Workpiece Grounding

[henrym]

woofer, KHK, thanks for the drawings!

so, you guys do effectively connect the workpiece to the welder's chassis and ground.

here's a nice bit from the Lincoln link:

According to ANSI Z49.1, "Safety in Welding, Cutting and Allied Processes," the workpiece or the metal table that the workpiece rests upon must be grounded. We must connect the workpiece or work table to a suitable ground, such as a metal building frame. The ground connection should be independent or separate from the welding circuit connection.

I guess the workpiece simply shall be grounded before connecting the welding work connection, and as such be connected to all grounded metallic objects in the area.

I suppose it makes sense to have all conductive objects maintain a similar or equal voltage. so a grounded welding table and work is a good idea.


I'm still curious about the effect the HF circuit has on the common house ground and all connected to it... but I guess it all goes to the ground anyway.

[woofer456]

I hope these thing I ramble about helps.

The reason I noted the work piece was earth ground optional is when I weld on a piece of rolling equipment there is no earth ground.
And yes my work bench is grounded to earth as I have a grid in my shop floor that I tack parts to and that supplies me with a welding ground without having the cable and clamp attached. the ground clamp is attached to the floor grid and the grid to the work bench and both are attached to earth.
Bob

[henrym]

cool. personally, I have not yet grounded any workpiece. I just was not sure about connecting a live welding lead to every grounded object in the house at once!

again on terminology, I sometimes accidentally refer to the work clamp as "ground clamp" myself, and I know I shouldn't...

The workpiece connection is not a ground clamp

"Ground clamp" and "ground lead" are common terms used by many welders. The workpiece is connected to a welding cable typically by means of a spring loaded clamp or screw clamp. Unfortunately, a workpiece connection is often incorrectly called a "ground clamp" by many welders and the workpiece lead is incorrectly called "ground lead." The welding cable does not bring a ground connection to the workpiece. The ground connection is separate from the workpiece connection.

~courtesy of the Lincoln link.

and here is a simple, right to the point summery regarding workpiece grounding:

Q: What can be done about high frequency (HF) interference from my TIG welder?

A: Most HF problems can be solved with proper grounding. There are three items that are important to connect to a ground stake that you must install. They are the welding table, the base of the welding machine, and the electrical box on the wall that the machine is connected to. In most cases, this eliminates most of the problems.

http://www.welding.com/articles/bparticle13.asp
my main interest is safety, but minimizing radiation of any kind is a good thing.

sooo I guess I ought to install a ground rod and connect it accordingly.


I think this has been a useful discussion.
Henry

[Gadget]

Ok, now that we have basic grounding covered here is an interesting question. What do you do when you are welding DCEP and your table has an earth ground?

[woofer456]

…It makes no difference DCEP, DCEN or AC, in order to strike an arc the welding circuit must be complete (the current the machine is putting out,) as far as earth ground it makes no difference (other than polarity) weather the negative or the positive side of your welding machine is earth ground. We are dealing with two different circuits the Circuit That Runs Your Machine (Household Current) and the Circuit That Your Machine Puts Out (The Welding Circuit)

…The household current is by far more dangerous than your welding current

…The main reason for earth ground is to eliminate getting a shock from the current that runs the machine (house hold current) not the current the machine puts out (welding current.)

…Lets face it you will get shocked from your welding circuit accessional if you weld long enough.

…If by chance there is a failure within your welding machine that causes the current running the machine to short to the case, and you have your machine connected to earth ground, chances are you won’t get shocked

…High Frequency interference of house hold (and other) appliances can be kept to a minimum if all welding equipment has earth ground.
Bob

[Gadget]

Thanks Bob.

[arandall]

[quote=woofer456;7799]…It makes no difference DCEP, DCEN or AC, in order to strike an arc the welding circuit must be complete (the current the machine is putting out,) as far as earth ground it makes no difference (other than polarity) weather the negative or the positive side of your welding machine is earth ground. We are dealing with two different circuits the Circuit That Runs Your Machine (Household Current) and the Circuit That Your Machine Puts Out (The Welding Circuit)

Woofer:

This makes a lot of sense to me.

Cheers,
Art R.

[matteh99]

Having two welding benches could cause problems. If the welder clamp is connected to bench 1 and you try to weld on bench 2 welding current will try to flow from bench 1 to bench 2. If they aren't connected at all nothing will happen if they are both grounded welding current will try to flow through the electrical wiring. So if you have two benches close to each other they should be connected electrically with a good enough connection to handle welding current. If they aren't and you hook the work clamp to one and weld on the other you will have issues. I don't know if you would get shocked but you could burn up electrical wiring.

Eric

[woofer456]

Welding current will only travel a vary short distance through earth so if you have earth ground connected to two benches and weld ground to only one there will be no weld current flow from the weld grounded bench to the earth grounded bench ... if you are having this problem,, I suggest you contact an electrician ….. Note!! a lot of people confuse the common pole in house current is ground. It Is Not. do not connect this to your work piece

[matteh99]

It was a theoretical problem.

Aren't all of the grounds in a house or shop electrical system connected? So the ground part of any outlet will have continuity to any other outlet. Wouldn't the two work bench scenario be the same as connecting the work clamp to the ground of one outlet and the welding electrode to another one? If you did that the welding current would flow through the electrical wiring from one outlet to another.

I see what you mean if both benches are just sitting on the ground but not connected to the ground of the electrical system.

Eric