane+Gas
 

Offline Bill W

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Re: Propane & Natural Gas Leak Detection
« Reply #1 on: May 20, 2020, 02:49:11 pm »
Think about which parts of each molecule contribute to the absorption.  You may be seeing the generic '-ane' C-H chemical bond rather than picking up methane in propane.

There are freely available spectra
Methane:
https://webbook.nist.gov/cgi/cbook.cgi?ID=C74828&Type=IR-SPEC&Index=1#IR-SPEC
Propane:
https://webbook.nist.gov/cgi/cbook.cgi?ID=C74986&Type=IR-SPEC&Index=1#IR-SPEC

Propane has a wider deeper absorption for the same area.  The extra C-C broaden the spectrum making it less 'well tuned'.

Bill
 
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Offline bap2703

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Re: Propane & Natural Gas Leak Detection
« Reply #2 on: May 20, 2020, 06:26:34 pm »
If you use a static setup where almost nothing moves except the gas AND you have access to know frames without gas things can get easy : take your frame without gas and use it to "flat field" your video.

But that won't solve your issue of methane and propane sharing absorption in your filter band.
 

Offline helius

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Re: Propane & Natural Gas Leak Detection
« Reply #3 on: May 20, 2020, 06:57:21 pm »
Is it even possible to detect hydrocarbons using infrared imaging?
I would have thought a spectrometer was required, if they have distinct Raman spectra (not familiar).
 

Offline bap2703

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Re: Propane & Natural Gas Leak Detection
« Reply #4 on: May 21, 2020, 08:47:27 am »
Yes it is, adammunich even gave you a nice video as an example.

Some gases have absorption peaks that happen to be where the atmosphere doesn't. That's especially true for greenhouse gases. They are named like this because they block the infrared radiated by the earth at around 290K, that aren't by the normal atmosphere.
That last sentence is equivalent to: we can see them with thermal cameras!

However the challenge is the amount of radiation: thermal cameras work because they collect infrared light over a large bandwidth. But gases typically absorb* over a tiny set of peaks. That means if you want contrast between gas/no gas you want to reduce the camera spectral bandwidth to be narrow. It wont see much, but it will do so with good contrast  |O
A spectrometer typically does the opposite job, working with ultra narrow bandwidth to provide good spectral resolution: it needs a very sensitive sensor --> a way to achieve that is to use a single big "pixel".
But there are also spectro-imaging instruments that are basically a camera-spectrometer. These are expensive and used for science and security (think army, satellites, airborne) - well Fraser might get one for $5 on ebay :D


* Note that gases absorb IR light from a hotter object behind them, but if the object is colder you will see the emission from the gas itself.
 

Offline Max Planck

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Re: Propane & Natural Gas Leak Detection
« Reply #5 on: May 21, 2020, 12:22:29 pm »
Quote
Our filter has a passband of only about 20 nm,

This is the source of your problem. You need a filter with a wider passband.

Max
 

Online agiorgitis

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Re: Propane & Natural Gas Leak Detection
« Reply #6 on: May 21, 2020, 09:48:51 pm »
Hey mate,

Check out my thread here, about visualizing SF6 gas.
https://www.eevblog.com/forum/thermal-imaging/sf6-filter-for-ir-camera/

I didn't use a filter, but the gas was only visible when using High Sensitivity Mode of Thermal studio or Research IR, to process the video.

On page 2 of my thread, I have uploaded some pictures (post 33) and a video (for which you'll have to rename to .wmv) at post 36

Something which really helped me a lot, later on, was bap2703's advice:
"The gas needs to be at a different temperature than what lies behind: you can try adding something colder or hotter in the background."
Best solution is to use the sky as your background, which is around -50oC
 

Offline EverydayMuffin

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Re: Propane & Natural Gas Leak Detection
« Reply #7 on: August 02, 2020, 04:10:00 pm »
I recently came across the below sensors from Pyreos, they make thin film pyroelectric sensors and they look for perfect for this application.

They have a dual channel sensor which is available with lots of different filters, including filters for Hydrocarbons (e.g. propane, butane, isobutane), SF6, Methane, CO2, NO and NO2.
Datasheet: https://pyreos.com/pyreos-analog-to-sensor-two-channels-datasheet

They also have a dual channel sensor which is optimised for hydrocarbon gas detection applications.
Datasheet: https://pyreos.com/pyreos-analog-to-sensor-for-hydrocarbons-two-channels-datasheet
« Last Edit: August 02, 2020, 04:20:06 pm by EverydayMuffin »
 
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Offline Bill W

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Re: Propane & Natural Gas Leak Detection
« Reply #8 on: August 02, 2020, 10:34:25 pm »
Here is the next two levels up in system building with that kind of detector:

https://www.sgxsensortech.com/sensor-selector/

Lamp / detector for analogue sensing (eg IR11EM)
Integrated micro for digital out (eg INIR-CD)

Another bit of EEV / Marconi / e2v Chelmsford that got sold off (to themselves), but then they were sold again to Poland / China

Bill

Offline adammunich

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Re: Propane & Natural Gas Leak Detection
« Reply #9 on: September 11, 2020, 11:39:21 pm »
Wow, these sensors are very cool. I wonder if we could use them along with long range optics to detect methane leaks in an oil field. The "telescope" could be slowly scanned along the field, watching for unlit flares.
 

Offline Klaus

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Re: Propane & Natural Gas Leak Detection
« Reply #10 on: September 12, 2020, 07:10:38 pm »
https://youtu.be/K9qDi8n5YZ8

Some explanation and demo.
 


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