Arc welding shock hazards in wet weather

[RedDirt]

What are the potential electrical shock hazards when arc welding while standing on wet ground? How can the risk be minimized?

I weld outside in the winter and sometimes the ground is wet. I weld on a concrete slab and pieces small enough to lift are welded on a plywood sheet atop wood saw horses. Sometimes the pieces are clamped for fit-up on a steel plate on the plywood top. Sometimes the concrete, ply, horses and fit-up steel plate are damp or wet.

I wear full protection including leather welding sleeves, welding gloves, high top boots with synthetic soles. The only exposed part of my body is the back of my head behind my helmet.

If a shower passes over I throw a tarp over my work then resume work when it has passed. When I weld in these conditions I stand on dry scrap plywood, but after repeated work this too gets somewhat wet. I don't know any other precautions to take but I still not sure if it is safe to weld like this.

BTW - My shop is a combination wood & metal working shop and no matter how well it is cleaned (or not) I still fear the errant welding spark will find its way into some unnoticed spot. So except for the occasional tacking together of small items inside the shop I prefer to do all my primary welding outside. I also weld outside because of the welding fumes. Anytime any welding or grinding is done inside the shop I don't leave for at least an hour and then check it again (for fire) at least once again later.

 

[jimmer2880]

to me, the most important piece of the welding equasion are a good pair of DRY leather gloves. I have found that when my leather gloves get damp (either from sweat, or from rain), I start to get a "tingle"

 

[2manyrocks]

http://files.aws.org/technical/facts/fs5-806.pdf

Goes through a list of things such as not putting your body in the wrong place, grounding the piece being welded to the ground (--not through the welding ground) having good insulation on your leads, etc., but for welding in damp locations there are three suggestions for the welding equipment used. One of the sugestions is to use DC welding, but I'm simply don't know if they mean you can switch to DC welding on an AC/DC arc welder or if they are referring to using some other specific type of DC welder.

Obviously, pipeline welders have to deal with these issues so there ought to be some good information somewhere on your question.

 

[RedDirt]

http://files.aws.org/technical/facts/fs5-806.pdf

...grounding the piece being welded to the ground (--not through the welding ground) having good insulation on your leads...

One of the suggestions is to use DC welding....

Most of the stuff in the referenced article I do but not the separate ground. I've run into this recommendation elsewhere but when I google (the always referenced) ANSI 249.1 "Safe Welding Practices" I get every article that contains the "reference to" but not the article itself!

It would be easy enough to pound in an eight foot ground rod in the welding area and run an alligator clipped ground wire to the work piece. Do you think this is what is meant by "grounding the piece to ground (--not through the welder)"? Does anyone here do this?

I wish I had a DC rig but don't so that's not an option for me.

 

[bjcsc]

Most of the stuff in the referenced article I do but not the separate ground. I've run into this recommendation elsewhere but when I google (the always referenced) ANSI 249.1 "Safe Welding Practices" I get every article that contains the "reference to" but not the article itself!

Well, here it is : ANSI Z49.1

It would be easy enough to pound in an eight foot ground rod in the welding area and run an alligator clipped ground wire to the work piece. Do you think this is what is meant by "grounding the piece to ground (--not through the welder)"? Does anyone here do this?

This info is on page 34 of the actual document (which is page 45 of the PDF) and appears to be what they recommend, although there is a terminology issue as they specifically call what we all call the "ground clamp/lead" the "work lead". Interesting...

 

[RedDirt]

Well, here it is : ANSI Z49.1



This info is on page 34 of the actual document (which is page 45 of the PDF) and appears to be what they recommend, although there is a terminology issue as they specifically call what we all call the "ground clamp/lead" the "work lead". Interesting...

Thanks for the document. BUNCH of good and interesting info here and I'll read the whole thing as soon as I have a chance. Nice to see a guide for recommended shades for different welding processes,etc, etc.

