Friday, October 4, 2013

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.

Saturday, September 7, 2013

"All Welding Shall Comply with AWS-D1.1"

I am a welding instructor/inspector. I have a business client that builds control panels and a potential client of theirs is requesting that they conform to AWS D1.1 standards on a control panel. Seems odd to me what the customer is wanting? Does or can a company become AWS D1.1 certified? Is there a certain process they have to go through to become a D1.1 facility? I tested some of their welders over a year ago to the sheet metal code. Looks like they would want them to conform to D1.6-Structural welding Code - Stainless Steel? Thanks for any help. I got your name from practical welding.

Hi John,
Let’s dispel a few myths: Companies are not AWS-D1.1 “Certified” or “AWS-D1.1 facilities”. They simply comply, or they do not, and they call on folks like you and I to insure that. It’s not uncommon for contract documents to call for compliance to AWS D1.1 when the work being requested falls outside the limitations of AWS D1.1. The code is so accepted throughout industry that often those calling it out are unaware of its requirements. It has become some-what of a “Boiler Plate”.
The D1.1 committee recognizes this. If you look to the Limitations of D1.1 noted in Cause 1 at 1.2 it states, “The code may be suitable to govern structural fabrications outside the scope of the intended purpose.” It then goes on to state that the user may be better off looking into the requirements of other D1 documents that are more practical for your application (I used a little creative liberty in that last line).
In your case, AWS D1.3 and AWS D1.6 are far more applicable. Focusing your procedure and welder qualification on these codes will (a.) comply with AWS D1.1 and (b.) save your company, or the company you are working with, boat loads of money.
You could certainly review the job requirements and develop the requirements to AWS D1.1, but you would find yourself doing PQR’s and Welder Qualifications that may not have been required if you had used the Pre-Qualified procedures laid out in AWS-D1.3 and AWS-D1.6.
Using documents like AWS-D1.2, D1.3, D1.4, D1.5 and D1.6 when your welding doesn’t quite fit in a D1.1 box is certainly considered acceptable when your contract documents read, “All welding shall comply with AWS-D1.1”.

Monday, May 27, 2013

Exfoliation and Bed Sheets

Preparing for a trip to Oregon for my little brothers wedding my wife Dianne bought me an Esquire magazine. “You just need to read this.” It sits around the house, showing up everyplace I find to relax for a moment. Finally, I pick it up. In amongst the men’s fragrances, schwanky alcoholic beverages and Mini Cooper ads is a section titled, “Grooming – Man at His Best”, sub-title “Summer Feet”. After reading about pumice stones, exfoliation and lotions it hits me, “This is why they bought this.”

Being one far too advanced to fall for simple trickery, I asked, “Is this why you got me this magazine?” Her response, “Well, you’re not going to find this stuff in your damn welding magazines.”

She’s right, so let’s change that. Let’s talk PPE & hygiene…

Starting at the top – Your hard hat has a service life that few folks monitor. It is designed to protect you once. When it does, we say thank you and replace both the shell and head band.

Days can get long and hot. I put hard hats, welding helmets and jock straps in the same category… I don’t share them, you shouldn’t either. Would it kill you to wash or replace the head band in both from time to time? Maybe you have helmets or face shields that are stored at equipment and used by others. Keep a disinfectant (wipe or spray) available for everyone to use.

You spend your whole shift singing into that Welding Hood. Break it down and clean it out with a little soap and water. It also wouldn’t hurt to wear a disposable respirator. It won’t do much for your singing, it tends to muffle the sound (your co-workers will appreciate that) but it should keep your lungs and helmet clean. Keep in mind that Positive Air Flow hoods have their own replaceable components. Change them regularly. And I don’t care how many generations have passed down your Huntsman, when it’s cracked we don’t duct tape it, we replace it.

Ear protection, whether muffs or molded or disposable, need cleaning or replacing regularly. For muffs or molded hearing protection, always follow the manufacturers’ recommendations for maintenance. For disposable hearing protection, replace them with a new set every time you remove them.

Protect your hands with gloves that are appropriate for the Weld Process you are using. Gloves for GTAW (Tig) can be significantly different than the gloves used for FCAW. Insure heat and light can not penetrate them. Replace gloves with any holes. Replace leather gloves that shrink up so bad you can’t get your trigger finger in them. Don’t get them wet and don’t get them oily. You hands are counting on you to protect them. Choosing a glove because it’s light could be a bad decision. Choose a glove because it’s right.
Leathers, flame retardant jackets, chaps need to be free from holes and frays. Unless they can be repaired by a Leathersmith, they should be replaced. Insure they cover any cotton clothing from ultraviolet rays. A day of exposure to the welding arc can be hell on your neck, wrists or crotch (ouch). Insure your PPE protects you completely.

