Welder Ground Lead

Status
Not open for further replies.
MAC702 said:
No, it's basically saying that in addition to your electrode lead and your work lead clamp, you ALSO make sure your weldment is grounded. It's a completely separate issue. In this type of situation, though, it's automatic because the grounding is also the work connection. It won't always be.
Click to expand...

Unless I'm missing something, infinity's picture just shows the work connections. The work connections should NOT be just connected to something that's grounded on the assumption that the work piece is also grounded. Any poor connection along the return path will be another welding location. Seems like a good chance that's what happened in this situation. I hope you are not advocating doing that way.
 
jaggedben said:
Unless I'm missing something, infinity's picture just shows the work connections. The work connections should NOT be just connected to something that's grounded on the assumption that the work piece is also grounded. Any poor connection along the return path will be another welding location. Seems like a good chance that's what happened in this situation. I hope you are not advocating doing that way.
Click to expand...

I've clearly stated that I thought the connection to MC cable was not appropriate. Yes, poor connections should be avoided.

An experienced weldor usually knows when he has a poor work connection, and will also minimize it by bringing his work connection as close as he can to a direct path. But he's also not going to run another 100 feet of welding lead just for the work clamp if there is already something available that experience tells him works well. I've no need to decide whether or not I should advocate a common practice.

I see nothing that indicated an assumption was made that the work piece (weldment) was conductive to the same material as the conduits in question. It was likely known, and easy to verify.
 
jaggedben said:
Unless I'm missing something, infinity's picture just shows the work connections. The work connections should NOT be just connected to something that's grounded on the assumption that the work piece is also grounded. Any poor connection along the return path will be another welding location. Seems like a good chance that's what happened in this situation. I hope you are not advocating doing that way.
Click to expand...
if thats the case then what exactly is the question/worry? to weld it you must clamp the work piece to one of the welding electrodes. hence why i was asking if the pic was showing any of those clamps as secondary clamps, etc.

any-hoo, if the clamps in the pic are primary clamps only and are not clamped onto the primary work piece, then all sorts of bad stuff can happen as ~200A makes its way around to/from the welding machine. as example, rmc could be egc jumpered at each end with say a #8 wire to the next hop of metal (eg; bushing nut that has egc screw).
 
FionaZuppa said:
if thats the case then what exactly is the question/worry? to weld it you must clamp the work piece to one of the welding electrodes. hence why i was asking if the pic was showing any of those clamps as secondary clamps, etc.

any-hoo, if the clamps in the pic are primary clamps only and are not clamped onto the primary work piece, then all sorts of bad stuff can happen as ~200A makes its way around to/from the welding machine. as example, rmc could be egc jumpered at each end with say a #8 wire to the next hop of metal (eg; bushing nut that has egc screw).
Click to expand...

You asked me what the worry was and then gave a perfect example of what to worry about.
 
MAC702 said:
I've clearly stated that I thought the connection to MC cable was not appropriate. Yes, poor connections should be avoided.

An experienced weldor usually knows when he has a poor work connection, and will also minimize it by bringing his work connection as close as he can to a direct path. But he's also not going to run another 100 feet of welding lead just for the work clamp if there is already something available that experience tells him works well. I've no need to decide whether or not I should advocate a common practice.

I see nothing that indicated an assumption was made that the work piece (weldment) was conductive to the same material as the conduits in question. It was likely known, and easy to verify.
Click to expand...

Ok, fair enough, we lack details. Infinity gave me the impression that the clamps were put to the EMT and just left there for work at various different locations around the building. Sounds lazy and assuming to me, but maybe I'm being too assuming. Seems like there's also a myth that you can just connect the clamp to 'ground' and be okay, but maybe I'm being too assuming.

