steel welding table as ground path?

By petermiddleton Date 01-09-2005 15:33

I read about tig welding(short magazine article) where the small workpiece being welded was laying on a steel table providing a contact ground as the the ground clamp was attached to the table. They also mentioned an additional ground rod incase the powerline ground was interupted but that didn't say how to hook it up? Would an additional ground (to a ground rod) be helpful? If so should I just double up that ground to my electrical system ground, or have a separate ground to the workpiece or worktable?

I am about to weld for the first time with my new/old Silver Beauty Mig Welder is the above method of grounding safe? If so should I get a piece of unpainted steel plate and use that to protect the steel welding cabinet that I want to paint and protect from slag etc.

I also have some old electic company (30k volt?) rubber insulating mats should I put one of those under my work cabinet (concrete floor). I am leery of standing on one as I guess if you did get shocked you would want to ground through your legs rather than encourage an arm to arm path?

Any and all beginning welding advice esp. Mig is welcome. Thanks in advance.

Regards Pete

By billvanderhoof (****)

Date 01-10-2005 04:01

The work cable from the machine should be connected to the table (or the work). For extra safety the table should also be connected to earth ground (a water or heating pipe or a conductive bar driven well into the ground) this connection would not be expected to carry a large current, just prevent the table from floating to a voltage where you could get a shock.

Arm to arm or arm to leg both pass close to the heart. Standing on a mat will eliminate one, dry gloves will help eliminate the other.

I don't remember ever getting a shock from a mig, that could just be luck.

Bill

By andyz Date 01-11-2005 00:00

If your welding table should be grounded should any piece you are welding be grounded? I weld both on a table (all steel) and other pieces just on the ground.

By Arcandflash (**)

Date 01-11-2005 04:43

Interesting question! I see the welding table being grounded protecting the weldor against input line voltage appearing on the output leads due to a component failure.
You could apply the same rationale to a workpiece sitting on the ground or on a wooden table. If the welder failed and you had the workpiece clamp attached to the work, then the work could be electrically live. So in this case it would be beneficial to have it grounded which would keep the work at 0 volts or cause the breaker to trip.
It is possible to theorize about situations where the grounded table/workpiece could make things worse but it's like seatbelts, sometimes you would be better off without one but most times it's safer with one.
I don't know how many electrical accidents are caused by welders failing and input line voltage appearing on the output leads. I don't suspect it happens very often so in that case the risk is minimal. Perhaps someone has some better data on this?