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4th Sep 2016, 04:00 PM #46Member: Blue and white apron brigade
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Apart from black holes all materials reflect visible and UV to some extent, the question is how much they reflect in relative terms.
Ttwo well know examples are the significant UV reflections from Galv and Al.
What is not that well known is the at 300nm, concrete can reflect about 2/3rds of the UV that Al reflects, and at 200nm concrete starts to reflect more than Al.
Even welding curtains still reflect about 1/4 of the UV from Al.
One concern would be with cheap helmets where the manufacturer may not be using the best available materials.
But it may not be the helmet material that is the problem.
- welding helmets are notorious for getting very dirty from grinding grit and dust and who knows what the UV reflectivity of that stuff is.
- wearing eye glasses under a helmet may catch UV and reflect into the back of a helmet and into the eye.
- some helmets are not that well fitting which would allow for more UV to sneak around the sides and top.
A greater concern than reflection from say building surfaces would have to be other welders working behind another welder.
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4th Sep 2016, 05:48 PM #47
Bob, when you say "Galv" would this refer to new looking galv? All the sheds I have done welding in have been made from very old dull galv.
Dean
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4th Sep 2016, 07:14 PM #48Senior Member
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Galv and aluminium will reflect a lot of visible light too. Also, for your reading glasses to reflect uv it would take total internal reflection but doesnt that mean angles over 45degrees? Not really possible in a helmet plus the polycarb or glass would attenuate the uv as it would have to pass through twice. I just spent some time searching for the risk of uv from reflections into your helmet from behind but i couldnt find anything other than forums which you kind of need to ignore if you are looking for facts. There are references to reflections being a risk to bystanders though.
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4th Sep 2016, 09:51 PM #49Member: Blue and white apron brigade
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Sure but concrete won't reflect as much visible light.
A welder wouldn't notice the visible light being reflected, from say concrete, back into their helmet especially because when the reflection fires up and hits the back, so does the arc at front and this will be what the welder focusses on.
Also, for your reading glasses to reflect uv it would take total internal reflection but doesnt that mean angles over 45degrees?
Not sure why it has to pass though twice - some UV will reflect off the back of whatever the very back of the lens is made of.
Try this. Put on a welding helmet and cover the front of the lens with something opaque, face away from a light source (i.e. light source at the back of the head) and let your eyes adjust to the darkness - what do you see? I have 3 welding helmets and on all three I can clearly see some light leaking around the gaps in the back and top of the helmet. If you can see visible light you may also be exposed to reflected UV.
I just spent some time searching for the risk of uv from reflections into your helmet from behind but i couldnt find anything other than forums which you kind of need to ignore if you are looking for facts. There are references to reflections being a risk to bystanders though.
Within seconds I found this https://books.google.com.au/books?id...0pipes&f=false
What happens is these guys know about this and for other reasons as well wear snoods which fill in the helmet gaps is probably why eye problems are not reported from these welders.
It may not be as much of a problem at lower currents and may only become more of one at higher currents. MY BIL works on Al vessels up to 40m long and he always wears a snood even on the outside of hulls - he uses 250+A and there is a heap of Al plate everywhere.
In my welding booth I have two compact fluoros above my head to light the work. Depending on how I hold my head I often see this light reflected in off the back of the helmet lens. In fact at times it is a damn nuisance and I have to turn it off.
Come to think of it my welding booth is made from Gav Miniorb and sheetmetal - I'm not what you would call a regular welder but I must look at getting a snood.
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4th Sep 2016, 10:05 PM #50Member: Blue and white apron brigade
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5th Sep 2016, 12:16 AM #51Senior Member
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I think concrete will reflect a lot of light to be honest. Anytime I've done new concrete in the sun, I can't look at it, its so white.
From what we've already discussed, the light from an arc that requires a shade 14 needs to be attenuated 54 db and the UV needs to be attenuated 64db for your eyes, to be safe welding. You'll appreciate light is just a radio wave and follows RF theory. As long as the total attenuation meets those figures, you are fine. There is a pathloss which is due to the fact the arc is an isotropic radiator, without considering if there's any attenuation from the atmosphere. I'd need to dig out my old stuff to calculate the path loss but I read while I was looking for OSH type reference to the need to block the back of your helmet, that its safe to look at an arc if you are 50ft away (it didn't say what current). UV will suffer a higher pathloss because its twice the frequency. Each reflection will cause more attenuation and for there to be any risk, every surface would need to be direct reflection with low attentuation. I saw something that said aluminium (probably the best reflector?) attenuated by only 2dB but that would be polished and direct reflection. You'll also be very aware of the visible light on that path because polished aluminium is almost a mirror. So I'd say if you were welding in a pipe with short path to the back of your helmet and assuming low attenuation for reflections, then you would be sensible to put a cloth over the back of your helmet. I doubt you'd be able to see for the visible light reflecting off your screen on the inside without doing that though.