Ah yes, terminology. We must be certain of these definitions and I admit I'm still a bit confused. Since I don't operate equipment like DC reverse polarity I forget and do the mentioned mistake of calling my "work lead/clamp" a "ground lead/clamp".

"Grounding shall be done by locating the work on a grounded metal floor... or by connection to a grounded building frame or other satisfactory ground"

I think what is being recommended is similar to my suggestion of running a separate ground wire from the work piece to a suitable ground. A "suitable ground" is not the building electrical ground system since it is not sized for this application.

The confusion sets in because then they say, "If the work terminal is grounded care should be taken that the workpiece is not separately grounded".

So my question now is: On a 220V 1PH AC welder, is the work terminal grounded?

To make sure we are talking the same language, we have two terminals for arc welding. The "electrode holder" terminal and the "work terminal".

 

[bjcsc]

To make sure we are talking the same language, we have two terminals for arc welding. The "electrode holder" terminal and the "work terminal".

Roger that. My understanding is that if the work station (table, etc.) is grounded, the work piece should have continuity with it and the work terminal. If the work station is not grounded, connect the work terminal directly to the work piece.

So my question now is: On a 220V 1PH AC welder, is the work terminal grounded?

By grounded do you mean continuous with the receptacle ground? If so, I always assumed that it was, but now I don't know


I wonder how any of this applies to welding in the field. Granted, much of it is earth grounded as it is metal sitting on the ground (track equipment, hay rings, etc.) but what about the rest? I have never earth grounded a work piece separately. Our shop has a concrete floor and we build up from there with the work terminal connected to the work piece. For small stuff we use a welding table with no earth ground. Hmmmm...

 

[RedDirt]

Roger that. My understanding is that if the work station (table, etc.) is grounded, the work piece should have continuity with it and the work terminal. If the work station is not grounded, connect the work terminal directly to the work piece.

Since I have no metal work tables/benches I always connect the work terminal directly to the workpiece, as close as practical to the welding spot.

By grounded do you mean continuous with the receptacle ground? If so, I always assumed that it was, but now I don't know

I'm in the same boat. I assumed it was but now I don't know. I guess this gets into how a 220V 1 PH electrical system works and what is happening to produce a welding arc. Beyond basic electrical wiring (residential construction) my understanding of how electricity actually works is vague and limited.

I think it works like this but I could be way off: I presume to produce an arc the electricity is "shorted out" between the 220V legs and receptacle ground. (This from the common misnomer calling the "work" terminal a "ground" terminal.) The welder transformer setting dictates how much amperage is being sent to the electrode and thus regulates the intensity of the arc. The equipment receptacle is wired with two 110v wires and a ground wire. It seems to me the "work" terminal is therefore grounded.

If the above is true then it seems the issue when welding in wet and damp conditions is that if the weldor makes bodily contact with the workpiece and he has good earth contact....path of least resisttance...the current passes through him to ground...bad news to the wife. This is an argument for a separate ground to the workpiece yet the safety instructions say, "If the work terminal is grounded care should be taken that the workpiece is not separately grounded". Very confusing! And further complicates those that do have grounded metal work tables, especially if it is outdoors and wet.

I wonder how any of this applies to welding in the field. Granted, much of it is earth grounded as it is metal sitting on the ground (track equipment, hay rings, etc.) but what about the rest? I have never earth grounded a work piece separately. Our shop has a concrete floor and we build up from there with the work terminal connected to the work piece. For small stuff we use a welding table with no earth ground. Hmmmm...

I agree. Hmmmm.... (But at least in your shop I presume you are not dealing with wet/damp conditions therefore the path of least resistance is back to the receptacle ground...asssuming you have the required clothing, shoes, etc.)

We need a welding instructor to weigh-in.

 

[Defective]

I think it works like this but I could be way off: I presume to produce an arc the electricity is "shorted out" between the 220V legs and receptacle ground. (This from the common misnomer calling the "work" terminal a "ground" terminal.)

