Thread: LNG leak
12-13-2004, 07:09 PM #1
- Join Date
- Sep 2004
- Quebec, Canada
Is it possible to detect a liquified natural gas leak using a TIC? Has anyone tried this? How dit it go?
12-14-2004, 10:08 AM #2
- Join Date
- Mar 2003
To answer this question you have to get into a pretty lengthy discussion, it is not a simple “Yes” or “No” answer.
When you say “detect a LNG leak” there are actually a couple of options:
1. Detect the vapor/cloud produced by the leak
2. Identify the source of the leak (i.e. the container, the exact location on a container or piping system, etc)
On number 1 the vapor/cloud – as a general rule Thermal Imagers do not “detect or see” gasses or vapors. If you think about it you can use them to “see through” smoke and fog. However in some instances if all of the conditions are just right you might be able to “detect or see” a LNG vapor/cloud. Remember the TI works off of temperature differences or variations in emissivity (reflect or absorb energy). As such it may “detect or see” the vapor/cloud if its properties are drastically different than the surrounding air (i.e. it is has a very large temperature difference than the surrounding air, it has something in it the surrounding air does not like water vapor from condensation, etc). Typically you will only be able to detect a LNG/Propane/Methane vapor/cloud very close to the source as it escapes, once it moves out from the source its concentration and temperature will very quickly match the surrounding air and make it “invisible to the TI”.
See the top pictures below for an example. (not easy to see, really need video)
On number 2 the origin of the leak – a thermal imager is very good at reading temperature differences, and an escaping compressed/liquefied gas is very good at causing a difference in temperature. The general rule is that the escaping gas will cool the immediate area where it escapes or it may cool the container it is escaping from. As such if you use the TI you may be able to ID a “cold spot” on a pipe/container, or compare containers and identify if one is significantly cooler than the others. Remember the faster the leak, the colder it will be, very small slow leaks may not cause a great change in temperature. For a good example of this lay out 3-4 SCBA cylinders, open 1 and let it bleed the air off pretty quickly, then come back with a TI and look at the cylinders, the one that is significantly colder than the others is the one that was “leaking”.
See the middle pictures below for an example.
Assuming that you are talking about a compressed gas that is liquefied you may also be able to identify and monitor a product/liquid level in a container and monitor it for a drop possibly indicating that the product is escaping/leaving the container. This one is another very lengthy explanation, you can check the Haz Mat forum http://cms.firehouse.com/forums2/sho...threadid=19178 for some more info.
See the bottom pictures below for an example.
PLEASE REMEMBER! - this is the 5 minute answer and it does not cover every detail, option, or scenario. It is a basic starting point, but there is a lot more to using a Thermal Imager in these types of scenarios. If you really want to cover it all you will need the 4-8 hour answer, along with the 4-8 hours of hands-on training to back it up. If you want more info on this type of training you can check with SAFE-IR,http://www.safe-ir.com
VERY IMPORTANT! – NO THERMAL IMAGER IS INTRINSICALLY SAFE!!!!! DO NOT intentionally enter a flammable /explosive atmosphere with a Thermal Imager. If you find yourself in a flammable /explosive atmosphere with a Thermal Imager DO NOT do anything to the Thermal Imager, simply remove the TI from the atmosphere. Your greatest chance of causing a spark or source of ignition is to do something like activating a switch or changing a battery. This subject has been debated many times, take it as you will, but you need to be aware of it.
If anyone has any experience with this please share it, real world examples are worth a hundred theoretical discussions.
Good Luck, Stay Safe,
Last edited by torichardson; 12-14-2004 at 11:50 AM.Mike Richardson
Captain, Training Officer
St Matthews FD, Louisville KY
TI Training = www.safe-ir.com
The information and views above are in no way associated with my employer, and are strictly my own.
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