Thread: TIG Welding voltage

Some years I had an incident with my Lincoln 250 welder and scratch start tig torch run through a Miller HF add on thing. The welds were coming out really nasty looking and I thought it might be because of insufficient shielding gas. So....I wet my lips held the torch to my mouth to see if I could detect the gas flow. Wham! Like a baseball bat in the teeth!!! There is no foot pedal so the torch is always "hot". Okay, so don't do that. Last night I was relating this story to a group of people and one guy (an EE) said that it was because of the high voltage. I replied that welders do not put out high voltage but high amperage. He insisted that only high voltage could cause pain like that. So have I been erroneously thinking that the welding was done with low voltage and high amperage all these years? I do suffer from not being able to understand electricity all that well so any input is welcome. Thanks.

It was probably just as likely from the HF. I have had my HF box on and the welder off and gotten a pretty good jolt. And yes the voltage output is fairly low at like "250 A at 30 VAC" (per millers website for a 250A machine) so if it wasn't the HF it would have been the Amps.

No, you got nailed by high voltage. Hi-frequency high voltage to be exact. The HF arc is somewhere around 3000 to 5000 volts at very little current. A couple milliamps at most.

The open circuit voltage without HF is about 80v. Depending on load and arc length that will drop from anywhere to 10 to 30v.

Originally Posted by Gazz

I do suffer from not being able to understand electricity all that well so any input is welcome. Thanks.

I can't argue with you on that statement. Especially after your wet lips to a electrically hot torch stunt.

I have been welding for over 30 years now and have never been shocked by an electric welder. When I was in college in the late 70's, we had a big TIG machine, I think it was a Linde, and I made a short "art" film of an extreme close up of an arc from that machine running up and down my bare hand. There was no pain and very little sensation at all. I had discovered that I could do that while welding aluminum and somehow drawing an arc on my skin. Typically, I am extremely cautious around electricity because of my lack of understanding of it. Since I had never had a shock nor even heard of anyone getting a shock from a welder it was not a concern when I raised that torch to my lips. I worked about 20 years in hi-tech building hi vacuum vessels which required lots of leak testing using a mass spectrometer helium leak detector. The way you tested gas flow with those was by wetting your lips and putting the nozzle/wand to them while adjusting the regulator. For the best results with that equipment, you needed a very small gas flow and that was about the only way you could do it. My training took over.

If you are not grounded to the welder you can make the HF jump to your finger without damage like you describe. You must have been touching a ground like perhaps leaning against the welding bench to get the shock you describe.

Early on I accidentally brushed the stick electrode across my lower lip as I raised my helmet. Felt like I got kicked by a mule. No HF involved, it was an AC buzzbox. Learned to use the other hand to raise my helmet right then and there.

Yes it definitely was the high voltage and HF that caused the pain. Electricity flows to the path of least resistance and your wet tongue was an excellent ground. I wouldn't do that again if I were you.

this is one of the funnist things ive read in long time.

you dont need high voltage to get a shock all you need is low resistance. we lost a welder years ago from a bad ground cable. the welder was inside a large pipe laying down it was hot so he was sweating they say the ground lead had a spot where the insulation was missing or broken when he moved it layed on his leg they think when he went to change the rod he completed the circuit and 20 minutes later when they went to tell him it was break time....well

dc hurts a little just sit on a beam while your sweating and try to replace the rod. dc likes to run on the outside of the body so shocks dont normally do much. ac likes to go into the body and hf ac realy hurts if you become the ground.

im sorry but the mental image of trying a tig touch on my lip still seems funny...at least you learned with out realy getting hurt.

Originally Posted by skrity

this is one of the funnist things ive read in long time.

I was gonna post that sentiment, but I had to wipe all the Dr.Pepper off my monitor and keyboard first!


Rex

As a kid, I learned not to test lawnmower ignitions by holding on to the lead to the spark plug. All it took was once. OUCH!

My Dad, who I've suspected for years was was trying subtle ways to kill me, told me that was the *proper* way to check for spark.

Gazz- Glad you're still with us but you damn near earned a Darwin award!! LMAO!

Just did a search and found this thread and wanted to throw in my .02. Lots of misunderstanding about electricals here. "High voltage" in this conversation doesn't mean anything unless you compare it to something.

The human body, dry, starts to conduct electicity around 40V. Wet, around 10-20V. Just put a 9V battery on your tongue. Your welder has an open circuit (no arc) voltage around 80V. So obviously anybody can get shocked, or electricuted, by welding voltages, especially if wet. Anybody who's leaked coolant on their glove can testify to that.

Normally, dry air is an insulator to electrical potentials up to several thousands of volts. So for a welder to work, it has to ionize the air in order to intiate an arc. Two ways to do that: strike an arc like a match, or through HF. High Frequency ionizes the air between the electrode and the work, lowering the resistance of the air to around 10-40 volts, depending on arc length. Once initiated, the arc itself keeps the air ionized.

So yea, if the HF wasn't on and you didn't touch the torch to you mouth, you probably wouldn't have gotten shocked. If your skin wasn't wet, you might have stood a chance. But your wet skin + the dry air + HF only needed 50V to complete the circuit, so your 80V welder just did what it does... make arcs.

I got zapped a few times before with the tig HF start voltage, I always put long sleeves on now.

