Welding safety: electrical shocks

[davesisk]

Hi Folks:

I just read this in a book I have called "Welding Essentials"...first time I had noticed the section, and I thought I share it with you:

1 mA (that's milli-amp, or 1/1000 amp): noticeable tingle
5 mA: very uncomfortable shock, possible burns.
50 mA: considerable burns, possible respiratory arrest, uncontrollable muscle contractions, possibility of injury from falls, some possibility of death.
1 amp: possible cardiac arrest, severe burns, possible death.
10 amps: cardiac arrest, probable death.

Wow, a mere 10 amps is very likely lethal, my welder will push 160 amps, and I know many folks here typically weld with 2-3 times that much current. I'd say safety is a must, eh?

Anyone know how much voltage is typically required to overcome the resistance of skin?

Dave

 

[Gary_in_Indiana]

<font color="blue"> Anyone know how much voltage is typically required to overcome the resistance of skin? </font>

No, and I'd just as soon not find out, either. /forums/images/graemlins/crazy.gif

 

[wroughtn_harv]

If you think a welder gives you a tingle wait until you dance with a plasma torch. /forums/images/graemlins/smirk.gif They have a leakage that'll make you dance without music.

One time a foreman and myself were welding up a batting cage. He was giving me guff, guy bonding thing. When we were fitting up the next piece I hit the piece instead of the framework with the stinger. He screamed in pain. He cussed me. I hit the piece again with the stinger. He cussed me again. It only took him about three more times to get the point that the bite was initiated by the cussin'.

When you have a problem employee it's always better if they quit than to fire them, just one of the facts of life we have to live with most days. We had one big old country bumpkin that wasn't worth throwing rocks with or at. I'd finally made up my mind that I couldn't wait until he quit. He was toast.

Then I had an idea. I was fabbing up a framework in the shop. I called him over to hold two pieces together tight so I could tack them. Per his way he didn't hold them tight, at least tight enough. I hit the one side with the stinger while the ground was on the other. If he'd held them tight like I'd told him there wouldn't have been a problem. As it was his knees buckled and he screamed about three times.

I looked up all innocent like as he stomped out of our shop and lives. Electricity is one of those things that can work for you. /forums/images/graemlins/grin.gif

Welding in a steady mist or even a shower will get you a tingle to a tickely tug. But the real danger is doing it under something like a truck or such where when you do the automatic jerk you come into contact with something. The old "it ain't the fall but the sudden stop at the bottom" addage live and well.

I've never heard of anyone actually knowing someone who died from welding amperage. I have known some who thought they were dying at the time. And lawd knows I've seen one or more lose what little religion they had via an electrical event.

But most of the time it's a scream--cuss--jump thing when the weldor becomes part and parcel to the welding process, not a fatal screw up, just a screw up. /forums/images/graemlins/blush.gif

 

[RonR]

Good points

I've hobby welded for 30 years. Biggest problem with shocks I've had was with the rod holder on one machine. It had a screw head that held the cable to the holder. The screw extended up to where you could touch it as you held the handle.

If conditions were right (damp, misty, etc), and you touched it, it gave you a tingle. Several wraps with electrical tape fixed it.

I never feared electrocution from it--just a respectable jolt.

Take Care,
Ron

 

[pruntyc]

Re: Good points

Of course just about anyone knows, its not a good idea to weld outside if it raining or if you are really grounded. I have never been shocked by a welder, even though I welded for many years for a living. But one fellow who was my pardner in welding in a fruehauf factory, was one of those people that got shocked easy. When we would water test a seam, and standing on the outside of a tank on cement, and it would be wet. He would get shocked almost every time he would strike a arc. It seems some of us aren't as easy to get it as others are. I never did and he did all the time.

