It's a Work Lead... it doesn't ground anything

Hello Mr. Cameron,

I am writing this regards to an article you had wrote about grounding/grounds. I do have some

questions in regards to said article.

First of all do you have any references to the way grounds should be connected?

Secondly you mentioned in your article that grounding to a structure should not be used if at all possible. My question in regards to this: If OSHA regulations state that it is okay to ground to structures why say no to this?

The reason I am asking is that where I am employed we use the building structure for grounding purposes and we have people who are getting shocked while welding. The material is 6061, using pulse Mig and GTAW. The machines are grounded to the structure and from said structure to said welding fixture using a jumper. In a nutshell I'm trying to find references whether they be OSHA or from some other agency in regards to grounding.

Any help or information would be greatly appreciated.

Thank you,

Chris A.

Chris,

Yours is the perfect example of how the terms "ground" and "work piece lead" get used interchangeably. This leads to a dangerous situation.

On a common welding power source you will find a + stud and a - stud. To one of these you would attach a conduit leading to the electrode (ie: a wire feeder, a stinger, a Tig torch). To the other you would connect a conduit leading to a Work Lead Clamp. The polarity required would determine if the work lead runs from the + or - stud.

In the article you’re referencing I state, "…the work place lead does not ground anything." When installing welding equipment that statement is critical to remember.

OSHA will require that equipment be grounded to protect people from electric shock. The way equipment is grounded has nothing to do with the + or - stud on the front of the welding machine. This is accomplished through the permanent power connection supplying the machine (the plug). Or by a separate clamp and wire connecting the case or frame of the machine to ground (like the building). Sometimes both the plug and one of these wire connections is used. Again, they have nothing to do with the + or - stud on the machine.

ANSI Z49.1 - Safety in Welding and Cutting will require that the work table (positioner, fixture) also be grounded. This is accomplished with a conduit connected to the table or positioner, connecting it to a "driven rod" or often, the building. Again I clarify, this has nothing to with the + or - studs.

When we use the term "ground" we are talking about protection of people and equipment. You would be much better off referring to the leads coming off a welder as an electrode lead and a work lead, or a positive lead and a negative lead, but neither is ever considered a ground.

PWC

Paul W Cameron

Pinholes and Purging

UPDATE:

In this original posting I talked about common solutions to Pin Holes.  My apologies for not picking up on this, but in his question Marv B. stated that prior to welding he “tried cleaning them [the components] with Brake Cleaner”.  Welding and Brake Cleaners can be a deadly combination.

There are many warnings on the “everyday” chemicals we use.  Often, I will simply assume that if it’s sold over the counter surely it must be safe.  But the SDS (Safety Data Sheet) for a can of brake cleaner may read, “Do not use this product near open flames, welding operations or excessive heat.  Vapors may decompose to harmful or fatal corrosive gasses such as hydrogen chloride and possibly phosgene.”  This can be debilitating or even deadly to the Welder or those around him/her.

There are many manufacturers of cleaners, removers and degreasers used throughout our industry.  Most are safe when used as directed, so pay attention to the product labeling and review the products Safety Data Sheet (SDS).  Please use caution when determining how your weldment will be cleaned.  Only use approved cleaners to the manufacturer’s instruction.  Read the warnings and review the products SDS.  As my old boss used to say, “Somebody wants you home tonight.”

Thanks to Steve 'Brewdude' Garn who shares his experience on welding and brake cleaners at (http://www.brewracingframes.com/safety-alert-brake-cleaner--phosgene-gas.html).  I also want to give a special Thanks to the loyal readers that pointed my over-site. You come to us for good advice and I should pay attention to details when giving it.

PWC

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Hi Paul,
I was doing a search over the internet and came across your contact information.  If you don’t mind, can you help me with a problem?
I am machining a Bearing Housing made out of 1045.  I have to plug and weld some cross holes.  I am using 1018 for the plugs.  I am also using a tig welder to eliminate too large of a weld.  My problem is that I am getting pin holes in my weld.  Is it because I am not preheating the part.  or is it because I am welding 1018 to 1045?
We didn’t machine the parts dry so maybe there is a light film of coolant on the parts but I tried cleaning them and that didn’t seem to help.
If you could reply back that would be great or go ahead and give me a call.
Thanks!!!
Marv B.

Hey Marv,
The welding of the materials shouldn’t be a problem.
Let me ask, the machined port looks to be made up of 3 different drilling operations.  Are all 3 completed before the plug is welded in?
The reason I ask…
If the port to be plugged is drilled first (others drilled after welding) trying to weld a plug in the hole creates a condition I’ve dealt with most of my career.  When trying to seal weld the only opening in any cavity the air (or gases) in that cavity heat and expand. During that expansion a pin-hole will form at some location in the weld (just on solidification) to allow that expanding gas to escape.  Molten metal makes a poor seal 
Pipe-Welders see this same condition when finishing the root pass in a purged pipe.  If they don’t build an alternative location for the gas to escape the gas will blow through the final weld crater.
I also dealt with this condition on Flare Bevel Groove welds on a robotic application of a manufacturer where I served as Weld Engineer.  We were able to remedy that with a punched whole on the faying surface of the joint.
Not sure if this is your condition, but if you’re trying to seal the only opening, it sure could be.
Let me know.
PWC

A Welding "Ground" doesn't ground anything!

What makes a good ground (Work Lead) connection and why is it important?

In a welding circuit, current needs to pass through as few connections as possible and the circuit it self needs to be as short as is practical.
On the positive (+) side current passes through the (+) stud connection, the feeder connection, the Gun connection and the contact tip (to the wire) connection. With the exception of the wire, all of those connections are typically, copper or brass.
On the negative (-) side current should passes through the (-) stud connection, the cable to the Work Lead (ground) clamp, possibly across a rotating surface and then to the work piece.
When any of these connections are anything less than clean copper or brass to clean copper or brass the possibility of a poor connection and a current and/or voltage loss exists. These losses can be great enough to run outside the parameters of the weld procedure causing spatter or a lack of fusion. That can get a welder into trouble.
Some good examples of poor connections would be:

• A Work Lead (ground) connected to a building column. 
• Using a steel building column and a steel bolt, this connection will oxidize (rust) and create resistance.
• A Work Lead (ground) connected to a steel plate run across the floor. 
• Of course the initial connection is the same as the building column. 
• When that steel plate isn't of a sufficient size (area) and that plate is joined by one or several welds (extra reduction in area) the condition are ripe for a drop in current and/or voltage.

The 2 conditions mentioned above also create a safety issue. Once a Work Lead (ground) contacts a building it gives current alternate routes. One of the most popular is through a jib or bridge crane.

Aside from creating havoc with the cranes electrical system, current passes through the lifting devices (cables, hooks and chains), heating them over and over and thus weakening them and making them susceptible to failure.
One last good example of a poor connection would be an unlubricated rotary clamp, or a rotary clamp lubricated with a lubricant that is not made for electrical connections.

A key to quality welding starts with a good quality circuit and a key component of that circuit is the condition of the Work Lead (ground).

Side Note: Notice I’ve replaced the word “ground” with “Work Lead”.  You should too.  Keep in mind, a welding “ground’ doesn’t ground anything.
PWC