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-   -   grounding the workpiece you're welding (http://www.diychatroom.com/f18/grounding-workpiece-youre-welding-80639/)

jarnold 09-06-2010 03:13 AM

grounding the workpiece you're welding
 
I'm alittle confused. I just brought a mig welder and the safety section in the op manual says that the workpiece needs to be grounded independent of the ground to the welder. If I have a workpiece to be welded that is touching the concrete floor in my shop, do I need to ground that piece in addition to the welder ground clamp?

vsheetz 09-06-2010 05:18 AM

You only need to clamp the ground clamp onto the work you are welding. You are looking to complete the circuit from the welding electrode wire, through the work, back to the welder.

bobelectric 09-06-2010 06:05 AM

I'm glad someone takes the time to really study the owners manual.

Speedy Petey 09-06-2010 08:48 AM

Quote:

Originally Posted by bobelectric (Post 496609)
I'm glad someone takes the time to really study the owners manual.

I completely agree, but in this case I am wondering what they are talking about.
Maybe it's a CYA move in case of a fault it will trip the breaker?

AllanJ 09-06-2010 08:59 AM

Quote:

Originally Posted by Speedy Petey (Post 496652)
IMaybe in case of a fault it will trip the breaker?

Yes.

Or at least prevent a surprise shock. Even for a fault producing a small voltage differential including a voltage differential with the concrete floor, that could cause the worker to lose control and perhaps burn himself.

Speedy Petey 09-06-2010 09:44 AM

I have done a LOT of work in working welding shops and I have never seen anyone ground a piece other than with the welder ground. :huh:

fabrk8r 09-06-2010 10:06 AM

I think what the manual writer meant by this statement:
Quote:

Originally Posted by jarnold (Post 496589)
workpiece needs to be grounded independent of the ground to the welder.

...is that the workpiece needs to be grounded using the dedicated ground clamp attached to the welder, and not by grounding through the welder's power supply.

It's definitely a CYA on the part of the company that manufactures the welder.

H. A. S. 09-06-2010 10:15 AM

Quote:

Originally Posted by Speedy Petey (Post 496667)
I have done a LOT of work in working welding shops and I have never seen anyone ground a piece other than with the welder ground. :huh:


Same here.:thumbsup:

nap 09-06-2010 11:26 AM

Quote:

Originally Posted by fabrk8r (Post 496672)
I think what the manual writer meant by this statement:

...is that the workpiece needs to be grounded using the dedicated ground clamp attached to the welder, and not by grounding through the welder's power supply.

It's definitely a CYA on the part of the company that manufactures the welder.

I believe fabrk8r has explained it properly. It is also a poor explanation by the manufacturer.

Stubbie 09-06-2010 11:29 AM

Just to expand the conversation I think there might be something to learn about what is really going on in a welding circuit. Underlines are mine. BTW I am by no means an expert on welding but this is how I understand things from what an old pipefitter has explained to me.

The terms 'ground lead' or 'ground clamp' are commonly used to describe the connection from the welding machine to the work ...the other connection being the electode lead or gun lead. A ground is not made with either the welding lead called a ground clamp or ground lead these are incorrectly used terms.... the correct term is work lead. What your doing is completing a current carrying welding circuit...:).
The welding machines frame is grounded via the equipment ground of the power supply... it has no connection to the work piece or metal work table through either the 'work lead' or 'electrode lead'..



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 earth ground, such as a metal building frame. The ground connection should be independent or separate from the welding circuit connections.

MY understanding is this is to 'bond' the work area so that the same potential exists to any two points you come in contact with while welding.. Few welders worry about this because they are wearing insulating gloves and clothing.

So I agree that you rarely see this done but appears to me it is recommended.

I'm not a welder so not sure if this would be disputed by others more schooled in the field.

Thought I would throw my understanding into the fire to see if it leads us to a correct understanding of grounding the work piece or table.

nap 09-06-2010 12:00 PM

Quote:

Originally Posted by Stubbie (Post 496705)

MY understanding is this is to 'bond' the work area so that the same potential exists to any two points you come in contact with while welding.. Few welders worry about this because they are wearing insulating gloves and clothing.

So I agree that you rarely see this done but appears to me it is recommended.
.

I've got to admit I have never been concerned with my workpiece being grounded.

fabrk8r 09-06-2010 12:40 PM

I have been a weldor for over 20 years and I have found over time there are several methods to ground your workpiece to create the necessary circuit to allow a successful weld.

The best way is to attach the ground clamp directly to the workpiece. To expand on this, some welding processes, TIG for example, can best be performed if the ground clamp is in very close proximity to the electrode. This prevents a straying arc common with the TIG process.

It isn't always necessary to have the ground clamped directly to your workpiece. If you are using a welding table that is a good conductor the ground can be clamped directly to the table, allowing easier repositioning of the workpiece, which is useful if there is a need to change the direction of the weld due to numerous odd angles. One drawback to using this method of grounding, as opposed to directly clamping the ground to the workpiece, is that the surface of the workpiece can be damaged through arcing because of poor contact to table. This will not be much of a concern if the workpiece is strictly functional and not decorative, but can ruin a project if using stainless steel or aluminum material.

One concern with a poor ground is that the weldor's own body can become the conductive path that completes the circuit. This is especially dangerous in wet situations or if the weldor is perspiring. I've received substantial shocks when welding due to having a poor ground, the ground coming detached, or from just not paying attention. I've had a good ground connection and still gotten a shock because I leaned up against my workpiece between where the ground was clamped and where I applied the electrode because I had my finger resting on the welding rod. I saw a co-worker fall from a ladder while welding in the rain because he had one hand on the steel stack he was welding and he touched the electrode with the other hand.

There are situations, such as when welding high up in a large factory, when it isn't practical to clamp the ground directly to the workpiece. In this situation a suitable ground can usually be had by clamping the ground lead to a steel beam or the building's metal siding. This allows the welder to be positioned far from the work using only a short ground lead with the long electrode lead being the only thing the weldor needs to be concerned with.

jarnold 09-06-2010 01:03 PM

Thanks guys for your input. Fabrk8r, when you refer to ground clamp in your last post, are you talking about the ground clamp from the welder?

nap 09-06-2010 01:24 PM

Quote:

Originally Posted by fabrk8r (Post 496732)
I have been a weldor for over 20 years and I have found over time there are several methods to ground your workpiece to create the necessary circuit to allow a successful weld.
h.

I believe you are misunderstanding the term "grounding" here. Your explanation speaks of the work lead (refer to post #10 by stubbie). Grounding is a totally different issue. The grounding has nothing to do with the function of the welding circuit. It is completely a safety issue.

fabrk8r 09-06-2010 01:39 PM

jarnold, yes, the ground clamp from the welder.

nap, the first post I added to this thread was to help clear up the confusion the OP has concerning the term "ground" in reference to the welding circuit.

The welding circuit ground is totally independent from the power source. For the welding process to occur there has to be a complete circuit and this circuit has nothing to do with the "earth" ground in the power circuit.


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