 

[trailertrash]

Now looks like a good time to ask a question that I 've wondered about for years I've welded off and on for years simply because I was better at it than anybody else available(free),now don't misunderstand this because I would'nt make a pimple on a good welders butt but I could (most times ) at least get the stick started with the least amount of cussing.One of the places that I worked at I used to maintain garbage trucks and several times I would get a pretty healthy zap when welding inside the dump body when it was wet which it usually was, I just figured this was due to being wet and setting or laying on the same surface that I was welding on, but a couple of days ago I was doing some welding here at the house and I've got a mobile table that I do alot of work on and I was leaning on the table struck an arc and zapped myself this brought back old memories only this time I want to know why . Scene: hot, humid,metal table, ground on work piece 12" from arc , and I was sweating where I was touching table?

 

[DavidJ]

Here's one explanation of why you were shocked. Take a look at the clamp surfaces, I'd bet they're not very large or very clean. Now you clamp that to a piece of metal and you don't have very big "connection" couple that with the fact that you were sweating (lower body resistance) and touching the table. When you strike the arc the electricity is searching for electrical ground. Since there's such a small "connection" to ground via the clamp all the electricity from the welder can't travel through the clamp, so it travels where ever it can to find ground, a small portion of the current passes through your body and you're shocked /forums/images/graemlins/shocked.gif

 

[chim]

Dave, many years ago, an instructor for an electronics course said one could be electrocuted with a flashlight battery, provided the skin didn't get in the way. He used the example of sticking a needle in one finger of each hand to eliminate the resistance of the skin and provide a path through the heart. This sounded far-fetched then, and still does. It may be quite possible, but I haven't heard of anyone being zorched by less than 120 volts. In practice, common voltages encountered are 12, 24, some 48, 120, 240, 277, 480 and higher. Phone circuits used to (and still may) use 90 volts for the ringer. "Deadly" could begin to be a concern at 60 volts, 72 volts or who knows where. My point is that if we go by the common voltages, there's a jump of almost 100 volts between ordinary low voltage circuits and the 120 available at your regular receptacle. Usually someone who says they got hit with 240 volts is wrong. In many cases, they get between a hot from a 240 volt line and ground. That's 120 volts, but still quite bad. The path of the current through the body is of great importance. Just last week on a medical show, there was an unfortunate guy who contacted high voltage. It more or less blew his fingers off and cooked the muscles in his lower arms. He lived, but was left with stumps. A limb could provide a path for current many times in excess of that required for electrocution (contacts made with finger and elbow on the same arm) and not damage the heart.

Without checking the specs on a welding machine, I can't say for sure what the output voltage is, but I believe it may be around 25 or so, and it probably varies from something quite a bit higher at "open-circuit" or before the arc is struck. I never heard of anyone being fried by a welding machine. I suppose it could easily happen if the machine was faulty. There have been concerns about the effect of the rather strong magnetic field on the human body.

Many electrocutions occur on 120v. I know of one guy in my town who thought he'd modify a regular vacuum cleaner so he could use it to clean an above-ground pool. Didn't work. He died. A sheetmetal worker came close to death on one of our projects several years ago when a GFI-protected outlet failed. He couldn't move for about a half an hour, and was hauled to the hospital via ambulance for examination. He had to return to the hospital a couple days later to confirm his kidneys were OK.

Sorry to get so long-winded, but the best answer on how much voltage is needed to overcome the skin's resistance is that 120 will definitely do the job, and somewhere less than that is the cutoff point. I just don't know where that point is.....................chim

 

[Gary_in_Indiana]

<font color="blue"> one could be electrocuted with a flashlight battery, provided the skin didn't get in the way... sticking a needle in one finger of each hand to eliminate the resistance of the skin and provide a path through the heart </font>

I can just picture someone somewhere with a pair of Mom's sewing needles and a battery from their flashlight swilling down their tenth beer shouting "Hey, y'all! Watch this..." /forums/images/graemlins/shocked.gif

 

[bgott]

You're lucky you were dealing with dummies. If you would have been dealing with a smart one he'd have just touched you about the time you struck the arc. The last guy in line gets the jolt. I worked with a mechanic that loved to grab a plug wire and touch whoever was walking by. One day he was under a hood and I saw him reaching out when I was walking by with the boss. I touched the boss about the time he touched me and that cured Sparky from his hijinks for at least a month. /forums/images/graemlins/grin.gif