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Old 04-07-12, 10:07 PM   #1
calstar 
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Eye protection

What is commonly used eye protection when oxy/acet brazing? Does the flame damage the eye, strain the eye, etc.? Bad idea to use nothing?

thanks, Brian
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Old 04-08-12, 12:35 AM   #2
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The source is radiation emitted from the glowing metal. Most people seem to prefer the fancy glass blowers glasses.

http://www.youtube.com/watch?v=gtZT5kCc0CQ
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Old 04-08-12, 01:12 AM   #3
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The source is radiation emitted from the glowing metal.
No this is quite wrong. The metal glows red hot which is not harmful to the eye.The spectrum of radiation from a hot body is governed by the Planck's law and is thus proportional to temperature. You cannot get any metal hot enough to emit significant UV by any practical means.

The radiation from the hot gas in the brazing flame is another matter - gases emit light in discrete spectral lines. If the flame is blue or white you can pretty much guarantee that it will have some UV content, so shading the eye is beneficial.

The light emitted by the plasma produced during welding is yet another matter - this will have enough high frequency energy to burn the skin by radiation if exposed for long enough and will severely damage the eye even with short term exposure - less than a minute at 1 metre can exceed the recommended daily exposure limit.

Last edited by Mark Kelly; 04-08-12 at 01:16 AM.
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Old 04-08-12, 03:29 PM   #4
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I don't think you are right Mark. The blue of the flame is the same for silver bronze or gas welding. It may emit UV but it must be pretty trivial. Silver welding is generally regarded as not requiring protection. Same flame. When you gas weld metal the white glow is sufficient to require protection, though others I have heard say you do not need glasses even for that. Everyone wears them though. And blacksmiths who forge weld large clumps of white hot metal rarely wear glasses. Normally they say looking into the forge is a problem though. So they either try to limit that, or wear glasses when scoping out the forge. Possibly the culprit is the flux, that glows on the joint. As the video points out, a lot of it is that the glasses make it easier to see what is going on in the work. I saw one welding video for aircraft where they said that corrective lenses had adequate UV protection, but they none the less wore tinted lenses.

http://www.tellmewherethisis.com/pos...d-sachs-why-go
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Old 04-08-12, 06:34 PM   #5
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I like a 4 or 5 for brazing... Darkened glasses also make it easier to see what's going on in the braze puddle. I prefer to cut/weld/braze with a faceshield instead of glasses... nice to use when grinding stuff. Glasses are cheap, eyes aren't... dunno why people braze without them, but I wouldn't recommend it.
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Old 04-08-12, 09:14 PM   #6
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I've seen pros use simple sun glasses, or no glasses, for silver and bronze brazing. Having said that i use light shaded Didydium (sp?) glasses for a little shading and some flux flair reduction. ARS.
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Old 04-09-12, 03:49 AM   #7
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I like a 4 or 5 for brazing... Darkened glasses also make it easier to see what's going on in the braze puddle. I prefer to cut/weld/braze with a faceshield instead of glasses... nice to use when grinding stuff. Glasses are cheap, eyes aren't... dunno why people braze without them, but I wouldn't recommend it.
... +1 ...

I use a #4 or #5 flip-down faceshield and far prefer it over goggles as well. I keep one dark and one clear hanging right above the torch to ensure that they are used diligently. Sunglasses or safety glasses may be ok for copper but not for steel.

Last edited by Stealthammer; 04-09-12 at 06:38 PM.
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Old 04-09-12, 05:03 AM   #8
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I don't think you are right Mark. The blue of the flame is the same for silver bronze or gas welding. It may emit UV but it must be pretty trivial. Silver welding is generally regarded as not requiring protection.
I was counselling caution with the emission from the flame, I haven't done the research to know what the spectrum is.

My disagreement was with your statement that it was the glowing metal which caused the problems. That's simply not the case as is shown by Planck's law.

The liquidus temperature of LFB is a little under 1200 K. The Planck distribution says that 0.1% of radiation is below 910/K um, so at that temperature 99.9% of the radiation will be over 750 nm wavelength. UV damage is caused by wavelengths below 400 nm.

This spectral distribution is why the hot metal glows red, not white. If you get your brazing metal to white heat you've done something severely wrong.

Last edited by Mark Kelly; 04-09-12 at 05:14 AM.
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Old 04-09-12, 06:20 AM   #9
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I have seen some information that says you should worry about IR. I use Phillips Safety Green IR ACE With #3 shade. They work fine for brazing, I find them a little too light for gas welding and use a #5 welding shade for that.
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Old 04-09-12, 05:06 PM   #10
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On looking into this further (pun intended) it appears that near IR can cause retinal burns, so your choice of lens looks appropriate.

Last edited by Mark Kelly; 04-09-12 at 05:12 PM.
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Old 04-09-12, 06:48 PM   #11
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I have enough problems with my eyes that I don't really feel like taking any chances. I hear about people using sunglasses or nothing at all and I just cringe. If nothing else, didymium and ACE make it lots easier to see what you are doing. The green welding shades don't help with that much.
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