grounding the workpiece you're welding

jarnold

Nap. I'm not misunderstanding the term. All I'm asking is: does the workpiece or metal table its on need to be grounded separate from the welder's work clamp. And does a metal piece resting on concrete constitute a ground. thanks

nap

yes, I am quite aware of that. The reason I said anything is you were speaking of putting the "ground clamp" close to your weld when working with GTAW welding.

the work clamp placement would be of concern for this but not the ground clamp. If things work well, the ground clamp should have no effects on the weld at all. It is only for the purpose of providing a 0 difference of potential between the work piece or table and any other conductor the operator might come into contact with. That 0 difference of potential will prevent current flow through the operator if he should contact both points at the same time.

fabrk8r

jarnold, the concrete, or earth, will not constitute a "ground" as far the the welding circuit. You'll need to connect the actual ground clamp the the workpiece, or table.

__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright

nap

I didn't say you were, at least I don't recall where I did. Maybe I missed something I said to you but I do not believe I did.

as stubbie provided, it should be.

not a dependable connection. When concrete is used as part of a grounding electrode in the NEC, it is only with metal being within the concrete and it is the metal that must be connected to.

nap

not trying to start an argument but where have you ever seen a welder with a "ground clamp"?

the ground connection being referred to in this situation has nothing to do with the machine.

jarnold

fabrk8r, Yes, I know the work clamp has to be clamped to the workpiece or table. But if you need to separately ground the workpiece for safety, does a workpiece connected to concrete constitute a ground.

fabrk8r

nap, I know it seems like it shouldn't matter where the ground clamp is positioned, and for most welding processes it won't, but there is something about the GTAW, or TIG, process that will make the arc deflect under certain circumstances.

I fabricate a lot of stainless steel sinks and countertops and when welding where three surfaces meet it is almost impossible to control the direction of the arc unless the ground is positioned very close to the weld. An added advantage to this is that since there is little distance between the ground and the electrode it makes it less likely that my body will short the circuit and get a shock, which commonly happens in out-of-position welding.

__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright

fabrk8r

nap, every welder I've ever seen has a ground clamp.

I'm sorry, I should have used more appropriate semantics...when I say ground clamp, I mean work clamp...I'm a fabricator, not an English teacher.


I apologize for the confusion. I know that all my fellow workers would look at me funny if I said "work clamp".

__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright

fabrk8r

jarnold, there is no need for a separate ground.

__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright

nap

but i ask again; have you actually seen a welder with a ground clamp?

it sounds like you are speaking of the work lead and I am not disagreeing with your points on that. I understand the process well enough to know what you are speaking of with the arc.

no. while there will likely be some connection to ground through the concrete, simply setting on the concrete itself is not an acceptable grounding point or connection. When you are directed to connect the table to "ground", it is implied the "ground" is the building grounding electrode system or equipment grounding system. Concrete in itself is not part of that system. The intent is to provide a 0 difference of potential between any two points you might contact. Since the building power is providing the power to the welder, the only ground that would provide a safety factor would the the premises power source grounding system. The concrete of the floor is not part of that system by itself.

nap

you are incorrect. Stubbie presented contrasting information from a dependable source.

the fact you and friends are getting shocked proves why you do need an actual ground connection. That would prevent, or at least minimize, the shocks you are experiencing.

fabrk8r

nap, yes, as I said every welder I've ever used, and I've used hundreds, had a ground clamp, or "work clamp" if you prefer.

Here is an example of an electrode holder, or stinger, on the left used for SMAW (shielded metal arc welding, or stick welding) and a common ground clamp on the right. Without either you'll have a hard time making a weld.

__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright

nap

that is the point and you even spoke to it as well. Technically it is not a ground clamp but a work clamp. This thread is dealing with actual grounding whether it be via a clamp or a permanent connection, which the work clamp does not provide. There should be (although I will admit it is rarely utilized from what I have seen) a ground connection to the work table and the work piece.

I cannot say I have ever seen a welder with an true ground clamp. (including the one you provided a picture of) .
Ground clamp is a commonly used misnomer used to indicate the work clamp.

Stubbie

sorry I had to run a few errands but when I returned I read thru my millermatic 225 manual and found this statement

Now the question is ....When is earth grounding of the work piece required ?

__________________
" One nice thing about the NEC articles ... you have lots of choices"

Stubbie

nap

well, I guess when ANSI standards are requrired to be followed:

btw, NEC 630.15 clearly states that the secondary of the welder shall not be considered as premises wiring fro the purpose of applying article 250 (Grounding and Bonding).

that would support your statement that the grounding must be separate of the work conductors.