Most welding standards will allow the manufacturer/fabricator to do whatever they want provided they can demonstrate their procedure/technique will produce the required mechanical properties such as soundness, ultimate tensile strength, etc.

That isn't to say I would be an advocate of welding over slag, but it would place the inspector in a rather awkward position to take a stand against a specific practice if it was proven to produce acceptable results.

A similar case in point would be the recent standard published by AWS on qualifying a welding procedure for welding over paint. I thought I was going to lose my lunch when I read that document. I guess it safe to say not all the AWS publications are pearls of wisdom. I would place welding over slag to be in the same company as the standard for welding over paint.

Best regards – Al

I don't believe many of us will take a position opposite of yours. However, the situation here is that the manufacturer hypothetically qualified the procedure without removing the slag between weld layers and was successful in meeting the code required mechanical properties, weld soundness, and visual acceptance criteria. He demonstrated the technique employed produced acceptable welds. In general, the welding standard, be it AWS or ASME, is going to permit the proven technique to be used for production welds. 

It is and was a hypothetical case. The reality is as you inferred; weld soundness and the required mechanical properties would most likely not be met should the technique employ either SMAW, SAW, or FCAW. On the other hand, I'm not so sure I would bet too many gold coins it couldn't be done with GMAW using bare electrode or even FCAW if the proper metal core electrode was employed.

If the manufacturer is successful in his qualification effort, the third party inspector would be hard pressed to justify taking a position of prohibiting the manufacturer’s ability to employ a proven process/procedure.

Joe’s argument of bringing it to the Engineer’s attention is prudent. Let the Engineer make his decision and then the Third Party Inspector’s responsibility is limited to “ensuring” the manufacturer complies with the Engineers decision.

Best regards - Al

Once again, I do not believe there are many of us that disagree with your position.

Like welders, not all "engineers" are experts in their field. Likewise, the CWI credential alone isn't sufficient to demonstrate a high level of expertise in our chosen field. There is or should be a level of practicality involved where a knowledgeable person steps back and recognizes what a code or standard allows may not necessarily be "good practice."

The code mandated welder performance tests are the minimum requirements that must be met. It is incumbent upon the manufacturer to take those steps and institute those procedures above and beyond code mandates needed to ensure their product meets safety requirements and customer expectations. Any company that fails to do so will fail at some point in time. While meeting the mandates I've listed, the company still has to make sufficient profit to weather various economic conditions.

In your situation, it would be prudent to test the welders to the specific procedure where in the slag is not removed between each weld pass. The reasoning is simple; you recognize that success in your application, i.e., utilizing a questionable "qualified procedure" is dependent on the welder's ability to implement the procedure properly. The economic success of your employer and your job is dependent on the welder's ability to produce acceptable welds. The welder's failure to properly implement the "qualified procedure" would ultimately result in the failure to meet code and customer expectations. Your customer base would quickly erode, along with profits, once welds started to fail in service. 

I have seen more than one engineer or inspector experience short careers because they "met code" without satisfying the customer's expectations. In short, they were idiots that didn't recognize that shooting a hole in the bottom of the boat to let the water out doesn't work when the boat is in the water.

Best regards - Al

Hi Richard

AWS D1.1 clearly states that slag must be removed. (I will attach an extract of the comments to D1.1 also.) No amount of "qualifying" of the WPS or WPQ without slag removal will make this requirement go away. This is because this requirement is a QC activity, and has nothing to do with qualifications per se. It would be like saying that I will qualify the WPS and WPQ without NDT, then I do not need to apply NDT on the job. The NDT activity can not be "qualified out". In the same way, the QC activity of slag removal can not be "qualified out". Just as it would be possible for the engineer to specify less stringent NDT requirements from that asked in the code, the engineer could specify different QC requirements, but please have a look at the definition of "engineer" in the code to see that this is not just anybody that has the title engineer.

I am not sure what product you are making. If it is just some low risk, low stress application, (e.g. potplant holder?) then the consequences for failure is so minor that it probably is not an issue. If on the other hand this application is in a fatigue loaded structure, or is experiencing high stress, and the failure could have significant safety, environmental or economic consequences, then there will be very few engineers (I certainly do not know any in the oil & gas & petro-chem industry.) that will accept this practice.

Regards
Niekie