He also asked how dangerous it was. I have no way to quantify that, but my position would be that if one is welding, say, building steel, then one should put the return clamp to other building steel and not to some EMT that may or may not be well bonded to the building steel. That is, unless you've specifically checked that the EMT is suitably well bonded to the building steel with bolted straps or similar. Otherwise, one could end up welding some bonding jumper as Fiona described, and starting a fire in a location you aren't even working near.
 
jaggedben said:
Ok, fair enough, we lack details. Infinity gave me the impression that the clamps were put to the EMT and just left there for work at various different locations around the building. Sounds lazy and assuming to me, but maybe I'm being too assuming. Seems like there's also a myth that you can just connect the clamp to 'ground' and be okay, but maybe I'm being too assuming.

He also asked how dangerous it was. I have no way to quantify that, but my position would be that if one is welding, say, building steel, then one should put the return clamp to other building steel and not to some EMT that may or may not be well bonded to the building steel. That is, unless you've specifically checked that the EMT is suitably well bonded to the building steel with bolted straps or similar. Otherwise, one could end up welding some bonding jumper as Fiona described, and starting a fire in a location you aren't even working near.
Click to expand...

The welding machines are grouped at specific location usually adjacent to a panel which powers them. The 10' lead with the clamp (usually the (-) on the machine goes to the nearest electrically connected metal, be it EMT, strut, MC cable, etc. From the machine the other lead is run all over the building sometimes 200' away to the work location.

Since the building is poured concrete there is no building steel. I'm assuming that in order for the welder to even work the machine current is flowing to the point where the electrical system and the metal being welded is connected, depending on the particulars this could be hundreds of feet away.
 
Often the job specs require both welding leads to be run to the work area and one of them directly connected to the item being welded. There have been fires from the practice of using conduit or building steel at one of the welding conductors. I have replaced a lot of LFMC, circuit conductors, some conduit (because the conductor insulation had melted and we could not remove them) and a couple of sets of load cells, because of this practice.
 
don_resqcapt19 said:
Often the job specs require both welding leads to be run to the work area and one of them directly connected to the item being welded. There have been fires from the practice of using conduit or building steel at one of the welding conductors. I have replaced a lot of LFMC, circuit conductors, some conduit (because the conductor insulation had melted and we could not remove them) and a couple of sets of load cells, because of this practice.
Click to expand...


I figured that there is some danger involved in this practice. As I stated earlier we did have a situation where when someone pushed a piece of feeder MC cable against a piece of EMT there was a sizeable arc. An investigation had shown that the welding lead had been attached directly to the MC cable on a higher floor.
 
don_resqcapt19 said:
Often the job specs require both welding leads to be run to the work area and one of them directly connected to the item being welded. There have been fires from the practice of using conduit or building steel at one of the welding conductors. I have replaced a lot of LFMC, circuit conductors, some conduit (because the conductor insulation had melted and we could not remove them) and a couple of sets of load cells, because of this practice.
Click to expand...
The conduit being welded together due to the welding current is no biggie in my mind: makes a better connection maybe?

The welding current running around on conductors and equipment would be one main concern. The melted conductors Don mentions being a good example. Stray current running across circuitry ground traces also comes to mind. There is a reason behind single-point bonding and eliminating ground currents.

The biggest concern that comes to kind is the stray current and potential to electrocute someone getting in that path.

I assume if the welding connection is weak the welders would just crank it up? Evidently not much concern about following basic instructions to clamp to the piece being welded.

What a stupid practice to just clamp to anything for convenience. And how slack the powers that be to permit it.
 
mivey said:
...I assume if the welding connection is weak the welders would just crank it up? Evidently not much concern about following basic instructions to clamp to the piece being welded.

What a stupid practice to just clamp to anything for convenience. And how slack the powers that be to permit it.
Click to expand...
You make a horrible assumption about welding practices and then lecture about welding practices. You can't just "crank it up" to get through a bad connection. Weldors are usually pretty picky about their settings and how smoothly their machines run.

It's another horrible assumption (and strawman) that they just "clamp to anything for convenience." There is usually thought involved in choosing among the convenient things. Mistakes will be made, just like electricians that make mistakes on jobs, too. I think the MC was a mistake.

