jsd,
Those are certainly broad parameters, and make no mistake, regardless of my argument I would certainly advocate limiting the parameters to less than those 'recommended', er, 'quoted', er, 'listed'. But not due to weld viability as such, but due to the fact that some welders would most likely not be able to handle those parameters.
You write WPS's for your worst guys, not your best.
I've welded .045 FCAW at those parameters without detriment (having done some testing).
We would go that cold on 2" sch 40 5G pipe (If memory serves ~21.5 was about as cold as I could get it and still feel comfortable-you had to or you'd blow a hole in it the size of your thumb-or at least I would-felt like stick rod to me) and that hot on the big stuff, not wanting to change our wire to 1/16"(unless we had a bunch'o big'ens), because we were lazy, and always racing for productivity (friendly competition).
I would say that its difficult to go wrong with the 10/7 regime from AWS, as recommended earlier(the reason why they put it there), but my belief is that it is more restricitive than necesary (but perhaps they're writing the code for the worst guys too-oops, I didn't imply idiot proof did I?).
But always always depending upon the alloy. The basic assumption for me here was C steel.
As a recommendation, and not meaning this condescendingly, given your question I wouldn't push the envelope like that, though I think the 10/7 is unnecessary as I've stated. If you want a hard number have your good welders run some beads, get their input and decide from there. Do some testing even, though management hates that stuff. If you're doing enough volume it can be justified.
How many times has this subject been tossed around?
One common question I see on a regular basis is, "Where do I find the values for voltage, amperage, wire feed speed, etc. to enter in the PQR?"
I see the same question for writing WPSs.
There are engineers and inspectors that are new to welding and are assigned the task of documenting the company's welding operations. It is unfortunate that many are totally unprepared for the task.
ASME seems to take the "hide your head in the sand" approach by covering their butt with their position that only qualified "welding engineers" write welding documents. Life would be grand if this was always the case, but most forum readers will agree this in not reality.
AWS and some military welding standards seems to take the conservative position that if the procedure passes all the required tests the acceptable ranges are X percentage above and below the values used to weld the test coupon. This may be a little too conservative for some folks, but at least it provides a rational approach to developing a production WPS. There is nothing that prohibits testing multiple coupons using different ranges to broaden the parameters listed in the production WPS. The goal is to develop a WPS that has predictable results.
As a starting point I usually use the magic of the Internet to contact the electrode manufacturer to ask for their recommendations for the welding parameters and to my glee, most have the information listed for all to see.
Once I qualify the initial WPS, I write a WPS just for qualifying welders. The ranges of the welding parameters are rather wide, thus allowing the welder plenty of latitude in how they set their machines. Fortunately, I have more than thirty years of welding experience to draw upon in making the final determination of what is a reasonable range for the welding parameters to be used in production. Between the allowable ranges permitted by the welding standard or the lack of direction by other codes, I write a WPS for production. The one goal of the WPS is to provide sufficient information to the welder to ensure the level of quality required is met. When justified by market demands, the WPS should also promote consistency between welders where the welds will be subject to the scrutiny of the consumer. It may be acceptable from a metallurgical standpoint to weld with weaves or stringers, but when the welds are viewed side by side by the consumer, it is best that the welder use similar techniques so they look similar. The handy dandy Excel spreadsheet with the statistical analysis tools is great way to establish a reasonable range when there are sufficient data points to analyze.
The last point that I feel is worth repeating is that the WPS should be written with the welder in mind. The information that has to be included is stipulated by the appropriate welding standard. Additional information that can be used by the welder should also be included. I use a system of annex to provide the added information needed by the welder such as a listing of material specifications included in a P number grouping (only those that will be used in production). Another annex lists the standard joint details with tolerances for groove angles, root openings, alignment, etc. A third annex is used for acceptance criteria appropriate for the work being performed.
I guess that the end of the rant for this evening.
Best regards - Al
Al,
First of all I don't believe there is what I would call a 'once and for all thread'.