Finally your boots, insure they are appropriate for your welding environment. Snow and rain can be hard on leather. Waterproofing can do wonders for your feet over a 10hr day. Keep your socks dry. Keeping a fresh pair can be great around lunch time. Gravity will insure all spatter and sparks land directly on top of your boots, make sure your laces are ready for that.

And as noted in Esquire; a pumice stone to the foot and a little lotion may just keep your significant other happy and lengthen the life of your bed sheets.


Monday, April 15, 2013

GMAW-S & Pre-Qualified Weld Procedures

The company I work for welds with GMAW-S and all of the Weld Procedure Specifications (WPS) that we have are from pre-qualified AWS-D1.1 welds. When I look in D1.1 I find that GMAW-S is not a pre-qualified transfer mode. Are all of our WPS's therefore null? If I understand D1.1 correctly we would need to have a PQR for all of our WPS's because they are GMAW-S, is this correct?

 It seems like GMAW-S is the most common, or at least a very
common, GMAW transfer mode why in the world is it not pre-qualified?

Thank you for your insight, Martin

Martin, Love the question(s). The short answer is... Yes, but just to clarify…

When you mention GMAW-S the transfer mode referred to is Short Circuit Transfer (See AWS-D1.1 Annex K, “GMAW-S”). You are right to note that GMAW-S’s use is wide spread. You are also correct that GMAW-S is not a pre-qualified process, per AWS-D1.1.

So what’s up with that?

AWS-D1.1 is the Structural Welding Code for Steel. Its intent is to be used with materials 1/8 inch thick and greater. The concern by those who determine the requirements for pre-qualified procedures is, welding using the Short Circuit Transfer mode has the potential to generate a lack of fusion. It has been my experience, after running hundreds of PQR’s, that this lack of fusion becomes consistent on material thicknesses over 3/16 of an inch in certain positions and progressions.

That’s not to say GMAW-S can not be used with a pre-qualified procedure. AWS-D1.3 is the Structural Welding Code for Sheet Steel. Its intent is to be used with material 3/16 inch thick and less. Clause 3 of AWS-D1.3 lays out the requirements for developing pre-qualified weld procedures using Short Circuit Transfer.

AWS D1.1 in Clause 1.2, “Limitations”, encourages the use of D1.3 on materials 3/16 inch thick and less. So using pre-qualified procedures for Short Circuit Transfer is do-able, it simply has to be done to a different Structural Welding Code.


Sunday, January 20, 2013

Color Coding of Tungsten Electrodes



Signed Reader

There are 2 common weld processes that use a non-consumable, tungsten electrode, Gas Tungsten Arc Welding (GTAW/Tig/HeliArc) and Plasma Arc Welding (PAW). These electrodes come in a variety of compositions or alloys. Each composition serves a specific purpose.

Pure tungsten electrodes (AWS classification EWP) contain 99.50% tungsten. These electrodes provide good arc stability for AC welding on aluminum and magnesium. Their color designation is GREEN.

2% thoriated tungsten electrodes (AWS classification EWTh-2) contain 1.70 to 2.20% thorium. They are the most commonly used. Unlike pure tungsten, these electrodes are exceptional for DC electrode negative or straight polarity on carbon and stainless steels. Their color designation is RED.

2% ceriated tungsten electrodes (AWS classification EWCe-2) contain 1.80 to 2.20% cerium. These electrodes perform best in DC welding at low current settings but can be used in AC or DC processes. Their color designation is ORANGE.

1.5% lanthanated tungsten electrodes (AWS classification EWLa-1.5) contain 1.30 to 1.70% lanthanum, or lanthana. These electrodes have many of the same advantages as ceriated electrodes. They also closely resemble the conductivity characteristics of 2% thoriated tungsten. Their color designation is GOLD

Zirconiated tungsten electrodes (AWS classification EWZr-1) contain 0.15 to 0.40% zirconium. It is ideal for AC welding and under no circumstance is zirconiated recommended for DC welding. Their color designation is BROWN.

Each of these electrodes placed side-by-side look identical. For that reason a color code system has been developed to designate each. Short of sending them to a lab for analysis ($$$) once the color designation is gone, there is no way to tell what type of tungsten you're holding.

As the hack Tig (GTAW) welder I am, I keep short, unmarked tungstens in old military stick match containers. Each container is clearly marked as to the type of tungsten inside. Along with that, I always-always-always break down my torch when I'm done and store the tungsten in its designated container.

This works for me in my garage. This would not be a good practice in a manufacturing or code environment.

Once the marking is removed the tungsten is not traceable and you just lost control of your weld process.