Electrical safety concerns during electrode changes

[mdhimes]

My question is regarding whether or not it is possible to be electrically shocked while changing an electrode on a Miller Maxstar 200. The welder is part of an automated welding system in which the TIG torch is mounted on servo slides. The system pulse welds stainless steel cylinders together. On some of the older welding systems around my shop that use Weld Logic welders it is necessary to first touch a grounding cable to the electrode prior to changing it to discharge any residual charge from the weld. Has anyone experienced being shocked when changing electrodes on their TIG welders?

Thanks in advance,
Matt Himes
Rosemount Inc.

[Sberry]

I dont think so, it has a very low ocv.

[SignWave]

Ideally, if you rgonna change an electrode and dont want to get zapped, it would be advisable to turn the machine off then ground out the electrode to earth, wait a few seconds, do your changing and turn it back on again.

Kinda like changing diapers: calm the baby down, lay them on the table, hold your nose, wipe clean, and put a new diaper on. all done!

[Steve]

If it is automated I would shut it off if possible, no chance of the automated shocking you. I don't trust automateds. Sometimes they automatically hurt you bad and they could care less either.

[Sberry]

I think one of the features of the Max'x is very low ocv, like 13 or so.

[6010]

You can get an electrician to measure the voltage after you cut the unit off. I am assuming you cut off the machine before you make your changes. The capacitors will discharge on their own over time, but it depends on the quality of the capacitors. They will only charge up to their peak input voltage. The National Electric Code considers anything over 50 volts to be hazardous. I am sure the open circuit voltage will be less than that. That is not to say 50 volts could not give you a good tingle, depending on if you were sweating and what you had been eating lately. What you eat affects your body resistance.

I see you work for Rosemount. I bought enough instrumentation from your company when I worked for a paper mill that I probably paid for your salary for several years. We standardized on Rosemount for our level, pressure, flow and temperature control. We started off Foxboro but changed because Rosemount gave good service. I am sure you have heard of Foxboro. Oh, most of our valves were Fisher. If they had a valve that would work in an application , then Fisher was the valve. The paper mill I worked for was built in 1990 and I am sure it was the last green field mill that will ever be built in this country.

Come to think of it, you work for a Blue Company

[mdhimes]

You can get an electrician to measure the voltage after you cut the unit off. I am assuming you cut off the machine before you make your changes. The capacitors will discharge on their own over time, but it depends on the quality of the capacitors. They will only charge up to their peak input voltage. The National Electric Code considers anything over 50 volts to be hazardous. I am sure the open circuit voltage will be less than that. That is not to say 50 volts could not give you a good tingle, depending on if you were sweating and what you had been eating lately. What you eat affects your body resistance.

I see you work for Rosemount. I bought enough instrumentation from your company when I worked for a paper mill that I probably paid for your salary for several years. We standardized on Rosemount for our level, pressure, flow and temperature control. We started off Foxboro but changed because Rosemount gave good service. I am sure you have heard of Foxboro. Oh, most of our valves were Fisher. If they had a valve that would work in an application , then Fisher was the valve. The paper mill I worked for was built in 1990 and I am sure it was the last green field mill that will ever be built in this country.

Come to think of it, you work for a Blue Company

Thanks for the info. I figured there was a voltage threshold that I should be aware of. As it turns out we've got such a variety of equipment on the floor that that has higher OCV so we will likely develop a standard practice of turning off the power and discharging the capacitors if necessary before changing electrodes.

Yep, I work for Rosemount in Minnesota. Pulp and paper is one of our main market segments. The harsh environments people put our transmitters in requires them to be tough, that said Rosemount has oodles of welding processes. LASER, plasma, resistance, projection, TIG, both automated and hand. Fun place to be if you're into metal!

Thanks again everyone.

Regards,
matt h.