Yup...way off.

The arc is produced across the output of a transformer. It never goes near the ground at all.

(note: this assumes a good old fashioned buzz-box, not one of them new-fangled all-electronic machines with no copper inside...)

The welder transformer setting dictates how much amperage is being sent to the electrode and thus regulates the intensity of the arc.

Sort of...close enough...

The equipment receptacle is wired with two 110v wires and a ground wire. It seems to me the "work" terminal is therefore grounded.

Nope. The receptacle is wired with both sides of a 220v circuit and a ground wire. This is VERY different from two 110v wires. Pick any two 110v wires in your shop and chances are 50/50 that they are 220v apart or at exactly the same potential. Just depends on which side of the incoming line they branch from. Your home and shop are actually wired for 220v and the 110v is split up from there.

The ground wire is there ONLY in case of trouble. It should never have any voltage applied to it if your equipment is in good working order.

Neither terminal is actually physically connected to any of the incoming wires. (see my comment about the transformer above...)

If the above is true then it seems the issue when welding in wet and damp conditions is that if the weldor makes bodily contact with the workpiece and he has good earth contact....path of least resisttance...the current passes through him to ground...bad news to the wife. This is an argument for a separate ground to the workpiece yet the safety instructions say, "If the work terminal is grounded care should be taken that the workpiece is not separately grounded". Very confusing! And further complicates those that do have grounded metal work tables, especially if it is outdoors and wet.

True, that wording is confusing. Especially if you think about the simple fact that the work lead is NOT a ground. Think about what would happen if you grounded one side of the 220v line feeding the input of your welder. Wouldn't be a particularly efficient way to run the machine...

I'd rather work on non-grounded materials in a damp situation than otherwise. I figure I'm taking chances working in the damp to start with. No reason to guarantee I've got something well grounded to lean against while I'm sticking a fresh rod in the stinger.

If you want to try an interesting experiment, thoroughly ground a piece of steel and run a bead on it with your AC machine. Next, lay that same piece of steel on a dry sheet of plywood and run a bead along beside the first one. Take careful note of how the arc acts in the two cases. Take a good look at the two beads. Bet you note some differences.

We need a welding instructor to weigh-in.

Not a welding instructor...sorry...

But, on the other hand, I am trained as an electrician and I HAVE re-built 3 different AC welders so far. (great way to get a nice machine cheap )

 

[RedDirt]

Yup...way off.

The arc is produced across the output of a transformer. It never goes near the ground at all.

Thank you for the clarification and your other comments. Though I still have a lot of gray areas (like I don't know HOW a transformer runs) you comments do make some of my research more understandable.

Nope. The receptacle is wired with both sides of a 220v circuit and a ground wire. This is VERY different from two 110v wires. Pick any two 110v wires in your shop and chances are 50/50 that they are 220v apart or at exactly the same potential. Just depends on which side of the incoming line they branch from. Your home and shop are actually wired for 220v and the 110v is split up from there.

This I understood. I was just trying to simplify by saying two 110V wires. This is not an area where one should simplify.

The ground wire is there ONLY in case of trouble. It should never have any voltage applied to it if your equipment is in good working order.

Now it's making more sense. I think this answers a critical question. The work terminal IS NOT grounded.

I'd rather work on non-grounded materials in a damp situation than otherwise. I figure I'm taking chances working in the damp to start with. No reason to guarantee I've got something well grounded to lean against while I'm sticking a fresh rod in the stinger.

I see your point. Maybe my method of good, dry personal protection and standing on a dry board is a better precaution than grounding the workpiece.

If you want to try an interesting experiment, thoroughly ground a piece of steel and run a bead on it with your AC machine. Next, lay that same piece of steel on a dry sheet of plywood and run a bead along beside the first one. Take careful note of how the arc acts in the two cases. Take a good look at the two beads. Bet you note some differences.

Do tell, please. What are the expected differences?