Chip head wayne, the body very much can conduct below 40 volts. Its just the lower the voltage the less noticeable the effects are. Try 12 volts ac so its a wave form and you can very much notice it compared to dc. Hf does not ionize air, it ionizes argon - your sheild gas. Its a lot easier to ionise argon than air for a hole bunch of diffrent reasons.

Just as a piece of info, the HF will indeed try to work without the ground being hooked up. A couple times lately I've tried to start the arc and forgot the clamp was laying on the torch cable/waterline sheath...in other words completely out of conductivity with the workpiece. However, a faint blue arc starts to form, its just the normal fat blue arc doesn't follow it....this is a signal to me to "hook up the ground clamp, you tool"

Originally Posted by adama

Chip head wayne, the body very much can conduct below 40 volts. Its just the lower the voltage the less noticeable the effects are.

Yup, that's what I meant. Just trying to simplify a little. Of course, the human body can conduct microvolts, you're doing it all the time, but the resistance is high enough, so the current will be low enough, so the effect won't be "baseball bat in the teeth." Guess I should have said the body starts to conduct dangerous amounts of electricity at 40V or something like that. I got the voltages out of a table in a manual from years ago.

Originally Posted by adama

Its a lot easier to ionise argon than air for a hole bunch of diffrent reasons.

Why is that? SMAW arcs happen in air, and on the same welder with the same settings. And when I forget to turn my gas on I still get an arc.
-Wayne

As frequency of AC goes higher, the characteristics of transmission change, and they start to mimic that of very high voltages. Even a half-dozen volts of Kilohertz range AC can leave a pretty good burn, and feel like a really nasty jolt. Furthermore, if you were to take an HF_capable AC voltmeter, and measure the voltage across two leads at regular intervals starting from the welding machine, and proceeding to the stinger, you'd see that the INDICATED voltage fluctuates... because the leads have both capacitance and inductance... they're a RESONANT circuit. You could find that while there's practically no voltage at one point, the voltage at ANOTHER point may be upwards of twice, to even three times the applied HF voltage. This is proof that Kirchhoff's Law doesn't necessary cover AC circuits.

The reason why ionization in Argon is much easier than in Air... is because Air is a variable mixture of many things, particularly things that are NOT inert, hence, likely to be a very active piece in chemical processes which cause reduction/oxidization reactions.

Yes, when you forget to turn on your gas, you'll still get an arc... Adam didn't say that you wouldn't... he said that it is 'easier' to ionize argon, rather than air... and if you were to observe the voltage from electrode to ground, you'd see that in order to strike the arc without shielding gas, that the OPEN CIRCUIT voltage swings much higher, and is much less stable, when going through an unregulated mix of gases (78% Nitrogen, 21% Oxygen, and just under 1% Argon, amidst many others), the result is extremely variable. Result is an unstable arc, poor weld quality, and short electrode life.

Realize that when you use a stick-welding system, you're applying a 'dome' of shielding gas over the weld by virtue of the 'flux' burning off of the welding rod. The rod 'gasses out' the flux anytime the rod is hot enough... which is why it's hard to 'start' an arc, but once the rod is hot, the arc starts and burns nicely.

Originally Posted by ChipHeadWayne

Yup, that's what I meant. Just trying to simplify a little. Of course, the human body can conduct microvolts, you're doing it all the time, but the resistance is high enough, so the current will be low enough, so the effect won't be "baseball bat in the teeth." Guess I should have said the body starts to conduct dangerous amounts of electricity at 40V or something like that. I got the voltages out of a table in a manual from years ago.



Why is that? SMAW arcs happen in air, and on the same welder with the same settings. And when I forget to turn my gas on I still get an arc.
-Wayne

Firstly SMAW does not happen in air, the flux burns releasing gasses that shield the pool of metal + help stabilise the arc, try breaking the flux of 1/4 of rod and try getting it to strike a stable arc!

You still get a arc but it will be at a lot higher voltage + not as stable. Is all to do with the mass of argon atoms and how they behave - at what point they form a plasma. Helium is even easier to get to form a plasma, hence why it runs hotter which can help with tigging aluminium in larger sections. You can strike a arc in any gas forming a plasma, problem is if there not very inert gasses + gas mixtures the electrodes or sources of the arc will be under incredibly rapid chemical attack. Oxygen in air causes rust in a few months at atmospheric - room temps, at thousands of degrease, its near instant!

Gotta remember, we don't weld with a arc, we weld with the heat generated + the chemical reactions going on in the plasma the current flow causes in the gas.

Originally Posted by matt_isserstedt

Just as a piece of info, the HF will indeed try to work without the ground being hooked up. A couple times lately I've tried to start the arc and forgot the clamp was laying on the torch cable/waterline sheath...in other words completely out of conductivity with the workpiece. However, a faint blue arc starts to form, its just the normal fat blue arc doesn't follow it....this is a signal to me to "hook up the ground clamp, you tool"

Those blue arcs are called "corona discharge" some real interesting stuff: Corona discharge - Wikipedia, the free encyclopedia

However, the OP probably doesn't have those. I don't know if anybody else read the part where he said "scratch start" but that means NO HF to start the arc, it means drag your tungsten across a starting block or your workpiece to establish an arc. My guess is that he got hit by around 78 V OCV that a lincoln 250 puts out normally.