ARC from MT YOKE

By jwright650 (*****)

Date 05-20-2011 14:32

I had the metal button burn a blister on my thumb when the switch burned out....does that count?

By L51174

Date 05-20-2011 15:18

Nope, the proper use of a GFCI prevents things like that :cool:

By Mikeqc1 (****)

Date 05-20-2011 15:59

i HAVE LOST 3 YOKES AT THIS PLACE NEVER HAVE I HAD ONE BURN OUT ON ME IN 10 YEARS.............COULD THERE BE AN ELECTRICAL PROBLEM? aNY ADVISE AT HOW I WOULD FIND OUT.
THE ARC WAS POWERFULL ENOUGH TO BURN THE STEEL I WAS INSPECTING AND IF I WAS PART OF THAT IM SURE IT WOULD WAKE ME UP.

By 803056

Date 05-20-2011 16:31

It soulds like there is a electrical grounding problem with the welding machine and the work lead. Somehow the current is feeding back through the electrical ground via the legs of the magnetic yoke.

Use the multimeter set on voltage and place a probe on the leg of the yoke and the other probe on the workpiece. If you see a voltage reading, there is a problem. This can happen if there are several welding benches interconnected to a common connection point. Even when the welder isn't welding, the bench is "live" if another welder is welding on his (interconnected) bench.

Best regards - Al

By Mikeqc1 (****)

Date 05-20-2011 18:15

THANK YOU I WILL DO JUST THAT.

By welderbrent (*****)

Date 05-20-2011 22:54

Al,

Could it also be that the grounding problem is only in the 120 system? Without proper wiring and/or grounding you could get that just from your power supply to the yoke couldn't you?

Have a Great Day, Brent

By 803056

Date 05-21-2011 04:24

I thought of that as well, but he said he had the same problem with a couple of yokes at the same facility. That makes me believe it is the way the welding benches (tables) are connected to the welders, perhaps they are not properly "grounded." Maybe there is a short in the welding machine or a bad ground or a bad component that is shorted.

I was walk through a shop a couple of years ago and I happened to touch two welding tables at the same time. The electrical shock nearly knocked me to my knees. Think about it for a minute; if the SMAW machine has an OCV of 80 to 84 volts and two machines are arranged so I provided a current path that creates a series circuit (with both machines), I become the conductor for 160 to 168 volts! Ouch!

Best regards - Al

By welderbrent (*****)

Date 05-22-2011 20:58

Try that same scenario in a driving rain storm in Seattle, WA at a sawmill in the middle of the night that we were trying to get back up and running. I went backward off my ladder from about 12-15 feet in the air and landed flat on my back in about 4" of water with anchor bolts sticking out of the concrete on each side of me. A few inches to either side and I would have been impaled.

Grounding is very important for the supply at the wall, the machine, and the people working in the area. Not sure if the ground would have made much difference when I was soaking wet from head to toe and there were several welders and other equipment operating. It was just a bad setup all the way around.

But if the 120 supply in the shop has an entire line without proper grounding it could have taken out more than one yoke and they may not have seen the connection since they were working in differing locations.

Just a thought.

Have a Great Day, Brent

By TimGary (****)

Date 05-23-2011 14:23

Al is right.
When a welding machine ground connection is not right, the current tries to find an additional ground and will try to ground through the plug on your yoke. I've seen a coup[le of yoke destroyed this way, until we figured out the problem.

Tim

By jwright650 (*****)

Date 05-23-2011 14:37 Edited 05-23-2011 14:39

We even lost a few grinders and mag drills that were laying on the beam that was being welded on....

...edit: it might not be totally the table grounding that is 100% to blame...sometimes the piece laying on the table doesn't ground itself through the table very well, so the welding arc is looking for a ground and finds one in the path of least resistance.

By CHGuilford (****)

Date 05-31-2011 16:43

I have run into that as well. In those cases it was due to a poor electrical grounding system within the building and from using the building's framework as welding ground connections.

Many folks like to put the ground lead on a column so they don't have to run a long lead. Then they may lean a piece of scrap from the weldment to another column. The problem is that those columns may not be grounded properly (many are not) so the welding current travels through a pathway of least resistance. (Ie: grinder & mag-drill grounding conductors; overhead crane hooks; people touching 2 tables; damp concrete floors) Many large machines are "grounded" to the building framing as well as through the electrical cables service connections.

If any of this sounds dangerous...that's because it is.