These debates keep popping up because they are important and unresolved issues(at least for those that are asking the question), and new people confronted with these issues keep coming into the forum. And even though there is definate redundancy some have not as yet discovered the Search function, AND, each time the subject comes up something a little different is added to it.
Also, I have no argument with the general jist of your ideas of PQR development and WPS's, at least as far as I perused them. But the issue is not good practice, the issue is whether or not it should be a code requirement. What you have when arguing for it to be a requirement is simply that, an argument, logic (good logic to be sure, but logic nonetheless). But I don't believe that logic alone can justify the generation of a code requirement. ASME far from hiding their heads in the sand (even though this may be the case sometimes-but having witnessed code activities and the debates of the ladies and gentlemen involved I believe its rare and very counter to their participation-lets not forget that ASME is a collection of individuals volunteering their time because they do care-though I'm sure there are exceptions-the problem being primarily, in my opinion, one of collectivity) perhaps overreact when faced with failures(and when I say overreact I do not mean that injury or death is unimportant-not at all-I mean that requirements have been imposed in the face of failures even when they are not exactly sure what caused the failure (usually it comes down to educated guesses)-just to err on the conservative side). So I ask, where are the failures that would justify this particular code requirement. The Section IX guys, many of which you know personally, do not seem to think they exist. If someone has evidence of such present it to ASME.
BPV and PP are minimum safety codes (see ASME Section IX para. 2 line 1-not necessarily speaking to you now Al) and even though something sounds like a good idea, and perhaps even IS a good idea does not mean it should be a code requirement.
As you may have surmised I am a minimalist when it comes to the code. I do not want to have to deal with a 20 volume set of Section IX's based upon good practice requirements (the growth is already enough with the changing industry and interpretations), becasue there is possibly 1000's of instances where good practice logic could be imposed in the code.
One other point. The bigger the code, the more it will be misunderstood. Good for consultants (many of which sit on code bodies and vote minimalist in a sense counter to their own income), not so good for the industry.
Sorry if I touched upon a raw nerve. Ouch!
There are basic philosophical differences between the codes developed by ASME and those developed by AWS. I want to laugh every time I hear someone say, "There's no useful information in the ASME Code!", "I can't design anything using Section XX.", "Where does it tell you what filler metal to use with base metal YY?" I'm not kidding, those are the types of comments I hear in the course I teach. Now I can tell them it is because of ASME's minimalist approach to writing codes. I used to reply that ASME codes "don't tell you how to build anything", but now I can tell them its ASME's minimalist's philosophy. :)
Now that I understand ASME uses the minimalist philosophy, it goes a long way in explaining why I see pressure vessel drawings with the notation: "Weld Here". ;)
You know I'm having a good time with this and I hope you aren't offended by my sense of humor. When you make the comment that you wouldn't want to see the ASME B&PV code expand to twenty volumes, I can only laugh at the thought of you and I trying to drag all that paper through the security lines at the airport! It's bad enough there's about 15 volumes now! :(
I know all too well how much time, effort, and money we committee members contribute to developing codes and standards for AWS and ASME. Never do I want to minimize what the committee volunteers do on behalf of the different societies like ASME, ASNT, or AWS. However, I do see some humor in what we do and how exasperating it can be to put all the time and effort into those endeavors only to have someone sucks the wind out of our sails with a comment like, "There's no useful information in that code!" Then again, maybe there is some truth to what they are trying to say.
I always enjoy stirring the puddle just to muddy the water. That's when the good discussions begin!
Best regards - Al
No raw nerve on my part. Stir it as much as you like Al. I can't imagine a scenario wherein I would be offended by your opinion and wit.
Motivated to respond enthusiastically? Of course.
Offended? Next time your in Houston and I offer to buy you a McRottweiler at McDonalds for dinner you might assume you've offended me. Other than that,,,,,,,,,,,
I enjoy spirited debate and discussion. How boring it would be if we all agreed.
Sometimes what comes outa collectivity is mud.
I'll look forward to that the next time I'm in Houston!
Best regards - Al
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