Author Topic: Electric arcs in arc welders  (Read 11581 times)

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Online Zero999

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Re: Electric arcs in arc welders
« Reply #25 on: March 07, 2015, 07:34:24 pm »
Is it easier for it to get inside when you are sweaty?
Yes. The skin is porous and sweat is a very good conductor.
Ive done the same before.  Was putzing with a rechargeable AA, and a LED, shorted across the top with the LED lead, and my finger on it.  Square indented burn in my finger tip, and it smelled pretty foul too.
I did exactly the same thing!

Quote
High current low voltage DC sources can be as dangerous or more dangerous than even mains, at least when it comes to metallic objects that the user is holding/wearing because of the risk of thermal burns, and the object welding itself in place.
Especially when there's batteries which can blow up. Always use a fuse, as near to the battery as possible, when powering a circuit from large batteries.
 

Offline gerathegTopic starter

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Re: Electric arcs in arc welders
« Reply #26 on: March 14, 2015, 07:06:49 pm »
Touched battery terminals across my hand with thumb and index finger. Why can't I think ahead about the consequences lol  |O  :clap: I touched them for no apparent reason other than to kill boredom without thinking I'd have current running through my body lol.
This time barely no feeling of a tingle from 12V battery, but still feel stupid for not thinking what I'm doing...

Anyway, what's the resistance across a dry finger? My meter reads it in the Mohms range, though Google says it should be in the Kohms range and with dry skin about 100Kohms.
 

Offline SeanB

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Re: Electric arcs in arc welders
« Reply #27 on: March 14, 2015, 07:16:26 pm »
I have drawn nearly meter long arcs with a standard arc welder, doing welding of steel. Just need still air and you can draw a pretty big though short lived arc out of them.

Was changing UPS batteries, and was asked to do it live.  No ways, I get shocked enough with the trays as is just lifting them in with dry skin and was not going to add 340VDC on top of the 170V bus half voltage. You cannot help but get some contact when you lift a 50kg box to load it in the slot, especially with the terminals being aligned with the sides.
 

Offline tautech

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Re: Electric arcs in arc welders
« Reply #28 on: March 14, 2015, 07:53:19 pm »
Thanks for the replies! I think I understand how arc welding works.
Be aware only one reply has stated the correct facts of how an arc is maintained.

With MMA (welding rods) the arc is maintained in an inert atmosphere produced by vaporising the flux coating which contains various additives to help start and maintain the arc, try welding after removing the flux coat or with a piece of plain wire as modern welding rods have additives in the alloy as well to help make the rod run smoother.

The sheiding of the arc and weld pool is of the utmost importance for good welds.
Try welding outside in a strong wind and you will find out.
This is when Mig is useless.  :--

To confuse matters more there are different types of electrode construction for AC, DC straight (electrode Negative) and DC reverse (electrode Positive).
Droplet transfer is improved when welding with DC straight as it mimicks electron flow. (- to +)

Then there are rods optimised for some welding positions and techniques. (Vertical uphand or downhand, Overhead, Cutting, Stove pipe, Overlays etc)
Plus the myriad of different metal types that can be welded.

But none of this is any different to safe practice with anything electrical......
Avoid wet conditions
Wear insulating footwear
Heavy Gloves can be useful for changing rods with a welder that bites (some do, especially high OC voltage models)
Work technique that mimimises the chance of electrical shock. (Methodology)

These days full body cover is the accepted norm when welding, on some sites electricians must cover up too.

I'd say take note of these modern workplace practises to keep yourself safe.

« Last Edit: March 14, 2015, 08:17:35 pm by tautech »
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