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 Post subject: Black Damp
PostPosted: Wed Oct 05, 2005 10:42 pm 
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Joined: Fri Jul 15, 2005 2:34 pm
Posts: 6872
Location: Within 60 Miles of the Northern Anthracite Field
Ok boys heres some info i put together tonight.

Black Damp CO2N2 is the term applied to any mixture of mine air that will extinguish a flame. Normal oxygen content in the air you breathe is approximately 20.93 percent. The chief gas characteristic of the damp is Carbon Dioxide and Nitrogen, in greater quantities than in normal air. This condition will be indicated on the flame of the safety lamp by a decrease both in brightness and height of flame. When a one inch flame is used, a reduction of one percent in the oxygen content in the air caused the flame to lower approximately 1/16 of an inch and also caused a perceptible change in color of the flame to red. A two percent oxygen reduction caused an unmistakable reddening, especially at the edges of the flame, only with a slight continued reduction in height. When the oxygen level is lowered three percent the flame height lowered another 1/16 and appeared detached from the wick. This reduction in flame height and illumination continued until at around 16.75 percent oxygen content the flame was extinguished. Black Damp is also heavier than air and will sink to the lowest part of the tunnel or mine and that is where it should be tested for. Here is a list of percent oxygen and its relationship to the lamp.


O2 content Percent Illumination
20.93 - 100%
20.7 - 90%
20.3 - 75%
19.9 - 70%
19.3 - 40%
18.9 - 28%
18.3 - 12%

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 Post subject:
PostPosted: Thu Oct 06, 2005 2:36 pm 
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Joined: Mon Jun 20, 2005 11:33 pm
Posts: 3080
Location: Above the Sterling Hill Mine
Chris,

This is real good work. But this tells us something that we have all been doing wrong. We have been using small flames. I guess we all figured it would react better and go out when the air is bad if the flame is small. But then again, you can't see the changes in height as well with a small flame.

After reading this, I did a test. I lite my lamp, setup a large 1 inch flame. I held my breath for like two minutes and breathed into the lamp. You can see the effects of the low oxygen right away on the flame just like you stated (I've done the same thing on my O2 meter in the past to see how it reacts to low O2). If memory serves, I think I have gotten the MSA Passport meter down to the low 12's by breathing on it if I hold my breath for a long time. I guess I can test it again to see..

Greg


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PostPosted: Thu Oct 06, 2005 3:07 pm 
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Joined: Fri Jul 15, 2005 2:34 pm
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Location: Within 60 Miles of the Northern Anthracite Field
nice, greg is just about passing out to check on mine theorys, excellent! i agree. after i did this research i thought the same thing. from now on 1 inch flames will be incorperated in the air quality testing.

chris

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