Four of the essential variables for procedure qualification include:
Welding Process / a change in welding process requires the WPS to be requalified.
P numbers (base metal) / a change in P number requires the WPS to be requalified.
F number (filler metal)/ a change in F number requires the WPS to be requalified.
A Number (weld deposit chemistry)/ a change in the A number requires the WPS to be requalified.
I alway keep in mind what the letters ASME stand for to keep my sanity when working with ASME Section IX:
Always, Sometimes, Maybe, and Except. Those four words are applicable to the four essential variables listed above. The tables contained in Article II lists the welding variables that apply to each welding process. The details of how those variables apply are listed in Article IV.
The sanity check is that a variable, when changed, will affect the mechanical properies of the weld are typically considered to be an essential variable. Thus, anytime an essential variable is changed beyond the permitted range listed in Article IV, the WPS will have to be requalified.
Moving to welder performance qualification, the welder follows a WPS that is already qualified, so we know the WPS will produce the necessary mechanical properties. What is being evaluated during performance qualification is welder skill. In essence, any welding variable that requires a certain skill on the part of the welder is an essential variable for the purpose of welder performance qualification. The essential variables for welder performance testing are listed in Article III. Article III references specific paragraphs in Article IV for the specifics and the ranges of qualification. In part, the essential variables for performance qualification include:
Welding process / a change requires requalification
F number / a change requires requalification with the exception (remember ASME?) F1 through F4 and in some cases F5, qualifying with a higher F number qualifies for a lower F number.
Base metal / a change may require requalification.
Position / a cange to a position for which the welder is not qualified requires requalification.
With or without backing / with backing is limited to double sided groove welds, partial joint penetration groove welds, and welds made with backing. Qualification without backing covers the welder with or without backing.
Those are the "highlights". You must refer to the code to get the specifics.
Best regards - Al
