You know this has been an interesting thread but, there are certain variables that should have been addressed by now... I took a nap because of my blood sugar being the way ti can get sometimes so I apologize for dropping off the thread for a few zzzzzzzzzzz... ;)
Seroiusly though, what are the type of discontinuities and/or defects are you encountering that you describe within the fusion zone? in between passes are the welders using a wire wheel to clean otu any residual slag that with some FCAW deposits can be very thin and unnoticable especially in low ligt conditions which brings me to the next question...
What is the type of environment the welder are working in? in other words, is it a controlled environment where moisture is controlled somewhat, or is the welding being done in an environment where the both the pipe and base plates as well as the backing bars are being subject to exposure to potential moisture pick-up due to it's close proximity to the ocean and can you monitor the relative humidity around the welding area's?
Finally, what I jsut re-read was very important with respect to process control... "Despite taking every precaution cleaning wise, and even MT'ing these roots I've still got an issue thats here or there but not all around. I've been monitoring the electrical parameters, and have noticed some 50-60 amp and 2-3 volt fluxuations from the shop supplied power. I'm wondering if this can be a viable solution to my issue?"
Well, a 50 to 60 amp fluctuation certainly can be worrisome as well as 2 to 3 volts as well but that can also be operator inconsistency in regards to technique as well although it might even just be that the equipment having some sensitive meters too... have you checked with an amp probe what you primary input power is coming inot the machines and do theses machines have power factor correction which would then make the issue moot?
Also, are the power sources such that one can lock the set parameters? Can you describe the equipment to me? Have you checked with another person the actual V/A output parameters from the business end of the guns as opposed to just relying on the meters on the machines themselves and have these machines/power sources been calibrated and if so, how were they calibrated? Is there any sort of minimal preheat at all being performed on the joint prior to welding of let's say, 150 degrees F?
I know I'm stretching it a bit but, when you're stymied by you results ,and you say that you have backed up just about everything with respect to possible fault conditions well, sometimes one needs to think outside of the box in order to find the root cause and that's why I'm asking these specific questions although, you have also revealed more since I stopped paying attention to the thread. :) :) :) Finally, if you're going to use 100% CO2, then why aren't they running the Kobelco equivalent from Japan which is designed specifically for CO2 as opposed to the Hobart wire that's better suited for a mixed shielding gas for optimal results...
Most if not all Domestic manufacturers of FCAW wire formulate their flux contents to favor mixed gas shielding rather than CO2 and the reason why the Kobelco wire is preferred is the fact that Japan is a nation where argon isn't as abundant as here in the states and they are then practically forced to develop their wires accordingly to run optimally with CO2... I'm confident that your results will improve if you find out that every nook and cranny revealed nothing yet you're still only getting a 30% reject rate... If you use an FCAW wire that's specifically designed for 100% CO2 ,you'll notice the difference almost immediately... It certainly something worth investigating! ;) ;) ;)
Respectfully,
Henry