Farmer Electrocuted By Faulty Welding Cable

[tcartwri]

What are the DC vs. the AC voltages of say, my Miller sticker? Ohm's Law may be on our side. BTW, I am almost always wearing rubber shoes or boots. Quack.

Doesn't matter if the current passes from hand to hand.... through your heart.

 

[Tobias Dunlap]

Does anyone know what voltages we are welding with at the stinger end? I'd like to know.

It depends on the machine. My SA200 works on a 40 volt circuit, DC 600, around 70 to 80. Ranger 225 works with 25. These are are with SMAW process. GMAW and FCAW on a CV circuit use anywhere from 12 to 40VDC.

I've only had one AC machine, it was a little miller roughneck and I think it worked with a 30 volt circuit but i'm not sure.

I'm curious to know what the voltage on my AC Tig unit high frequency pilot is. If you feather the controls just right, you can make little lightning bolts dance on your thumbnail.

 

[Mace Canute]

If conditions are "right", 12 volts DC can be lethal. Years ago, when I was at Lineman's school when I was an apprentice, the instructor told of of an instance where a farmer was electrocuted while trying to boost his combine. Two ends of the booster cables hooked up to one battery and he apparently had both clamps in his hands, one in each hand, and was in the process of putting them on the other battery posts simultaneously. (I've seen people do that for some unknown reason:confused3 Anyways they figured that with it being a hot day and him sweating like the proverbial pig and squeezing a ratty old pair of clamps hard...clamps which were well wore and lacked a considerable amount of insulation on them...his natural skin resistance was low enough and he made a good enough contact with each hand that current flowed from hand to hand and his heart went into fibrillation which lead to cardiac arrest.

From Wiki (where else, eh? )

60 mA of AC (rms, 60 Hz) or 300-500 mA of DC can cause fibrillation. A sustained electric shock from AC at 120 V, 60 Hz is an especially dangerous source of ventricular fibrillation because it usually exceeds the let-go threshold, while not delivering enough initial energy to propel the person away from the source. However, the potential seriousness of the shock depends on paths through the body that the currents take. Death caused by an electric shock is called electrocution.

If the voltage is less than 200 V, then the human skin, more precisely the stratum corneum (the outermost layer of the epidermis), is the main contributor to the impedance of the body in the case of a macroshock-the passing of current between two contact points on the skin. The characteristics of the skin are non-linear however. If the voltage is above 450-500 V, then dielectric breakdown of the skin occurs. The protection offered by the skin is lowered by perspiration, and this is accelerated if electricity causes muscles to contract above the let-go threshold for a sustained period of time.

If an electrical circuit is established by electrodes introduced in the body, bypassing the skin, then the potential for lethality is much higher if a circuit through the heart is established. This is known as a microshock. Currents of only 10 μA can be sufficient to cause fibrillation in this case.

BTW...a mA is a thousandth of an amp and a μA is a millionth of an amp.

 

[Short Game]

...enough initial energy to propel the person away from the source.

Like when I get bit by a spark plug wire and crack my elbow on the recoil? I hate it when that happens.

I've been solidly across 12, and even 24, volts DC. I have never felt a thing when this has happened. Some people have told me they can feel a car battery and I've always wondered what they feel. A guy in high school got his ring welded into a 12 volt circuit and that gave him a really nasty burn.

Since I was a small child, I've taken quite a few 120 AC shocks without a problem, including solid contact through both hands, and a couple of those, even soaking wet. I would play with 120. I was a weird kid. Now I'm a weird old man. I think maybe I learned to take shocks. But anyway, I sure hope it never happens to me with 240v. I don't think I'd like that. I guess maybe I just have a high skin resistance. Your mileage may vary (for that matter, so might mine). Do not try this at home.

I don't fear electricity, but I damned well respect it.

 

[k0ua]

I have felt 12v DC battery voltage, You have to be sweating like the proverbial pig, but if you lay a very sweaty arm across the terminals with one of them near your elbow you can feel it. I have worked a lot with 48-52 volt battery voltage, and you can feel that if you hands are slightly damp. The worst shock I ever received was changing out a tube on a TV tuner, and came in contact with a feed-through capacitor supplying about 330 volts B+ voltage to the plates of the tuner tubes. Now let me tell you, that will get your attention. Fortunately for me, it went in my fingers and out my arm to the chassis, and not through my heart or I would not be here writing this.

James K0UA

 

[Short Game]

Before I went on the diesel boats, I was in the electronics shop on a submarine tender. One of the tools we used was a cobbled together, non-UL approved, gizmo for checking submarine cable insulation for pin holes. It was made from a regular military flashlight case. It had a three inch, sharp, steel probe sticking out from what had been the light bulb end and a simple small lamp cord at the other end.

I found it laying there on the bench in the shop and wondered, "what the flip is this?" I picked it up and plugged it in. It vibrated vigorously at 60 cycles. I thought, "hmmm, it's an engraver tool," and I reached out and felt the probe end with my left hand. I shot an arc about four inches long from my hip to the work bench. BTW, that hurt.

They told me it was a simple step-up coil that generated about 250,000V. I never found out who left it laying there.