But if an EMT run goes up the five floors I need, and is the only convenient thing for my work connection, and my pipe is well connected to the EMT supports on the other end, I'd be using it so I only need to bring up the electrode lead, unless the electrician was there and didn't like it. I'll get along, and not play the "I've been welding for 30 years" card.
 
MAC702 said:
You make a horrible assumption about welding practices and then lecture about welding practices. You can't just "crank it up" to get through a bad connection. Weldors are usually pretty picky about their settings and how smoothly their machines run.

It's another horrible assumption (and strawman) that they just "clamp to anything for convenience." There is usually thought involved in choosing among the convenient things. Mistakes will be made, just like electricians that make mistakes on jobs, too. I think the MC was a mistake.

But if an EMT run goes up the five floors I need, and is the only convenient thing for my work connection, and my pipe is well connected to the EMT supports on the other end, I'd be using it so I only need to bring up the electrode lead, unless the electrician was there and didn't like it. I'll get along, and not play the "I've been welding for 30 years" card.
Click to expand...
You can certainly crank it up to help overcome a poor connection.

If they were all picky they would all be more selective about where they connect the work leads. Apparently not all are picky.

I'm sure mistakes are made. I'm sure some are in need of better training. I'm sure some don't give a big hoot. I'm sure some are top-notch. A mixed bag like in any trade.
 
mivey said:
You can certainly crank it up to help overcome a poor connection.

If they were all picky they would all be more selective about where they connect the work leads. Apparently not all are picky.

I'm sure mistakes are made. I'm sure some are in need of better training. I'm sure some don't give a big hoot. I'm sure some are top-notch. A mixed bag like in any trade.
Click to expand...

A poor connection is going to make erratic arc quality at the weld and piss off a weldor. He won't tolerate that for very long at all, especially welding pipe. We don't want to "help overcome" it. We want to eliminate it.

Picky means picking something that works. From experience, we know that EMT almost always does when it's the only easy thing we can grab. I think the fact that this is common rather shows that the vast majority of weldors know how to find things are solidly connected up to their weldment. Indeed, it's among the first things we learn, and the first thing to check when the arc isn't what we expect.
 
In my opinion all it takes to create a very dagerous situation (burn down a building) is a wee bit of ignorance on the part of a welder who apprenticed with a guy who did this all the time but never explained the theory to his helper. There's no safety factor. Dumb idea.
 
MAC702 said:
A poor connection is going to make erratic arc quality at the weld and piss off a weldor. He won't tolerate that for very long at all, especially welding pipe. We don't want to "help overcome" it. We want to eliminate it.

Picky means picking something that works. From experience, we know that EMT almost always does when it's the only easy thing we can grab. I think the fact that this is common rather shows that the vast majority of weldors know how to find things are solidly connected up to their weldment. Indeed, it's among the first things we learn, and the first thing to check when the arc isn't what we expect.
Click to expand...
I hear ya. But being easy and common doesn't equate to it being a great idea. Lots of bad habits are habits because they are easy and common.
 
zbang said:
Better the EMT than the sprinkler pipes...which I have also seen. (The sprinkler pipes are probably a better conductor, but still; just run another lead.)
Click to expand...

Is this because they sometimes use rubber gaskets between fittings? If they are all threaded, it sounds like a great conductor. What's the objection? "Not MY pipes?"
 
jaggedben said:
In my opinion all it takes to create a very dagerous situation (burn down a building) is a wee bit of ignorance on the part of a welder who apprenticed with a guy who did this all the time but never explained the theory to his helper. There's no safety factor. Dumb idea.
Click to expand...

Replace "weldor" with "electrician" and we can think of a dozen scenarios that make this still make sense.

I'm sure the connection to the MC was brought up to the person who did it, and he has learned that it was a bad idea. He'll be the least likely person to ever do it again.
 
MAC702 said:
Replace "weldor" with "electrician" and we can think of a dozen scenarios that make this still make sense.
Click to expand...

I don't follow. It's still a risky choice with a small margin for error, as attested to by Don's post. EMT strikes me as only somewhat safer than MC.
 
Status
Not open for further replies.
Top