Arc/UV/IR reflections

By Fabricadabra Date 03-29-2019 12:47

The plant manager decided to hang plastic mirror balls (the security type, about 20" diameter) above one of the welding areas. It is about 15 to 18 feet in the air, hanging above welding booths. The plant manager seems confident the arc reflections will be harmless and safety manager agrees but seems open minded. My gut tells me they are wrong but I haven't had much luck finding any definitive info or sources on it either way. I have found a few articles claiming reflections are effective up to 50' but OSHA doesn't show much about arc reflections. If anyone knows anything or has ever dealt with a similar issue, all input/questions are appreciated.

Thanks

By 803056

Date 03-29-2019 13:20

It is probably a good thing to ask question whenever safety is an issue.

The saving grace in this case is the convex mirrors you are talking about spreads light over a larger area in contrast to a concave mirror that concentrates the light (UV). In effect, it increases the "distance" between the light source and the viewer.

The intensity of light decreases at a rate of the distance squared if the distance is in the line of sight. The convex mirror spreads to light over a broader area, so in essence, it increases the "distance" between the light source and the viewer. There are formulas to calculate the intensity of the light, but without knowing the distances from the light source and the mirror and the radius of the mirror, and the distance between the mirror and the viewer, no definitive answer can be provided.

In any case, there is still a chance someone exposed to the UV can receive an arc flash if they are exposed to the UV long enough or if they look at the mirror long enough.

In my humble opinion, it [url=]isn't [/url]a good idea to place a mirror, flat, concave, or convex, above a welding station unless it has the necessary UV filters in place. There is little difference between the mirror and having a galvanized sheet metal roof. Working in the same area as a welder under a galvanize sheet metal roof will still give you an arc flash, it just takes a little longer.

Al

By Fabricadabra Date 03-29-2019 14:11

Thank you for the timely response!

What you said makes perfect sense. I will do my best to find out the distances and try to figure out the formula. If this ever gets officially figured out and settled I will post back for reference.

I personally think ANY chance of UV/IR exposure is not worth the limited view into a weld booth just for "supervising" reasons.. :roll:

By 803056

Date 03-29-2019 15:27

I agree.

They make translucent curtains that filter out the harmful UV. Management can still see whether the welder is OK.

A company I worked for years ago used to have the fire-resistant cotton flash curtains. One evening one of the welders didn't show up for coffee break. When they went to get him, they found him under a small vessel that had toppled over onto him. He was unconscious when they found him. We had no idea of how long he was unconscious. He required two back operations and was out for nearly a year. They replaced the cotton curtains with the translucent plastic curtains a couple of days after the accident.

The bottom line is, the translucent flash curtains allow management or other workers to see that the welder working in the booth is OK, not just to see they aren’t goofing off.

Al

By Fabricadabra Date 03-29-2019 17:19

That's the kicker. All of our booths are made of red or black (dark green) translucent plastic curtains. Every booth has at least 2 very bright LED light strips in it, which makes it clear who, how many, and what is in the booth. The mirror ball seems like an unnecessary redundancy that may just add more UV exposure.

At the end of the day, one would think it's a lot easier to scrap the mirror idea rather than to do all the equations. Looks like i have some math ahead of me if I want to make a case for it. :cool: