Just to let those who gave me advise with respect to pulling out 180 feet of 500MCM, it was a piece of cake. I used a kellum grip on each of the 3 500's, used a tugger for part of the extraction, then used human effort for the rest. Pulling the new 500's into the conduit was as well a peice of cake. My guys and I were complete in 6 1/2 hours including termination and clean up. Not bad since none of the guys helping me had ever done this type of work. Did I mention that my guys were a combination of millwrights, a cnc tech, and a maintenance electrician!! I was very impressed!
Well.....that 500 MCM wire that I isolated a few weeks earlier because of a path to ground.....It was practically blown in half!!!!! Mabey 9 strands holding it together. Looks like it was resting on a sharp edge when originally installed, and over 2 years of the presses vibrating the whole building, that corner worked it's way through the insulation. I filed those sharp edges away to prevent this from happening again!