AWS D1.1 Prequalified Essential Variables 1

[mr_inspectorpants]

I am a wet-behind-the-ears CWI operating in California, and have a quick question for anyone willing to entertain. I am reviewing some welding procedures for a company, and am a little confused regarding tables 3.6 & 3.7 in the AWS D1.1-2015. Table 3.6 is titled "Prequalified WPS Requirements" and table 3.7 is titled "Prequalified WPS Variables." What exactly is the difference between the two tables, and furthermore why would voltage not be an essential variable for SMAW?

I apologize if this is not the right forum to be asking this in, it's just that the AWS forum is no longer accepting new user registrations and I figured I could reach out here. Thank you in advance for any help you could offer a new guy

 

[gtaw]

Remember that a prequalified WPS is written and is ready to be used for production without any testing. As such, it is prescriptive. There are limitations and restrictions that must be met in order for the WPS to be prequalified. If any of the variables is not in compliance, the WPS is not prequalified. The WPS that doesn't meet all the prequalification requirements must be qualified by testing before it can be used for production.

A manual welding process is one where the welder has control of variables such as arc length. The arc length influences the arc voltage. The longer the arc length, the higher the arc voltage. The welder controls the arc length; thus, the arc voltage isn't something that is "dialed in" by turning a knob on the welding machine.

That's not the case with a semiautomatic welding process such as GMAW or FCAW. The arc voltage is set by the welder by turning a knob on the welding machine. The welding machine will do what it must to maintain the voltage set by the welder, hence the welding machine is said to be self-regulating.

Variables essential the the operation of the welding process will be limited by the code for prequalified WPSs. So, for a manual welding process, arc voltage is not an "essential" variable, but in the case of a semiautomatic welding process, the variable, arc voltage, will have to be addressed.

Remember, codes are developed by committees comprised of volunteers. Each committee member has a vote and majority rules. Not everyone on the committee will agree with everything being voted on, but there is consensus among the committee members. They are trying to develop a code that isn't overly restrictive, but one that will meet the needs of industry.


Best regards - Al

 

[mr_inspectorpants]

Thanks for the quick response Al!

So are all of the variables in both tables 3.6 and 3.7 considered essential for a prequalified WPS? And why two tables instead of just combining all of the essential variables into one table? Sorry for the redundant questions, again I'm still a bit green and it feels like there aren't a lot of places to go asking code questions!

 

[gtaw]

You might also like to take a look at Annex P for more direction on the content of a prequalified WPS. This resource is often overlooked.

As for why the code is laid out as it is, you would have to attend the committee meetings to hear their justifications.


Best regards - Al