ac Arc welding hazards

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vinod
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ac Arc welding hazards

Post by vinod » Sun Oct 31, 2010 9:31 am

I know, for ac arc welding ground terminal of transformer should connect to work piece and electrode should be with positive terminal.

For the initial arc formation there should be direct contact between both positive and negative terminals.

My doubt is that, why this will not create any short circuit problems as of high amperage with low voltage situation ?

Does it cause any serious injury if we touch the work piece at the time of welding as of high amperage with low voltage situation ?
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psycho
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Re: ac Arc welding hazards

Post by psycho » Sun Oct 31, 2010 10:18 am

When I was in the Navy, I remember getting shocked pretty good once.

I was welding up a fan bracket to the ceiling. I was sitting on a big steel storage box that was welded to the deck of the ship. Since everything is steel on a Naval ship, you can hook your ground anywhere. My coveralls were drenched with sweat (We were in the Indian Ocean at the time). Every time I put a new rod into the stinger, I did, in fact get stung.

While I can't say the electrical theories behind your question, I can say that under certain conditions, you can get a jolt with a welding electrode. I don't remember being shocked while welding before or since then, though...

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MrAl
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Re: ac Arc welding hazards

Post by MrAl » Sun Oct 31, 2010 11:52 am

Hi there,

When the rod touches the work piece it may be a near short circuit, but once the arc appears it is no longer a short circuit and instead has the characteristics of an arc, which are not the same as a short circuit. The arc itself has a resistance just like a resistor after a certain point in the voltage characteristic, so it presents a load to the circuit rather than a direct short circuit.
LEDs vs Bulbs, LEDs are winning.

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reloadron
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Re: ac Arc welding hazards

Post by reloadron » Sun Oct 31, 2010 5:36 pm

vinod wrote:I know, for ac arc welding ground terminal of transformer should connect to work piece and electrode should be with positive terminal.

For the initial arc formation there should be direct contact between both positive and negative terminals.

My doubt is that, why this will not create any short circuit problems as of high amperage with low voltage situation ?

Does it cause any serious injury if we touch the work piece at the time of welding as of high amperage with low voltage situation ?
Actually there are a few small errors in there. When doing AC arc welding there is no positive or negative electrode, it is AC and the current changes direction 50 or 60 times per second. When there is direct contact between the rod and workpiece there is as MrAl mentions a brief short circuit which quickly becomes the arc. This is a "touch start". The distance between the rod and workpiece is the arc gap and the voltage drop across that gap is the arc voltage.

Also, when doing a DC arc weld generally the + output is connected to the workpiece and the - output is connected to the stick. This allows the material to flow nicely from the stick (material) to the workpiece. This is the most popular configuration for stick welding with DC.

Ron

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vinod
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indian arc weld machine

Post by vinod » Sun Oct 31, 2010 6:59 pm

This is our very very old(but still using without any protective clothing !!!)
typical Indian arc welding machine.

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dacflyer
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Re: ac Arc welding hazards

Post by dacflyer » Wed Nov 03, 2010 3:43 am

now you know why they call the electrode handle a stinger..lol

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vinod
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transformer polarity

Post by vinod » Thu Nov 04, 2010 9:27 am

as shown below,in every ac welding transformer there will be separate outs
for both Earth & Electrode holder.

Why there is such a restriction exists- as we can interchange ac transformer secondary points as we
desired ?

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gerty
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Re: ac Arc welding hazards

Post by gerty » Thu Nov 04, 2010 10:48 am

Why would you want to "interchange" welder outputs?

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reloadron
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Re: ac Arc welding hazards

Post by reloadron » Fri Nov 05, 2010 4:05 pm

gerty wrote:Why would you want to "interchange" welder outputs?
He is getting at the fact that his earlier picture shows a machine that uses multiple taps on the transformer to afford different weld currents, however, the newer machine is more limited (restricted) as to available outputs. This is common in lower end simple AC machines. Higher end machines allow a wide range of current selection as well as AC or DC welding current.

What you have is just the nature of the beast.

Ron

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Re: ac Arc welding hazards

Post by gerty » Fri Nov 05, 2010 10:55 pm

I thought he was referring to changing polarity of an AC welder

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reloadron
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Re: ac Arc welding hazards

Post by reloadron » Sat Nov 06, 2010 3:17 am

gerty wrote:I thought he was referring to changing polarity of an AC welder
Originally that is how I read it also? Beats the heck out of me? I commented on that but he never mentioned it again so I am clueless. :)

Ron

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Re: ac Arc welding hazards

Post by Dimbulb » Sun Dec 19, 2010 11:03 am

the fusion of metal where the powdered coating and a spray of molten material is normally concidered, however below the arc digs into the molten pool where a vortex exists, the walls of this inverted cone are melted while the swirling stream mixes and solidifies. the length of the arc controls the temperature.

It is my opinion that cooking a chicken over an open fire is healthy, but as we go to more and more extremes of temperature, pressure, velocity that there will be more and
more cancerous exposure to the human body. You could look at medical histories of steel mill production worker. The magnetic waves from the welding cable would be more pronounced in a coil than straight line. This point is not taught in a welding class and of course the UV is intense.

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