The sequence of operations may be your problem.
Drop the factor of 1000 and all the fudge factors. I don't know where or how the inspector is deriving those factors. Do the math, get the answer in terms of J/inch. The number will be pretty impressive. Now divide by 1000 to get the answer in terms of kJ/inch.
We did a heat input post a few weeks ago, didn't we?
Best regards - Al
I suppose that Al did already make the fundamental point.
Likewise I'm sure that you are certainly right with what you say.
Not having the second sight I'm afraid to be unable to understand why the inspector's dealing this way with this subject.
One explanation, to me, might be that he's trying to set some meaningful (whatever that is) frame of minimum and maximum points for those values required to compute "heat input".
Not aware which GMAW principle you employ - CV or pulsed GMAW(?) - maybe the inspector does set these values to cover the dynamics of the latter. To be honest, however, the values themselve nonetheless appear quite arbitrary to me or generalising rather, based perhaps on his own made experience.
GMAW-P, as well as low power constant voltage process modes, e.g. short arc, interrupted in their (arc) regularity by short circuits or similar 'perturbations' are hardly calculable using the "regular heat input" approach. But continuing this here would certainly end up in a philosophical discussion.
Anyway, I suggest to have gained some experience in scientific "arc measurement" methodologies.
From that I dare to claim that - almost - everything in (arc) welding depends on statisitics or average values - simply because of being highly dynamic or non-linear. And, in my experience, the higher the data output accuracy requirements to meet the "worse" (i.e. complex) it gets to represent reality.
That being said and necessarily confessing to have absolutely no experience with producing WPS's complying with AWS (US) codes; I nonetheless cannot see some real contradiction between yours or Al's opinion and the inspector's one. At least near to the bottom line.
Actually, the inspector is doing nothing different than yourself, see the embedded image.
However, assuming that you're employing a CV mode (spray transfer?) while assuring your contact tube to work distance (CTWD) to remain constant, then, the inspector should provide arguments for his approach. Then, in my opinion, the noise measurable along the distance welded per minute should prove negligible. I.e. your process conditions should prove virtually stationary or "constant".
On the other hand. If you're employing spray transfer and your welding sequence is joined by tangible CTWD variation then, as frequently discussed on this forum, some measurable variation in current is likely to occur which again may affect "heat input". Then however, these variations shall need specific quantification before putting them as factors in your WPS.
Hence, if the inspectors is relating to average values (as in the JPEG embedded), then he could easily follow your approach, because of representing even these average values between minimum and maximum.
In my opinion there are - at least - 3 different options left hence, finally:
1. You're using CV spray mode maintaining CTWD and travel speed constant through welding. Thus no minima/maxima in voltage, current and travel speed are expectable, hence the 'regular' approach appears reasonable or justifiable.
2. You're using CV spray transfer mode and variations occur during the welding sequence in current, voltage and travel speed. Then - according to your inspector - these variations should fit in the frame determined by himself. Otherwise, they would require accurate evaluation before stating them as correlation factors in your WPS.
3. You're using GMAW-P. Then, in my eyes, neither the 'regular' nor the inspector's mathematical approach would point you towards reasonable and reliable "heat input" values.
Difficult to advise anything here to cut the Gordian knot, but maybe you could show the inspector that - actually - you and him are on the same page of the same book, having a "different" approach though to read it.
Otherwise I would suggest the inspector should prove on where these specific values do come from. And if both he really stands his ground on this and in case of employing CV spray transfer, well, then he should sign his name under the assurance that (explicitly for his 2nd approach) 261 Ampere and 18.6 V at simultaneously increased travel speed will lead to the same results vs. those values set by yourself.
I'm not sure wether all that can contribute in answering your question(s) or whether I am simply missing something fundamental here. If so, I'm always more than willing to learn and being corrected is not as bad as it maybe sounds.
Anyway, quite interesting thread and I would be glad if you could finally share the subject's outcome.
FCAW is the process, I see and understand what you have shown and it all works. Basically you are working the the mid point, the A290, V20 and TS 11, I gave is the average, but now calculate using his method and you will see that the low will be 21 kJ/in, and in his eyes disqualifies the WPS. Maybe I am just missing his reasoning, I threw in the towel and sent in management. If he would just throw out the travel speed enhancement then I can make it work.
I like putting in ranges as my variables on the WPS and leaving out the +/-, I'd rather my welders not have to calculate, just do it like it is written. But his group (California OSHPD) is insistent that I use single values and put in Table 4.5 (d1.1) +/- allowance (A290 +/-10%).
Thanks
Richard,
Thank you.
I did of course compute what you'd mentioned.
As you say. His arguments for connecting lower electrical power with higher weld travel speed remain hidden at the very least. The reason for me to say that actually he should prove that lower electrical output over higher travel speed can lead to reliable and acceptable results - according to your WPS requirements.
Anyway. It finally would be interesting to learn whether and if, how your management could jump this hurdle.
Thanks again.