I won't take this any further, but I must admit to not being concerned at all about UV reflecting into the back of my helmet - unless I'm in an enclosed aluminium pipe.
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12th Sep 2016, 06:02 PM #52Senior Member
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for what its worth, I wear prescription glasses then put on a pair of antiflash safety glasses then my mid ranged priced, auto welding helmet.
I have 'older' eyes but have no problem seeing well enough through the antiflash glasses and helmet to strike an arc with a stick welder in good light.
I got into the habit of wearing antiflash glasses when I worked in a big multi tasking metal shop where I was always on the move and at times subject to the stray 'flash' from the welding shop.
Yeah I know now there's curtains all around them, but these were the days where I regularly walked across 6 inch I beams 3 stories above the ground while the building frames were under construction, just like dozens of other guys. Stupid now!!
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17th Sep 2016, 10:36 AM #53
The one thing that must be grasped is .... welding produces exceptionally large amounts of UV light especially high current welding.
A very very small fraction of an exceptionally large amount is still a lot and enough to cause damage and/or discomfort.
In general people have a very poor understanding of how very small fractions of very large amounts can still be large amounts.
People consistently over estimate the level of protection provided by protective equipment.
People consistently underestimate the ill effects from leakages and bypasses in protective equipment.
Dismissing causes thinking that it can't be this or that , because of lack of appreciation of the scale and proportion of the problem is all too common.
DON'T be over confident about the protection your lenses provide.
DON'T dismiss, leakages, reflections, impropper fitting and impropper use of PPE.
If there is a problem ..... and it is obvious that significant numbers of people have a problem ...... don't dismiss things saying it can't be this or that bassed on perception.
Those very small factions of extraordinarily large quantities can bite you on the @&$!.
cheersAny thing with sharp teeth eats meat.
Most powertools have sharp teeth.
People are made of meat.
Abrasives can be just as dangerous as a blade.....and 10 times more painfull.
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17th Sep 2016, 04:15 PM #54Senior Member
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Its a miracle we are not all blind.
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18th Sep 2016, 03:45 PM #55
Actually the incidence in eye and hearing damage among welders is pretty high.
Hearing damage is reasonably easy for others to be aware of probably over 70% of welders will have an aquired hearing loss
How many welders have less than perfect vision as a result ....... cataracts, poor night vision, patchy vision, blind spots, funny weird blinky stuff, headaches ... excetara ...... we just don't know because we don't know what they do or don't see AND visual screening pretty much stops at a basic eye test, a quick squiz at the back of the eye and occular pressures.
cheersAny thing with sharp teeth eats meat.
Most powertools have sharp teeth.
People are made of meat.
Abrasives can be just as dangerous as a blade.....and 10 times more painfull.
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18th Sep 2016, 11:16 PM #56Most Valued Member
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19th Sep 2016, 12:11 PM #57Member: Blue and white apron brigade
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There have been some long term studies of welder's vision.
None of the studies showed clearly identifiable visual acuity effects in US or European welders.
Two studies that showed definitive results for loss of colour vision were in India, and more recently in Spain.
We've all seen the quality of OHS displayed by Indian and other third world welders, not sure what the regs would be in Spain.
There probably is a high level EU OHS directive but one wonders how seriously they would take it in practice.
The Spanish study article is available here.
Prevalence of color vision deficiency among arc welders - hows your spanish?
The Spanish study showed that 15% of welders that have welded for more than 4 Years suffer from some form of identifiable colour blindness compare to 2% of those in a control group.
There is also a direct relationship between numbers of years in the welding trade and the extent of the loss of colour vision.
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21st Sep 2016, 10:23 PM #58
We don't know a great deal about vision loss and inparement in general .... well not in the level of detail we know about other complaints.
We have some pretty coarse information about some stuff.
If you have been around the workshops and tradespeople ...... you will know that it is fairly common for people to complain about a variety of eye malodies.
What we don't know about is the long term results
cheersAny thing with sharp teeth eats meat.
Most powertools have sharp teeth.
People are made of meat.
Abrasives can be just as dangerous as a blade.....and 10 times more painfull.
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22nd Sep 2016, 12:45 AM #59Member: Blue and white apron brigade
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I'm not sure about this. About 95% of people in Australia above the age of 65 wear glasses. As a part of getting replacements glasses most people would undergo an eye health check as well as the standard visual acuity tests. I'd say we are a very well covered in this regards perhaps more so than any other body sense, and for blokes probably more than any other organ. My optician is a bit of a gadget freak and does a bewildering array of tests probably because he has the gear but also because he knows I'm diabetic and need a bit more checking out.
There has been no correlation of loss of visual acuity with welding exposure probably because so many other things start to affect our eye as we age. I don't think they will ever be able to tease out the effects - well probably not in our lifetimes anyway.
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